DIY interlock for generator

frenchelectrican

Those are fine with non GFCI / AFCI's circuits but I have done few of them before and I am not too crazy with Reliance transfer switch espcally with goofy OCPD button that one reason why I genrally stay away from them and use the correct subpanel with interlock far less headache and still be on the code without issue.

The other reason why I genrally stay away from Reliance is they can really fill the breaker panel pretty good and make a mess in the main panel.

Merci,
Marc

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The answer will be based on NEC ( National Electrical code ) or CEC ( Cananda Electrical code ) or ECF ( Electrique Code France )

tmulkey

This is my Idea that I had the other day. I am not sure it if meets code or not. I have a couple of spare 50 amp breakers so I don't have to pay for that, and all of the other breakers would move out of my existing box. I did inquire with the local electrical inspector, and he say you may make a 120 Volt only panel by tying busses together but the panel had to be labeled "120 Volts ONLY" and the tie has to be the right gauge wire to handle potential load. He suggested bringing in the entrance from the main panel on a breaker and then tying the bus together on the main lugs for the sub panel.

i haven't ran the back feeding part for a generator by him yet though.

The Ideal here is that the Double pole breaker for the Gen. can only be engaged when the main breaker is disconnected. One pole brings the Gen power in and the other pole energizes the other bus. This allows me to still draw my circuits off of both sides of the transformer for a balanced load when under normal power but when the generator is engaged the whole panel goes 120 Volts from the Gen.

I have read that is is legal to run 120 off of a single pole in a double pole breaker, but i haven't found the actual NEC code for it.

The panel is $39, The Interlock is $25 (From Square D) The breakers I already have from when I they replaced my electric service 6 years ago (Insurance Company paid for it, because of storm damage and they wanted all new from the entrance to the panel and all breakers) They left me all the old stuff so I have it all.

This diagram is only showing the hot wires at this point, not the neural or ground. i will isolate the ground and neutral buss and run two separate wires from the main. The Gen will also be grounded to the same ground rod as the main panel outside.

Would appreciate feedback or comments.

Auger01

Consider this instead. It was designed to go into a knockout:

http://www.homedepot.com/buy/relianc...-kit-pk30.html

LVDIY

I was not aware of this, thanks! None of the circuits I'm planning on running on the generator are GFCI, so I guess I'm in the clear.

However, this is making me rethink the idea of installing an interlock kit instead of the transfer switch.

I only have 4 circuits I want to power in an emergency, so while the flexibility of being able to power any circuit is nice, it's not a big deal to me. The one thing that made me decide on a transfer switch was really the ability to balance the load for the circuits I choose in order for my generator to run more efficiently. Some people really stress this as very important. How big of a deal is this?

The difference in price would be about $150 for me between the interlock kit and getting one of those pre wired reliance panels.

puttster

Thanks Auger, yours looks better and is available locally.
So my DIY will cost $50 for the interlock, $25 for the socket and $10 for a 30 amp 2pole breaker. Looks like the 25 foot cable at $100! is actually the big expense.

This thread has been very helpful!

puttster

AandPDan

It can be a big deal. You really should be balancing the load as best possible. By default, 240 volt loads are balanced. You can always move the other circuits that you want to run up or down a slot in the breaker panel, so that you balance out your usual loads.

It only gives you the flexibility to run any circuit, you don't have to. You are still limited in what you can run as well.

Good luck with your project.

puttster

I was thinking a transfer switch would lock you in to one assumed load. If the kids moved in to the extra bedroom and your wife wanted a window AC unit in hers, and moved your belongings out to the garage, you'd be stuck

puttster

One last question. I'll have a 10 ga cable from the generator to the receptacle on the beaker panel box. What is the minimum gauge needed from the receptacle to the breakers (about 18")? Generator is a 4000 watt peak and breakers will be dual of 15 amps each.

tylernt

By receptacle, you mean an inlet with male prongs, right?

What size is your backfeed breaker? If 30A, use 10ga. If 20A, use 12ga. If 15A, use 14ga. The size of the generator breakers is unimportant, go by backfeed breaker size.

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puttster

Yes, male prongs. Not sure what is the difference in the backfeed and the generator breaker. I was talking about the one on the manual interlock, looks like two breakers together, 15+15 = 30A.

putts

rrolleston

A double pole breaker that is 15 amps is not 15 + 15 = 30. A 15 amp double pole breaker is just 15 amps.

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puttster

Ahh, a walk out to the box shows I was wrong. It will be a 30A breaker, so 10 ga wire. Thanks all.

khfactor

Siemens Load Center P4260B1225CU is my Load Center here. I upgraded (rather lateral'ed) my Main Load Center from SIEMENS G4040MB1200.

Bought the whole new Load Center Assembly and just swapped the "GUT" out. In the process, I ended up going from 200A to 225A. Surprisingly I found the P4260B1225CU Load Center from Amazon.com for $169 including shipping.

I had to DREMEL cut the piece of metal (on the Dead Cover) between the Main Breaker and the Generator Breaker, otherwise the interlock "feature" of the KIT would not work. How many of you all had to do what I did, I am wondering.... See pics below.

Note the small sticker on the kit that said, "UL LISTED". I guess this is why Siemens can demand and fetch $50 for a lousy small piece of metal.... Tse.. tse..

rrolleston

How did you upgrade to 225 amp without upgrading the service cable?

__________________
Please ask me about my special discount for people that shut up and stay out of my way! With Electricity there is the right way to do it and the dead way. Just because it works does not make it safe.

LVDIY

You are right that an interlock is more flexible in picking what circuits you want to use, but I am only looking to power essential circuits like the fridge, furnace, sump pump and a few outlets. My generator is small, so I can't power much more than that anyway. I finally decided on a reliance transfer switch and just got done installing it. It works great, and even though it only gives me 6 circuits, that's really all I need.

It was easy to install, but I do see now what someone else said about the wires filling up your main panel...