| Nexus Smart Switch ATS installation question for backup gen This is a question about installing a Nexus Smart Switch ATS for a NG Generac backup generator.
This is at a friend's house. He was sold the generator and the 200A Nexus Smart Switch ATS (»www.norwall.com/product_pdfs/144···3_om.pdf).
He has two 200A panels fed from the meter. All of the circuits that need to be fed from the backup generator are in one panel, and my friend prefers that all of the circuits in that panel be fed from the backup generator.
The generator has been installed and he had a couple of licensed electricians come in to look at the setup and give him quotes for installing the ATS. But they seemed a bit confused about the "smart switch" ATS. He even called the company while with one of the electricians to have the company's techs explain to the electrician how it worked.
One of the electricians emailed him the following list of work items as part of his proposal:
• Provide labor and material to install customer supplied 200 amp transfer switch under main panels.
• Provide and install (1) 125 amp main breaker in right panel to feed transfer switch.
• Provide and install one 200 amp 30 circuit main lug panel for circuits to go into from main panels and be feed from transfer switch.
• Provide and install conduit from transfer switch to generator, pull high voltage and low voltage wire's.
• System start-up/diagnostic evaluation.
• File for electrical permit and call for inspection.
My friend is following up with the electrician to get clarification, but he asked me if I could get some information on this independently.
Question 1. Is item 3 necessary? (And if the answer is "no", then is item 2 necessary?)
Why would a third panel be necessary when all of the needed circuits are already in a single existing panel and the generator can handle the load? (The ATS can also automatically shed some loads if necessary. The A/C will be on this panel and its load can be shed by the smart switch.) I'm not sure if it matters, but my friend has previously powered these circuits by a much less capable, portable generator during outages.
Question 2. Since there is more than one main panel, is there any danger of a backfeed? What should he look for to ensure that this won't happen? |
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 Killa200Premium
join:2005-12-02
Southeast TN | Need more info on the current house setup. Does the meter assembly contain disconnects for each of the existing mains panels, or are the 200amp disconnects for each panel located in said panels? Looking at the model it seems the ATS has no mains disconnect onboard. |
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| said by Killa200:Looking at the model it seems the ATS has no mains disconnect onboard. Actually, both section 1.3.2 and the drawings in the manual show a breaker on the utility side, either 100A, 150A, or 200A depending on the ATS model. I don't see why you couldn't just go right from the meter to this ATS to that one existing panel.
/M |
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 whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:8 | reply to vircotto
It depends. My guess is the electrician did not look at the ATS manual. On the other hand, other items are necessary (contactors for the load shed). Also the electrician states:
"Provide and install conduit from transfer switch to generator, pull high voltage and low voltage wire's."
The low-voltage (control) wires have to be in a separate conduit. Likewise, he makes no mention of which control wires. To do it right there are a lot of them. What the electrician is going to install in the way of controls should be explicitly stated or your friend is going to end up being very unhappy. (Wiring includes air-conditioner thermostat wiring; and controls to the load-shed contactors.)
I assume the switch is rated for 200A (and it should based on the rating of the sub-panel). You state 'both panels are fed from the meter'. We don't know if one is a subpanel. We don't know if there is a single main disconnect switch. We don't know if the panels are main lug or main breaker. Does the generator have a main breaker or disconnect? Find out the answers to these questions, and let us know. Then we could recommend how to install it and what equipment is required. |
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| reply to vircotto
The transfer switch needs to be service rated, meaning there is a main disconnect inside. If not then a 200A disconnect needs to be installed ahead of it.
The transfer switch simply gets places inline with the service entrance cable, between the meter and panel. This is true even with two panels.
#'s 2 & 3 are both completely unnecessary in the description above.
With the transfer between the meter and the one panel there is NO chance of backfeeding anything since the transfer is breaking the line and only allowing the genny to feed that one panel.
Depending on the distance the control wiring and the power wiring CAN be in the same conduit. In fact every pre-wired standby genset I have ever done has come this way from the factory. You just have to be sure to use the correct conductors. |
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whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:8 | said by Speedy Petey:The transfer switch needs to be service rated. Its not.
said by Speedy Petey:The transfer switch simply gets places inline with the service entrance cable, between the meter and panel. This is true even with two panels. Its not service rated and can not be. Whether its true with two panels, depends on if that's the way one wants it. The op doesn't. Wants one panel.
said by Speedy Petey:Depending on the distance the control wiring and the power wiring CAN be in the same conduit. Unless its the manufacturer states it can not be, as this manufacturer states. (As well as a number of other factors including code requirements.)As well, here, part of the control wiring are the air-conditioning thermostat wires; which typically can not be placed in the same conduit with ac power wiring. Regardless, its a poor practice. |
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 nunyaWho is John Galt?Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:5
 ·Charter
 ·voip.ms
| reply to vircotto
I've installed this particular switch several times, and it's not that difficult. It's a nice switch with some extra options for load controls.
What I am imagining is your friend has a 320 Amp single phase service that runs in to the meter can. From there, 2 200A feeders come out, one to each panel. Correct?
It sounds like maybe the electricians your friend called were idiots.
Some pictures for clarification would be great.
--
...because I care. |
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| reply to whizkid3
said by whizkid3:Unless its the manufacturer states it can not be, as this manufacturer states. (As well as a number of other factors including code requirements.)As well, here, part of the control wiring are the air-conditioning thermostat wires; which typically can not be placed in the same conduit with ac power wiring. Regardless, its a poor practice.
Just as a point of clarification, the wiring we are talking about is the control wiring from the transfer to the genny. This is the 240v sensing circuit along with the low voltage control and battery charge circuitry. All the wiring is THHN so the actual voltage is irrelevant. The distance plays a role as longer distance can cause induced voltage on the low voltage circuits.
Personally I was not talking about the A/C thermostat wiring as the OP never mentioned that. |
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whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:8 | said by Speedy Petey:Just as a point of clarification, the wiring we are talking about is the control wiring from the transfer to the genny. This is the 240v sensing circuit along with the low voltage control and battery charge circuitry. All the wiring is THHN so the actual voltage is irrelevant. The distance plays a role as longer distance can cause induced voltage on the low voltage circuits. Understood. See the photo above, and bear in mind, the manufacturer's instructions clearly require this wiring in separate conduits. The sensing circuits may have sensitivities that you are not aware of but the manufacturer is. I have seen where mfr's only require separate conduits (and/or different gauge wiring) depending on length. |
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| reply to vircotto
Wow! Thanks, folks!
Here are images of the meter and the panels where the conduits come in. |
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| reply to nunya
@nunya
My friends doesn't know what is running in to the meter, but believes that each of the two panels is fed separately. (I just posted the pictures he sent me.) |
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| reply to whizkid3
@whizkid
My friend checked the ATS panel and verified it is 200 A and has a utility disconnect.
He believes one panel is not a subpanel, but that each is fed separately. (There are two conduits from the meter that go in to the house. He believes each panel is fed by wires from a different conduit.)
Does the picture of the panels answer the question about main lugs or breakers?
The generator (a 20kW Generac) has a disconnect.
BTW, can you explain the issue about whether or not the ATS is "service rated"? If not, should it not be used?
Thanks! |
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| reply to Speedy Petey
@Speedy Petey
My friend said that there is a utility disconnect on the ATS. Is that different from what you mentioned? |
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nunyaWho is John Galt?Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:5 Reviews:
·Charter
·voip.ms
| reply to vircotto
The RTS200A3 is service rated. Most of the new Generac / Guardian / Siemens ATS are service rated.
What that means is the 3 conductor SEU cable would be run into the ATS. From the ATS, a 4-wire SER cable would be run from the ATS to the panel (it would be better to use conduit instead of SER).
The panel will have to be "split out". To put it simply, that means the neutrals and grounds must be separated in the panel.
Having everything he wants to power by genset already in one panel makes this a gravy install. He just needs to call someone who knows their ass from a hole in the ground.
I'm a little confused by your friends service, as the pictures aren't too detailed. The existing SEU cables almost look too thin for 200A. Do you recall the breaker rating on the panel main breakers. Was it perhaps 100A, 125A, or 150A?
The garden base looks like a CL320, but the meter is a CL200 with no multiplier. I know some GE meters are marked "funny" and can actually be CL320 and still marked as CL200. Their documentation is hard to follow.
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...because I care. |
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| I work near my friend's house, so after I saw your post, I ran over there to look at the panel. I don't see any markings on the 4 breakers that are ganged together (in each panel), so I'll have to go back when he is there to remove the cover.
(I once zapped myself messing with my dad's 4-circuit 60A service fuse box, so now I don't touch 'em. Learned my lesson.  ) |
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sk1939
join:2010-10-23
france
kudos:6 | reply to nunya
Basing off of what BG&E usually hands out for meters, I would say that it is a CL200, rather than a 320. My guess is that he has a 200A service split 2 ways, and each panel is 100A. It's a bizarre installation imo. |
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whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:8 | said by sk1939:My guess is that he has a 200A service split 2 ways, and each panel is 100A. He could also have a 200A service and (2) 125A, 150A, 175A or 200A panels. Can't tell. And it's kind of important.
I see the OP's friend has the GE 'PowerMark Gold' load-centers; with the 4-breaker main-breaker.
said by vircotto:I work near my friend's house, so after I saw your post, I ran over there to look at the panel. I don't see any markings on the 4 breakers that are ganged together (in each panel), so I'll have to go back when he is there to remove the cover. All you probably needed was a flashlight. The breakers are indeed marked - often the amp rating is molded into the handle. You will unlikely find any more information inside unless it was factory assembled and they through a sticker on that is unique for that size main breaker. |
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| Okay, thanks! I'll look again tomorrow morning before I start work. |
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| reply to whizkid3
Okay, here is a pic of the main breakers. I see that it shows "200" on the bar that connects the four breakers together. |
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sk1939
join:2010-10-23
france
kudos:6 | That wire still looks a little small to be feeding a 200A service considering it should be a 2/0 copper or 4/0 aluminium. |
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