ECN Forum Forums General Topics of the Trade General Discussion Area 200A Auto-transfer switches

I would be removing the service cable from the current 200a panel and installing that into the ATS. (This cable comes from the meter.)

Then I would be comming out of the ATS with 4 conductor, back to the 200a panel which would now need to be phased out.

Would I need 'Service Rated' for this application?

Can someone clear this up when it would need to be 'Service Rated' and when it would not. Maybe an example or 2.

Thank you for the help so far,

[This message has been edited by Trick440 (edited 11-09-2006).]

What exactly does "service rated" mean? It's not a term I hear a lot; I guess I have always just assumed things like 200A panels and disconnects were "service rated"?

NEC 100.1

Service Equipment. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constiture the main control and cutoff of the supply.

Sounds like if you cable this ATS directly to the meter, it's service equipment, but if you stick a disconnect switch/OCP between the meter and the switch, it's not. Would that save you $200 between materials and labor to stick an extra enclosed breaker in there?

[This message has been edited by SteveFehr (edited 11-09-2006).]

Equipment is "service rated" because there are different requirements. I believe the correct terminology is "Suitable for use as Service Equipment."

I think there is a higher interrupting rating (AIC) required. Things have to be mounted more securely. There are provisions for the neutral wire, and different grounding options.

In many cases, these differences are not readily visible.

Reno's got it - essencially it would need to be listed/rated as "Suitable for use as Service Equipment" if it is anywhere between the MCOP (Main CB) and the meter. And yep, if on the service conductors it opens another set of cans of worms involving the POCO. If say it were on a feeded to a panel only handling those loads (As they often are) then the POCO has no buisiness with you. As you would be on the protected side of the the main service breaker.

So now a question... A home that had a service calc that required 200A - only calc'ed 12KW as a "Connected Load" for the generator? How's that? I know the code offers alot of leeway in generator sizing for this application - but I don't think it would be a wise idea unless the owner had to manually swap over each load. If it say happened in peak use time you could be dropping POCO - then dropping in the generator on over-load. Say if an AC and Oven were on... Which is why often these are sized for either the whole house load - no call backs for over load drop. Or only for a few 'emergency' loads. (Refer, sump pumps a few lights and outlets here and there - but not the hot-tub, pool and entertainment center) If it takes on the whole house automaticly, the generator just might shut down right then and the owner might not know what to shut off. So in this case you have two options a bigger generator, or a ATS with an ammeter installed and instruction book about load shedding. Oh - or a load shedding shunt trip circuit.... It's not hard - but pricey. Use under-voltage trip shunts to drop all non-essential loads when POCO goes out, then the owner can turn them back on manualy after the generator connects. You would have to set it up with a momentary switch that would have to be flipped manually to latch a relay to re-power the shunts so the they could be reset only on generator power. But they would have to be re-set anyway even if the POCO came back on....

But an "Essential" panel, and "Non-essential" panel would be cheaper.

[This message has been edited by e57 (edited 11-09-2006).]

Sweet answers.

Thanks E57, for the insite about the huge power draw. We know its a small genny but didn't think about that.

Timne to talk this guy into a different route.

Well it depends on what he has as a load... If he has a 200a service for the sake of having a 200a, he may have a load demand that is far less. But it has all the bells and whistles and 100 amps of general lighting, and two 60a AC units - then no.

But the options of an essential and non-essential panel or larger gennie is a common method of doing it, and he should be informed of the options. Either way you get what you pay for. A few thousand more for seperation of the whole works, or simular amount of money more for a 30-50kW. Which the latter is enough to power him fully and a neighbor or two maybe? Depending on equipment loads? The only time I have ever seen a 200a service pull 200a is at X-mas during a catered party w/ 20kw in lights and caterers on hot plates.... I just questioned the size because powering 50A of an available 200 sounded odd. Often a service of that size will be that size due to something large as a load....

His service is actually 2, 200A panels. With most 220v devices in the other panel. So guess thats figured out.

I'll be pushing for putting the essential circuits into one panel and the non essentials in the other. Sounds like the best angle.

Thats why I made this post.... to become informed of my options.

Ahhh.... So it's say a 320C/400A service? (2)200's in a meter/main combo w/ (2)200 lug panels, or a meter pan and (2)200 main panels?

Sounds as if one whole panel is general lights andrecept load? They may be lightly loaded, but the gennie should be sized for the load or in the very least a high demand of that load. Otherwise a small gennie would be defeating the purpose of being there when you need it if they are out there changing fuses, or flipping breakers. A generator salesman is going to give you the opinion that it needs to be sized a 100-150% of the load - but that is not nessesarily true...
http://www.generatorjoe.net/page.asp?id=40 http://www.dynagen.com/page.aspx?id=96259

Motor starting can drive it up a bit, but most are intermitant... IMO But you can guarantee that if everything else is off, what can be on - will be on.... So 100%+ is good. But my own opinion would be ~80% demand plus motor starting. Diesel likes a load.... Gas doesn't.

One of the nice things about an ATS, or more correctly certain ones. They can excercize the generator and load bank it on the house loads.

Another part of this is who gets to maintain it? It will need oil changes, and all things automotive, spare tire rotation.

Just to further renosteinke's comment.
The SUSE labeling does in fact mean that the switch must be rated for whatever the PoCo's available fault current level is, you will need to find that out before you purchase it to be certain. For an industrial/commercial site that can be high compared to a residential site, that's why the price is higher. You probably will not need it to be that high, but even so you will still need that SUSE label if you connect it as you have indicated, and the ATS manufacturers (those that even offer SUSE labels because not all do) only make them for the larger market so you may be stuck with the spendier ones.

I've got a similar setup on my own home, 200A single phase service, 200A whole house ATS, and 12 Kw generator.





Since the ATS is not service entrance rated, a 200A main breaker is between the meter and ATS as shown below:



I know, I should've painted the walls before I put up the plywood, but I was excited with my new toys... you know how it is. In any event...

I can run the entire house no problem... 240V 18,000 BTU A/C, as well three smaller 120V A/C's a 5,000 BTU, 6,000 BTU, and 8,000 BTU, not to mention refrigerator, oil furnace, dehumidifier, attic exhaust fan, three computers, two televisions, toaster, dishwasher, microwave, and just about every single light in the house (mostly 75W cans) you name it... I really wanted to push it for the purposes of testing. At one point, I was reading a total of 50.6 amps on one leg, and 46.9 on the other leg with stable Hz. Had my wife turn on her 1,850 watt hairdryer and only then did the genny shut down on overload and Hz drop (50A genny breaker didn't trip).

I have oil heat and hot water, and natural gas for the stoves and dryer, so my electrical requirements aren't really that steep. If I had electric heat, hot water, stove and dryer, all bets would be off for this unit. Was fine with 100A 12 breaker panel before, but I wanted a 40 breaker panel for the rewire for lots of dedicated circuits.

Let's face it, few homes truly need 200A service... you get 200A for the number of dedicated circuits.

Joe


[This message has been edited by JJM (edited 11-10-2006).]

[This message has been edited by JJM (edited 11-10-2006).]