# Flush-mounted Power Inlet with Interlock



## Power User (Feb 28, 2021)

Hi all, I'm having an interlock installed soon and looking for a power inlet that is flush mounted to drywall. Our panel is flush mounted indoors and it would be nice to match. I've considered going with a manual transfer switch to accomplish this but I'd rather not be forced to select circuits ahead of time.

It will currently be used with a Honda EU2200i (modified for tri-fuel) or inverter with LiFePO4 or car battery. I'm planning on a 30A inlet with an adapter for the 15A sources. Not for powering the whole house of course, just the critical loads.

Is an outdoor power inlet up to code used indoors?


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## Old man here (Nov 5, 2020)

Are you only needing one for 125V?
Amazon.com: 30Amp RV Power Inlet Box Nema L5-30P 30A Camper RV Power Inlet, 30A 125V Marine Shore Twist Lock Power Inlet for Camper RV, with Cover Cap White: Home Improvement


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## Power User (Feb 28, 2021)

Old man here said:


> Are you only needing one for 125V?
> Amazon.com: 30Amp RV Power Inlet Box Nema L5-30P 30A Camper RV Power Inlet, 30A 125V Marine Shore Twist Lock Power Inlet for Camper RV, with Cover Cap White: Home Improvement


Yes, I've seen that one but I didn't think it could be installed into drywall without a box. Can that be mounted into drywall without any other support?


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## Old man here (Nov 5, 2020)

Power User said:


> Yes, I've seen that one but I didn't think it could be installed into drywall without a box. Can that be mounted into drywall without any other support?


Sorry, can't answer that. Maybe you should have your electrician find what you need.


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## Power User (Feb 28, 2021)

Old man here said:


> Sorry, can't answer that. Maybe you should have your electrician find what you need.


I will run everything by him of course, just trying to get prepared before asking him to review.


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## exmar (Jun 29, 2015)

Curious, why do you want a power inlet for a generator which, by design, is weather proof and designed to be mounted outdoors, inside? The generator is going to be OUTSIDE? Even if it's in a finished garage, it should be outside. Running the power cord through a window? Saving the cost of penetrating a exterior wall? Also, those twist lock connectors require a bit of force to connect and disconnect so it needs to be securely mounted, not just on drywall.


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## Power User (Feb 28, 2021)

exmar said:


> Curious, why do you want a power inlet for a generator which, by design, is weather proof and designed to be mounted outdoors, inside? The generator is going to be OUTSIDE? Even if it's in a finished garage, it should be outside.


The generator runs outside in front of garage. The electric service panel is inside the garage. The inlet could be on the outside but I will use it with an inverter/battery setup also so I'd rather not have it outside. It would be just on the other side of the panel anyway if it was put on the outside wall.



exmar said:


> Running the power cord through a window? Saving the cost of penetrating a exterior wall?


The generator power cord runs inside under the garage door or in a small opening at the bottom of the garage door side.



exmar said:


> Also, those twist lock connectors require a bit of force to connect and disconnect so it needs to be securely mounted, not just on drywall.


Sorry, I didn't mean to indicate it would mount only on drywall. Ideally it would mount like a flush manual transfer switch. Like this which is something I'm considering.


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## exmar (Jun 29, 2015)

All is good. The transfer switch you've selected is a good choice as you only have 120V and would have to isolate the critical circuits you want to power. An inverter fed by a car battery (unless the car was outside idling) won't last very long compared to the 1800W steady state the Honda will provide. 1800W isn't a lot for critical loads in a house, particularly if there's a frig involved.


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## Power User (Feb 28, 2021)

exmar said:


> All is good. The transfer switch you've selected is a good choice as you only have 120V and would have to isolate the critical circuits you want to power.


It would be a nice clean install, but I don't really want the transfer switch. I want the flush-mounted power inlet to use with an interlock and circuit breaker.



exmar said:


> An inverter fed by a car battery (unless the car was outside idling) won't last very long compared to the 1800W steady state the Honda will provide.


The car would be idling in this scenario. It's only for use if generator and inverter/LiFePO4 are not available. Using car as generator works really nice with a hybrid vehicle, especially the newer Toyota Highlander with built-in 1500W inverter tied to main battery, not 12v.



exmar said:


> 1800W isn't a lot for critical loads in a house, particularly if there's a frig involved.


Our fridge is easy to handle with the generator or inverter/battery. It has a startup ~1100w and then only uses ~140w when intermittently running.


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## exmar (Jun 29, 2015)

The interlock and 2P breaker is the cheapest and easiest way to go. As you only have 120V you'll have to be "creative" in wiring the plug to 1.) Get the 120V to both sides of your load center or 2.) Just have the 120V on one side and swap critical loads around so they're on that side. I got "creative" as I have one generator that is only 120V and just made a much simpler install. Also, down the road you might want to get a bigger generator with 120/240V, which actually happened to me as I was at Lowe's and they were selling some at 55% off.


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## Power User (Feb 28, 2021)

exmar said:


> The interlock and 2P breaker is the cheapest and easiest way to go. As you only have 120V you'll have to be "creative" in wiring the plug to 1.) Get the 120V to both sides of your load center or 2.) Just have the 120V on one side and swap critical loads around so they're on that side. I got "creative" as I have one generator that is only 120V and just made a much simpler install.


As luck would have it, the circuits I really need are on the right bus bar. There are 2 on the left that I'd like to add if possible, though the jury is still out on being able to start one of the furnaces. And the microwave is optional.










This is still new to me, so with the interlock 2P breaker it won't span both bus bars for 120v each?



exmar said:


> Also, down the road you might want to get a bigger generator with 120/240V, which actually happened to me as I was at Lowe's and they were selling some at 55% off.


In the "2 is 1, 1 is none" idea, I'm more likely to add a companion EU2200i than buy a larger generator.


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## exmar (Jun 29, 2015)

Each side of the 2P breaker will feed one side. That would normally be two 120V feeds or 240V between them. You only have 120V, not 120/240V. What I did is take two 120V plugs, wired into a 120/240V plug to feed both sides. It's simple to accomplish, but not to describe in writing, talk to an electrician. Make sure you tell them that your expansion plans are for an additional 120V unit which would work well with the "two into one" described above. You do realize that adding an additional 120V unit will not provide 240V for AC's, etc. There are other ways to accomplish this, e.g. just jumper the generator side of the 2P breaker together, but, again, talk to an electrician.


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## Generator-Jim (Mar 4, 2021)

The right adapter/cord will get power to both sides of the panel. I have an L14-30 inlet on the back of my house wired into my panel. Look for a cord that has "Two hots bridged". Here are examples depending on what plug is on your generator.
TT-30P to L14-30R and this is a cool one (2)5-15 Plug to Generator L14-30
Someone correct me if I'm wrong but this should power both sides of a L14-30 power cord and carry 120 to both sides of your panel.


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## Power User (Feb 28, 2021)

exmar said:


> Each side of the 2P breaker will feed one side. That would normally be two 120V feeds or 240V between them. You only have 120V, not 120/240V. What I did is take two 120V plugs, wired into a 120/240V plug to feed both sides. It's simple to accomplish, but not to describe in writing, talk to an electrician. Make sure you tell them that your expansion plans are for an additional 120V unit which would work well with the "two into one" described above. You do realize that adding an additional 120V unit will not provide 240V for AC's, etc. There are other ways to accomplish this, e.g. just jumper the generator side of the 2P breaker together, but, again, talk to an electrician.


It sounds like the transfer switch is simpler considering this issue, or moving the 2 left leg breakers to the right side. The first furnace breaker will have to be moved regardless for the interlock breaker.


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## Power User (Feb 28, 2021)

Generator-Jim said:


> The right adapter/cord will get power to both sides of the panel. I have an L14-30 inlet on the back of my house wired into my panel. Look for a cord that has "Two hots bridged". Here are examples depending on what plug is on your generator.
> TT-30P to L14-30R and this is a cool one (2)5-15 Plug to Generator L14-30
> Someone correct me if I'm wrong but this should power both sides of a L14-30 power cord and carry 120 to both sides of your panel.


That second cable is interesting. I was thinking that 2 power inlets could be used for each generator receptacle outlet, but that is a nice option.


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## exmar (Jun 29, 2015)

Yes, the "Cool one" mentioned above will work. Additional point, you may have to separate the ground and neutral on the generator to meet code, I'm not familiar with Hondas. How those are arranged on your "built in" vehicle inverter I have no idea.


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## exmar (Jun 29, 2015)

Your comment about the "built in" vehicle inverter made me curious so I looked into it a little. What the attached link "seems" to indicate is that this is for limited use inside the vehicle or via an extension cord to power self contained external loads. I'm not sure that using it in place of a generator and trying to power your house would work. Thinking about introducing it to external ground and neutral connections when it was designed to be self contained. Perhaps if you power an inverter which provides adequate isolation that could power your house. 






DC-AC Inverters | Toyota Industries Corporation


豊田自動織機のカーエレクトロニクス事業では、ハイブリッド自動車向けの最大出力1500WのACインバーター、補機バッテリーの直流を交流に変換する400W、100WのACインバーターを開発・製造しています。



www.toyota-industries.com


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## Power User (Feb 28, 2021)

exmar said:


> Additional point, you may have to separate the ground and neutral on the generator to meet code, I'm not familiar with Hondas.


The Honda has a floating neutral.



exmar said:


> How those are arranged on your "built in" vehicle inverter I have no idea.


Sorry, I was just mentioning the new Highlander with built-in inverter is pretty cool, I don't have one. There is a thread here on people using it. The new Ford F150 hybrid is even better, it has an option for a 7500w inverter generator.

I have a Giandel 1200w inverter and some portable power stations that are inverter/charger/battery combos.


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## Power User (Feb 28, 2021)

exmar said:


> Your comment about the "built in" vehicle inverter made me curious so I looked into it a little. What the attached link "seems" to indicate is that this is for limited use inside the vehicle or via an extension cord to power self contained external loads. I'm not sure that using it in place of a generator and trying to power your house would work. Thinking about introducing it to external ground and neutral connections when it was designed to be self contained. Perhaps if you power an inverter which provides adequate isolation that could power your house.


That may be Toyota's intention, but people have gone beyond that.


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## somedumbguy (Sep 17, 2020)

Power User said:


> As luck would have it, the circuits I really need are on the right bus bar. There are 2 on the left that I'd like to add if possible, though the jury is still out on being able to start one of the furnaces. And the microwave is optional.


Power User, I'm confused about your comment here about the "right bus bar". Your picture circles a group of circuits on the right side of the panel. Is that what you mean? I believe the bus bars are indicated by the "A" or "B" next to the circuit number on the panel label, not by presence of the breaker on the right or left side. The bus bars actually interleave underneath the breakers so that both A and B are available on both the right and left sides; this allows a 240V breaker to be installed on one side. (Look at your AC and Dryer circuits; they wouldn't work otherwise). Later you say "... with the interlock 2P breaker it won't span both bus bars for 120v each? ". If you are pushing the same 120V input to both the A and B bus bars, I believe you are right. In other words, if you are using a single 120V source to power both bus bars, 120 would be available at all circuit positions. No need to move anything. But remember your 240V circuits will not work. (I think those breakers should be turned off when you operate this way with the generator.) I'm not and electrician; I'd be interested to see if your electrician thinks this is all up to code.


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## Power User (Feb 28, 2021)

somedumbguy said:


> The bus bars actually interleave underneath the breakers so that both A and B are available on both the right and left sides; this allows a 240V breaker to be installed on one side. (Look at your AC and Dryer circuits; they wouldn't work otherwise).


That's correct, I didn't learn that until about a week ago. Thanks for chiming in.



somedumbguy said:


> Later you say "... with the interlock 2P breaker it won't span both bus bars for 120v each? ". If you are pushing the same 120V input to both the A and B bus bars, I believe you are right. In other words, if you are using a single 120V source to power both bus bars, 120 would be available at all circuit positions. No need to move anything. But remember your 240V circuits will not work. (I think those breakers should be turned off when you operate this way with the generator.) I'm not and electrician; I'd be interested to see if your electrician thinks this is all up to code.


I thought it would be that simple but there are apparently some gotchas others have pointed out when feeding 120v to both legs. My electrician is recommending the manual transfer switch, so looks like we are going that route.


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## Airstreamer67 (Oct 3, 2020)

I chose a manual transfer switch too. It is simple, easy to use and absolutely reliable. With a throw of the lever, I transfer part of my home's electric load to my home generator after it is warmed up, properly connected and ready for service.

This is why and how my transfer switch is wired the way it is:

Since my main generator is only 6000W and my backup 4500W, I chose to forgo any 240V circuits for use with my generators. Therefore, I had my sub-panel wired only for all of my 120V circuits. That way, I don't worry about any of my 240V circuits while on my home generator, because those loads would completely use-up and/or exceed the capacity of the generators I use in emergencies. Besides that, I don't want a large enough generator to handle those loads because of the amount of fuel I'd have to haul home. That's a choice I made and am happy with it.

So, all of my 240V circuits stayed in the original main breaker box. As a result, that portion of my home's load stays on the utility side at all times. When I throw the transfer switch so I can use my home generator, the 240V loads are not affected because they stay connected to the utility side at all times. One advantage of doing it this way is that when the utility grid power is restored after an outage, the clock on my oven in the kitchen comes on. During an outage, every time I go into the kitchen, I glance at that clock. When it comes on, I know the utility grid is back in service and I can shut down the genset. If I didn't have the clock, I believe I'd turn on the oven light when the power goes out so it could tell me when the grid is back in service. Knowing when grid service is available again is a valuable thing to me.

Makes me happy.


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## Power User (Feb 28, 2021)

Airstreamer67 said:


> One advantage of doing it this way is that when the utility grid power is restored after an outage, the clock on my oven in the kitchen comes on. During an outage, every time I go into the kitchen, I glance at that clock. When it comes on, I know the utility grid is back in service and I can shut down the genset. If I didn't have the clock, I believe I'd turn on the oven light when the power goes out so it could tell me when the grid is back in service. Knowing when grid service is available again is a valuable thing to me.


I'm counting on that too, definitely a pro. I did see that Reliance has a solution that will sound an alert when grid power is restored that would serve that purpose with an interlocked setup.

Another pro for the transfer switch is that I can test loads with generator, portable power station, and battery/inverter without shutting off the main breaker.


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## Old man here (Nov 5, 2020)

Power User said:


> I'm counting on that too, definitely a pro. I did see that Reliance has a solution that will sound an alert when grid power is restored that would serve that purpose with an interlocked setup.
> 
> Another pro for the transfer switch is that I can test loads with generator, portable power station, and battery/inverter without shutting off the main breaker.


I have one of the Reliance Controls THP108 EMW3561925 mounted on my electrical panel. Works great but let me tell you that when the power comes back on, you may need to change your shorts! That thing is so loud and shrill you can hear it a block away!


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