ATS or Relay...

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Julio Trujillo

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San Juan, Puerto Rico
I think I got a new one. At my utility, someone proposed the use of a high amp relay instead of an ATS for multiple client service. Think of a condo; one generator can supply emergency power for all people, but the generator can't supply the meters. The current options are submetering or an ATS for each meter.

An ATS for each meter is expensive and takes space (a separate enclosure or a bigger meterbank), if a relay could be used, it would be a smaller and lighter device. The proponent indicates that this is already used in other countries, particularly for 100 A services.

Has anyone heard about this? Is it a viable option?
 
Julio Trujillo said:
I think I got a new one. At my utility, someone proposed the use of a high amp relay instead of an ATS for multiple client service. Think of a condo; one generator can supply emergency power for all people, but the generator can't supply the meters. The current options are submetering or an ATS for each meter.

An ATS for each meter is expensive and takes space (a separate enclosure or a bigger meterbank), if a relay could be used, it would be a smaller and lighter device. The proponent indicates that this is already used in other countries, particularly for 100 A services.

Has anyone heard about this? Is it a viable option?
Click to expand...

An ATS is a type of automatically-controlled relay. A relay which is rated to handle the current, listed for use as service equipment, and controlled by something which switches it when utility power fails... would be an ATS. You could use a contactor that's not listed for service entrance use if it's behind another disconnect, but it's still going to be big and expensive, and still is really just an ATS.

I suppose the key difference between most ATS's and most contactors is that ATS's tend not to require power to remain in position (they use motor-driven mechanisms) rather than a contactor which usually uses an electromagnetic mechanism and requires power to stay activated. Not sure how much difference that would actually make in size and cost, once everything else is factored in (enclosures, controls, etc.). The really easy way to use a contactor as an ATS without any additional control circuitry is to wire the coil and the normally-open contacts to utility power, the generator to the normally-closed contacts, and the load to the common terminals. This is a clever solution but has the disadvantage that the coil is activated at all times during normal utility operation.
 
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No.

To be connected here, an ATS must be listed under UL-1008 (or equal from any other NRTL, but none of the others tackle ATS as far as I know). You can’t roll your own here. Article 700, "Emergency Systems" covers this at the basic level, then if it's a health care related facility, there are further requirements.

700.5 Transfer Equipment.
(A) General. Transfer equipment, including automatic transfer
switches, shall be automatic, identified for emergency use,
and approved by the authority having jurisdiction. Transfer
equipment shaH be designed and installed to prevent the inadvertent
interconnection of normal and emergency sources of
supply in any operation of the transfer equipment.
Click to expand...

Every AHJ I have encountered will have a requirement for UL-1008 on an ATS.
 
Julio Trujillo said:
I think I got a new one. At my utility, someone proposed the use of a high amp relay instead of an ATS for multiple client service. Think of a condo; one generator can supply emergency power for all people, but the generator can't supply the meters. The current options are submetering or an ATS for each meter.

An ATS for each meter is expensive and takes space (a separate enclosure or a bigger meterbank), if a relay could be used, it would be a smaller and lighter device. The proponent indicates that this is already used in other countries, particularly for 100 A services.

Has anyone heard about this? Is it a viable option?
Click to expand...

As Jraef mentioned no and for the reasons he mentioned. While he mentioned Article 700.5, I think he meant Article 702.5. Same end result. I am just pointing out that this would not be an article 700 system but rather a 702 system.

Is this a situation where the POCO would be doing this or just giving their blessing? If it was under your control as the POCO you could just power the whole service and simply read all the meters before you start and stop and deduct the KWH registered while on the generator.
I note that this is Puerto Rico. There is no POCO here on the mainland that would get anywhere close to this.
 
texie said:
As Jraef mentioned no and for the reasons he mentioned. While he mentioned Article 700.5, I think he meant Article 702.5. Same end result. I am just pointing out that this would not be an article 700 system but rather a 702 system.

Is this a situation where the POCO would be doing this or just giving their blessing? If it was under your control as the POCO you could just power the whole service and simply read all the meters before you start and stop and deduct the KWH registered while on the generator.
I note that this is Puerto Rico. There is no POCO here on the mainland that would get anywhere close to this.
Click to expand...

Yeah, you are right. I got to 700.5 and stopped there, but the subtle difference is "required" emergency system vs "optional". Good catch.
 
OK, ok...this is not a grammatical inquiry, I understand the operation, and my question is in a practical sense.

From the articles cited, it seems that a relay could qualify, correct? But I understand that it, probably, isn't code accepted, because of UL requirements and such. What's interesting is that, operation wise, it should work; the size would be bigger, but not as big as a normal ATS.

So, has anyone seen a relay being used as an ATS (doesn't have to be US)? Also, do you know of relay brands that could work (100A and 200A)?

And Texie, what is POCO (pardon my ignorance)?
 
The “relays” (by which I assume you mean contactors) only do the switching portion of an Automatic Transfer Switch. The other two parts, the Transfer and the Automatic are more problematic.

The Transfer function, when you use contactors, will result in one contactor being energized continually while on PoCo source (Power Company by the way). That means your operation will come to a screeching halt when that coil eventually burns out. It may be 5 or 10 or 20 years, but the day it happens, whatever you do ceases and any perceived dollar savings compared to a proper ATS flies right out the window and takes a few thousand of its closest friends with it. You will notice that listed ATS units are typically designed with special double-throw mechanically latching contactors or motorized circuit breakers for that reason.

The Automatic aspect is much more difficult than you think. An ATS has the proper line sensing, generator starting and Transfer delays required for proper operation and protection built in. For you to design and implement that will very likely cost you more in terms of the cost of your time and materials, plus YOU accept ALL of the risk of having forgotten something or having it not function as expected, causing a shutdown and a jettison of cash in the form of unscheduled down time again.

Yes I have seen it done with contactors for IEC based systems, and yes, the outcome was as predicted. At the time, I worked for an IEC manufacturer and we were sued over the down time costs because of the failure after just 4 years. But as it turned out, we were just executing what their own Engineer requested and designed (and we had that documented).

It comes down to one of my favorite tag lines in this (I think) forum:
“Just because you can, doesn’t mean you should.”
 
The ATS used in Great Britain sometimes is a great example... it basically applies to each breaker and takes the place of the screwdriver interconnect, electrically... the one breaker cannot open if the other one is open and vice versa... but they do not even have to be on same group of breakers... I have seen it used so if power shut off to one breaker bunch, the breaker on other bunch opens automatically... of course, panels here are different. Will look in my notes and see what the brand was I was looking at on You tube the other day..think Was a seimans brand.
 
I understand there are many types of relays, even programmable, so timing and delays can be set. Also, why must the source contact coil be energized all the time? Design a logic that uses a normally close contact for the source, which transfers when the generator starts or a battery makes the initial contact. Besides, 10 or 20 years is a good lifetime.

I think technology is available for adequate construction; Adamjamma seems to have found an application, let's see it.

Sometimes there is stuff out there that we just don't know about, or a company or utility hasn't look for it. I've found stuff; a hydrant lock manufacturer that has special locks for meters and test switch, a briefcase type testing unit for power and instrument transformers, that digital 9S and 16S meters are universal, etc. Recently we found that small, window type CTs, can be used, safely, for 38 KV lines, and as such, they can be used for any power distribution metering.
 
Adamjamma said:
The ATS used in Great Britain sometimes is a great example... it basically applies to each breaker and takes the place of the screwdriver interconnect, electrically... the one breaker cannot open if the other one is open and vice versa... but they do not even have to be on same group of breakers... I have seen it used so if power shut off to one breaker bunch, the breaker on other bunch opens automatically... of course, panels here are different. Will look in my notes and see what the brand was I was looking at on You tube the other day..think Was a seimans brand.
Click to expand...
Are you referring to what we call a "walking beam mechanism" that is connected to the handles of both breakers such that moving one handle On moves the other one Off? That would be a MANUAL Transformer Switch (MTS). The "Automatic" in the ATS means it needs no intervention or action by a human whatsoever once it is set up.

Julio,
Maybe we are missing a big issue here; what do YOU consider "high amp" in your initial posting? Because if you are thinking 10A or 20A as "high", then we have been prattling on needlessly...

But if you are thinking 400A, try to find a 400A 3 pole contactor with Normally Closed contacts... I'm not saying they don't exist, they do. But they are rare, and rare means expensive. You will (again) not save anything trying to do that on your own.
 
In my first post I mention 100A and 200A, what would be normally used for a home or apt. The focus is on multiple clients, this usually means meterbanks. Of course, a higher amp system could be consider in the future, but 100A or 200A relay system for a meterbank, could be less expensive (considering hardware and space) than a normal ATS system.
 
no..having trouble finding it.. found the one post in punjabi or something like that..but cannot find the english post... It is a relay system on the breakers that automatically keeps the one breaker from energising if the other Breaker is powered. But if other breaker loses power the one breaker turns on. Originally it used an interlock between the breakers, but was on its own section of a board, and was used in a three phase system, with four wires between them..

It was touted as the next generation of ATS. But, cannot find it. Probably on one of my discs in Jamaica..lol... about three years old.
 
Julio, there are many ways to accomplish what you want. None of them are legal besides using a rated ATS. At least to my limited knowledge of NEC code.

It is one thing to have a theoretical discussion, quite another to ask for a practical solution. I’m not sure which you are asking for.
 
Jraef said:
Are you referring to what we call a "walking beam mechanism" that is connected to the handles of both breakers such that moving one handle On moves the other one Off? That would be a MANUAL Transformer Switch (MTS). The "Automatic" in the ATS means it needs no intervention or action by a human whatsoever once it is set up.
Click to expand...
I have seen ATS's that use motorized walking-beam mechanisms.
 
The one I am talking about had a small mechanism that went in one side of the breaker and moved or blocked the arm, controlled by the relay. The second one went between both breakers and did sAme thing but again, controlled by relay that clipped on side of breaker. Here in uk they have items that clip on side of main breakers or they slot next to main breakers... as relays, surge devices, afci, etc... saw a guys setup where he basically built a three section breaker system, with surge and afci at top, RCD on the levels below, what we call a split board here... the one afci or RCD controls several breakers. More common than full mcbos
 
Russs57 said:
Julio, there are many ways to accomplish what you want. None of them are legal besides using a rated ATS. At least to my limited knowledge of NEC code.

It is one thing to have a theoretical discussion, quite another to ask for a practical solution. I’m not sure which you are asking for.
Click to expand...

Agree with Russ here Julio. Your relay idea would need to be approved by the AHJ to be installed.

You can implement a transfer scheme with circuit breakers, they use relays. Do you just really want to use a contactor?
 
This is not my idea. A contractor wants to submit a proposal for using 100A relays instead of a normal ATS; I asked him for documentation which hasn't send. So, I'm researching about the hardware and it's possibilities, particularly, when it's being used somewhere else...says him.

Let me provide another path... Microgrid systems, even though inverters have internal switching, need a disconnecting device at the service entrance. Manufacturers and installers will use relay controlled switches, but also mention the use of relays themselves as the disconnecting means. So, there seems to be some hardware that qualifies.

Regulation for microgrids in Puerto Rico is still developing, but constructions are being authorized; soon I will see one of those.
 
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