Lax residential generator inspections

[nizak]

Been to 2 newer construction homes in the past few weeks where in both cases generators have been installed and passed inspection.
In both cases the homes had electric range,dryer, A/C and the one had electric water heater in addition.

Both houses had 11kw units installed by the same company with 200A service rated transfer switches. Neither home had any load shedding modules.

Two different inspectors passed both installs.

Seems as if not much attention is paid to generator installation.

FWIW both inspectors were part time and both installs where in somewhat rural areas.

If the contractor is going to go so far as to get a permit , why not install per code?

 

[infinity]

I know some people feel rather cavalier about overloading optional standby generators for a home. I've heard a code official say, NEC aside, that he doesn't care if the generator is too small as it's a design issue. If it's too small then it won't work.

 

[ActionDave]

I know some people feel rather cavalier about overloading optional standby generators for a home. I've heard a code official say, NEC aside, that he doesn't care if the generator is too small as it's a design issue. If it's too small then it won't work.

Score one for common sense.

 

[Tony S]

11KVA for a standby set is more than enough. The occupants know they’re on standby so common sense comes in to play or doesn’t it?

My own house had a 7KVA set which was used quite regularly during winter. Living at 1200’ elevation you get used to power outages, sometimes for a week or more. I’d taken the precaution of fitting a motor O/L and a contactor to the output, I knew what the wife was like. Even she only managed to cause it to trip once in about ten years.

 

[infinity]

Score one for common sense.

I believe that the comment was in one of Mike Holt's videos.

 

[iceworm]

Been to 2 newer construction homes in the past few weeks where in both cases generators have been installed and passed inspection.
In both cases the homes had electric range,dryer, A/C and the one had electric water heater in addition.

Both houses had 11kw units installed by the same company with 200A service rated transfer switches. Neither home had any load shedding modules.

Two different inspectors passed both installs. ...

Just curious: Were the transfer switches Automatic or Manual?

ice

 

[GoldDigger]

11KVA for a standby set is more than enough. The occupants know they’re on standby so common sense comes in to play or doesn’t it?

I have never seen an ATS with common sense.
What the NEC is concerned about is what happens at the moment the power fails. If the occupants somehow know that the power is going to fail in ten minutes, then they can sensibly reduce the load.
For other than legally required circuits, the NEC does not specify any size requirements as long as the transfer is manual.

 

[Tony S]

Unless there is a big UPS back up to bridge the gap between outage and gen set start up which I doubt there will be in a domestic installation, I think the householder may just notice they’re on standby power.

Now we get back to over sizing generators and load shedding.

 

[mbrooke]

I have never seen an ATS with common sense.
What the NEC is concerned about is what happens at the moment the power fails. If the occupants somehow know that the power is going to fail in ten minutes, then they can sensibly reduce the load.
For other than legally required circuits, the NEC does not specify any size requirements as long as the transfer is manual.

They have load shedding ATS switches

 

[GoldDigger]

They have load shedding ATS switches

I would call that uncommonly good sense. :angel:

 

[mbrooke]

I would call that uncommonly good sense. :angel:

I think its the only way to be NEC complaint when using an auto transfer switch?

 

[GoldDigger]

I think its the only way to be NEC complaint when using an auto transfer switch?

No. The other way is to use a grossly oversized generator rated for the full calculated load (not the service size.)
It is, however, the only practical way....

 

[mbrooke]

No. The other way is to use a grossly oversized generator rated for the full calculated load (not the service size.)
It is, however, the only practical way....

I agree, Id rather load shed. I know with diesel units (though not common in resi) not enough load can wet stack the unit.

 

[GoldDigger]

I agree, Id rather load shed. I know with diesel units (though not common in resi) not enough load can wet stack the unit.

It is, unfortunately, common in off grid homes with only one size generator, with or without solar PV.

 

[cowboyjwc]

So maybe I'm missing something. If they have a transfer switch, then the power should be going somewhere else other than the main panel. The main panel should not be back fed with the main breaker in the closed position as that would feed back on the utility lines, which is a no no. That's why solar systems shut down where there is no AC power.

 

[ActionDave]

So maybe I'm missing something. If they have a transfer switch, then the power should be going somewhere else other than the main panel. The main panel should not be back fed with the main breaker in the closed position as that would feed back on the utility lines, which is a no no. That's why solar systems shut down where there is no AC power.

I think you are missing something. You can have a transfer switch after the service disco and still isolate the generator from the utility. That's what the switch is for.