Adding a Generator to Existing Service

[faresos]

Hello Every One:

I'm working on a small building where it's powered from a utility 150KVA (4160- 208Y/120V) pad mounted transformer. The Transformer secondary service conductor is owned by the utility Co and it terminate into a can labeled MLO and feeds a five meters via none-fused disconnect switches a head of each meter. Each meter feeds a panelboard (w/MCB) inside the building (total five panelboards - one for each tenant). The client has requested to add a generator to backup the entire building. My first thought was to intercept the secondary feeder and provide a service rated automatic transfer switch (ATS) near the utility transformer and also located the generator near the transformer as well. The challenge is, the secondary line is owned by the utility and not sure if they will let me intercept their line to add the ATS but I already contacted the utility and will wait on their response. My questions:

1. The ATS needs to be service rated and 4-poles, correct?
2. Can I use non-service rated ATS and leave everything as is as far the grounding and bonding of the service at the meters cans at the building? Or I have to have a disconnect a head of the ATS?
3. Is there better way doing it than what I describe above?

Your help is really appreciated

 

[Designer69]

I don't think you need SE ATS. There is no other way other than ahead of the can as you say.

 

[zbang]

"Secondary feeder"? From the sound of it, those are service conductors, not a feeder.

This scheme will put the generator ahead of the meters, which I assume are PoCo-owned and they generally don't like customer equipment there. And you'd be paying the PoCo for using generator power since it flows through the meter.

Without a massive rewired, I don't off-hand see a good way of providing multi-tenant generator power.

Might help to draw up a one-line diagram and post that here.

 

[ron]

Maybe a generator with a single output breaker feeding a panelboard (size depending on the size of the gen output breaker) and a distribution breaker serving each of (5) ATS's, one per service. That way you avoid the service entrance ratings.

All of this is Article 702, so no need for special segregation or start times.

 

[faresos]

Maybe a generator with a single output breaker feeding a panelboard (size depending on the size of the gen output breaker) and a distribution breaker serving each of (5) ATS's, one per service. That way you avoid the service entrance ratings.

All of this is Article 702, so no need for special segregation or start times.

That's what I was trying to avoid providing (5) ATS's. Another option (maybe) is to have the utility co to provide the main meter at the transformer and provide sub-meters (by the client) for each space.

 

[Designer69]

get a lighting contactor 208–240 coil voltage, 5 pole. Make sure poles are rated at least 200A (if this even exists) eaton might have one.


wire each output from 5 meters to a contact. Now you have 1 ATS and 1 contactor.

 

[zbang]

Not sure how that's going to work, not enough contacts- If the panels are 3-phase, then you'll need three contacts per panel, so five 3-pole contactors (after the individual meters). And you still need the ATS to control things. It would be simpler to convert to one service/meter, put the ATS after that, then sub-meter (which is more work and expense for the landlord).

However you look at this, it's not a simple deal.