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Standby Sizing Calculator

Generac Guardian™ 20kW Aluminum Standby Generator System (200A Service Disconnect + AC Shedding)

Generac Guardian™ 20kW Aluminum Standby Generator System (200A Service Disconnect + AC Shedding)
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Model: 5875
(Based on expert analysis, manufacturer ratings and customer reviews)
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5
Number of Reviews (165)
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  • Product Description
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  • 73
    Product Q&A
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Product Description
+
Grade
Style
Run Watts
20,000
Rated Watts
Voltage
120/240 Single-Phase
Fuel
Engine
Grade
Emergency
Style
Standby (Air Cooled)
Run Watts
20,000
Voltage
120/240 Single-Phase
Fuel
LP/Natural Gas
Engine
Generac OHVI


Product Video Disclaimer: "PED is not responsible for any variances from the product in this video and the item you purchase. Please review all product specs prior to purchase."

Features
Features
  • Smart Circuit Standby Generator System
  • Restores power to your entire electrical panel automatically
  • Digital Load Management (DLM) protects against overload
  • Nexus Smart Switch™ (RTSD200A3 - Included)
  • DLM technology allows for the smart control of 2 air conditioners
  • Service Rated: Mounts between meter and main service panel
  • 200 amp aluminum indoor/outdoor (NEMA 3R) cabinet
  • Nexus™ Digital Controller
  • Provides system status to compatible Nexus™ wireless monitors
  • Aluminum Sound-Attenuated Weather Proof Enclosure
  • Lightweight material offers superior corrosion resistance
  • Reduces sound pressure to a low 66 dB(A)
  • Attractive styling with lockable access doors
  • Automatic Voltage Regulator
  • Regulates ouput voltage to ±1% which prevents damaging spikes
  • Safe for sensitive electronics like computers and televisions
  • Generac OHVI Air-Cooled Engine
  • Full pressure lubrication system w/ 2 year oil change interval
  • 1' flexible fuel line and DVD manual included
  • Listed to UL2200 Engine/Generator Standard for Safety
Specifications
Product Specs
Voltage
120/240 Single-Phase
Frequency
60 Hertz
Rated Watts
20000 Watts
Surge Watts
20000 Watts
Fuel Type
LP/Natural Gas
NG Power Capacity
18000 Watts
LP Power Capacity
20000 Watts
NG Fuel Consumption @ 50% Load
206 ft³/hr
LP Fuel Consumption @ 50% Load
1.89 gallons/hr
Rated Amps
83 Amps
Decibel Rating @ 7m Learn More Sound levels are measured in decibels (dB). The lower the decibel rating, the less noise the product makes. As an example, a ticking watch is 20 dB while on the other end of the scale, a lawn mower is around 90 dB.
66 dbA
Transfer Switch
Automatic (Included)
Transfer Switch Amperage
200-Amps
Battery
Not Included (525 CCA)
Enclosure
Aluminum
A/C Ton Rating
2 x 5-Tons
Mounting Pad
Composite (Included)
Transfer Switch Style
Service Disconnect
ATS Load Shedding
Built-In
ATS Poles
2 Poles
ATS Service Disconnect
Yes
Cooling System
Air Cooled
UL Listed
Yes
Grade Type
Emergency
Engine
Engine Brand
Generac OHVI
CC
999 CC
Consumer Engine Warranty
3 Years
Commercial Engine Warranty
3 Years
Engine RPM
3600 RPM
Low Oil Alert/Shutdown
Yes
Overview
Weight
541 Pounds
Made in USA
Yes
Consumer Warranty
3 Years
Commercial Warranty
3 Years
Product Style
Standby Generator
Product Length
48 Inches
Product Width
25 Inches
Product Height
29 Inches
UPC
696471058758
Grade
Style
Run Watts
20,000
Rated Watts
Voltage
120/240 Single-Phase
Fuel
Engine
Grade
Emergency
Style
Standby (Air Cooled)
Run Watts
20,000
Voltage
120/240 Single-Phase
Fuel
LP/Natural Gas
Engine
Generac OHVI


Product Video Disclaimer: "PED is not responsible for any variances from the product in this video and the item you purchase. Please review all product specs prior to purchase."

Features
Features
  • Smart Circuit Standby Generator System
  • Restores power to your entire electrical panel automatically
  • Digital Load Management (DLM) protects against overload
  • Nexus Smart Switch™ (RTSD200A3 - Included)
  • DLM technology allows for the smart control of 2 air conditioners
  • Service Rated: Mounts between meter and main service panel
  • 200 amp aluminum indoor/outdoor (NEMA 3R) cabinet
  • Nexus™ Digital Controller
  • Provides system status to compatible Nexus™ wireless monitors
  • Aluminum Sound-Attenuated Weather Proof Enclosure
  • Lightweight material offers superior corrosion resistance
  • Reduces sound pressure to a low 66 dB(A)
  • Attractive styling with lockable access doors
  • Automatic Voltage Regulator
  • Regulates ouput voltage to ±1% which prevents damaging spikes
  • Safe for sensitive electronics like computers and televisions
  • Generac OHVI Air-Cooled Engine
  • Full pressure lubrication system w/ 2 year oil change interval
  • 1' flexible fuel line and DVD manual included
  • Listed to UL2200 Engine/Generator Standard for Safety
Specifications
Product Specs
Voltage
120/240 Single-Phase
Frequency
60 Hertz
Rated Watts
20000 Watts
Surge Watts
20000 Watts
Fuel Type
LP/Natural Gas
NG Power Capacity
18000 Watts
LP Power Capacity
20000 Watts
NG Fuel Consumption @ 50% Load
206 ft³/hr
LP Fuel Consumption @ 50% Load
1.89 gallons/hr
Rated Amps
83 Amps
Decibel Rating @ 7m Learn More Sound levels are measured in decibels (dB). The lower the decibel rating, the less noise the product makes. As an example, a ticking watch is 20 dB while on the other end of the scale, a lawn mower is around 90 dB.
66 dbA
Transfer Switch
Automatic (Included)
Transfer Switch Amperage
200-Amps
Battery
Not Included (525 CCA)
Enclosure
Aluminum
A/C Ton Rating
2 x 5-Tons
Mounting Pad
Composite (Included)
Transfer Switch Style
Service Disconnect
ATS Load Shedding
Built-In
ATS Poles
2 Poles
ATS Service Disconnect
Yes
Cooling System
Air Cooled
UL Listed
Yes
Grade Type
Emergency
Engine
Engine Brand
Generac OHVI
CC
999 CC
Consumer Engine Warranty
3 Years
Commercial Engine Warranty
3 Years
Engine RPM
3600 RPM
Low Oil Alert/Shutdown
Yes
Overview
Weight
541 Pounds
Made in USA
Yes
Consumer Warranty
3 Years
Commercial Warranty
3 Years
Product Style
Standby Generator
Product Length
48 Inches
Product Width
25 Inches
Product Height
29 Inches
UPC
696471058758
Product Specs
+
Specifications
Product Specs
Voltage
120/240 Single-Phase
Frequency
60 Hertz
Rated Watts
20000 Watts
Surge Watts
20000 Watts
Fuel Type
LP/Natural Gas
NG Power Capacity
18000 Watts
LP Power Capacity
20000 Watts
NG Fuel Consumption @ 50% Load
206 ft³/hr
LP Fuel Consumption @ 50% Load
1.89 gallons/hr
Rated Amps
83 Amps
Decibel Rating @ 7m Learn More Sound levels are measured in decibels (dB). The lower the decibel rating, the less noise the product makes. As an example, a ticking watch is 20 dB while on the other end of the scale, a lawn mower is around 90 dB.
66 dbA
Transfer Switch
Automatic (Included)
Transfer Switch Amperage
200-Amps
Battery
Not Included (525 CCA)
Enclosure
Aluminum
A/C Ton Rating
2 x 5-Tons
Mounting Pad
Composite (Included)
Transfer Switch Style
Service Disconnect
ATS Load Shedding
Built-In
ATS Poles
2 Poles
ATS Service Disconnect
Yes
Cooling System
Air Cooled
UL Listed
Yes
Grade Type
Emergency
Engine
Engine Brand
Generac OHVI
CC
999 CC
Consumer Engine Warranty
3 Years
Commercial Engine Warranty
3 Years
Engine RPM
3600 RPM
Low Oil Alert/Shutdown
Yes
Overview
Weight
541 Pounds
Made in USA
Yes
Consumer Warranty
3 Years
Commercial Warranty
3 Years
Product Style
Standby Generator
Product Length
48 Inches
Product Width
25 Inches
Product Height
29 Inches
UPC
696471058758
Reviews
(165)
+
Generac Guardian 5875 Reviews & Ratings
75% of Reviewers Recommend This Product
Product Q&A
(73)
+
Search Product Q&A's Answered by Jared, the Generator Expert
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I am interested in the Generac 20KW generator for my house. The problem is that the generator would need to be installed on the oposite side of where my electric service comes in to the house. It is a 200 amp service. The generator would be roughly 60 feet from the main panel. Can this be done?
Brad Mellon 
from Illinois 
September 09, 2013
Answer
Thank you for your interest in Electric Generators Direct!

The configuration that you have described is certainly feasible. We would suggest that you confer with a licensed and knowledgeable electrician in order to ensure the proper installation of your Standby system.
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What is the difference between the Generac model 5875 and their new model 6244 since they are the same size?
Jim 
from Illinois 
May 02, 2013
Answer
Generac's model 5875 was the best selling generator on the market and Generac went ahead and improved on the design, warranty and ease of installation after listening to consumer reviews and technicians.

They bumped up the warranty an additional 2 years to give it a solid 5 year overall which is one of the highest rated on the market.

They improved on the generator controller by upgrading to a new technology and moved from their very good Nexus design to the new and improved Evolution controller. This new controller has a back-lit interface with LED's that shows the generator status at a glance.

The new Evolution controller includes maintenance reminders and logs, battery condition (no guessing) and over a half-dozen additional alarms the Nexus controller did not have. This thing rocks!

They upgraded the engine to include a no choke carburetor which helps with all weather starting. They changed the fuel selector for natural gas and LP to an easy knob that is easy to access and change fuel type with ease (No tools required).

For the installers they made several changes to help with installation costs and time, minimize errors and accommodate current and future electric code interpretations by re-engineered some of the wiring connections.

With the changes to the carb and engine they were able to change the low fuel pressure rating for Natural Gas down from 5" of Water Column to 3.5" of Water Column. This will help tremendously with low fuel pressure areas in the country so the meters do not need to be changed as often.

With all of these upgrades they have performed I believe Generac's newest model is one of the best out there and comes highly recommended.
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Is the transfer swith a Nexus Smart switch unit?
Jerome Palko 
from Pennsylvania 
April 26, 2013
Answer
Yes, the switch that comes with generator model 5875 would be model RTSD200A3 and is a Nexus Smart Switch so it matches the Nexus controller inside the generator.
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What is the oil capacity of the 20kw generac guardians?
Bryan Sullivan 
from New Jersey 
March 09, 2013
Answer
Oil Capacity is 1.9 Quarts Including the Oil Filter.

Spec Sheet
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Does model 5875 come with a pad? How much are the DLM modules?
Lee Steiner 
from Indiana 
February 12, 2013
Answer
All of the Generac home standby generators come with a pre-installed composite pad to protect the bottom of the generator but a sold base needs to be installed such as concrete, crushed stone or pea gravel with a minimum of 3 inches thickness.

Here is the link to the DLM module on the site which shows price and availability....

Generac Model 5937 DLM Module
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I just brought the 20kW Generac generator with 200 RTS Automatic Transfer Switch. I will be installing to a 200 amp panel. The transfer switch will be about 8' from the generator. What size wire do I need to run from generator and transfer switch? I will be running the same size wire from my meter to the transfer switch and back to my panel that is there now.
Randy Brown 
from Tennessee 
February 10, 2013
Answer
You will need to check with the contractor that is handling the installation in order to determine the correct wire gauges. There are a number of variables that will affect this size. In many instances, it is common to see the local building department amend codes that also regulate these specifics. Unfortunately, given my remote location, i am unable to assist in determining this.




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Can this unit be installed indoors with proper exhaust venting? If not, is there another model more suited to an interior installation?
Richard Ward 
from Georgia 
February 08, 2013
Answer
We do not offer any generators for indoor installations, all models much be installed outdoors with proper clearances from buildings to allow for proper ventilation.

There really are no indoor installation generators on the market today due to very strict regulations by OSHA, NFPA and generator manufacturers as it is extremely dangerous due to the carbon monoxide these units produce which is deadly.

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Could you tell me what size LP tank I would need for a 20kW Generac Home Standby Generator? Could I use two tanks or one big one?
John Dimsdale 
from North Carolina 
February 06, 2013
Answer
The minimum LP tank size recommended by Generac would be 200 Gallon depending on the ambient temperature in your area.

It is a good idea to contact your local LP supplier and let them know that you will be installing one of these units that have a BTU rating of 294,000 BTU/HR and they can help you properly size it based on your specific location.
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I just had my 5875 installed last week. No one can figure out where the 4 screws with the rubber bottom go. Can you help?
Tony Moscatello 
from Pennsylvania 
January 28, 2013
Answer
The 4 screws with the rubber bottoms are for the battery compartment and used to help support the battery off of the base of the generator.
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JIM, WHAT IS THE NOICE OUTPUT DURING THE WEEKLY TESTING MODE? WHERE CAN I FIND THE DOCUMENTATION ON YOUR RESPONSE AS I NEED A VARIANCE AND THE DECIBEL OUTPUT IS REQUIRE DURING THE WEEKLY RUN?
BOB BACIGALUPI 
from New Jersey 
January 07, 2013
Answer
This information is found on the Generac spec sheet for this model located under the specs link on the generator page.....

Sound output in dB(A) at 23 ft. with generator operating at normal load - 66

Sound output in dB(A) at 23 ft. with generator in Quiet-Test™ low speed exercise mode - 60

Spec Sheet
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Where can I download repair and parts manuals for Generac 5875? Thanks, Warren Stryker
Warren Stryker 
from Florida 
January 07, 2013
Answer
With the use of your serial number you can access the manuals via the Generac website under their service section....

Generac Manual Search
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Is the communication wiring considered class 2 from generator to transfer switch?
Buck's And Son Electric 
from New Jersey 
October 18, 2012
Answer
Wire sizing is based on the distance and all wiring must be the correct size and type, and must conform to all local codes, standards and regulations.

You will need to check with the AHJ (Authority Having Jurisdiction) as to what they require for the installation based on local your specific codes.
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On a propane install what size line is required from the tank to the generator?
Randy Walters 
from Kentucky 
October 10, 2012
Answer
The pipe size is based on the distance the generator is from the fuel source.

The 20kW requirements are:

LP -

3/4" - Max 15 Feet
1" Pipe - Max 115 Feet
1-1/4" Pipe - Max 480 Feet

NG -

3/4" - Cannot Use
1" Pipe - Max 20 Feet
1-1/4" Pipe - Max 130 Feet
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Are mounting bolts for concrete install included in unit packaging?
Walter 
from South Carolina 
October 06, 2012
Answer
Generac does not provide the concrete mounting bolts with the generator because it is optional to permanently mount it to concrete.
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Does the 5870 construction (enclosure make up) meet NFPA 37 condition 2 requirement?
Bob 
from New Jersey 
October 02, 2012
Answer
Subsection 4.1.4 of NFPA 37 reads as follows:

“4.1.4 Engines Located Outdoors. Engines, and their weatherproof housings if provided, that are installed outdoors shall be located at least 1.5 m (5 ft) from openings in walls and at least 1.5 m (5 ft) from structures having combustible walls.
A minimum separation shall not be required where the following conditions exist:

(1) The adjacent wall of the structure has a fire resistance rating of at least 1 hour.
(2)* The weatherproof enclosure is constructed of noncombustible materials and it has been demonstrated that a fire within the enclosure will not ignite combustible materials outside the enclosure.”

A4.1.4 (2) Means of demonstrating compliance are by means of full scale fire test or by calculation procedures.
Because of the limited spaces that are frequently available for installation, it has become apparent that exception (2) would be beneficial for many residential and commercial installations. With that in mind, the manufacturer contracted with an independent testing laboratory to run full scale fire tests to assure that the
enclosure would not ignite combustible materials outside the enclosure.

Per Generac Owner's Manual (All 8, 10, 14, 17 & 20kW Air Cooled Automatic Standby Generator):

The criteria was to determine the worst case fire scenario within the generator and to determine the ignitability of items outside the engine enclosure at various distances. The enclosure is constructed of non-combustible materials and the results and conclusions from the independent testing lab indicated that any fire within the generator enclosure would not pose any ignition risk to nearby
combustibles or structures, with or without fire service personnel response.

Based on this testing and the requirements of NFPA 37, Sec 4.1.4, the guidelines for installation of the generators listed above are changed to 18 inches (457mm) from the back side of the generator to a stationary wall or building. For adequate maintenance and airflow clearance, the area above the generator should be at least 4 feet with a minimum of 3 feet at the front and ends of the enclosure.
This would include trees, shrubs and vegetation that could obstruct airflow. See the diagram on the installation drawing within the owner’s manual on under the specs link for details.

Generator exhaust contains DEADLY carbon monoxide gas. This dangerous gas can cause unconsciousness or death. Do not place the unit near windows, doors, fresh air intakes (furnaces, etc.) or any openings in the building or structure, including windows and doors of an attached garage.
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I have received my 20Kw Generac 5875. Was it shipped with oil or do I need to add oil before i start it up? Or is it just a break in oil (the oil on the dip stickis very light) that needs to be removed and filled with what I will be using in this area? Shipment was timely and arrived n excellent condition.
Larry 
from Washington 
September 30, 2012
Answer
These units have been run and tested at the factory prior to being shipped and do not require any type of break-in.

This unit comes filled with oil from the factory. Check the oil level and add the appropriate amount if necessary.
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Jim, First I want to say that I love your site. Very helpful information in making up my mind on sizing a perfect standby generator. I am looking at the 5875, and am almost sold. I question I need to determing is the largest wire size that the nexus smart switch that comes in this package, and the breaker in the 5875 can handle. I am in a situation where I need to install the generator on the opposite side of the house as my load center. Initial calculation is that I will need #2 wire to run from the generator to the smart switch. Can the breaker lugs on the generator and the smart switch handle #2 wire? In the manuals posted on line I only see torque specs down to #4 wire. Appreciate your input
David Bunk 
from Virginia 
September 27, 2012
Answer
Generator Main line breaker (100A): #4 - 1/0 AWG Cu or #2 - 1/0 AWG Al.

Switch Lug Range (RTSD200A3): 400 MCM - #4
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I have a Generac 5875 w/smart switch. Do I have to wire my ac to one of the DLM at the generator set? Can I use a separate DLM module if needed instead? Thanks Chris
Chris Allen 
from Pennsylvania 
September 27, 2012
Answer
To wire your AC to the generator you can only connect to the AC 1 connection inside the automatic transfer switches load manager via the thermostat wires (24vac).

A DLM module is not needed since your AC unit outside already has a contactor that is activated by your thermostat. The generators load manager will interrupt that signal not allowing the AC to come on if the generator does not have enough power capacity available.
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I have 150 amp service -- can I use a 200 amp transfer switch?
Eric 
from Michigan 
September 23, 2012
Answer
A transfer switch is a simple electrical pass through and can be used in a 150A service but some local codes require a matching amperage switch.

You will need to check with your local certified electrician or electrical inspector to verify your local codes.

If you need a 150A switch you can purchase the generator and switch separately.

Generator Model: 5884

Model 5884

Switch Model: RTSD150A3

Model RTSD150A3
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Does "low oil alert" mean this engine will shut down if low oil is detected, like most portables?
Jeff 
from Virginia 
August 31, 2012
Answer
Yes. The machine will shut down if the oil pressure dips below the safe limit.
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hello does this unit run on vapor or liquid propane
Clifford Millaudon 
from Louisiana 
August 31, 2012
Answer
It runs on low pressure, vapor at 11" WC.
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can i install this generator myself
John 
from Louisiana 
August 31, 2012
Answer
If you have the experience, yes. Many of our customers do, or at least do a good portion of the install and leave the more difficult tasks ( or ones where special tool apply like cutting threads on gas pipe etc) to the pro's.

You can definitely act as the general contractor and do most of the layout work and as much of the connections as you are capable of. Just be sure to follow local codes.
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Jim, getting ready to order the Generac 5875 20kw generator from you guys for LP. What is recommended LP tank size for this or can you give me some kine of estimate on daily gas consumption?
Scott Williams 
from Virginia 
August 15, 2012
Answer
The fuel consumption for this unit per Generac specifications is:

Half Load: 1.89 gallons/hr
Full Load: 2.90 gallons/hr

1.89 x 24 = 45.36 gallons/day

2.90 x 24 = 69.6 gallons/day
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I'm going to build a house in the spring of 2013 and I want to have a standby generator installed when the house is built. What would be the best size generator? I plan on having a geothermal heating/ac system and the house will be all electric.
Dan 
from Kansas 
August 06, 2012
Answer
Thank you for visiting Electric Generators Direct. In regards to your question, the generator size is determined by the starting amperage load of the equipment you are planning on powering when you lose power.

The starting amperage load will be much larger than the running load and proper calculations need to be done to properly size a unit.

We recommend having a certified electrician do your wattage calculations as every home is different.

The electrician would calculate with the following formula to properly size the generator which should be sized at 80% of its running capacity to allow enough flexibility to handle large intermittent loads and still keep voltage output at proper levels.

(Starting Amps x Volts = Watts)

Note: Geo-Thermal systems can require a tremendous amount of starting current and all calculations should be done onsite professionally.
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Jim I have my concrete slab ready. I wii be ordering Monday. I am wondering what size bolts it uses when mounting to slab? so I will know what size mounting holes I need to drill for fasteners. Thanks Paul
Paul 
from Alabama 
July 29, 2012
Answer
According to Generac you would use 3/8 inch lag bolts.
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What size copper tubing is required for a 20kW Generator to connect the Propane gas?
Linda Whitsell 
from Missouri 
July 28, 2012
Answer
Fuel pipe sizing is base on the distance from the fuel source. The 20kW Generac has the following requirements:

For Propane:

3/4" pipe - max 15 feet
1" pipe - max 115 feet
1-1/4" pipe - max 480 feet

For Natural Gas:

1" pipe - max 20 feet
1-1/4" pipe - max 130 feet
1-1/2" pipe - max 305 feet
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Hey Jim, looked everything over pretty close but can not find where the exhaust exits,this is important to me because of location and carbon monoxide poisoning thank you for your time.
Joe 
from Virginia 
July 19, 2012
Answer
The exhaust is emitted from the left side of the unit. This is listed in the installation drawings.

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Does this unit need a winter heater?
Alan Whitefield 
from Michigan 
July 16, 2012
Answer
Generac does offer a cold weather kit but its use would be dependent on your local area and what the weather is like.

Generac suggests using the cold weather kit in regions when temperatures drop below 32 degrees F regularly.

Generac Cold Weather Kit for 14 - 20kW Home Standby Generators
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Jim, I wanted to know about financing?
George 
from Ohio 
July 15, 2012
Answer
George,

The only form of financing we offer would be "Bill Me Later" which offers no payments for 6 months and no interest during the 6 months....click link for details.

Bill Me Later

All other forms of payment are with most major credit cards, check or PayPal.
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Do I need a separate gas regulator for the 5875 or will the one on the generator be sufficient?
Tim Hancock 
from Missouri 
July 15, 2012
Answer
You will definitely need a separate regulator to control the fuel flow to the generator.

Natural Gas: 5-7 Inches of Water Column (0.18-0.25 psi)

Liquid Propane (Vapor): 10-12 Inches of Water Column (0.36-0.43 psi)
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Where do you connect the 12VDC battery charger?
Darrell 
from Texas 
July 15, 2012
Answer
The Generac Guardian home standby generators have a built in battery charger in the controller inside the generator called the battery sentinel.

This charger will only charge the battery when needed so it will not overload the battery and the controller in the generator monitors the battery and will notify you when there is a battery issue.
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Can I hook up a Generac guardian 5875 to two 200 amp panels? Thanks
Tamer Bader 
from Maryland 
July 14, 2012
Answer
Yes, you can connect 2 - 200A switches to the 20kw Generac generator. One switch will be the master and the other will be its slave and do what the master does.

This allows you to utilize both load managers in the switches which gives you more flexibility.
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With model 5875 what is the model of the transfer switch that comes with the unit?
Mike Champion 
from Virginia 
July 14, 2012
Answer
The switch that comes with Model 5875 is the RTSD200A3. Here is the link to the switch page which has the spec sheet and installation manual.

Generac RTSD200A3 Automatic Transfer Switch
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I have a 20kW Generac with an appropriately sized 200 amp ATS that I purchased two years ago from you guys. I didn't think to ask my electrician at the time about how to connect to both of my 200 amp panels in my house. Instead we moved a few circuits and ties it into one of the panels. I now understand I may be able to connect a second ATS in this configuration to the second 200 amp panel. I'll never use the entire 20 kW load and I want my entire house on back-up generator. Can you prescribe this? If so please specify how it should be configured and which ATS I should buy
Don Roy 
from Maryland 
July 01, 2012
Answer
You can connect a second switch to the panel as long as you do not exceed the capacity of the generator.

You will need to consult with your electrician to verify you would not overload the generator.

One of the biggest benefits is that you will be able to connect to both load managers in the switches so you can load shed some large items to prevent the overloading.

The correct switch to purchase and install would be the RTSD200A3 Nexus Smart Switch which is the same switch that you already have with your model 5875.

The switches would work as a master and slave with the original switch telling the second switch to come on when properly connected by your installing electrician.
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Does the 200A transfer switch come prewired like the 100amp switch?
Al Privitera 
from New York 
June 19, 2012
Answer
The 200A transfer switches are not prewired since they are designed for whole house installations. The connection lengths can vary and the switch can be mounted indoor or outdoor which will alter the length of wiring needed.

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What size concrete pad do I need to build for the model 5875?
Nick 
from New York 
May 28, 2012
Answer
The generator dimensions can be found in the installation drawing on the site under the specs link and below (click link).

It is recommended to go a minimum of 6 inches beyond the generator size to allow for a stable base.

Installation Drawing
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How can you hook up LP & NG at the same time using a cut off value on each gas source?
John 
from Virginia 
May 16, 2012
Answer
This is not recommended by Generac, these units are not designed to be connected to two separate fuel types. There are changes that need to be done to the unit when selecting which type of fuel you are using when the unit is being installed.

They come from the manufacturer set-up to operate on natural gas and would be converted in the field to use propane.
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Jim, what is the phone# where I can order a 20KW Generac propane generator w/transfer switch? Can I pay by check? Somewhere I saw "Save 2% by paying with check". Is this true?
Fran Downing 
from Minnesota 
May 08, 2012
Answer
You can either place your order online by adding item# 5875 to the cart and following the checkout procedure or contact customer support at 877-437-7998 and one of the CSR's can assist with placing your order. The following link takes you to the product page:

Model 5875

We do offer pay by check with a 2% savings, you would need to mail a paper check and when the check is received by our accounting department you will be notified via email.

From date of email notification we hold the order for 5 business days and then process and ship the order on the 5th day. See our check policy below:

Pay By Check Policy
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References are made to "AC units" throughout the Q&A. Are "AC units" actually heat pumps? Are there any special considerations concerning heat pumps?
Mike 
from Pennsylvania 
April 16, 2012
Answer
Heat pump systems typically require a tremendous amount of current at start-up so applications with them require a certified electrician to calculate the starting amperage loads to calculate the actual wattage needed.
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Where do I get the installation instructions for the Generac Home Standby Generators?
T Wanamaker 
from New York 
March 12, 2012
Answer
The unit comes with the installation instructions or you can find them on the Generac website. The instructions you get without the serial number will be basic.

Generac Manual Search
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Do I need a battery charger for the 5875 generator?
Carl Giusto 
from Texas 
March 07, 2012
Answer
The battery charger is built into the controller inside the generator.
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In regards to the first question under your Q&A. Are there 2 DLMs included with the ATS on the 5875? I have 2 200amp service and considering an extra ATS/smart switch so are there 2 DLMs that come with the unit and are there 2DLMs that come with the seperate purchase of an additional ATS/smart switch and is it true that each DLM is capable of only 1 high drawing appliance? (model RTSD200A3)
Paul 
from Connecticut 
February 25, 2012
Answer
The unit does not come with two actual DLM modules, it is set up to handle 2 AC units without additional DLM modules.

Standard AC units already have a contactor controlled by the thermostat so that control wiring gets routed through the ATS (automatic transfer switch) load manager from t-stat to switch to AC unit.

Actual DLM modules are used for appliances/equipment that does not already have a control system or contactor such as a water heater or electric oven. The DLM acts as a on/off switch controlled by the ATS load manager via the use of low voltage wire.

You can add up to 4 DLM modules per ATS as priorities 1 - 4.
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Are two DLM included in the Generac Guardian series 5875 with the purchase of the unit?
Richard Bull 
from Pennsylvania 
February 12, 2012
Answer
There are 2 AC connections in the Generac Nexus Smart Switch™ which the thermostat wire is run to. So, when the thermostat calls for air/heat and the generator has enough power it will allow the call to go through, thus allowing the AC unit/units to run.

To connect to 2 AC units the DLM modules are not necessary since the AC unit already has a built in contactor/relay controlled by your thermostat.

The DLM modules are for loads (up to 50A) that do not have any control options such as electric ovens or electric water heaters. The DLM acts as a contactor/relay which the transfer switch tell to open or close (on/off) depending on the available wattage from the generator.
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What is the water column operating pressure of the Generac model 5875?
Jeff Miedema 
from Indiana 
January 29, 2012
Answer
You will find the information listed on page 8 of the owner's manual which can be found on the website under the specs link just to the left of the Q&A link.

Natural Gas - 5 - 7 inches WC (0.18 - 0.25 psi)

Liquid Propane Vapor - 10 - 12 inches WC (0.36 - 0.43 psi)
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Hi Jim,is there any codes to how far from a window the standby generator must be. Thank You Frank
Frank Gelsomino 
from Connecticut 
January 24, 2012
Answer
NFPA 37 - 4.1.4 Engines Located Outdoors. Engines, and their weatherproof housings if provided, that are installed outdoors shall be located at least 1.5 m (5 ft) from openings in walls and at least 1.5 m (5 ft) from structures having combustible walls. A minimum separation shall not be required where either of the following conditions exist:

(1) The adjacent wall of the structure has a fire resistance rating of at least 1 hour.
(2)*The weatherproof enclosure is constructed of noncombustible materials and has been demonstrated that a fire within the enclosure will not ignite combustible materials outside the enclosure.

The above code is referenced in NFPA 70 - Article 445 Generator Locations.

You do need to reference with your local inspector what the requirements are for your local city codes along with the requirements in your area for noncombustible materials.

Always consult with a certified electrician on all installation procedures and processes.
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What are the BTU's on model 5875?
Vic 
from New Jersey 
January 20, 2012
Answer
The BTU for the 20kW Generac 5875 are:

1/2 Load: 206,000 BTU/HR

FULL Load: 294,000 BTU/HR

To calculate:

1 CU-FT = 1000 BTU

(Example: 20kW Generac uses 206 CU-FT/HR x 1000 BTU = 206000 BTU/HR)
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Hi Jim, Your top Q&A on this is regarding the use of a second smart-switch to take care of a second 200 amp panel. Can you provide some more details on the wiring of this to the generator and to each other? Does one switch act as master the other as slave? Any wiring diagrams would be appreciated. Do you sell the appropriate switch?
Jack 
from New York 
January 04, 2012
Answer
Jack,

Below you will find a link to the one drawing I have that covers a couple ways to do a multi-switch set up. Typically they are done as master and slave.

Dual Service Entrance Switch Connections
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Hi Jim, I have two 200 amp breaker panels in my basement that are directly feed by the meter. Should I just buy an extra rtsd200a3 smart transfer switch for the second breaker panel?
Bob 
from  
November 27, 2011
Answer
Bob,

That is a great way to go while using the additional load shed manager in the second switch so you have a better opportunity to prevent overloading of the generator. Make sure your installing electrician uses these features at a minimum of connecting your AC units. These are the largest starting loads and when using the load manager if the generator does not have the wattage available to start them it will lock them out for a bit.
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Hi Jim, I'm thinking of buying the #5875. How do I decide if I need the DLM digital load management module? Also, if I live in NY state (near NY City) do I need the cold weather kit? Thanks, Adam
Adam Abramowitz 
from New York 
October 01, 2011
Answer
This model will come with digital load modules on it so you can power up to 2 air conditioners without buying an additional digital load module.

If you are interested in powering an additional high surge watt appliance you might consider adding an additional DLM, but most people don't need them.

If the weather ever dips below freezing it is best to consider the cold weather kit. If you ever get below 10 degrees it is a must.
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what size pipe for 20kw model 5875 connecting to lp or ng
Mario Deramo 
from New York 
September 27, 2011
Answer
Mario,

The 20kW unit has a 1/2" pipe connection but, the pipe run diameter is based on the distance from the fuel source.

Minimum pipe size - 1" - with max distance 20 ft
- 1-1/4" with max distance 130 ft
- 1-1/2" with max distance 305 ft
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Jim, How much ventilation does a typical genertor require? I just bought the Generac 5875 unit and was hoping to locate it underneath my deck. We have lattice material (with fairly large gaps) covering the underside of the deck. Would it be safe to put it there or does it need to be fully out in the open? I believe there is plenty of air flow beneath the deck.
Chris G. 
from Connecticut 
August 28, 2011
Answer
A Generac home standby generator requires 3 feet clearance on the sides, 4 feet clearance from the top, a minimum of 18 inches from the back of the unit (code permitting). A minimum of 5 feet is required from any window, door or ventillation opening due to exhaust.
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I am looking at a Generac Guardian Series™ 5875 - 20kW Smart Circuit Standby Generator System (Aluminum Enclosure). Would this be enough for a 2 bedroom, 2 bath town home app. 1400 sq ft?
Charlie Roethlinger 
from North Carolina 
August 27, 2011
Answer
Yes, this can power a small townhouse with no problem.

In fact, it might even be too large.

For example, the 17kW Essential Circuit Generator can energize 16 circuits in your main electric panel.

If you have 16 or less circuits, you can actually purchase a smaller system.

Here's an article than can help:

How to Pick the Perfect Essential Circuit Standby Generator
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For a 20 KW nat gas unit which brand to you recommend and why? For use in Dallas. Thanks Jim
Jim 
from Texas 
August 19, 2011
Answer
I highly recommend the Generac model 5875 as Generac has the newest technology and the best engine in the industry with their OHVI Industrial engine. This engine is the only one that is specifically designed for generator use and is built in Wisconsin. The most environmentally friendly generator on the market - consumes less fuel and releases fewer emissions. Generac is the number 1 selling generator in the US.

Generac 20kW Model 5875
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I live in central Indiana and need to know if I would need a cold start kit. I also need the cost as I am trying to consider the total cost of purchasing your 5875-20k. I am on a tight budget and don't want any surprises.
Frank Edwards 
from Indiana 
July 04, 2011
Answer
Generac recommends the cold weather kit for climates that drop below 30 Degrees during the cold months. The link below shows the cold weather kit for model 5875:

Cold Weather Kit for 14 - 20kW Generac Standby Generators
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Hi I want to buy to a country where every thing is European 240v 50 hertz do you have that?
Seifu Lessanework 
from Michigan 
May 05, 2011
Answer
Hello,
I'm sorry, but we currently don't offer 50hz generators.

Thanks for inquiring -

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Is there any issues with a residential NP gas meter being able to supply the 20 kw model at capacity?
Roddie 
from Louisiana 
May 05, 2011
Answer
Typically there aren't any issues, however, the Generac 5875 does require 206 ftł/hr @ a 50% load factor. The generator, combined with any other household appliances that also draw fuel will have to be added up to ensure the needed cubic feet is available at a minimum of 7"of water column.

If you get the meter checked by your utility company they can verify all of this for you, or swap meters if required.

Thanks!
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I need to know how to hook up a generac 5875 generator. I'm the electrican. I can't pull anything up on internet showing this. How to install. It says quick and easy. Can you please help.
Dale Inman 
from North Carolina 
April 26, 2011
Answer
You can view the installation guide from the link below by entering the model number exactly as 0058750. This gives you access to all of the manuals, drawings and wiring diagrams. This should help with the installation.

Manual Search
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What is a composite pad ?
CHARLES BLYTHE 
from North Carolina 
April 08, 2011
Answer
The composite pad is a strong, lightweight mounting pad provided to simplify the installation. By including the pad with the generator, installation time and cost is reduced since a concrete base is no longer a requirement.
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for an average home is a nexus smart circuit versus just a standard 16 ats which one is necessary and why i am looking at buying a 17kw-20 kw generac
Michael Salvato 
from Florida 
March 31, 2011
Answer
The Nexus Smart Switch is wired directly to the whole panel and certain large circuits, such as AC or pumps, can be wired in the load shedding capabilities so the generator does not overload. With the 16ckt ATS the generator is only wired to the select 16 circuits which have to be sized correctly for the generators capability and only those circuits are powered when power is lost.

It really depends on the equipment in your home as far as which transfer switch system you want to go with.

Proper sizing of the generator is crucial to the success of any generator installation and requires a good working knowledge of electricity and its characteristics, as well as the varying requirements of the electrical equipment comprising the load. When analyzing the electrical load, consult the manufacturer’s nameplate on each major appliance or piece of equipment to determine its starting and running requirements in terms of watts, amps and voltage. When choosing the generator output select a rating that is approximately 20 to 25% higher than the peak load (for example, if the load is about 8 kilowatts, select a 10 kW generator). A higher rated generator will operate comfortably at approximately 80% of its full capacity and will provide a margin of flexibility if the load increases in the future.
A certified electrician should be consulted for proper sizing and installation of any generator.
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Does the Generac 5875 + 12v battery ship with everything needed for a complete installation or will any additional wiring, connectors, etc. be needed. In the event there is damage incurred in shipping that prevents installation or operation what is your policy.
Cliff Heavrin 
from Kentucky 
March 28, 2011
Answer
All of the wiring and connectors are to be provided by your installer. This prepackaged unit comes with the generator and transfer switch only. The battery is purchased separately.

The unit must be inspected at time of delivery for any shipping damage. Once you sign the BOL (Bill of Lading) you are saying you received the unit in good condition and we should be contacted immediately if any major shipping damage has occurred. If there are issues with the unit after installation you must contact a local Generac dealer for assistance and warranty work. Our return policy covers shipping damage.

Return Policy

You can find a local dealer from the following link:

Dealer Locator
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Jim does this unit come with a smart transfer switch?
Brian Kelly 
from New Jersey 
March 07, 2011
Answer
Yes, this unit comes with a 200A Nexus Smart Switch model RTSD200A3.
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How long can the 20kw propane generator run continuously?
Alan Marcet 
from California 
February 13, 2011
Answer
These units are designed for emergency back up to lost utility power and if you lose power for an extended amount of time these units can handle running for weeks if necessary. Please note that these units are not designed to run as a primary power source and if installed in this capacity the warranty will be void.

Generac does offer one primary power/off the grid type standby generator which is model 5818 and is specifically designed for extremely long run times.

Model 5818 EcoGen
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Hello Jim, do you have, or can you recommend stand-by generator installers for the Houston, Texas area? We are in the N.W. Houston area.
David Reece 
from Texas 
February 13, 2011
Answer
Since we do not get involved in the installation process and since we ship all over the continental US we do not have a list of installers to provide. You can contact a local Generac dealer who may do installations at a reasonable price and will provide you with the best installation knowledge. You do not necessarily have to purchase a Generac generator from them to utilize their installation and they would be your resource for maintenance and warranty repairs.

Service Dealers
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How far does a generator has to be from my house?
Jim 
from Massachusetts 
February 04, 2011
Answer
The manufacturer recommends the back side of the unit to be set no less then 18 inches from any non-combustible surface and the sides of the unit need at least 36 inches for proper intake and exhaust.

Note: It is recommended to check with your city, county and state codes as they may differ from the manufacturers recommendations.
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What are the BTU requirements for the Generac 20kW Standby Generators?
Rich 
from Oregon 
January 29, 2011
Answer
The BTU requirements can be found in the owner's manual which is listed in the specs tab. For the 20kW Generac Standby unit the BTU requirement is 294,000 BTU/HR.

Owners Manual
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I would like to compare the 20KW 5875 and an equivalent 17KW smart circuit unit. The 17 has adequate capacity for my whole house normal loads. Any reason to oversize?
Ron Jones 
from Washington 
January 26, 2011
Answer
To oversize a generator is a great plus as it relieves tremendous starting load from the unit and increases the longevity of the unit due to less stress.

Proper sizing of the generator is crucial to the success of any installation and requires a good working knowledge of electricity and its characteristics, as well as the varying requirements of the electrical equipment comprising the load.

When analyzing the electrical load, consult the manufacturer’s nameplate on each major appliance or piece of equipment to determine its starting and running requirements in terms of watts, amps and voltage.

When choosing the generator output select a rating that is approximately 20 to 25% higher than the peak load (for example, if the load is about 8 kilowatts, select a 10 kW generator). A higher rated generator will operate comfortably at approximately 80% of its full capacity and will provide a margin of flexibility if the load increases in the future.
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What size battery do I need?
James Fritch 
from Pennsylvania 
January 25, 2011
Answer
The battery is a Group 26R with 525 cold cranking amps - which is often difficult to find locally.

However, don't get too caught up in the specs. We already sized the battery for this model.

Click on the "Add 12V Start Battery" box when ordering.

The current battery price is listed below the generator pricing by the check box.

We don't sell the batteries individually because they are hazardous materials that must ship via freight. If you bought one individually, it would cost more to ship than the battery is worth.

Since this generator is already shipping via semi-truck, we shrink wrap them together, and the battery tags along for the ride.
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What kind of oil comes in the generator, and when it is time to change it? Can I run Mobile 1 Synthetic 5W30 year round in central Oklahoma?
Ron Hopper 
from Oklahoma 
January 24, 2011
Answer
The Generac standby generators are shipped with 5W30 oil in them and Generac does give the option to use 5W30 Synthetic in needed. The owner's manual covers all oil options and temperature ranges. Oil changes are determined by use and maintenance is also covered in the manual.

Owners Manual
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I originally thought of going with the 17kw and decided (I think) that I'm wanting to go with the 20kw 5875 so that I can mount on the outside of the house and run the 200 amp panel that is on the inside of the house. Am I correct that everything can be outside except main wires going to panel? And it does run the 200 amp service? Thanks
Greg French 
from Washington 
January 21, 2011
Answer
Yes, the included transfer switch with model 5875 is NEMA 3R rated (Indoor/Outdoor) and the only wires entering the home would be the control and power wiring.

This system can connect to a 200A main breaker but depending on the starting amperage loads on the items you intend to power in your home would determine if the 20kW generator is a sufficient size for your needs, as every home installation is different. It is recommended to have a "certified" electrician or Generac installation dealer determine you wattage needs by doing the wattage calculations on the equipment in your home. This is usually the person or company that would also do your generator installation.

The following article can assist you with additional information.

How to Pick the Perfect Home Standby Generator
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How about the Propane tank size? Do you sell those or do I go to a local dealer to install a good sized tank? Also, I figure I need only about 12 KW or so with a smart generator set - how quiet can one of those be?
Tom McDonald 
from Georgia 
January 21, 2011
Answer
Propane tank size is really determined by your backup needs and how much time you feel would be sufficient for backup. Generac recommends a minimum of 150gal with a 20kW would be a good starting point as the fuel consumption at 1/2 load is 1.89 Gal/Hr. Propane tanks would be purchased or rented from your local Propane dealer.

The generators running decibel rating on model 5875 (20kw) is rated at 63 db(A) at 7m and each of their standby models differ by a couple of db(A)'s.
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Can this generator be anchored to the slab? If so, can you provide an anchor bolt layout
Gregg Deemer 
from Texas 
January 21, 2011
Answer
Generac's model 5885, as with all of their standby generators, are anchored to the pallet at all 4 corners with special anchors which can be used to anchor the unit directly to your concrete base using concrete bolts.
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I noticed that Kohler states you do not need a concrete pad when using their composite shell generator. My question is; does the same go for the Generac model 5875? Can the transfer switch that comes with model 5875 be substituted for a 100A transfer switch? Thank you, Kevin Acres Electric Corp.
KEVIN BESANCON 
from Florida 
January 21, 2011
Answer
Generac states that you can use pea gravel as a sufficient base for their standby generators 8kW to 20kW.

To be able to substitute the transfer switch Generac offers the generator alone under model 5887 and a suitable transfer switch can then be purchased separately.

Generac 5887
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Hi Jim, I live in Alaska and own a 5875 20KW Home standby Generac. I need to get a cold weather kit. I am looking at the Generac Cold Weather Kit for 14-20kW Home Standby Generators (992/999cc). First, is this the correct product for my generator and second, is it a "plug and play' install? I understand I will need to change the oil to synthetic 5W30 so my guess is I'll need a maintenance kit as well. The generator has less than 3 hours on it. Many thanks, - Bill Thomson
Bill Thomson 
from Alaska 
January 21, 2011
Answer
That is the correct cold weather kit for the Generac Guardian 20kW model 5875 (or 5887) and it is a plug and play type unit, however, it is recommended by Generac to have a certified electrician install it due to the high voltage connection.
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