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Old 11-21-2008, 06:44 PM   #1
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Manual transfer switch to power an existing sub-panel


Hello, I live in the New Orleans area and I wanted to install a manual transfer switch so I did not have to run extension cords every time a hurricane results in an interruption of the electricity supply.

I have a 15Kw diesel generator - a Lister HR2 with a Winpower 15Kw gen head.

My home was built in 1997. The main panel is 200amp and it is located on one side of the house, right next to the meter. There is a 200 amp subpanel in the attached garage (on the opposite side of the house as the main panel). The sub-panel is fed by a breaker in the main panel - actually there's two identical breakers, each 100amp, located side by side, with the switches tied together - a handle tie - that feeds the sub-panel.

That sub-panel supplies the side of the house that includes the kitchen. It supplies one three ton A/C unit, the dryer, and an electric water heater, but I would shut off the breakers to these appliances during the time period the generator would be in use (I'm only interested in having the convenience of using the light switches and outlets).

My idea is that I want to feed that entire sub-panel (only) with my manual transfer switch.

My question are:

1. What brand and model of manual transfer switch would you recommend for this application?
2. This should be a relatively simple task for an experienced and licensed electrician due to the fact that only one ciruit breaker is involved, right?

I will be hiring an electrician to do the work for me, but I wanted to get informed prior to contracting with anyone.

Sorry if this topic has been covered before! I tried to do a search but did not come up with anything.

Thank you for your input! Joe Stewart

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Old 11-22-2008, 03:18 AM   #2
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Manual transfer switch to power an existing sub-panel


That's a pretty massive generator. I assume it's not on wheels?

I think what I'd do is a mechanical backfeed interlock on the subpanel, with a backfed double pole 70 amp breaker on the subpanel.

The mechanical interlock prevents the breaker for the generator from being turned on at the same time as the main for the subpanel (Does the subpanel have a main?)


http://www.interlockkit.com/


Last edited by Gigs; 11-22-2008 at 03:22 AM.
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Old 11-22-2008, 03:50 AM   #3
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Manual transfer switch to power an existing sub-panel


Hi, thanks for the reply!

The sub panel does not have a main breaker, but there is knockout for one (located above all the smaller breaker switches, the knockout is separate and distinct from all the smaller breakers). I could have the electrician install a main breaker on the subpanel. The subpanel is a model E-52977 Eaton Powermaster (it also says "challenger" on the latch on the door).

I will study this interesting interlock device. Thanks for the link! Does that aluminum plate function as the "transfer switch"? - No complicated electrical devices necessary? I'm sure I'll discover this in the course of investigation, but if someone could give me the short answer: What other items, besides this aluminum plate interlock device, would be required in order to hook up my generator to the supanel? Seems too easy!

Another question: Can I plug in the genny at some point near the subpanel? I was under the impression that I had to mount the hardware near the meter and the main panel. I guess that question should be posed to the local municipal codes representative.

Concerning the genny, it weighs about 1500 lbs and is mounted on a steel skid. I put the skid on top of two (2) furniture dollies, so that I can roll it around the garage. Its probably too large of a generator for my application.

Thanks again. Joe Stewart
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Old 11-22-2008, 04:10 AM   #4
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Manual transfer switch to power an existing sub-panel


Well, I went to the Interlock kit website and it looks like I'm reamed! The measurements on my "Challenger" sub panel don't jive with the measurements they give for the interlock kit offered for Challenger panels (kit K-2010), although the overall configuration of my panel is the same as the photo of the K-2010 specs (main breaker cut out is located above the columns, but my "distance from columns" is 1-1/4 inch and my "left offset" appears to be zero!). So in order for me to use one of these devices, I would have to install a different model subpanel? What might be my best option? Thanks! J. Stewart
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Old 11-22-2008, 04:10 AM   #5
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Manual transfer switch to power an existing sub-panel


The aluminum plate just "enforces" a proper sequence of switching. It forces you to turn the subpanel main off before you can turn the generator breaker one. This prevents backfeeding upstream to your main panel or even worse upstream to the pole and shocking a lineman working to fix the power.

In theory, you don't even need this plate, you could just always remember to switch the main off before switching the generator breaker on. The code requires this interlock so that you don't forget, since it's a major safety issue if you do. As a bonus is prevents feeding line power into your generator too, which is also a good thing. Your generator wouldn't like being slammed into sync with the grid when the power came back.

As for hooking it up, if you want it to be portable, you need what's called an inlet. This is a box that looks like an outlet except it's male. You then use a male-female very heavy gauge extension cord. I can't seem to find inlets for 70 amps range. Those are usually hard wired. Here's a 50 amp inlet though.

http://www.electricgeneratorsdirect....B50/p1092.html

You would then make a super heavy duty extension cord with 6 gauge cable and the proper twist-lock ends.

So the inlet would be wired to the breaker by the electrician, and then when you want to use it, you use this super heavy duty extension cord to hook the generator to the inlet. Start the generator and then after it's stable, flip the breakers in the proper order enforced by the interlock.
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Old 11-22-2008, 04:15 AM   #6
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Manual transfer switch to power an existing sub-panel


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Originally Posted by joestewart View Post
So in order for me to use one of these devices, I would have to install a different model subpanel? What might be my best option? Thanks! J. Stewart
If the mechanical interlock won't work for you, something like this is also an option.

http://www.electricgeneratorsdirect....10C/p1133.html
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Old 11-22-2008, 07:27 PM   #7
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Manual transfer switch to power an existing sub-panel


Here is a link for a 100 Amp DPDT transfer switch.

A switch like this one should be able to handle anything your 15kW unit can muster.

Last edited by kbsparky; 11-22-2008 at 07:29 PM.
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Old 11-23-2008, 08:53 AM   #8
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Manual transfer switch to power an existing sub-panel


Heh, that single transfer switch costs more than the fully integrated generator power center I linked to.
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Old 11-23-2008, 01:01 PM   #9
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Manual transfer switch to power an existing sub-panel


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Originally Posted by Gigs View Post
Heh, that single transfer switch costs more than the fully integrated generator power center I linked to.
I think the Op is looking to keep his existing load center and put in a single transfer switch between the main panel and the sub panel he's working with. You might be better off with a different sub panel, one that uses the same breakers, but has a main that you can use an interlock kit with and just back feed a 70 amp breaker.
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Old 11-23-2008, 06:00 PM   #10
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Manual transfer switch to power an existing sub-panel


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Originally Posted by theatretch85 View Post
I think the Op is looking to keep his existing load center and put in a single transfer switch between the main panel and the sub panel he's working with. You might be better off with a different sub panel, one that uses the same breakers, but has a main that you can use an interlock kit with and just back feed a 70 amp breaker.
Thanks for the reply. That is what I think I will do. I will buy a new subpanel that has an interlock kit available. I'll have the electrician install the panel, the interlock kit, the backfeed breaker and the heavy duty lug to plug into. Thanks again! A huge help in figuring out an economical and prudent approach. Now I can talk to the electrical contractor with at least a somewhat solid knowledge base. J. Stewart
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Old 11-23-2009, 02:30 PM   #11
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Manual transfer switch to power an existing sub-panel


Saw your post. The interlockkit company makes custom kits but sometimes they already have one that fits but it is not listed or it is listed under another manufacture (most of the manufactures made panels under other names). Try calling.

Dan

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