Whole House Generator Sizing

[kwired]

Thanks Hurk and understood. You've provided a lot of useful information that many of us, I'm sure, didn't know or weren't aware of. BTW, I think deep down inside you really enjoy typing.:lol:

Though I think you got the point let me see if I can shorten what Hurk said ( just a little)

With MTS the user monitors what load is connected, and has to actually be present to operate the transfer switch otherwise there is no overloading if no transfer.

With an ATS the only supervision of the load should the operator not be present at the time is whatever load shedding methods are used, otherwise all load connected to the transfer switch is transferred and will operate whether it is is too much for the generator or not.

I think I covered it pretty well in two sentences instead of two chapters

 

[goldstar]

Though I think you got the point let me see if I can shorten what Hurk said ( just a little)

With MTS the user monitors what load is connected, and has to actually be present to operate the transfer switch otherwise there is no overloading if no transfer.

With an ATS the only supervision of the load should the operator not be present at the time is whatever load shedding methods are used, otherwise all load connected to the transfer switch is transferred and will operate whether it is is too much for the generator or not.

I think I covered it pretty well in two sentences instead of two chapters

Thanks KW. I understand that you have to size the generator for the actual load that's going to be operated during the transfer. What I'm not in agreement with is having to size the generator with what appliances or devices might be used (and what I meant by the HO controlling the loads) should the HO decide to use them during a power outage (i.e double wall oven, welder, window AC unit, etc.) If you try to figure every wierd possibility in you'll end up with an enormous unit and you'll probably never sell a gen-set. Just my opinion.

BTW, I looked back through my posts in this thread and I did mis-speak once by suggesting that the HO would be able to control loads like the pool motor or spa tub. These would have to be controlled by the load management system. I humbly apologize to all those I've aggravated.

 

[GoldDigger]

Thanks KW. I understand that you have to size the generator for the actual load that's going to be operated during the transfer. What I'm not in agreement with is having to size the generator with what appliances or devices might be used (and what I meant by the HO controlling the loads) should the HO decide to use them during a power outage (i.e double wall oven, welder, window AC unit, etc.) If you try to figure every wierd possibility in you'll end up with an enormous unit and you'll probably never sell a gen-set. Just my opinion.

And here we return once again to the bone of contention. Nobody is denying that the HO has the opportunity to control what loads he or she turns on during the outage. What the code says in effect, and what the generator damage arguments justify, is that the HO must also strictly control the loads used BEFORE the outage. If the HO downsizes the main breaker to match the capacity of the generator, that would be safe, but not code-compliant if the calculated load exceeds the breaker size (specific lifestyle load?)
The calculated load deliberately does not include every weird possibility. But it hits the high points.