Whole house generator- Electrical Contractors?

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Old 03-27-10, 07:43 AM
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Whole house generator- Electrical Contractors?

Is it wrong to expect an electrical contractor to do a load calculation on my house to determine what size whole house generator is required (by 2008 code) to power it?

I brought a contractor in for an estimate on a generator installation with a 200 amp transfer switch in order to power my entire house. However, he was only willing to talk about the small transfer switch/6 circuit sub panel that he normally installs.
 
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Old 03-27-10, 08:14 AM
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You need to find another electrician.

Someone who can think BIG!

Businesses, phone companies, hospitals, high rise buildings, city water or sewage treatment plants, and things like 911 emergency call centers will have large generators for back-up power.

Might call around to some of these in your area and find out who their electrical contractor is.
 
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Old 03-27-10, 08:30 AM
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P.S. Electricians (and other contractors) who do work primarily for homeowners are used to people screaming bloody murder with estimates in the hundreds of dollars.

So they are in that "mode" of assuming the homeowner wants a minimal system and the homeowner will scream about the price for just that.

So make it clear you want to power your entire house, want a load calculation, and are able to pay for this. (But that you still want competitive bids of course! )
 
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Old 03-27-10, 10:25 AM
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Find another contractor, but don't expect the estimate to be in the hundreds of dollars.
 
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Old 03-27-10, 10:33 AM
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I fully understand the probable cost, and I will be calling other EC's. I just wanted to be sure that a load calc was something that I could reasonably expect for this situation.
 
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Old 03-27-10, 11:00 AM
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To be honest we, well my boss , doesn't really do a load calculation on paper. He pretty much looks at the job to determine what would be required. He has been doing it a lot longer than I have and has the experience. It has not failed him yet. That said, it would really be up to you to provide the information they need to do the calculation. Amp draw of the appliances, square feet of the house, etc.

There are plenty online load calculators to use. You could do it your self just for fun.
 
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Old 03-27-10, 11:03 AM
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I suggest you compare the costs with the benefits. What is the benefit of powering the entire house when you can have a less expensive system with adquate power for living in relative comfort during the emergency period?

A full-power SBS may require expensive alterations to the Service equiptments and conductors.
 
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Old 03-27-10, 11:27 AM
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Originally Posted by Tolyn Ironhand View Post
To be honest we, well my boss , doesn't really do a load calculation on paper. He pretty much looks at the job to determine what would be required. He has been doing it a lot longer than I have and has the experience. It has not failed him yet. That said, it would really be up to you to provide the information they need to do the calculation. Amp draw of the appliances, square feet of the house, etc.

There are plenty online load calculators to use. You could do it your self just for fun.
In order to pass inspection, isn't it possible that the inspector will want to see a load calc to be sure that the generator that was installed is large enough to power the whole house?
 
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Old 03-27-10, 01:35 PM
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If you want a SBS with a power-capacity equal to the KVA rating of the Service , then the generator rating in KVA = the Service rating in KVA.

The inspector would base his approval on the the KVA rating of the installed generator and the rating of the generator protective devices.

The relevant Code Art is 702.5 (B) System Capacity , (2) (a) Full load which reads--

"The SBS shall be capable of supplying the full-load that is transferred ( to the generator ) by the automatic transfer equiptment". In your plan the "full-load" is the "load" on the Service Conductors.

No need for a load-calculation when the generator KVA rating equals the Service KVA rating.

"
 
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Old 03-27-10, 01:36 PM
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Typically, load calculations are none of the inspector's business. If it is necessary to provide calcs, the contractor will have to provide them in order to obtain the permit. The inspector's job is to inspect the installation for compliance to code. Many times inspectors will try to be and do more than what they are really there for. I have seen more than one inspector who wanted to re-engineer a job.
 
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Old 03-27-10, 01:38 PM
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Originally Posted by VoltageHz View Post
In order to pass inspection, isn't it possible that the inspector will want to see a load calc to be sure that the generator that was installed is large enough to power the whole house?
After all we are pretty famuair what it will work and what not and we almost automatique to know excatally what it will need for proper size generator in resdentail useage however in Commercal / Industrail useage we have to list everything what they will be using in generator mode and what not so it will really cover alot more than what DIY forum will cover in here.

I do pull permits for generator installment in both Wisconsin and France so most case they will ask what size generator if going with MTS mode but ATS that will varies a bit depending on the location and what it requred on the code and per Wisconsin Electrique code we have to sized the ATS to the main breaker size and the size of generator can go up to the size of main breakers { it will be either 20 or 45 KW depending on the size of main breaker }

Merci,Marc
 
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Old 03-28-10, 09:08 AM
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Originally Posted by VoltageHz View Post
Is it wrong to expect an electrical contractor to do a load calculation on my house to determine what size whole house generator is required (by 2008 code) to power it?

I brought a contractor in for an estimate on a generator installation with a 200 amp transfer switch in order to power my entire house. However, he was only willing to talk about the small transfer switch/6 circuit sub panel that he normally installs.
As I am sure somebody else has already mentioned, you need a high-end residential or a commercial contractor. There is a huge difference.

A commercial estimator with a large firm is sometimes a very experienced electrician. He or she will be used to seeing Requests for Proposals and detailed specs from professional customers.

If you want detailed load calcs and want to know what materials they are proposing, just put in your RFP that at an agreed-upon date, contractor shall provide detailed calculations and a bill of materials for customer approval. You will pay for this, though, unless they think you're going to be a gravy train. Sometimes their terms will be that you pay a fee in advance and if you choose them for the work, that amount is subtracted from the bid price.

No one works for free. This is where a lot of homeowners get hung up. Many contractors offer "Free Estimates" for competitive reasons, and certain homeowners tend to interpret that as "Itemized BOM and detailed specifications of work to be done". However to the typical contractor it means "Work and materials to code, $xxx".

As with any technical project, if you have detailed requirements beyond code but you cannot articulate them in an industry-standard way (RFP), you get somebody else to do that for you. An architect would have or contract with various engineers and designers to get the proper specs set before putting a project out for bid.
 
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Old 03-28-10, 09:18 AM
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Originally Posted by VoltageHz View Post
I brought a contractor in for an estimate on a generator installation with a 200 amp transfer switch in order to power my entire house. However, he was only willing to talk about the small transfer switch/6 circuit sub panel that he normally installs.
That actually sounds a lot more like a Home Depot installer and I don't think that is what you are looking for from what you have said.
 
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Old 03-28-10, 12:26 PM
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Originally Posted by ArgMeMatey View Post
If you want detailed load calcs and want to know what materials they are proposing, just put in your RFP that at an agreed-upon date, contractor shall provide detailed calculations and a bill of materials for customer approval. You will pay for this, though, unless they think you're going to be a gravy train. Sometimes their terms will be that you pay a fee in advance and if you choose them for the work, that amount is subtracted from the bid price.

No one works for free. This is where a lot of homeowners get hung up. Many contractors offer "Free Estimates" for competitive reasons, and certain homeowners tend to interpret that as "Itemized BOM and detailed specifications of work to be done". However to the typical contractor it means "Work and materials to code, $xxx".
.
These are very good points. A complete load calculation is quite time consuming. A contractor is not going to do one unless he knows he has the job and will be paid for his time. How does he give the bid then? Pretty much gut feeling. He looks at the job specs required and can roughly determine what he will need to complete it. This is where estimating comes in. Sometimes things pop up that he missed and he takes it in the shorts (no pun intended) Sometimes it goes the other way.
 
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