Dual ATS's allowed?

[Coppersmith]

A company that sells whole house generators has asked me to install the equipment they sold to a residence with two 150 amp panels. I've only seen pictures. There appears to be one big meter can back-to-back with the panels. I'm assuming the load side of the meter has a set of double lugs with each set feeding a panel. I was told they sold the HO two ATS's. Is it proper to use two ATS's or should I tell them they really need one 320-400 amp ATS instead?

Two ATS's means I would have to either run two sets of feeders from the generator, or double lug one of the ATS to get a jumper over to the second ATS. And obviously, the generator startup controls could only come from one ATS. I would have to cap off the other.

Two ATS seems like more work and I'm not sure it's code compliant. But I don't want to rock the boat on a sale already made.

Thoughts?

 

[mkgrady]

Nothing wrong with two Ats’s. Yes just use one set of control wires. I would run one feeder from gen to a splice box or I would run to a mlo panel with two output breakers. For example, if the gen output breaker is 100 amps I would run a 100 amp feeder to a mlo with two 50, 60 or 70 amp breakers.

 

[texie]

A company that sells whole house generators has asked me to install the equipment they sold to a residence with two 150 amp panels. I've only seen pictures. There appears to be one big meter can back-to-back with the panels. I'm assuming the load side of the meter has a set of double lugs with each set feeding a panel. I was told they sold the HO two ATS's. Is it proper to use two ATS's or should I tell them they really need one 320-400 amp ATS instead?

Two ATS's means I would have to either run two sets of feeders from the generator, or double lug one of the ATS to get a jumper over to the second ATS. And obviously, the generator startup controls could only come from one ATS. I would have to cap off the other.

Two ATS seems like more work and I'm not sure it's code compliant. But I don't want to rock the boat on a sale already made.

Thoughts?

The NEC does not care how many ATSs on a system. In fact, in the commercial/industrial world it is typical to have multiple ATSs, even many.
But there are some things to consider here. You need to find out more details. If this is typical resi grade stuff such as Generac or the like it will be different than if you are using "standard" equipment such as is the norm in the commercial/industrial world. The 2 types are vastly different in how the generator and ATSs "talk" to each other. In any case you do not want an ATS with the controls not be connected to the system.

 

[LarryFine]

I have done this, too. One Generac genny to two Generac ATS's, wired as a master and a slave. Control wiring from master to genny, and from slave to master. How to do this is in the manual. For the feeder, I believe I ran full-sized conductors to a J-box between the ATS's where I used 3-terminal splices like Ilsco. It was a few years ago.

Another option is to select which loads need and need not be supplied, and relocate all the "needs" to one panel, and use only one ATS. This can also simplify the installation by eliminating the need for load shedding. In either case, interrupt the feeder(s) between the meter and the panel(s) with service-rated ATS(s) flanking the panel(s).