ATS, EPO, and other TLA's

[Open Neutral]

Large residence, with pool; fed with 400A 3ph 240/120 open delta. Solar grid tie, backup inverters, and a standby generator. We'll supply several motors with 3-ph, and house loads with 240/120v off the "lighter" winding.

I'm debating the merits of approaches on automatic transfer switches. We need both transfer from PoCo to the generator, and a manually activated emergency power off function [Big Red Button with molly-guard]. Can/should I combine these functions? It appears some ATS's are in effect "Double-throw, center off" but the spec sheets go to lengths to be incomprehensible. The alternative would be a main disconnect with a trip coil, I'd guess.

On the ATS&EPO side, it's less space, fewer things to fail. But it may well be more expensive as the ATS must be "service" rated, and be center-off.

Thoughts?

[BTW, a side issue is implementing EPO on the inverters. They have no usable control input so I'll likely have to have a trip coil in the DC breaker.]

 

[hillbilly1]

The 120/240 is actually the 'heavier' (larger transformer) winding because the majority of the load is normally single phase + the other legs of the three phase combined. The breaker or molded case transferswitch type usually have a "go to neutral" function where both breakers are open, but I have not seen any in that small of amperage. If your wanting to kill both utility and generator power at the same time, you could use a shunt trip breaker on the load side of the transfer switch. Shut down of the generator can also be accomplished by an extra set of contacts in your EPO switch.

 

[Open Neutral]

I've just started to look at ATS's & welcome suggestions. I've been looking at the GE Zenith but I need a dumber switch than that; the inverters shall control the generator start/stop, for example.

I'd not considered a separate main downstream of the transfer switch. Hmm.

 

[iwire]

Why in the world would you need an EPO?

 

[Open Neutral]

Why in the world would you need an EPO?

Several reasons:

1) The house is in an isolated [~4 twisty miles up from real road] location, in a seismically active & fire-prone area. It will have multiple sources: PoCo, inverters, generators. I was concerned about CalFire responding, pulling the meter...and the generator starting.

2) I then had a long discussion with the Fire Marshal, who told me they no longer pull meters; instead they call PG&E and wait....

Given it's a RF dead zone, I wonder if they could even be heard. Plus 30 min for PG&E unless the guy arrives in a Jet Ranger.

3) It appears this will be a CT fed if not CT/VT meter; so pulling it is of little use, I'd think. [Have not fully grokked that part of the GreenBook...]

4) The client likes the idea as do I.

So you could say "want" but....

 

[widnerkj]

I'm a field service guy for russelectric, so if you want to learn more about ATS's that's not a problem. I can answer most ATS questions you have. If you are in the market for a "dumb" ATS, I'd reccomend trolling ebay for an old russ ats of the "MCB" variety. As they are our "stupid proof" relay systems back in the day. I won't lie though, russ systems are expinsive as hell. But good deals are to be found on ebay if you search hard enough. I'll apologize in advance for the shamefull promotion of the company I work for, but I kind of like them. And to fit your criteria, an old dual motor mcb type switch sounds right down your alley. And if you need a copy of the prints or some advice on setting it up, I can do that.

 

[masterinbama]

I would also lean towards the shunt trip and auxiliary contact approach. The simpler you keep it the more reliable it will be.

 

[iwire]

To each their own, every control added is a potential source of failure so I would not add anything not directly required by code. But of course if the customer wants it and will pay for it I will be glad to provide it.

The FD has not pulled meters here in a long time, if they want the power cut they call the power company. It might be an hour but it is just property, it can be replaced.

 

[hillbilly1]

Most locals now require a disco on the outside for new installations mainly for that purpose anyway.

 

[Open Neutral]

Most locals now require a disco on the outside for new installations mainly for that purpose anyway.

Amazingly Santa Cruz County does not require an EPO, but do require a label if you have one. Plus, they assume the meter is on the house.

The FD has not pulled meters here in a long time, if they want the power cut they call the power company. It might be an hour but it is just property, it can be replaced.

If you had ever lost everything you own in a fire; you might feel differently, I'd think. This house is carefully placed in a forest; burn it down and what's the land worth then? Plus, it's 10X as complex as the average Levittttown special; with grid-tie, backup inverters, main and aux generators, etc.

I would also lean towards the shunt trip and auxiliary contact approach. The simpler you keep it the more reliable it will be.

Well, maybe, but a ATS designed to have an "OFF" mode would have one less breaker, etc. So which is simpler?

Re: Russ unit; don't see any at present but will keep searching. Have not completed a search for data on other brands.