Generator inlet plug install-need advice on wire size/type, etc...

[IHDiesel73L]

We just got power back after four days out in Northwest NJ due to the early snowfall on trees that still have most if not all of their leaves. My town looks like a bomb hit it with the amount of splintered trees, broken poles, downed wires, etc... I have a generator and it allowed me to save the food in our refrigerator and chest freezer (a whole season worth of venison), keep the blower on my wood furnace running, and drain our sumps every few hours to keep the basement from flooding, but I was doing that with extension cords run through a window and all over the house. Far from ideal. It seems like we're getting these days long outages due to downed trees from storms at least once a year now, so it's time to install an inlet plug/interlock switch so that I can safely feed power to the panel and use breakers to route it wherever I need it. If I upgrade my generator I can also run my electric HWH as well-we were nice and warm but the cold showers were a little rough.

Right now I have a very basic generator-it's a Craftsman/Generac 4500W/7.8HP unit that's really intended for use on a jobsite. I got it free because it was not running-all it needed was a good carb cleaning. In addition to the 120V/15A household receptacles it has a 240V/30A receptacle as well. So given that I could simply buy a 30A inlet plug, wire to handle 30A, and a 30A breaker for the panel and be done with it. However, I notice that there are also 50A plugs. Since I plan to upgrade my generator anyway, would it be wise to install a 50A setup right off the bat? Based on my needs I think the biggest unit I would probably go with would be between 8 and 10kW. If I do go that route, I know what I need in terms of a plug and breaker, but what size/type of wire do I need? 6 gauge? Solid or braided?

 

[RoyJackson]

If you're going to do something like this, you should really bring a qualified electrician in to either do the job, or provide advice that would meet any codes your area may have as well as add the switch to ensure the power you generate doesn't bleed in to the outside powerlines.
Also, there's a good thread on the dangers of Carbon Monoxide (CO) stemming from using generators...definitely worth the read!

Good luck and be safe!!

 

[devildog1]

We just got power back after four days out in Northwest NJ due to the early snowfall on trees that still have most if not all of their leaves. My town looks like a bomb hit it with the amount of splintered trees, broken poles, downed wires, etc... I have a generator and it allowed me to save the food in our refrigerator and chest freezer (a whole season worth of venison), keep the blower on my wood furnace running, and drain our sumps every few hours to keep the basement from flooding, but I was doing that with extension cords run through a window and all over the house. Far from ideal. It seems like we're getting these days long outages due to downed trees from storms at least once a year now, so it's time to install an inlet plug/interlock switch so that I can safely feed power to the panel and use breakers to route it wherever I need it. If I upgrade my generator I can also run my electric HWH as well-we were nice and warm but the cold showers were a little rough.

Right now I have a very basic generator-it's a Craftsman/Generac 4500W/7.8HP unit that's really intended for use on a jobsite. I got it free because it was not running-all it needed was a good carb cleaning. In addition to the 120V/15A household receptacles it has a 240V/30A receptacle as well. So given that I could simply buy a 30A inlet plug, wire to handle 30A, and a 30A breaker for the panel and be done with it. However, I notice that there are also 50A plugs. Since I plan to upgrade my generator anyway, would it be wise to install a 50A setup right off the bat?Depending on your needs 50 A would still not operate all that you stated you wanted to run, and to run your HWH. Most HWH electric that is, have upper and lower cal rods, they can be 3,500 to 4,500 watts for a 40 gal HWH. See why you wouldn't have enough generator? It all depends on how much $$ you want to spend and what you need to operate . Transfer switch is the way to go if your not sure about pulling mains.Based on my needs I think the biggest unit I would probably go with would be between 8 and 10kW. If I do go that route, I know what I need in terms of a plug and breaker, but what size/type of wire do I need? 6 gauge? Solid or braided?

DevilDog

 

[IHDiesel73L]

If you're going to do something like this, you should really bring a qualified electrician in to either do the job, or provide advice that would meet any codes your area may have as well as add the switch to ensure the power you generate doesn't bleed in to the outside powerlines.

I will be seeking advice from an electrician but will do the work myself.

Also, there's a good thread on the dangers of Carbon Monoxide (CO) stemming from using generators...definitely worth the read!

I will check it out. Part of the reason I want to install the inlet plug is so that I don't have to worry so much about voltage drop. Using the regular 15A receptacles with extension cords I had to be conscious of how long my cords were. With the inlet plug and the 240V/30A connection I'll be able to build a shelter for the generator well away from the house-especially the outside air intake for my wood furnace.

Depending on your needs 50 A would still not operate all that you stated you wanted to run, and to run your HWH. Most HWH electric that is, have upper and lower cal rods, they can be 3,500 to 4,500 watts for a 40 gal HWH.

I should have been more clear. I would not expect to be able to run the HWH heater at the same time as any other appliance. I would just cycle it manually by turning off all other breakers and letting it heat it up by itself for an hour or two maybe first thing in the morning or overnight. It's an 80 gallon and very well insulated. We lost power at 3:00 p.m. on Saturday and I was still able to take a very warm, but not hot shower at 6:00 p.m. on Sunday. I'm not sure of the wattage of my HWH elements, but it's only served by a 30A breaker.

It all depends on how much $$ you want to spend and what you need to operate . Transfer switch is the way to go if your not sure about pulling mains.

I'm going to be using a simple interlock switch:

Generator InterLock Kit

It's very simple-you just mount a breaker for the generator in the slots right below the main breaker and the sliding switch ensures that the main cannot be switched on if the generator breaker is switched on and vice versa.

 

[billybobjimmyjoejack]

I have a transfer switch for my system and I also installed one for my brother. I would recommend one for your application. They are far more versatile than the interlock you are looking at.
You can control the circuits that require more watts of power by just flipping a switch or two.
You would buy a large enough transfer switch to accommodate the larger generator that you plan on buying in the future. It can be used with the smaller generator that you have now, you just won't be able to use all of the circuits at one time.
Generac has an installation video that comes with their transfer switchs that is easy to follow.

 

[IHDiesel73L]

I have a transfer switch for my system and I also installed one for my brother. I would recommend one for your application. They are far more versatile than the interlock you are looking at.
You can control the circuits that require more watts of power by just flipping a switch or two.

Maybe I'm not understanding this correctly, but the way I see it, the advantage of the panel interlock is that I can power anything on my main panel rather than having to install a separate panel and having to choose what to power from that. For example, I have a very small, two bedroom one bath ranch. One day I hope to add a second floor, which of course will necessitate adding circuits to my main panel (I have a 200A service and plenty of space so this is not a problem), so with the interlock, anything I add is automatically able to be powered by the generator if need be, assuming I have enough capacity. If I am wrong on this someone please explain-I have a good working understanding of these things but am by no means an expert.

 

[BobRip]

Maybe I'm not understanding this correctly, but the way I see it, the advantage of the panel interlock is that I can power anything on my main panel rather than having to install a separate panel and having to choose what to power from that. For example, I have a very small, two bedroom one bath ranch. One day I hope to add a second floor, which of course will necessitate adding circuits to my main panel (I have a 200A service and plenty of space so this is not a problem), so with the interlock, anything I add is automatically able to be powered by the generator if need be, assuming I have enough capacity. If I am wrong on this someone please explain-I have a good working understanding of these things but am by no means an expert.

I have the interlock bracket and it works fine. I like it for the reasons you stated.
I would definitely go with the 50 amp breaker. The hot water heater is probably 4500 watts, but I am not sure of that. Your generator will just run that. One of the advantages of the smaller generator is lower fuel consumption. Sometimes getting fuel can be difficult. Trees may block the road, the gas station may not have power, and the ones that do run out of fuel quickly. Most of the time you will only be using a small percentage of the capacity. If you get a bigger one, keep the smaller one.

 

[edlegault]

Install a manual "On-Off-On" transfer switch rated for your grid supply. One of the "On" sides goes to the grid, the off disconnects your house from everything and the other "On" connection goes to your generator connection. This is what is required to completely isolate your generator from the grid. No other subpanels needed. Just flip the breakers in your existing panel to power the circuits you wish to power from the generator. You'll need an electrician to install this between your main panel and the grid entrance.

 

[grsthegreat]

they really don't make an interlock switch for an existing 200 amp main breaker panel. The problem is you have to remember to manually shut off the 200 amp breaker and since this isn't done at the same time automatically that the interlock would be thrown, its against the NEC codes.

What most generator manufacturers are doing with the larger permanent mount gen sets are providing 100 and 200 amp automatic transfer switches.

These simply install right next to your existing panel and wire between the existing panel and the generator.

HOWEVER you first have to do a load calc. I have installed these in houses which have a small 50 amp actual load while all major appliances are turned on, as gas heat, gas water heater and gas range were in use.

In an all electric house, i have seen actual registered loads (amp meter) of 150 amps while all the above are running.

The generator needs to be sized correctly.
A 4500 watt generator will only provide 18.75 amps at 240 volts
a 10,000 watt will provide 41.6 amps at 204
a 20kw generator will provide 83.3 amps at 240 volts.

some people will argue that they can simply turn off the larger circuits, but unless the generator you have can automatically shed these larger loads, most electrical inspectors wont allow their install by a qualified electrician.

When i come onto jobs that want to use a 50 amp generator on an existing 200 amp service, i generally have to add a generator panel right next to and interconnected with the main panel. Then i physically move the circuits that i want the generator to power up (up to 50 amps max continuous load). This panel will have a simple manual interconnect switch that will simultaneously disconnect the generator and the utility power so both cannot ever run at the same time. I then run a #6 copper line to an outdoor generator ready receptacle. The owner only needs to move the generator over to this outlet and plug it in. Then switch over the panel manually.

They also make replacement main panels that have provisions for either an automatic or a manual transfer switch. These panels have a split bus and are 100% legal for generator. I have used alot of these for retrofits for houses with undersized generators, especially where there is no room for another panel. I LOVE them. few hours work and its up and running.
I use the Siemens panel. It has a provision to be easily changed to a fully automatic system in the future if the owner upgrades his generator.

 

[tmajor]

Maybe I'm not understanding this correctly, but the way I see it, the advantage of the panel interlock is that I can power anything on my main panel rather than having to install a separate panel and having to choose what to power from that.

You understand it correctly.

Also, search for your panel and see if your panel manufacturer has an Interlock kit available. I know Square D and others have them. They seem to be cheaper from the panel manufacturer.

Also, see my thread, on same.