Generator installation questions

[goldstar]

Scenario #1 :

I ordered a 55 KW, 3 phase generator several months ago through a dealership (actually an electrical supply house). The generator is being installed at a summer day camp facility and is being used to supply emergency power for (4) 3 phase pool motors only. The utility power feeding the existing breaker panel is currently a 3-pole, 100 amp breaker and has never tripped on overload. The salesman who designed and spec'd the generator decided to propose a 55KW unit. There was never any mention of the size wire to be run to the unit. The utility wiring feeding the breaker panel is # 2, copper, THHN. I chose to bump the feeders to the generator up to #1, copper, THHN based on NEC 445.13 and table 310.16 (rated at 150 amps - 90 degree column). The unit came shipped in with a 200 amp main breaker. ( The wires feeding the main breaker from the generator are paralled # 6's)

Question : Am I in violation with the wire size between the generator and disconnect switch ?

Scenario # 2 :

I ordered a 17KW portable generator that came with a 16 circuit, Siemens' main lug emergency panel for the same facility but for the 1st floor of the office building. The panel, itself (as per the label on the cover), is rated at 125 amps. There are two breakers (2-P 50 amp on standby and 2-P 60 amp on utility) installed at the top and are interconnected so that neither breaker can be on while the other is on. However, because Siemens decided to install the 50 amp breaker as the standby and the 60 amp breaker as the utility service they've placed a label on the cover stating that the panel is only rated for 60 amps.

Question #2 : (Assuming the label is there for standby electrical service only) If I replace the 2-P 60 amp breaker with a 2-p 100 amp serving as the utility feed into the main lug panel and then another 100 amp to serve an existing lighting load only panel on the load side, will I be in violation ? Bear in mind, this panel will NEVER come anywhere near maximum load either under utility or standby power.

Thanks in advance:smile: . Any comments (pro or con) will be appreciated

 

[augie47]

Scenario #1 :

I ordered a 55 KW, 3 phase generator several months ago through a dealership (actually an electrical supply house). The generator is being installed at a summer day camp facility and is being used to supply emergency power for (4) 3 phase pool motors only. The utility power feeding the existing breaker panel is currently a 3-pole, 100 amp breaker and has never tripped on overload. The salesman who designed and spec'd the generator decided to propose a 55KW unit. There was never any mention of the size wire to be run to the unit. The utility wiring feeding the breaker panel is # 2, copper, THHN. I chose to bump the feeders to the generator up to #1, copper, THHN based on NEC 445.13

445.13 would have nothing to do with your feeders. That would address the wiring to the generator breaker.

and table 310.16 (rated at 150 amps - 90 degree column). The unit came shipped in with a 200 amp main breaker. ( The wires feeding the main breaker from the generator are paralled # 6's)

Question : Am I in violation with the wire size between the generator and disconnect switch ?

yes. Your #1 would be rated 130 amps, which would be good for a 130 amp load and a 150 max amp breaker

Scenario # 2 :

I ordered a 17KW portable generator that came with a 16 circuit, Siemens' main lug emergency panel for the same facility but for the 1st floor of the office building. The panel, itself (as per the label on the cover), is rated at 125 amps. There are two breakers (2-P 50 amp on standby and 2-P 60 amp on utility) installed at the top and are interconnected so that neither breaker can be on while the other is on. However, because Siemens decided to install the 50 amp breaker as the standby and the 60 amp breaker as the utility service they've placed a label on the cover stating that the panel is only rated for 60 amps.

Question #2 : (Assuming the label is there for standby electrical service only) If I replace the 2-P 60 amp breaker with a 2-p 100 amp serving as the utility feed into the main lug panel and then another 100 amp to serve an existing lighting load only panel on the load side, will I be in violation ? Bear in mind, this panel will NEVER come anywhere near maximum load either under utility or standby power.

Thanks in advance:smile: . Any comments (pro or con) will be appreciated

If the panel is actually a 100 amp buss panel, in real terms you would be fine, but in terms of listing/labeling would would be in violation.

 

[goldstar]

Thanks Gus. I guess deep down I really knew the answers but was hoping I might have missed something.

 

[Pierre C Belarge]

Scenario #1 :

( The wires feeding the main breaker from the generator are paralled # 6's)

Question : Am I in violation with the wire size between the generator and disconnect switch ?



Thanks in advance:smile: . Any comments (pro or con) will be appreciated

You need to review 310.4 in regards to the size you installed.

 

[iwire]

You need to review 310.4 in regards to the size you installed.

The parallel 6 AWGs are factory wiring from the windings to the units breaker. :smile:

The unit came shipped in with a 200 amp main breaker. ( The wires feeding the main breaker from the generator are paralleled # 6's)

 

[goldstar]

You need to review 310.4 in regards to the size you installed.

Pierre, what part of 310.4 should I be looking at ? The conductors I installed are #1's in 120' of 2" PVC between the generator and the transfer switch.

The parallel 6 AWGs are factory wiring from the windings to the units breaker.

That's correct Bob. Irrespective of the 200 amp breaker on the generator, there will never be a case where this load will ever be anywhere near 100 amps, not to mention 200. However, on the far outside chance that a problem developes I'm figuring that the generator's parallel # 6's will break down long before the #1's will. This generator was probably an over-kill for this application.

 

[iwire]

Scenario #1 is questionable unless you can apply the outside tap rules.

 

[iwire]

If I replace the 2-P 60 amp breaker with a 2-p 100 amp serving as the utility feed into the main lug panel and then another 100 amp to serve an existing lighting load only panel on the load side, will I be in violation ?

IMO yes that would be a viotion of 110.3(B)

Bear in mind, this panel will NEVER come anywhere near maximum load either under utility or standby power.

That really has nothing to do with it.

 

[goldstar]

IMO yes that would be a viotion of 110.3(B)

If it's labeled to be used as a 60 amp panel then that's understood.

Now, if I purchase the same Siemens main lug breaker panel from the supply house, (but not the one labeled through the gen-set manufacturer) and I install the breakers and the transfer switch interlock set for the breakers, (in essence fabricating the panel myself) would I then be in violation ? Remember, the listing on the Siemens panel door cover indicates that is rated for 125 amps. It was the gen-set manufacturer that placed a label on the panel indicating that it should be used only for a 60 amp max load. I know I'm getting kind of wierd here but logic tells me that the panel should be rated for more than what it is labeled for (irrespective of what the generator output is) and the gen-set mfr. is just making sure they're in a "CYA" situation. Air conditioning and other heavy loads are not part of the emergency circuit panel. I can't imagine the lighting and receptacle loads being anywhere near 60 amps at 240 volts.

BTW, once the interlock kit is installed on the 60 amp generator and 100 amp utility breakers they are, in effect, locked into the panel and cannot be removed unless that kit is removed.