service entrance rated transfer switch ahead of metering?

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twils75 said:
Is it legal to place a service entrance rated transfer switch ahead of a triple stack modular meter assembly? Im looking to provide a gen service to a single premises which consists of one 200A service and two 100A services.
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We've never installed a service rated ATS ahead of any metering but it does beg some thought.

I would think that if you get the local POCO involved and provide a one line clearly showing your proposal, it could possibly fly. The reason being is that we frequently install multi-tenant metering that is served from a single or multiple disconnects before the tenant meters. What you propose is quite similar.

In addition, if it does fly, then only one ATS would be required, as one would not normally monitor just one service in this scenario, but the entire location, as the loss of power to just one premises would probably indicate some other problem specific to that premises and a problem that the generator would not resolve and could actually compound.

Also in this scenario, a tenant being disconnected from the utility (removal of the meter), for whatever reason would not be seen as an outage by the transfer switch. The ATS is looking at incoming utility power, nothing else.

One additional note, obviously in this setup, the generator must be capable of carrying the full available load.
 
Many generators are capable of controlling multiple transfer switches, even to the point of staggered transfer.

If you have access:

In the general area install a disconnect for each feeder. Run the gen power into the area and use the tap rules to hit each disconnect. Then hit the transfer switches from each indivdual disconnect, one for each feeder, wiring all this after the meter pack. ( Obviously wire in line from meter bank, load, and gen power from disconnect, to transfer switch ).

If in your application you have access to Service Rated Transfer Switches in those amperages and they are compatible with your gen then disregard adding the separate disconnects.

That way you will feed each panel after the meter, a single breaker is used on the genset to feed a gutter with taps into each disconnect, meeting overcurrent protection issues. Power doesn't run through POCO meter.

Hopefully you have this kind of access after the 3 meter bank or room on an outside wall.
Also there is the issue of the sensing leads but this is a start.

What brand and size are you working with?
 
It is not entirely unheard of to install a gen on the line side of the metering. It's not very common, but I have seen it. It is not addressed by the NEC. The utility company would have the final say, and of course the customer should be made aware that the meter will be running when they are on generator power.
I was recently involved in an installation like this, and I had a discussion with the POCO engineer. They basically just turned a blind eye to it. They would not approve it but they weren't going to require it to be changed either.
 
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