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Panel interlock for generator.

Posted by bus_driver (My Page) on
Sat, Jul 13, 13 at 20:16

The question will be further down. Some discussions elsewhere focus on the fact that removing the panel cover defeats some of the interlocks so long as the cover is removed. True, but any system can be defeated. I have two panels to accommodate the 50-some circuits in my house. A transfer switch would be VERY difficult to install.
SquareD makes an interlock kit for my main panel.
The problem I will face is that the main breaker is off when the generator breaker is on-- the generator breaker is backfed by the generator. So nothing will indicate that the POCO has restored power. Seems that I once saw on a website a device that will alert that the power is restored. Big hassle to pull the meter to shout off power and make connections ahead of the main breaker for a light as an indicator-- not to mention that it would require overcurrent protection or be very illegal and dangerous.
So is there such an indicator?

Here is a link that might be useful: Too expensive-- but illustrates the concept.


Follow-Up Postings:

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RE: Panel interlock for generator.

It's quite common to place such a device with it's own overcurrent protection ahead of the main breaker. Yes, the main breaker is the service disconnect, this means you will have to get someone qualified to pull the meter. In many cases, this is the power company themselves (in some cases an electrician can pull the meter, but the power company is still required to come back and reseal it again.

Generally, the solution is to just look at other cues: do you neighbors have power? Are the street lights on? Some transformers have pilot lights (as do cable TV equipment that may be on poles around etc....).

You could also carefully just apply a meter to the incoming lugs.

An electrician could wire a small light bulb and inline fuse across the main lugs for you I suspect.


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RE: Panel interlock for generator.

You could try this

Here is a link that might be useful: Powerback Utility Return


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RE: Panel interlock for generator.

I'll second wirenut's suggestion.

I bought one myself a couple years ago, but unfortunately, my panel (with a built-in meter socket) had no place to get the sensor wrapped around. Just take a look first to see if you can wrap it before the main disconnect or the meter.


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RE: Panel interlock for generator.

That Reliance unit is the only one that my own search has found. Reviews posted online are mixed- as they are for most products. I do have space for the sensor wire.
Good idea about watching for lights at the neighbors but my remote location makes that impractical-- and you had no way to know that until now. It would be a good solution for many situations.
A single pole fuse or breaker off the service entrance conductors before the main breaker would be good-- but quite a hassle to arrange. The recent 36 hour outage would have been the best opportunity as I knew that the outage was due to a downed line on another part of my property and would know when the downed line was being reinstalled. So I may do that if it happens again- which may not ever occur. But it has happened twice in the last 10 years.
I have no other ideas at the moment but am still "contemplating".


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RE: Panel interlock for generator.

Having the meter pulled so you can put one on the mains isn't that unreasonable. In fact, if you have the generator ready to go, you don't even need to lose power to the house for the duration of waiting for the poco to come back and turn it on :)


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RE: Panel interlock for generator.

Pulling the meter is $250.00 whether I do it or the POCO does it. The exception is if an inspection follows and the inspector calls them. Too much hassle for me.
Many years ago I worked 4160 volts in a manhole. This is 120 volts to ground. So with no load on the panel, I will install the conductor with the panel live. In the lug with the 3/0 copper. I know it is 3/0 as I am the one who purchased and installed it. Not by any means suggesting that anyone else work with the equipment energized.
The conductor will be a short piece of #12 stranded with fully insulated 1/4" female spade connector on the loose end so that removing or changing any associated items later (if desired) will be easy.


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RE: Panel interlock for generator.

Some users of the Reliance Alert complain about the sound not being very loud. I suspect that the battery strength determines the sound level. And one would be likely to forget to check the battery regularly if outages are infrequent. A dead battery would render it useless. But the concept is admirable.


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RE: Panel interlock for generator.

Just put in the battery sometime after the power goes off. There is no real need for it when you have normal power.

It sure would be more versatile if it had a remote that could be kept nearby.


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RE: Panel interlock for generator.

One of my goals is to keep all conductors without premises overcurrent protection within the panel. For example. the service entrance conductors are.not premises protected until they get to the main breaker. For the conductor to be plugged into the pigtail mentioned above, one possibility is to use a pigtail lamp socket with a plug fuse for that protection and keep it inside the panel. Not the neatest of setups, but functional and as free of hazard as any other possibility that is on the horizon at the moment. The alarm device will be a bell or buzzer as the panel is in the basement and rather out of sight.


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RE: Panel interlock for generator.

What is the lowest-rated Edison fuse that is available?


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RE: Panel interlock for generator.

I suspect that some very low ratings have been made. I have a few at 10 amperes in my inventory.

Here is a link that might be useful: Fuses


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RE: Panel interlock for generator.

It is great to use what is sitting on the shelf, but the pigtail arrangement will be bulky. You might be considering a transformer to run the bell or buzzer.

You can probably get a pretty compact fuse holder for little money and use a sub-amp fuse along with an AC Sonalert. Some of the latter work at 240V and are really loud. You could probably hear it mounted inside the panel @ 100db(A) and the whole package might fit in a shot glass.


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RE: Panel interlock for generator.

In pondering this problem I've considered panel mounting a neon pilot lamp wired direct to the lugs. As far as fusing it- I would propose to wire the lamp with number 28 AWG or smaller to make it self-fused. By "smaller" I mean magnet wire inside spaghetti.

Otherwise the feed side of the fuse holder would be unfused and any conductor 16 AWG or so would be more of a hazard than unfused 28.

I haven't actually done this, just think it might work. I don't know why panels couldn't have this built in.

Here is a link that might be useful: Neon Pilot Lamp


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RE: Panel interlock for generator.

Because most panels aren't used as retrofit transfer switches.

My transfer switch has pilot lights for both the line and generator side.


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RE: Panel interlock for generator.

Agreed that a transformer and a 24 volt signaling device would have some advantages. 24 volt devices are plentiful. But the transformer would be energized all the time. A 120 volt output affords greater versatility in that a transformer could be mounted outside the panel if desired and downstream of the mandatory switch to be used to silence the device at times of normal power supply. I'm still arguing with myself about some of these final details and trying to think of all the possible drawbacks to any of the possible arrangements.


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RE: Panel interlock for generator.

BD, I think you may have misunderstood my post. I proposed using a 240 or 120V son alert, no transformer. They can be had loud enough to cause hearing damage up close for any period. (I don't know the cost.) The whole package can go inside the panel. An inline fuse or circuit breaker could double as the switch.


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RE: Panel interlock for generator.

And how would one access a switch placed inside the panel? Any circuit breakers are downstream of the main. So how would that work?


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RE: Panel interlock for generator.

Put it in the same place you were going to put the pigtail socket. It will be a lot smaller. I'd drill a hole in the interior cover for a surface-mounted fuse holder or circuit breaker.


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