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Joined: Feb 2006
Posts: 22
Existing Assisted Living Facility with 2000A service 3P4W/120/240. Customer would like to be able to connect a Mobile Generator to system in case of power failure. Customer also has 3 other locations and would like to be able to have the same option at those as well. The above builiding is the largest service and 2 of the others are single phase.


On the above 2000A 3P/120/240 system would a Utility allow
an exterior manual transfer switch and exterior connection for hookup of a Generator. The building doesn't have space for any interior equipment. The cost to seperate loads or install automatic equipment would cost (150-k+? easy)if there were room. There is a Utility owned pad mounted tranformer on site (about 60' away). I was thinking of running new load conduits from transformer to an exterior wall of the electrical room. Then from there into the manual transfer switch. The connection from the Generator would be at this location (lugs or connector). Then run from transfer switch to existing switchgear. Does this sound like something a Utility would approve?

If so any suggestions for temp power to the building during relocation of feeders? Would a Utility and local J approve the use of a generator for a few days during upgrade - It could be the unit the Customer purchased (y/n)?

Any suggestion on manufacturer's who make this equipment?

Any suggestions on gen. manufacturer's of mobile equipment that can handle multiple power requirements for the different buildings? The buildings are up to 4 hours away from each other and the thought is that buying one would service whichever building was in need and if necessary rent other units if the situation should require temp power for more than one building.

Thanks in advance.

Last edited by BobV3CORP; 07/03/09 12:33 AM.

Joined: Jul 2002
Posts: 8,432
Likes: 3
I would say (bear in mind I am on the other side of the world from you), go and have a talk to the local utility office about your plans, you'd be amazed at how much you can pick up, just with an informal talk with say, one of their planning staff (or similar).
It would be best to do this now, before wires get pulled.

Electricians should never fear the utlities, after all, it is a team effort.

Others will no doubt reply to this thread, they will have a lot better idea of what you have in mind, than myself.
I can't help but think though that an ATS installed on the exterior of a building, may not fly.

Joined: Nov 2006
Posts: 23
We install them on the outside all the time, just need a NEMA3 rated switch.The only thing I see is around here we are required to have a disconnecting means before the switch, so you would need a disco and a transfer switch, but I agree with Mike(trumpy) talk to your utility, and AHJ before making any plans, or quoting any prices. We install lots of them just as you describe, with a cam lock plug for a portable genset, so the owner can move the set to other locations.

Joined: Mar 2003
Posts: 849
You can buy from most Generator Companys a (looks like a small box car) with a trasfer switch,generator & main all in it.The way we used to do it at Casinos (they Do NOT want to have dn time period).Buy one of theses self contained units run a new feed from Secondary side of Transformer & then from Unit to Switchgear. Then (most time there was room for extra conduits) , We'd even pull wire & be ready to terminate ,We would shut dn building pull off existing terms both ends put on new ones . Pull out existing wires when after gear was engerized.(with 70-E now that could be a problem).Question you say you have a 3 phase 4 vwire 120/240 that must be a Delta thus a high leg right. Another note you can have a transfer switch ahead of a main IF its a Service rated transfer switch.

Joined: Feb 2006
Posts: 22
Thanks for the input. I'll check back for any more thoughts.


Joined: Apr 2002
Posts: 7,333
Likes: 7
First stop would be the utility co in your area.
Second stop would be the local AHJ in area

Here in NJ, if you were proposing such an install, you must have drawings/specs from a Lic Arch or EE/PE for permit submittal, review and approval.

I have a 2k amp proposed install that came in for review/approval basically consisting of a 3R gen tie-in enclosure (for portable genset) and a Kirk key setup in lieu of a transfer switch. That's one of next weeks review jobs.

Joined: Mar 2005
Posts: 1,213
If you want to back up the entire facility, this is pretty straightforward and done all the time. There's no reason the utility shouldn't allow a NEMA 3R external transfer switch. So long as you meet NEC requirements (not hard to do), it shouldn't be an issue with the AHJ either. (Bear in mind the length of the outage to do what you're discussing, too.)

The transfer switch will either need to be service rated or have a service-rated disconnect installed between the transfer switch and the service. Portable generators in this size are way beyond connectors, so you're looking at lugs and temporary cables. I would recommend installing a terminal box (w/ securable disconnect) beside the transfer switch so that you can connect/disconnect the generator without having to secure power to the building.

The generator doesn't necessarily have to be large enough to supply everything, but the transfer switch would still need to be 2000A rated. And you can't configure it for automatic start unless it's rated to 100% of your load. Make sure to reserve space, too- a 600kW generator w/fuel tank will fill a semi. Also be prepared to transport a LOT of fuel, as you're looking at as much as 50gal/hr and the fuel tanks on portable generators typically only last 2 days, and sometimes just a few hours.

Joined: Apr 2002
Posts: 7,333
Likes: 7
The rest of comments to your OP:

There should be no issue running the facility on a genset while you are working on the electrical system.

Any name brand genset/xfr switch would be appropriate. Local service tech, preferably factory would mean a lot if I was choosing.

Purchase vs rental is a financial decision and availability of rental equip quickly. MPO is rental thru local factory authorised 24/7 dealer.

Rental equip I used (As EC) was all selectable voltage, and units ranging from 5KW 120/240 to 2MW 277/480. The 2 MW was 53' unit, 55-60 gal/hr; 750 gal OB tank; 750 gal remote tank. Tis may be a worse case scenario.

As to connectors....asSteve said....lugs for 500/600 KCMil.; rental units come with cam lock cabling at additional $$$


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