Transfer switch advice

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Old 02-06-13, 06:52 PM
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Transfer switch advice

Looking to purchase a transfer switch and install myself. I do NOT have a generator. I'm only wiring 120v circuits.

Considering one of these well received and reasonably priced switches:Looking for a little advice:
  1. Both say "30 amps" but support a 7,500 watt generator. 7,500w / 120v = 62.5 amp. What am I doing wrong?
  2. What gauge wire is needed between the transfer switch and outside generator plug? Is 10g sufficient?
  3. If I were to plug in a 10,000 watt generator, would it be the end of the world? A friend would let me borrow his 10,000w generator and I'd really like to not have to spend any more money on a heavier transfer switch. I'd rather cycle appliances to keep the load down. The generator would be operated only under my supervision. Good idea? Bad idea?
Thanks for any replies.

(In case anyone's wondering, I'm only powering the refrigerator, boiler, microwave, a slew of CFL lights, and a TV/DVD or two).
 

Last edited by k19_1234; 02-06-13 at 06:55 PM. Reason: Additional information
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Old 02-06-13, 07:58 PM
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Looking for a little advice:
A good place to start on thois topic is by reading Congratulations! You have a Generator.

1. Both say "30 amps" but support a 7,500 watt generator. 7,500w / 120v = 62.5 amp. What am I doing wrong?
Using 120V. Your house has single-phase 240V service. 7500W/240V=31.25A.

2. What gauge wire is needed between the transfer switch and outside generator plug? Is 10g sufficient?
#10 AWG is sufficient for any circuit protected at 30A.

3. If I were to plug in a 10,000 watt generator, would it be the end of the world? A friend would let me borrow his 10,000w generator and I'd really like to not have to spend any more money on a heavier transfer switch. I'd rather cycle appliances to keep the load down. The generator would be operated only under my supervision. Good idea? Bad idea?
If you can limit the output from the generator to 30A or less, it might be safe.

I'm only wiring 120v circuits.
How are you planning to balance the loads?
 
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Old 02-07-13, 08:46 AM
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How are you planning to balance the loads?
If I get the 6 circuit switch:

A-15 - Boiler
B-15 - Upstairs circuit
C-20 - Microwave

D-20 - Fridge
E-15 - TV/DVD circuit
F-15 - CFL Lighting circuit

Does this make sense?
 
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Old 02-07-13, 08:57 AM
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What I meant was "How are you planning to balance the loads across two 120V legs that share a neutral?" Are you actually planning to feed 240/120V into your transfer panel?

Tech Note: We call small panels that are connected to both a utility feed and an emergency feed, and only have a few circuits in them, "transfer panels." We use "transfer switch" to refer to a switch that is connected to both a utility feed and an emergency feed, and is used to transfer the incoming feed for the entire service. It's just a convention, for clarity.
 
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Old 02-07-13, 06:45 PM
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What I meant was "How are you planning to balance the loads across two 120V legs that share a neutral?" Are you actually planning to feed 240/120V into your transfer panel?
Please forgive my ignorance as I'm still learning. The setup comes with a 30 Amp Outdoor Power Inlet Box. I'd run a 10/3 NM-B Wire from the Outdoor Power Inlet Box to the transfer panel. One hot goes to the right side (ABC), the other hot to the left side (DEF). Is there a better way to set this up?
 
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Old 02-07-13, 07:12 PM
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Is there a better way to set this up?

No your fine. Nash was only commenting because you stated 120v only. Actually you are supplying 240/120. Basically 120 to both sides of the panel.

The gen should be 7500 running max watts with those switches. Surge watts higher then this is ok since its short bursts.
 
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Old 02-08-13, 03:33 AM
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I have the Reliance 6 switch panel. I believe what Nashkat1 meant by balancing your loads is trying to keep the wattage as even as possible on each leg.

Your loads are very similar to mine, between 25 to 30 amps total. You may want to switch the microwave to E and the tv/dvr to C. That should better even out the max potential amp draw on each leg.

Two reasons for this, Your outlet on the generator if rated for 30 amps will have a 14 or 15 amp breaker for each leg so you don't want all your heavier loads on one side or you'll be tripping the breaker.

The generator also runs more efficiently with the loads balanced.

I get by with a 3600 watt generator for power outages and it uses about 4 gallons of gas every 12 hours. If you have frequent outages or long duration outages, the 10K watt will kill you for gas expense. It's more than you need.

The switch panel is nice though. No need to have extension cords strung all over the house
 
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Old 02-08-13, 12:49 PM
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Don't rule out an interlock for your main panel. It can be cheaper, and offer greater flexibility in what loads you run.

Another advantage: most transfer panels, such as the models you've shown, don't support AFCI or GFCI breaker equipped circuits.

Check with the panel manufacturer for a kit.
 
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Old 02-08-13, 05:57 PM
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No your fine. Nash was only commenting because you stated 120v only. Actually you are supplying 240/120. Basically 120 to both sides of the panel.
Ahhh ok, that makes sense. Thanks.

Another advantage: most transfer panels, such as the models you've shown, don't support AFCI or GFCI breaker equipped circuits.
For my understanding, since the switch bypasses the breaker, I would obviously lose the AFCI/ GFCI functionality, correct? A lot of the circuits in my home have GFCI receptacles, so that protection would still be in play, correct?

I'll definitely look into the interlock system. Thanks.
 
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Old 02-08-13, 06:26 PM
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For my understanding, since the switch bypasses the breaker, I would obviously lose the AFCI/ GFCI functionality, correct? A lot of the circuits in my home have GFCI receptacles, so that protection would still be in play, correct?
Correct. GFCI receptacles will still be protected. It is how these panels bypass the breakers that causes the problem.
 
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Old 02-08-13, 09:13 PM
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Definitely a question for the pros: Are these interlock systems frowned upon by the electrical community? Ingenious idea but does have of hint of being a hack job. The assurance to cut power to the main feed seems to rest on a separate system (ie a sliding piece of metal attached to your main panel).

The only con is I have is having to free up slots #2 and #4 in my panel but I love the idea otherwise.

I'll ask my town's inspector what he thinks but he probably won't care as long as I pay for a permit.
 
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Old 02-09-13, 11:06 AM
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Definitely a question for the pros: Are these interlock systems frowned upon by the electrical community? Ingenious idea but does have of hint of being a hack job. The assurance to cut power to the main feed seems to rest on a separate system (ie a sliding piece of metal attached to your main panel).

The only con is I have is having to free up slots #2 and #4 in my panel but I love the idea otherwise.

I'll ask my town's inspector what he thinks but he probably won't care as long as I pay for a permit.
Some jurisdictions may approve the installation of a panel interlock if the interlock is made for that panel by the company that makes the panel - basically a factory assembly. In general, though, they are not permitted because one critical function of a transfer switch - preventing the backflow of your emergency power to the damaged utility system - can be defeated by simply removing the cover from the panel.

All codes is local, so that's definitely where you need to go for an answer.

Tech Note: Supplying circuits that require AFCI protection for the entire circuit without providing that protection would violate the adopted code in most jurisdictions. That protection could be supplied by mounting an AFCI receptacle immediately adjacent to the emergency panel and running the wiring through that first. Of course, there's the cost of the receptacles and boxes, plus the extra wiring, to take into account.
 
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Old 02-09-13, 01:13 PM
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In general, though, they are not permitted because one critical function of a transfer switch - preventing the backflow of your emergency power to the damaged utility system - can be defeated by simply removing the cover from the panel.
Not all interlocks can be defeated by removing the panel cover. On Siemens and Murray panels, for example, the interlock is snap locked onto the circuit breakers.

Check with your AHJ.
 
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Old 02-09-13, 09:18 PM
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On Siemens and Murray panels, for example, the interlock is snap locked onto the circuit breakers.
Thank you for the specific examples of an "interlock... made for that panel by the company that makes the panel," which might be permittable. And now two of us have said "Check with your AHJ."

K19, If the interlock you're considering is mounted to the panel deadfront, and goes on and comes off with that, I wouldn't bother asking, regardless of who made it.
 
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Old 02-13-13, 01:08 PM
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Town inspector said interlock kids have been adopted.

Nash, wouldn't installing an interlock kit underneath the panel cover require modification of the panel cover itself?

I was looking for something like this, which I assume sits directly on top of the panel cover. My box is a Square D, blue version (again, sorry my electrical terminology isn't the best!). My setup is similar to this.
 
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Old 02-14-13, 12:11 PM
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Town inspector said interlock kids have been adopted.
He may have meant that interlock kits that meet certain criteria have been approved.

Nash, wouldn't installing an interlock kit underneath the panel cover require modification of the panel cover itself?
Not necessarily. the deadfront cover could just mount over it.

I was looking for something like this, which I assume sits directly on top of the panel cover. My box is a Square D, blue version (again, sorry my electrical terminology isn't the best!). My setup is similar to this.
The one you linked to appears to mount to the panel enclosure, independently, behind the cover. If your Square D panel is a QO load center, you may have found the interlock kit you need. The sticker inside the door of your panel should tell you what model you have.

Originally Posted by Nashkat1
an "interlock... made for that panel by the company that makes the panel,"... might be permittable.
If this isn't a match, Square D might make one that is.

Originally Posted by Nashkat1
, If the interlock you're considering is mounted to the panel deadfront, and goes on and comes off with that...
It appears that it doesn't. In fact, it appears to be a device designed to make both double feeding and defeating the device difficult.
 
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Old 02-15-13, 12:49 PM
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Correction, I have a Square D HomeLine box. I just purchased this (and here) particular model kit. My setup will ultimately look like this when finished.

He may have meant that interlock kits that meet certain criteria have been approved.
Correct. He indicated that I couldn't fashion my own piece of metal (not that I was going to).

What I'm still having a hard time comprehending is how would an interlock kit work if it were mounted underneath the deadfront cover? Isn't the purpose of a deadfront cover to separate the user from the circuitry? How would the sliding interlock metal piece or handle from the piece get exposed through the cover? I have a feeling I might be using the term "interlock kit" too loosely...
 
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Old 02-18-13, 08:46 AM
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The sliding metal piece touches the metal panel cover and the plastic breaker handles. It does not touch any live terminals or wires.
 
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Old 02-18-13, 09:15 AM
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For those as blind as me here is what it looks like but I still don't see how taking the cover off wouldn't defeat it..

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Old 02-18-13, 07:21 PM
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What I'm still having a hard time comprehending is how would an interlock kit work if it were mounted underneath the deadfront cover?
Why not? If a frame for the slider was mounted directly to the enclosure, and the slider rode in that, and then the deadfront covered all of that along with everything else, then the interlock should remain in place and be operable whether the deadfront was in place or not. The only other option is to mount it to the deadfront, which would defeat its ability to prevent backfeeding to the utility every time the deadfront was removed.

Isn't the purpose of a deadfront cover to separate the user from the circuitry?
It does that. It also, as a primary purpose, contains any arcs or other events which could endanger the property and its occupants, confining them within the fire-resistant enclosure.

How would the sliding interlock metal piece or handle from the piece get exposed through the cover?
Through an opening made for it.
 
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Old 02-18-13, 07:31 PM
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I still don't see how taking the cover off wouldn't defeat it.
See post #20. I think the leg for supporting the slider frame off the back of the enclosure is clearer in the earlier image from HD - Square D by Schneider Electric QO Cover Generator and QOM2 Frame Size Main Breaker Interlock Kit - than in the later image from Big Blue - Square D Load Center Panel Cover. That's how this is looking to me, at any rate.
 
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Old 03-18-13, 02:45 PM
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Interlock Kits

For those of you who have Murray, ITE, or Siemens breaker panels, here are a series of sliding interlock kits that work. To my certain knowledge, the first two (ECSBPK01 and '02) meet all four NEC criteria for an approved interlock mechanism:

1) Both breakers must NEVER be ON simultaneously,
2) Both breakers must be able to be OFF simultaneously,
3) Both breakers must be affixed to the panel (beyond normal stab-mounting);
4) This protection MUST remain in place even when the dead-front cover is removed.

The Siemens kits and Amazon prices (as of 18 MAR 13) are:
ECSBPK01 - Double-pole stab-mount breakers across from each other, ~$22.34
ECSBPK02 - Double-pole stab-mount breakers side-by-side mount, ~$21.22
ECSBPK03 - Double-pole stab-mount breaker, left-side with top-mount 200A Main, ~$49.95
ECCBPK04 - Double-pole stab-mount breaker, left-side with top-mount 100A Main, ~$55.50
ECSBPK05 - Double-pole stab-mount breaker, right-side with top-mount 200A Main, ~$17.84
ECSBPK06 - Double-pole stab-mount breaker, left-side with top-mount QN or MD-T type 100A Main, ~$85.51

Hope this helps,

Steve


All are available from Amazon.com or special orderable from Lowe's.
 

Last edited by Circuit Breaker; 03-18-13 at 02:48 PM. Reason: typo
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Old 03-18-13, 07:33 PM
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I still don't see how taking the cover off wouldn't defeat it.
See post #20. I think the leg for supporting the slider frame off the back of the enclosure is clearer in the earlier image from HD - Square D by Schneider Electric QO Cover Generator and QOM2 Frame Size Main Breaker Interlock Kit - than in the later image from Big Blue - Square D Load Center Panel Cover. That's how this is looking to me, at any rate.
I'm like ray, I don't see how removing the cover and door wouldn't defeat the interlock. I am pretty sure the Square D interlock kit just attaches to the front of the cover (or dead front) and not under the cover. Any instructions available?

Has anyone on the board actually installed the Square D interlock kit?
 
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