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Generator Interlock

Old 09-09-2020, 10:13 AM
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Default Generator Interlock

I recently bought a portable generator in case a hurricane knocks out power. The plan is to run a small window unit A/C in the master bedroom, the fridge, and a couple of fans/lights. I've done some reading online and the most cost effective way to power the house is to have an interlock kit installed that allows the generator to feed the panel but requires the main breaker from the grid be turned off before you can turn on the breakers for the generator.

I had an electrician come out to give me a quote on installing an interlock kit and receptacle but he said it's not to code so he can't do it. He said the only way he can do it is to install a manual transfer switch and a separate panel that's the fed from the transfer switch, which is really pricey. He couldn't tell me where the code says it's not allowed and I haven't been able to find anything online that says it can't be setup this way, just that a interlock of some sort is required so the grid isn't back-fed. Has anyone in the state successfully had an electrician set it up this way or can point me to the code that days it's not appropriate?
Old 09-09-2020, 10:18 AM
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It's either DIY or call the county, ask if it's to code and do it the right way. If the county says code would allow this, call another electrician.
Old 09-09-2020, 11:18 AM
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I just used an external connector, like this:
Amazon Amazon
and ran to a dedicated outlet in the house. My generator has 2x 15A 110V and 1x 20A 220V. So I used three of the power inlet boxes like this:
  • One outdoor inlet connecting one of the generator's 110V 15A outlets to a dedicated outlet in the house.
  • Another outdoor inlet connecting the generator's other 110V 15A outlet to a second dedicated outlet in the house.
  • A third outdoor inlet connecting the generator's 220V 20A outlet to two 110V 10A outlets in the house.

Now I can connect all the generator outputs to the house using three cables and pull the full available current. I also used a couple of these single transfer switches on the well and pool pumps so our second generator can run either of those
Amazon Amazon
.
Old 09-09-2020, 11:26 AM
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I had the transfer switch put in by another electrician as the first said he could do the interlock like you mentioned, but when it came down to it it was not up to code. the transfer switch was pricey but its done right and when we move it's another selling point.
Old 09-09-2020, 11:27 AM
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Here you go: how it looks outside, and how it looks on the opposite side of that wall. I just drilled a hole through the exterior wall and ran Romex through 1/2" conduit from outside to inside, then added a dedicated outlet right alongside the normal power outlet. The grey one just goes through the wall to the generator connector outside and I can just plug in whatever I need right there. I have one in the bedroom for lights and a portable AC unit, two in the kitchen for fridge, microwave etc. and one on the utility room (for the beer fridge!!!!).



Old 09-09-2020, 02:12 PM
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I went with the EZ Generator Switch.Its a manuel system and very easy to install.Each box controls a single circuit.Vey flexible.
Old 09-09-2020, 02:24 PM
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I just shut off main breaker... then plug my 50amp gen plug .... into a weatherproof box Rated at 50 Amp Of course the key to the whole thing is shutting off the main breaker before doing anything.... everything is locked up in the shed.... nobody else can touch it at my house.... Im not gonna blow myself up Im just careful .... but god forbid if you forget. .
Old 09-09-2020, 03:01 PM
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Originally Posted by Bruce1505 View Post
I just shut off main breaker... then plug my 50amp gen plug .... into a weatherproof box Rated at 50 Amp Of course the key to the whole thing is shutting off the main breaker before doing anything.... everything is locked up in the shed.... nobody else can touch it at my house.... Im not gonna blow myself up Im just careful .... but god forbid if you forget. .
Lol, you definitely don't want to back feed the grid,right about that.If and when they find you the games will begin.
Old 09-09-2020, 06:40 PM
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The interlock is allowed. Code requires that the two circuits must be prevented from being energized at the same time. Tell him to go back and read the book instead of listening to someone tell him it’s not. Hint: do the panel manufacturers make a U L listed accessory that is not code compliant?
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Old 09-10-2020, 06:51 AM
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Pro Tran Reliance transfer switch with 6 circuits can be purchased for under $300. The install is straightforward and DIY with basic electrical knowledge. There are several videos online. You don't have to worry about interlock and backfeed, you just fire up the generator, plug it in, and flip the circuit switches you want to use. Mine is wired for 6 different zones in the house but I really only need it to run 2 refrigerators and power to the master bedroom. You can install a separate genset plug outside but I chose to install mine on the wall next to the main house breaker panel and snake the cord under the corner of the garage door.
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Old 09-10-2020, 07:49 AM
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Backfeeding works, but is dangerous as hell if not properly done. Run an extension cord?
Old 09-10-2020, 07:57 AM
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I had a separate subpanel installed with an interlocking main breaker and moved selected circuits to it. It's powered off the main panel normally. In the event of power failure, I just plug in the genset, start and then throw the interlocked breaker.
Freezers, fridges, modems, computers, selected TV's and lights are powered.
Old 09-10-2020, 08:05 AM
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I just had this done. Electrician put in a whole new main panel w the dual breakers and lock out and then the box w the plug from the the generator.
Was about 1400 including parts and took him about 4 hrs.
I used to back feed too but decided to go the safe route
Old 09-10-2020, 01:33 PM
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Several other local electricians all say the interlock kit is fine and that they install them all the time. Not sure why the first guy that came out said he couldn't do it. Maybe the company he works for has a policy not to install them and push the more expensive transfer switch?
Old 09-10-2020, 01:39 PM
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Originally Posted by RHartline View Post
The interlock is allowed. Code requires that the two circuits must be prevented from being energized at the same time. Tell him to go back and read the book instead of listening to someone tell him its not. Hint: do the panel manufacturers make a U L listed accessory that is not code compliant?
^^^^^^^
This
A listed interlock for your panel is legal in the Fla electrical code and a local yokel can not over ride that. They need to get an exception to the unified code past the Florida Building Commission
Old 09-10-2020, 10:11 PM
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Originally Posted by JP11283 View Post
Several other local electricians all say the interlock kit is fine and that they install them all the time. Not sure why the first guy that came out said he couldn't do it. Maybe the company he works for has a policy not to install them and push the more expensive transfer switch?
Can somebody educate me on the difference? I did some research and settled on a ProTran transfer switch. About $310 for everything and installed myself in under 2 hours. Seems much cheaper than an electrician and safer. I was accounting for the fact that I have a 6250 portable genset and only want to run a few circuits and burn minimal gas...Im guessing I could get 12 hours or more per 7.5 gallon tank at around 50% power. Im not trying to power the entire house. So what would be better about the interlock?
Old 09-11-2020, 08:16 AM
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Interlock works great for me. It's simple, inexpensive and safe. I can power any circuit(s) in my house within my generator's capacity.
Old 09-11-2020, 09:37 AM
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Originally Posted by K-dawg View Post
Interlock works great for me. It's simple, inexpensive and safe. I can power any circuit(s) in my house within my generator's capacity.
Exactly.

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Old 09-12-2020, 07:17 PM
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The advantage of the interlock is that you can power any circuit if you really want to. A transfer switch will limit you to the number of circuits in the transfer switch. The limitation as to which circuits when is the size of your generator. For example, you can turn everything else off and, if you have the right size generator, turn on your hot water heater. Heat up a tank of water, then turn it off and other things back on. The tank will hold the water hot for hours. The limitation is the generator size but you can switch loads around to whatever your need may be at the time.
Old 09-12-2020, 07:30 PM
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Originally Posted by RHartline View Post
The advantage of the interlock is that you can power any circuit if you really want to. A transfer switch will limit you to the number of circuits in the transfer switch. The limitation as to which circuits when is the size of your generator. For example, you can turn everything else off and, if you have the right size generator, turn on your hot water heater. Heat up a tank of water, then turn it off and other things back on. The tank will hold the water hot for hours. The limitation is the generator size but you can switch loads around to whatever your need may be at the time.
That's the other reason I wanted an interlock, besides the price.

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