Article 700 Emergency power components

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Steve.Evans

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Starting with a 700.2 compliant Emergency Power System, also known as Life Safety, with a generator meeting NFPA 110 and an ATS listed under UL1008.
Customer wants to add a portable generator docking station with quick-connect plugs (aka CamLok plugs) and a manual transfer switch, also UL1008 listed.
However, the manual ATS can only be listed as a Article 702, Optional Standby Systems, component. Will this effect the Article 700.2 compliant Emergency Power System?

Existing:
ATS.JPG

Proposed:
ATS+MTS.JPG

Where PG is permanent generator and TG is temp generator.

Thanks, in advance, for your help.
Steve
 
In my opinion the temp generator would also have to utilize an ATS and have provisions for automatic start.

Many larger rental units have provisions for that.
 
Article 700 EPS

Article 700 EPS

iwire said:
In my opinion the temp generator would also have to utilize an ATS and have provisions for automatic start.

Many larger rental units have provisions for that.
Click to expand...

That makes sense, but the cost ... purchase/installation plus life-cycle maintenance... is a consideration. And introducing more possible points of failure.
 
Anytime the MTS is placed in its alternate position, you will essentially disable the entire emergency distribution system. But you would be doing the same thing whenever you tag out the generator for scheduled maintenance. What I don't know is how a building is supposed to deal with planned outages of this nature.

However, back to the original question, I am curious as to what the installation of this additional generator is intended to accomplish. When and how would it be used? For example, I recall one building I designed that included similar provisions for connecting a portable generator. The article 700 load requirements were handled by unit equipment with individual batteries, so the generator was strictly for article 702. The building had a number of freezers that were storing some valuable core samples from above the artic circle. The freezers could maintain temperature without the normal utility power for about 8 hours. That gave plenty of time to call the generator company, for them to drive their truck to the site and plug in their mobile generator. Are you talking about a similar intent?

If the owner is looking at this portable generator as a backup to the permanent generator, then you don't get to take credit for its existence unless you do the things that Bob mentioned.
 
MTS in Emergency power system

MTS in Emergency power system

First of all, thanks for the posts, guys. I appreciate and enjoy a good technical discussion.

Charlie: the portable genset is for backup in case the primary is out of service for whatever reason. The site is a building that has been classified as requiring a Emergency System for Life Safety, not just 701 (legally required) or 702 (optional). Art.700 requires backup power for compliance and if there is only 1 genset and it is out of service, can the building be occupied? I suspect not.

Thus the MTS and portable genset connections. The ATS would still be in service downstream of the output of the MTS. The genset start circuit would be installed and tested. It is just that the backup source would be the temp gen and not the permanent gen. Thus they would be maintaining Art 700 compliance.

iwire: re-reading your post, that would mean we would have 1 ATSs in series. Seems like an odd solution that might introduce more points of possible failure.

Again, thank you,
Steve
 
So the idea is to have the temporary generator brought on site and connected to the MTS, manually place the MTS into its alternate position (and perhaps LOTO it into that position), add the control features that would allow the temporary generator to be automatically started upon loss of the utility normal source, and then take the permanent generator out of service? If so, then I think this should be fine. You won't need the new transfer switch to be an ATS, because it would never be used except in the manner described above. You would not be counting on the operation of the MTS as part of the article 700 system's operation. What I don't know are the requirements that the temporary generator would have to meet, in order to qualify it as an article 700 power source.
 
I would prefer to see the MTS placed on the utility side of the ATS.

Another option might be a special order 3 position ATS to replace the existing ATS.
 
It would be my view that the arrangement proposed by the OP would not be compliant as an Art. 700 system. I have done systems exactly as he described but they were Art 702 applications so Art. 700.5 and NFPA 110 was not an issue. I think that by interposing the MTS in the emergency feeder you have violated 700.5 (an MTS can't be listed for emergency use) and the basic requirements of NFPA 110 that this would have to be supervised and annunciated in case the MTS was left in the wrong position. Keep in mind that even if a transfer switch is listed to UL 1008 it may not be listed for use in an Art. 700 system.
I do think that using 2, listed for emergency use, ATS switches this could be compliant (and has been done). Even if the permanent machine fails and the portable machine is not present you have still met the requirements as the second, portable machine is not required in the first place.
FWI, Cummins has some info on this subject of using 2 transfer switches that I remembered reading on this subject sometime back and I relocated it here (starting on page 87):

https://powersuite.cummins.com/PS5/...nary_Asset/pdf/Commercial/technical/T-011.pdf
 
I think a key point is being missed here, provided that I correctly described the intended operation in post 6 above. The MTS would not be used as part of the article 700 distribution system. They would not be relying on the MTS as the means of transferring power in the event of a loss of normal utility power. The MTS would only come into play if it is locked into the alternate position while the normal utility is still available. That allows the temporary generator to become the article 700 power source. The MTS would remain in that position until the scheduled maintenance on the permanent generator was completed.
 
I could see the use of the MTS on the emergency side as going either way, compliant, or non-compliant with the inspector making the final call.

If the MTS is moved to the utility side, its a non-issue.
 
charlie b said:
I think a key point is being missed here, provided that I correctly described the intended operation in post 6 above. The MTS would not be used as part of the article 700 distribution system. They would not be relying on the MTS as the means of transferring power in the event of a loss of normal utility power. The MTS would only come into play if it is locked into the alternate position while the normal utility is still available. That allows the temporary generator to become the article 700 power source. The MTS would remain in that position until the scheduled maintenance on the permanent generator was completed.
Click to expand...

Oh, I hear ya, I just don't think that an MTS anywhere in the feeder circuit of the emergency source meets the letter of 700.5. I just don't think most AHJ's would be comfortable with this. For example, what if through a misunderstanding an ill-informed employee inadvertently locks it in the wrong position and nobody notices? The intent and spirit of of NEC 700 and NFPA 110 are such that they are trying to prevent leaving an emergency system in an in-operable state by accident as these types of things would have to be annunciated.
As I said, I think that if both switches were NFPA 110 ATS rated the portable genset would be fine. While the OP didn't mention the size, in the larger sizes the transfer switch cost difference between a rated ATS and an MTS may not be that great anyway as in the larger sizes they are basically an ATS anyway, less some controls. Certainly the space a labor would be similar.
 
Article 700 EPS

Article 700 EPS

Thank you again, gentlemen, for your thoughtful replies. It is our intent to be used as Charlie B said where the MTS would not really be considered as part of the 700-compliant EPS. We talked about and I like the idea of alarming when MTS is on alternate gen (or in disconnected position).
I keep thinking that we are trying to make the system better by providing a quick way to connect a temp gen should the permanent gen fail.
By the way, I understand there is a push to make something like this be required for 700 systems. Right now a system may be 700-compliant with only 1 gen. If that gen fails or out on service, the building will need to be evacuated.
Of course the redundant gen or redundant utility configurations make good sense, too. Money talks, though, and planning for the second or third level contingency failure does not make it past the planning stage very often.
I guess the next step is contacting an AHJ. Let you know what I discover.
All the best and thanks again,
Steve
 
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