Apartment Building Temp Generator

[mkgrady]

I install a lot of 30 amp 125/250 volt inlets for homes and use an interlock between the MCB and generator breaker in the main panel for a home. This is a pretty inexpensive job for a customer and they are left with the flexibility to turn on whatever the generator can handle. I coach the customer on what can be run off the generator without overloading it.

Now I'm looking at a job to bid to power an apartment building. Actually there are three buildings of about 45 apartments each. They suffered through an outage last winter and eventually brought in a temp generator for each building to power the boiler room and the public area lights. The buildings were not set up to connect generators so there was a lot of temp cords running around the electric room and open panel covers to make the temp connections. I was not involved with any of that work. I'm told the town government is pressing the management company to be ready for the next outage by installing power inlets to simplify and make safe the connection of generators next time they loose power.

So my question is can this be done simply like I would power a home? Can I somehow interlock the main with a generator feeder? Would a Kirk Key Interlock type thing work or something like that? The alternative to an interlock is going to be a lot of work. Each building has a 120/208 volt, 1200 amp service with a three section switchboard (GE THFB Panelboard 1981 vintage) One section is the incoming underground feed and the main switch. The other two sections feed all the apartments, elevator, common lighting panel and boiler panel. They only want to feed the boiler panel and the common area lighting panel and in one building they want to feed a common kitchen area so the residents from all three buildings can eat in an emergency situation.

The alternative to an interlock will entail re-feeding these critical loads from a new panel that will be powered through a manual transfer switch. Normal power will come from a new circuit in the existing switchboard and emergency power will come from the generator inlet. Seems if there is an easier way to do this they could save a ton of money. They just turned down an offer from another company north of 100 grand to install three standby generators due to the cost.

 

[tom baker]

I am not sure what the question is...

 

[david]

it seems to me you would want to distribute the branch circuits to the loads that are considered necessary (essential) from panels that can be transferred to the generator in each of the buildings

 

[greenspark1]

A little hard to visualize the setup, but a key interlock sounds ideal. Not sure if Kirk keys will fit or are listed for the equipment. Else you could do something similar using LOTO devices and shared keys. Less dummy proof but much less expensive.

 

[mkgrady]

I am not sure what the question is...

I can picture how to do this the hard way using a manual transfer switch that would feed the essential feeders from either the normal source or from a generator. This will require a fair amount of labor and materials. My question is how can this be done more simply using some kind of interlock between the main disconnect and a generator breaker?

 

[mkgrady]

A little hard to visualize the setup, but a key interlock sounds ideal. Not sure if Kirk keys will fit or are listed for the equipment. Else you could do something similar using LOTO devices and shared keys. Less dummy proof but much less expensive.

Something like this is what I had in mind but I can't picture how to do it.

 

[mkgrady]

it seems to me you would want to distribute the branch circuits to the loads that are considered necessary (essential) from panels that can be transferred to the generator in each of the buildings

The main switchboard feeds the two or three critical panels that I want to feed during an outage.

I want to add a circuit to the switchboard that would be connected to a temporary generator inlet. I need to make it impossible to close this breaker if the main disconnect is closed. I want to interlock them somehow butI can't picture how to do it.

During an outage a generator will be brought to each building and connected to the inlet. The main disconnect would be shut off so that the generator breaker could be closed. All outgoing circuits in the switchboard will be manually opened so as not to overload the generator except for the two or three critical circuits.

 

[GoldDigger]

You could do the same thing with a manual transfer switch rated for the full load. Then you simply need to have a procedure in place to disconnect enough non-essential loads before throwing the manual transfer switch.
Another way to get a similar result without requiring a service rated transfer switch would be to add downstream transfer switches on each essential load which will allow them to be switched from their branch or feeder breaker to the generator inlet.
Either of those is going to be easier to understand and maintain than a cobbled together interlock system, will avoid hassles with the AHJ, and will likely cost less in the end.
You do not need an automatic transfer switch with load shedding or a critical load sub panel because the generator will have to be brought in and manually connected anyway.
IMHO, the biggest problem with your simple interlocked backfeed system will be getting it accepted.


Tapatalk!

 

[mkgrady]

You could do the same thing with a manual transfer switch rated for the full load. Then you simply need to have a procedure in place to disconnect enough non-essential loads before throwing the manual transfer switch.
Another way to get a similar result without requiring a service rated transfer switch would be to add downstream transfer switches on each essential load which will allow them to be switched from their branch or feeder breaker to the generator inlet.
Either of those is going to be easier to understand and maintain than a cobbled together interlock system, will avoid hassles with the AHJ, and will likely cost less in the end.
You do not need an automatic transfer switch with load shedding or a critical load sub panel because the generator will have to be brought in and manually connected anyway.
IMHO, the biggest problem with your simple interlocked backfeed system will be getting it accepted.


Tapatalk!

Are you suggesting a manual TS rated the same as the 1200 amp main? I agree that would work but it sure would be expensive.

On your other suggestion I think you are saying to put a manual TS ahead of each critical load panel and have the generator inlet feed the critical feed side of each TS. I guess if I put a load center between the inlet and each TS I could us smaller wires to match the load of each critical panel.