In the thread about generator neutral bonding, it was mentioned that Transfer Switches must be listed (which means UL1008 in 2002). However, in reading the code (702.6), I only see an explicit listing requirement if there is supplementary overcurrent protection inside the transfer equipment (like those Gentran switches or a loadcenter type). I see most other references for transfer equipment to be "AHJ approved" and "approved for intended use". The word listed is tossed around a lot in the health care facilities section too, so perhaps in those applications listing is also a requirement.
Do I understand this correctly, or must all transfer switches be UL1008 approved regardless if they contain overcurrent protection? Is my "double pole safety switch" (which is listed as a switch and not transfer switch) being used per NEC 702 not allowed to be used as a transfer switch?
Mike's references seem to indicate that just approval and intended use is sufficient. There are a lot of people selling transfer equipment, it just isn't always listed as such per UL 1008. Some vendors tell you you're in violation if you're not installing a UL 1008 listed switch which I still don't believe is correct.
Peirre, yes I meant double throw!!! I realize that transfer equipment must be used. The question is would a simple double pole double throw center off switch be sufficient if the manufacturer said it was suitable for "transfer equipment", it has a sufficient amp rating, and is only listed as a switch (UL98)?
Mark Kent, WA
Re: Transfer Switch Listing#91479 01/18/0505:14 PM01/18/0505:14 PM
Gentlemen- & Ladies if your listening. If I'm inspecting a job that involves a job that specs out a "Transfer Switch" You can bet your bippie that I will be looking for somthing that is "Listed for the purpose" If I'm looking at a simple residential generator / DPDT switch I probably won't have a problem. Gentran makes some equipment that I find to be very well constructed and it has a UL label ta boot. I personally have a DPDT Wadsworth switch that I use with my generator and I find it very acceptable. It sure beats the scenario of the 'electrician" who known better. back feeding a dryer or range plug with a cord with two male caps on it and making sure he turns the main off in his panel.
Re: Transfer Switch Listing#91480 01/18/0505:17 PM01/18/0505:17 PM
I had someone ask me why they couldn't just break into the 1 or 2 120v circuits they wanted to back up, install a regular "2 way" snap switch on each and feed the other side with a "male" socket and extension cord from the generator. I didn't have an answer.
Re: Transfer Switch Listing#91481 01/18/0505:45 PM01/18/0505:45 PM
There is a new Exception to 702.6 which may provide an answer to the question of using such switches for transferring portable power supplies.
The exception allows portable generators without transfer equipment per 702.6 if 1. The conditions of maintenance and supervision ensure qualified persons maintain the system. 2. The normal power is physically isolated by a lockable disconnect, or by means of disconnecting the normal supply.
I think the exception re-enforces the requirement for approved transfer equipment unless the condition of the exception is applicable.
[This message has been edited by cpal (edited 01-18-2005).]
Re: Transfer Switch Listing#91482 01/18/0506:16 PM01/18/0506:16 PM
I think you ned to pay particulat attention to the specific part of the code that is being applied. The transfer switch is one area where the rules differ depending on whether the generator is used for optional, back-up, emergency, or health care purposes. Some of these applications require an automatic transfer switch. Others will allow for a manual switch-over. Should you use a manual switch, please keep in mind that you will be connecting/disconnecting under load, and size accordingly.
Re: Transfer Switch Listing#91484 01/18/0510:37 PM01/18/0510:37 PM
"The exception allows portable generators without transfer equipment per 702.6 if 1. The conditions of maintenance and supervision ensure qualified persons maintain the system. 2. The normal power is physically isolated by a lockable disconnect, or by means of disconnecting the normal supply.
I think the exception re-enforces the requirement for approved transfer equipment unless the condition of the exception is applicable."
The wording of this seems to be talking about procedures of switching off the service disconnect and attaching a generator. I was talking about a double throw switch that makes backfeeding the grid impossible and could be considered transfer equipment in the literal sense. Certainly as much so as one of those breaker interlock toggles.