Parallel Transfer Switches

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frogneck77

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Shelton,CT
I have a customer who has a 400 Amp service and would like a generator to power his entire house. The meter has (2) 200 AMP main breakers feeding 2 40 circuit panels @ 20' apart from each other. I have heard of installing 2 transfer switches in parallel in certain applications, but I cant find any info in the manuals in reference to wiring diagrams for the transfer switches we use-Guardian. Any suggestions or advice would be appreciated.BTW- I havent priced the job yet
 
Guess you'd have to use two, 200 amp ATS's and feed both of the ATS's generator terminals with the one generator.

I seriously doubt the customer really needs or wants both panels backed up. I very much suspect that once he sees the price tag on such a genset, a much smaller "emergency panel" constructed by moving the important circuits to a subpanel would become a more attractive option. I've done generator panels in homes with a 400 amp service that only needed 30 amps in generator capacity for the important things. Of course, everyone has a different idea of what's important.
 
Also froggy, if your customer wants everything on a generator make sure he doesnt skimp on the Gen. You wouldnt want "dirty" power ruinning his computers and tv's and such.
 
I have explained to the homeowner ballpark prices for 15KW to 50KW gensets and he wants the big one. Ive installed alot of generators but have never had to wire multiple transfer switches. Not sure about the control aspect.
Bill
 
Froggy, I recently inquired about this with Generac, and the basic instructions were to run the 240v control conductors from only one TS but the 12v control conductors to both.
 
LarryFine said:
Froggy, I recently inquired about this with Generac, and the basic instructions were to run the 240v control conductors from only one TS but the 12v control conductors to both.
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That makes sense... the 240v tells the generator the status of the power and charges the battery, and the control wiring just tells the transfer switch to change over... if you ran the 240v side from both TS, you would have a 50% chance of a short...:wink:
 
Something to remember in this installation.

The generator may have up to a 400 amp overcurrent device. You will need to supply a trough with the proper size conductors and then tap out of the trough into the two different transfer switches.
Why are the panels so far away from each other? What happened to grouping of service disconnnects?
 
Two Transfers

Two Transfers

If you are using a generator other than a Guardian, Cutler Hammer has a nice 400 amp switch with 2 - 200 amp load side breakers and a 400 amp main.
I'll warn you that it is pricey but if the customer is willing to pay, it is the only way to fly.
Catalog # ATV3LDC20400WRU, about $4,000 for the switch
 
LarryFine said:
This brings up a question: can brands of generators and T/S's be readily mixed?
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The answer to that (IMO) is it depends.

We mix and match gens and ATS all the time however these are generally larger commercial units.

Some of the smaller home units seem to be proprietary.
 
Mix Transfers and Gens

Mix Transfers and Gens

As far as I know, any transfer switch with a two wire start can be used with any generator that uses two wire start.
The Guardian product is a little different because it's logic is in the control panel in the generator.
I don't believe that you can use any switch other than Guardian with Guardian.
I think that you have to use Briggs and Stratton with Briggs but it is just an OEM Cutler Hammer.
Our favorite switches are Cutler Hammer and DynaGen.
We use them with a variety of manufacturers.
 
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dezwitinc said:
The Guardian product is a little different because it's logic is in the control panel in the generator.
Click to expand...

Another issue I have seen is the battery charger location.

Some are mounted to the gen set, some are internal to the ATS and still others are entirely stand alone.
 
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