Generator and ATS setups

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sw_ross

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Most of my experience with residential use of generators involves use of an inlet plug and a method of manually selecting specific circuits to operate during an outage.

I don't have much experience with using ATS's and sizing generators to handle the load of a house. It's something I want/need to get more knowledge about.

Does a generator that is operated by a ATS have to be sized based on total load Calc of the residence? Or can the generator be sized based on the historical usage of the residence?

I have a customer that is interested in getting a generator setup and mentioned "something in the neighborhood of 10kw".
What info do I need to know before choosing the size of the generator? He kindve wants it to be a "whole house" setup using an ATS. Not something where he has to manually select the circuits that are controlled.

Thanks for input!
 
Sizing generator

Sizing generator

So the generator size (in a whole house application ) is based on a load Calc for the home?

I assume there'd be an 80% rule involved as well?

I saw that Generac has an ATS that is rated for 200 amps. I assume this is what would be necessary for a 200 amp panel? Or is the ATS also sized for the load Calc?

Generac talked about a typical home with a 200 amp panel typically requiring a 16-22 kW generator?
 
sw_ross said:
So the generator size (in a whole house application ) is based on a load Calc for the home?

I assume there'd be an 80% rule involved as well?

I saw that Generac has an ATS that is rated for 200 amps. I assume this is what would be necessary for a 200 amp panel? Or is the ATS also sized for the load Calc?

Generac talked about a typical home with a 200 amp panel typically requiring a 16-22 kW generator?
Click to expand...

A common way to go is to do a load calculation for the service but exclude loads you can automatically shed through the ATS control switches. Typically AC, electric ovens, electric dryers, hot tubs, etc. It doesn't mean things you can shed will not run, they just won't run all at the same time. When the generator is sensing it is straining it shuts off the lowest priority load and works its way up to the higher priority loads. 22KW generator is going to easily handle everything you want to run most of the time. You can go smaller but it may mean shedding more nonessential loads
 
sw_ross said:
Most of my experience with residential use of generators involves use of an inlet plug and a method of manually selecting specific circuits to operate during an outage.

I don't have much experience with using ATS's and sizing generators to handle the load of a house. It's something I want/need to get more knowledge about.

Does a generator that is operated by a ATS have to be sized based on total load Calc of the residence? Or can the generator be sized based on the historical usage of the residence?

I have a customer that is interested in getting a generator setup and mentioned "something in the neighborhood of 10kw".
What info do I need to know before choosing the size of the generator? He kindve wants it to be a "whole house" setup using an ATS. Not something where he has to manually select the circuits that are controlled.

Thanks for input!
Click to expand...
Check Out
http://ask-the-electrician.com/generator-sizing-calculation.html#beginAdv
 
Like a previous poster indicated, you don't have to size the genset / ATS for the whole load, if you don't want to.
Simply install a sub-panel and transfer the home runs from loads you want from the existing panel to the sub-panel.
Connect your ATS to Sub-Panel.
Or do load shedding as mentioned previous.:thumbsup::thumbsup:
 
whole house ATS rating

whole house ATS rating

Doesn't the ATS have to be sized to match the MB or FB for subpanel? When on com power, full loadstill goes through the contacts of the ATS do they not? What am i missing here?
 
sw_ross said:
So the generator size (in a whole house application ) is based on a load Calc for the home?

I assume there'd be an 80% rule involved as well?

I saw that Generac has an ATS that is rated for 200 amps. I assume this is what would be necessary for a 200 amp panel? Or is the ATS also sized for the load Calc?

Generac talked about a typical home with a 200 amp panel typically requiring a 16-22 kW generator?
Click to expand...

Yes. A typical home with a 200A service has more than enough capacity to run all loads, and even tho a 22kW unit is good for 'just 90' amps, it's pretty difficult in the average home to get a 90A total draw for more than a few minutes. Start-ups of dryers, ranges, ovens, HVAC units and water heaters will do it, tho once their thermostats start cycling, sustaining that 90A wont usually happen.

10kW isn't going to do whole house very well unless most/all heating loads are via something other than electricity, like NG, propane, wood stove, etc. It's still 40A tho, so it'll run more than the frig, lights, fans, computers, small kitchen appliances and so on.
 
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