Whole house generators

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Greg1707

Senior Member
Location
Alexandria, VA
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Business owner Electrical contractor
Since the Derecho storm blew through my area I have received several inquiries regarding whole house standy generators. I have a couple of questions that I would like to pose to this august body.

1. Gas Line: For a 10 or 14 kw is the gas line usually simple or are there complications with insufficient supply and pressure?
2. Over all experience. In the big picture, are these installs generally problem free and profitable to pursue.

Thanks.
 
Definitely worth it. I would get another trade experienced with gas line installation involved and have them price and verify the gas source.
 
Greg1707 said:
Since the Derecho storm blew through my area I have received several inquiries regarding whole house standy generators. I have a couple of questions that I would like to pose to this august body.

1. Gas Line: For a 10 or 14 kw is the gas line usually simple or are there complications with insufficient supply and pressure?
2. Over all experience. In the big picture, are these installs generally problem free and profitable to pursue.

Thanks.
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Let some one else do the gas lines. Usually the size that is recommended is 3/4- 1 inch.
Let the customer buy the unit. As with Generac unless you are a certified dealer/service tech. they will not talk to you. Have them register the unit that way when they need warranty work they can contact a service dealer them selves and you are out of the headache.
 
One way or another I would provide a plan for servicing, a generator I put in 6 or so years ago, I had the customer sign up with a fellow contractor service plan, at least once a year she calls me to get his phone #. Sorta defeats the purpose.
 
ceb58 said:
Let some one else do the gas lines. Usually the size that is recommended is 3/4- 1 inch.
Let the customer buy the unit. As with Generac unless you are a certified dealer/service tech. they will not talk to you. Have them register the unit that way when they need warranty work they can contact a service dealer them selves and you are out of the headache.
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Just like adding a relatively major load to an electrical system you (your gas man) need to determine if the supply can handle the additional load. There is a good chance the piping will handle it, but additional regulator(s) could be needed to get it done correctly. Raising pressure will allow more gas to flow, but then existing appliances may need additional regulators to reduce to right pressure again and who knows, raising pressure may create other problems - gas man is supposed to know gas codes better than electrician anyway let him do that part.
 
In some locations around here they have insane noise and location requirements. You have to have a large piece of property, there is a minimum distance from the house as well as from the neighboring property. You also have to hire an acoustical engineer to certify the the noise level is below a certain limit at the neighbors house. Needless to say the customer has to really want a generator and have deep pockets.

If you are using natural gas you have to have a licensed plumber pull a permit to handle the gas piping and he will determine whether the existing gas service is capable of handling the generator. This is not something you should attempt to do yourself.

-Hal
 
Greg1707 said:
1. Gas Line: For a 10 or 14 kw is the gas line usually simple or are there complications with insufficient supply and pressure?
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Generally speaking, you're pretty safe if you have the plumber install a 1" gas line for these size units. However, the plumber should be the one doing the calculations to determine the proper size so, have him make a survey and give you an estimate before you solidify your price to your potential customer. Also, many gas meters are series 250. That means they can only deliver 250 cu ft/min of gas and the gas company may determine that you may have to bump up to a series 400 gas meter. Good luck with that. I've had one customer waiting over a month to get a rep out to his house to make that determination. And never, never, never log onto a plumbing forum and ask any questions. They're not very receptive or friendly to electricians
2. Over all experience. In the big picture, are these installs generally problem free and profitable to pursue.
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Just like any other specialty installation, you have to pay for your education with these things. Essential circuits gen-set installs are much easier to do than whole house installs. Essential circuits systems come pre-fabbed and total installation time is much shorter than whole house installs where you have to figure out and install each conduit run, wire size and length, xfer switch size, separate neutrals and grounds in main breaker panel and install interface control wiring to AC units to name a few things. Good luck on your first time out.
 
hbiss said:
In some locations around here they have insane noise and location requirements. You have to have a large piece of property, there is a minimum distance from the house as well as from the neighboring property. You also have to hire an acoustical engineer to certify the the noise level is below a certain limit at the neighbors house. Needless to say the customer has to really want a generator and have deep pockets.

If you are using natural gas you have to have a licensed plumber pull a permit to handle the gas piping and he will determine whether the existing gas service is capable of handling the generator. This is not something you should attempt to do yourself.

-Hal
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I have seen many generators that are quieter than yard maintenance equipment. If the power is out are the neighbors going to complain about the noise from your generator? I guess if they don't have one maybe they will as they will have nothing else running to drown out any noise it does make:happyyes: Better not be into hot rod cars either or you will have lots of complaints.
 
GAs lines

GAs lines

Thanks for all of the comments. I intend to work with a plumber. I was just trying to get an idea if most installs have a pretty simple gas installation or there is lots more involved which would drive up the cost. There are a lot issues involved with generators: gas, suitable site and clearances and sizing. Also questions about service and warranty. To sell these installs could require a lot of time on my part.
Thanks for the info.
 
Be careful with descriptions. Many big box hardware stores sell "Whole House Generators" that are not. They will say a 60 amp generator can handle your "whole house" but they rarely do.
 
mike107 said:
Be careful with descriptions. Many big box hardware stores sell "Whole House Generators" that are not. They will say a 60 amp generator can handle your "whole house" but they rarely do.
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A lot depends on the size of the house and the total connected load. I have a 10 KW unit hooked up to my house and it handles the load just fine. The biggest load I have connected is a 3-ton AC unit. I have no intention of running this during a power outage yet the unit will handle it. If people want to run their double wall oven, 2 pool motors, a spa tub, (3) 3-ton AC units, 4 hair dryers for their daughters, 2 microwave units, etc, then yes, you are correct. And yes, I have had customers that wanted to be able to do just that but when I told them what the price was and that the unit will be the size of their car they backed off.
 
goldstar said:
A lot depends on the size of the house and the total connected load. I have a 10 KW unit hooked up to my house and it handles the load just fine. The biggest load I have connected is a 3-ton AC unit. I have no intention of running this during a power outage yet the unit will handle it. If people want to run their double wall oven, 2 pool motors, a spa tub, (3) 3-ton AC units, 4 hair dryers for their daughters, 2 microwave units, etc, then yes, you are correct. And yes, I have had customers that wanted to be able to do just that but when I told them what the price was and that the unit will be the size of their car they backed off.
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People don't realize just how much power they actually use. When it is all delivered through those relatively small wires it is not easy to visualize how much they can carry - then they also don't realize stepping up voltage means even more power can be pushed through the same size of wire. Now buy a generator and one that is by no means very big as far as output goes is much bigger than they expect. Many buy little 3000 -5000 watt portable units and think they will be able to run the whole house with it during a utility outage, and electric heating is fairly common here but you have to tell them they better either buy a generator like goldstar has described (as big as a car) or make sure you at least have a gas fireplace or some other heat source if you don't want to spend so much on a generator.
 
It's worth repeating some of the common 'stumbling blocks' in a generator install. In no particular order, these are:

1) The generator brand is the least important part of the job;

2) The transfer switch is the heart of the job, and need to be at least as large as the service to the house;

3) Periodic exercise of the generator, under load, is critical to reliability;

4) Size the genny to the power actually used, rather than the size of the service. Very few '200 amp' services ever draw even half that;

5) Noise is a very important factor. The 'sound kits' are well worth it. You ought to be able to stand right next to it and carry on a normal conversation. If nothing else, this will make the genny less visible to theives;

6) Speaking of which, the genny should be tied into the alarm system, firmly anchored, and in (at least) a fenced in enclosure; and,

7) The customer will probably need a new gas meter, and the GasCo might veto the project.

In the end, the job will involve several trades:
-Electrician;
-Cement guy;
-Alarm guy (Alarmist?);
-Plumber.

Often the genny supplier hold a contractors' license and can put together a package.
 
I used to work for a Generac dealer. Generac provides a slide rule calculator that computes the size of gas line needed. It's kind of like voltage drop, long distances require bigger pipes. The plumber will need to install a regulator as well. The bigger the gen, the bigger the gas service.

As far as sizing the gen, you need to do a load data calc on the house. You can use a smaller gen, but you may need to load shed the big loads like the AC's. Generator transfer switches come with a double pole load shed relay, which gives a 10 minute delay on startup. You do that by running the 24v control of the AC through the relay. You can use any number of load sheds. Or you can install a panel and put just the loads you want on the gen in it and transfer that instead of the whole service. The transfer switches also have exercisers in them that will run the gen once a week.

A 20k gen will run most typical 3 bedroom houses with 200 amp services.

Generac.com and several other sites have online generator sizing calculators.
 
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I won a "free" 20KW whole house generator. Once I found how much it would cost for a propane tank (no natural gas in my area), and the materials to do a proper hook-up I sold the unit and decided to keep my emergency equipment only setup. The cost scares most customers away from doing the job correctly. If you already had natural gas available the story would be much different.
 
renosteinke said:
It's worth repeating some of the common 'stumbling blocks' in a generator install. In no particular order, these are:

1) The generator brand is the least important part of the job;

2) The transfer switch is the heart of the job, and need to be at least as large as the service to the house;

3) Periodic exercise of the generator, under load, is critical to reliability;

4) Size the genny to the power actually used, rather than the size of the service. Very few '200 amp' services ever draw even half that;

5) Noise is a very important factor. The 'sound kits' are well worth it. You ought to be able to stand right next to it and carry on a normal conversation. If nothing else, this will make the genny less visible to theives;

6) Speaking of which, the genny should be tied into the alarm system, firmly anchored, and in (at least) a fenced in enclosure; and,

7) The customer will probably need a new gas meter, and the GasCo might veto the project.

In the end, the job will involve several trades:
-Electrician;
-Cement guy;
-Alarm guy (Alarmist?);
-Plumber.

Often the genny supplier hold a contractors' license and can put together a package.
Click to expand...

I would change #2 to say - transfer switch needs sized to amount of load to be transferred, or size of service if transfering entire service.

haskindm said:
I won a "free" 20KW whole house generator. Once I found how much it would cost for a propane tank (no natural gas in my area), and the materials to do a proper hook-up I sold the unit and decided to keep my emergency equipment only setup. The cost scares most customers away from doing the job correctly. If you already had natural gas available the story would be much different.
Click to expand...

Same is true when customer already purchased a portable generator and wants electrician to make it possible to connect it to the house for backup power. They often think you are going to make them a double male ended cord and it will not cost very much. Then when you mention price of transfer switch alone they can't believe it would cost that much to make that thing power the house. And the time they want this done is either when there has been a major incident and there is no power or within first six months after something like that has happened.

I have temporarily connected many generators during a widespread outage, by connecting them to main breaker and disconnecting service entrance conductors so that they have to call me back when utility power is restored to disconnect it again, and inform them the only proper way to connect it so that I don't have to do it that way is with a proper transfer switch.
 
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