2 generators at the same time

Status
Not open for further replies.
R

rickg

Member
Location
Rhode Island
Could I get some opinions please.

A municipal facility has proposed adding 2 5kw portable generators as a backup to the backup automatic generator that picks up the entire building load upon utility failure. The proposal is to install 2 - 30 amp inlets at the same location on the exterior of building. From each inlet we go to a manual transfer switch ajacent to the sub panel served (both sub panels are in the same building but in different locations). These 2 portable generators are not electrically connected in any way. The plan is for these generators to operate at the same time: #1 for the panel that powers the well pump, #2 for the panel that powers vital communications.
Also would there have to be a disconnect for each generator grouped together at the point of entry of both generator feeders? Would the twist lock at each inlet suffice as the required disconnects? The transfer switches are well inside the building.
After thinking on this for several hours a light went on in my head...
Would having the 2 portable generators be in violation of NEC rules about multiple services to a building, (the 2 generators being the multiple services)? Maybe not if there are 2 disconnects grouped together?
Suggestions, comments? Please.

Thanks all,
Rick
 
Re: 2 generators at the same time

They are spending a dollar to save a nickel.
First, what type of standby system would they be considered? Art 700, 701 or 702?
The generator is considered a feeder. A disconnect is required, the disconnect essentially has to be service rated.
There are transfer switched for the generators, right?
 
Re: 2 generators at the same time

Tom
IMO this is an optional stand by system article 702.
Apparently some time ago there was a power failure, the generator that is capable operating the entire building came on line via the auto transfer switch, while on generator power one of the contacts of the auto transfer switch let go & they lost the water pump or communications dispatch. So now they want a back up to the automatic generator system. This is to be a completely manual system to be connected & operated by public works employees. Again very select loads... dispatch radio & well pump. At this time I am not concerned with the loads, just the fact that there 2 portable generators connected to 2 transfer switches (transfer switches are in different locations in same building). I am leaning toward this being a code compliant installation if 2 disconnects are installed grouped together where the feeders enter the building. Also need to meet the signage rules.
Rick
 
Re: 2 generators at the same time

Mulitple services only applies to utility power, not to on site generators.

I don't see why a twist lock plug couldn't serve as a disconnect.

Can't the auto transfer switch be operated manually if the auto function fails?

Steve
 
Re: 2 generators at the same time

Steve66
yes an TS can be operated manually. ;) Unless of course you have a bypass isolation switch setup that would be able to do this for a properly trained person.
 
Re: 2 generators at the same time

Steve66
I am sure this auto transfer/generator can be manually operated. As I understand in this case a contact inside the transfer switch went bad & they lost 1 leg.
As this is not a service, maybe the 2 twistlocks can serve as the disconnects.
Rick
 
Re: 2 generators at the same time

Would regular maintainence and a monthly start up be a better alterative?
 
Re: 2 generators at the same time

Also need to meet the signage rules.
Rick

You are one of the few that are aware of this.

The generator is a feeder. In washinton state the gen must within 15 feet of the building or an additonal disconnect is required.
 
Re: 2 generators at the same time

This is just a thought,consiter using T.S.'s as phase transfers and save the cost of 2 Gen.s and all the piping and fancy signage? If more than 2 phases go bad on existing Gen. T.S. than their in trouble anyway.
 
Status
Not open for further replies.
Top