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Generator interlocks
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Posted by joe_cnc (My Page) on Thu, Jul 2, 09 at 1:52
| First off I am on a fixed income and don't have alot of money to spend but I do want the job done right and up to code.Due to semi frequent power outages I am planning on buying a cheap Chicago electric 3500/3000 gas genset for $318 out the door.I only plan to run the fridge,gas furnace and some lights off it.I would like not to have extension cords all over which is why I would like to install a genset interlock on my sqaure D homeline 100 amp service panel.I saw them for around $150.The problem is there is no room for the genset backfeed breaker.I have heard of piggy back breakers but am not sure if they have them for my panel or if it would over load the panel.I already have 2 double pole 30 amp breakers in the panel.1 for a halogen cook top and the other for a 220 5hp 60 gal compressor.Is it possible for me to run a sub panel off the main panel so I could fit the genset backfeed breaker in the main panel for the interlock? If not could I at least wire a 15 amp furnace transfer switch off the main panel to feed the furnace.The interlock I would have a electrician wire.The furnace tranfer switch I would probably wire myself if not to difficult.Any ideas and advice would be very greatly appreciated. |
Follow-Up Postings:
RE: Generator interlocks
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| I don't know which Square D panel you have, but chances are you can put Tandem or Quads (single or two pole breakers) in to free up some space for your feed. Yes, your other option to out of room in the main panel is to install a sub panel. The breaker in your panel will not be a BACKFEED. BACKFEED is what you are trying to prevent. It's just the feed to the switched circuits when the power is on. |
RE: Generator interlocks
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| Here is a small transfer switch made just for furnace use. Looks like it would take minutes to install. (Not connected with the seller, but have used this brand before) |
Here is a link that might be useful: Furnace switch
RE: Generator interlocks
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| I think the OP is planning on using a mechanical interlock made by Interlockit. These do require a backfed 2 pole breaker installed in a specific position. Yes, you can install a sub-panel, but installing tandem breakers would be less trouble. Sq D does not manufacture very many combinations, but, you can get a 2 pole 30 that has either 2 single pole 15 or 2 single pole 20 amp breaker that will take up 2 full size spaces. Part #s are HOMT151530 or HOMT202030. This is based on an old catalog, so maybe they have expanded their line. |
RE: Generator interlocks
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| Oh, yech. It's Yes, then move some of the other breakers to tandems/quads if you can then put in a new breaker for the backfeed. Note that you need to install the Back-Fed breaker retraining clip to be legal. It's a small priced item, but I suspect your home center doesn't carry it, you'll have to go to a real electrical distributor. Looks like the breaker needs to be up at the top of the panel anyhow or else the kludge won't reach. |
RE: Generator interlocks
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| Thanks Ron,Wayne and Tom I appreciate your advice greatly.I have another question.The genset I plan on buying also has a 120/240 connector lock recepticle.If I am able to get the correct tandem breakers to fit the panel allowing room for the genset breaker on the interlock is it practicle (code wise) To re-wire a pre-existing 120 constant live recepticle in my garage with a twist lock connector for the generator if it is switched or has a disconnect?The 120 feed from the house to the garage is 10ft using 12ga.So the genset would be lock connected and the recepticle would be lock connected.My garage has two feeds a standard 120 and 220.The 220 line is a dedicated cicuit for my 5hp 60 gal air compressor which is dis-connected when not in use at the garage with a fused knive shut off and at the main indoor service panel with its own double pole 30 amp breaker.Is it possible to run a lock connector off the fused knive disconnect box for the 220 as a genset feed which powers my air compressor?I don't know if that would meet NEC but it should since I have the fused knive switch shut off right there.So would that be possible as a feed from my garage to the indoor panel for the genset?What do you think would be best code wise the 120 or 220 set up?Thanks again for the advice you have all been very helpfull. |
RE: Generator interlocks
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| Ron your correct my panel has a 100 amp double pole main breaker just above the left bank of regular breakers.I would locate the genset breaker just below it.I havn't been able to find the correct genset interlock for my panel but did run across a company that said they could custum build one with the correct dimensions and a picture.I don't think the genset breaker strap should be a problem I could make one if necasary.As far as the tandem breakers go I havn't been able to source them yet.I hope their not to hard to find.Anyway I hope maybe you or someone else can help me on my second post concerning a feed from my garage to the main service panel.I think it is possible to do but I am not sure how to do it correctly and meet NEC code.I would like to do as much of the simple wiring as possible and just have the electrician check it and ok it before he does his hook ups.As I said I'm on a fixed income but would rather wait and save the money to do the job safely and NEC compliant than to use a widow maker with out a main interlock.I believe this job can be done cost effectively and correctly.I just need some advice on the best way to go.Thanks Ron and I hope to get more post because I am aware that even the best of us can get tunnel vision sometimes and I'm trying to avoid that on my own behalf.Thanks again everyone I appreciate anything you may be able to contribute to these posts of myne. |
RE: Generator interlocks
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| Tandems and Quads are available for your panel. I'd be surprised if the home center didn't have at least some 15 or 20A ones. Lowes has them for $8 on their web page http://www.lowes.com/lowes/lkn?action=productDetail&productId=8991-296-HOMT2020CP&lpage=none You can backfeed a breaker but it needs to be mechanically fastened down (normally the Homeline breakers just snap into the bus). SquareD makes a device to do this. Of course and then you need the interlock you were looking at. The clip is here if you can't find it anywhere else |
Here is a link that might be useful: Backfeed clip.
RE: Generator interlocks
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| Thanks Ron I think thats the way to go.I'll run a twist lock off the 220 fused knife disconnect.Have the electrician move the 30 amp double pole breaker under the 100 amp main and strap it.Then have him run a couple tandem breakers so the 30 amp double has a home.Then all he has to do is drill a few holes and install the interlock on the face plate.Sounds to good to be true!Unless I missed something.If I did please let me know rather know now than have sparkie come out and say that won't work you have to do it like this and then the bill jumps up and.........you get my drift.Thanks again Ron I really appreciate your input! |
RE: Generator interlocks
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| Sounds good. As long as you have the interlock (and the clip holding the breaker) and you write your self a note (I'd put a sticker on the breakers) as to which breakers you want to turn off so that you don't overload the breaker. |
RE: Generator interlocks
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| Thanks again Ron your a very helpfull and knowledgable person.I plan on taking every precaution to not overload the genset or any circuits I run.I have worked around heavy machinary all my life and know its allways better to be safe than sorry.I have seen to many get seriously hurt on the job.To be honest I'd like to be able and erase some the injuries Ive seen people suffer exept if I did that what would I have learned. Thanks again I appreciate all your advice. |
RE: Generator interlocks
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| It'll cost some more money, but I have the same Square D interlock but have an outside inlet wired up. It was convenient to plug in the generator during the last outage. There isn't easy access to the panel at my place for a temporary wire, plus you want the generator a good distance from windows, doors, etc, for the CO. |
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