Auto-transfer switch for generator

[sw_ross]

Have a customer that owns a rural farm with a variety of out-buildings. He has a 100kw generator and wants it set up to run the farm in a power outage.

I only have experience with smaller, manually controlled transfer switches.

Q1- I’m assuming that the service conductors would feed into the auto xfer switch, and all loads (outbuildings) would be fed from load side of that?

Q2- the service is a 320 to the farm. How best to size the xfer switch?

Q3- best way to feed various loads (outbuildings) from xfer switch?

Q4- I’m assuming there has to be a way (control circuit?) that senses a power outage and tells the generator to turn on?

Q5- What are power requirements of this control circuit?

He wants the generator positioned by the barn (it would have access to power for block heater and battery charging). But that’s about 200 feet from the service (and possibly the xfer switch?).

I would assume there’d have to be some control wiring between generator and xfer switch?

This generator is a surplus generator from the oil field. It’ll put out 1-phase 120/240, 3-phase (all voltages)! Kinda crazy...

Thanks for any input!

 

[ActionDave]

Have a customer that owns a rural farm with a variety of out-buildings. He has a 100kw generator and wants it set up to run the farm in a power outage.

I only have experience with smaller, manually controlled transfer switches.

Q1- I’m assuming that the service conductors would feed into the auto xfer switch, and all loads (outbuildings) would be fed from load side of that

Most ATS are service rated but you can put them in after the service disco.

Q2- the service is a 320 to the farm. How best to size the xfer switch?

400A

Q3- best way to feed various loads (outbuildings) from xfer switch?

Set a sub panel for all the loads you want fed by the genny.

Q4- I’m assuming there has to be a way (control circuit?) that senses a power outage and tells the generator to turn on?

Q5- What are power requirements of this control circuit

It's two little wires. That's part of the circuitry you have to run between the ATS along with a battery charger and sometimes a warmer. Probably a couple of 20A circuits. Should be on the instruction sheet.

He wants the generator positioned by the barn (it would have access to power for block heater and battery charging). But that’s about 200 feet from the service (and possibly the xfer switch?).

I would assume there’d have to be some control wiring between generator and xfer switch?

200' is no problem but you may not need to.

This generator is a surplus generator from the oil field. It’ll put out -phase 120/240, 3-phase (all voltages)! Kinda crazy...

Thanks for any input!

That is not unusual for a large generator. It can be intimidating but arranging the leads to suit the power needed is very doable.

 

[steve66]

The ATS senses the power outage, and will start the generator. It will also sense when utility power is restored, and shut down the generator after a cool down period.

 

[sw_ross]

Thanks!

Thanks!

Thanks for the responses!

In terms of transfer switches, I've been told it's important to have the same manufacturer switch as the generator?

Thanks!

 

[GoldDigger]

Thanks for the responses!

In terms of transfer switches, I've been told it's important to have the same manufacturer switch as the generator?

Thanks!

That would mostly be important if the ATS is responsible for stopping and starting the generator.
There are a wide variety of design standards for generator starting and monitoring, and adapting from one to another via relays or even a PLC can be problematic.
Using the recommended model ATS from the same manufacturer (or vendor) can avoid those issues and make testing more predictable.

Sent from my XT1585 using Tapatalk

 

[steve66]

Thanks for the responses!

In terms of transfer switches, I've been told it's important to have the same manufacturer switch as the generator?

Thanks!

That's true for some residential style generators, like the small generac Olympian models. The generator may be made to work with a particular model (or models) of ATS, and no other ATS will work.

But every commercial generator I've ever seen simply takes a set of dry contacts to start the generator. And every commercial ATS I've ever seen provides a set of dry contacts for starting the generator.

I see more ASCO ATS's than any other brand, and ASCO doesn't even make generators.

Of course, I suppose it can't hurt to stick with the same brand. A one point location for service and maintenance of both the generator and ATS is usually better.