Wiring for generator and compressor.

[APG12]

Hey guys I’m in the process of a complete garage renovation and in the next couple of months I will be spray foaming and sheetrocking. I have future plans for a whole house generator and an air compressor, which are not currently in the budget.

I’d like to install electrical runs to the panel for these two units, since once the insulation is in, there’s no going back. I haven’t sized either unit, so I’m not really sure where to begin. Generator will likely be minimum 22kw and compressor I have no idea as I’m not that well versed.

Can anyone give me any recommendations on what to run that leaves me some room to play with? Thanks for any help that you guys can give me!

 

[mm08822]

Take pics of panel area in garage and outside by meter.

Where do you think generator will be relative to main panel?

List all major electrical loads, sq ft of house.

Where will compressor go? Maybe you can run a cable in the wall now to an outlet box and blank it off till needed. Would need size of compressor to size cable.

 

[Bert_]

8-2 NM will run a 5 horse compressor, 6-2 would run a 7 1/2. Either one will run a smaller compressor obviously.

If you're wanting a generator that size or maybe even more I'd be installing a real transfer switch not just an interlock. Do you want automatic transfer or manual?

 

[APG12]

I’ll take pictures in a little while. Generator will be on the opposite side of the two car garage where I already have a in ground propane tank.

House is 2500 sq ft with all typical loads plus central air and a mini split. Maybe a future hot tub.

I’m trying to avoid sizing anything right now as my needs might change in a couple years when I will likely do the install, which I know makes it difficult to run wiring.

Can I just go overkill now to get it done?

 

[APG12]

8-2 NM will run a 5 horse compressor, 6-2 would run a 7 1/2. Either one will run a smaller compressor obviously.

If you're wanting a generator that size or maybe even more I'd be installing a real transfer switch not just an interlock. Do you want automatic transfer or manual?

Good info, thanks. Generator will be professionally installed when it comes time. I’ll have to price out the options when I get to that point.

 

[Bert_]

Manual or automatic transfer either way the wire won't go into the panel so there might not be much point of running it now. there would be a transfer switch installed ahead of your main panel.

 

[APG12]

Wouldn’t the transfer switch generally be installed next to the panel?

 

[mm08822]

Wouldn’t the transfer switch generally be installed next to the panel?

They can be and i prefer that inside.

But they are rated nema 3 for exterior locations.

Load shed modules and ac interlocks will probably be needed. These are most convenient mounted near the panel. They can go close to each load but is a pia for startup/ troublezhooting.

You may want to consider a conduit or feeder to basement for a sub panel.

What is above garage?

 

[APG12]

Above the garage is master and 2 kids bedrooms, which is the main reason for the spray foam.

 

[wyliesdiesels]

I would run conduit to the generator location and compressor location.

This way you can add the wire later since you dont know what size you will be going with

If you pick a certain size wire now, then doen the road decide you want something bigger, you are stuck.

With conduit, you can pull the right size wire later.

 

[larry4406]

I would run conduit to the generator location and compressor location.

This way you can add the wire later since you dont know what size you will be going with

If you pick a certain size wire now, then doen the road decide you want something bigger, you are stuck.

With conduit, you can pull the right size wire later.

I agree with this option.

 

[APG12]

I would run conduit to the generator location and compressor location.

This way you can add the wire later since you dont know what size you will be going with

If you pick a certain size wire now, then doen the road decide you want something bigger, you are stuck.

With conduit, you can pull the right size wire later.

That was my back up plan, but thought it would be easier to pull the wire now. What size conduit would you guys recommend?

 

[yeldogt]

All depends on what -- "renovation" actually means. Plan out the locations ..

22k was the largest air cooled unit w/propane when I got mine last year. Went with the cummins unit and it's cheaper to order the combination w/ transfer switch. Ordered online and got everything at once since it's all part of the free ship. load relays/remote panel -- I also got the pad since it's high quality and has the mounting points w/ threaded SS anchors.

Gen needs to be 10 feet from Propane tank. Gen also has some other requirements -- look them up and see where you want it -- or has to go.

I went with a 22k because it will take care of most loads and it's fuel efficient. It was cheaper vs going smaller and doing a separate panel. The cummins will do two load shed controls -- so 4 loads can be managed if the gen can't do them all at once. Code says it has to be able to run or shed.

The transfer switch goes between the meter and the generator. Many times people can place the transfer switch outside and cut the line between the meter and existing panel -- splice in the switch and run the two lines to the gen out of the transfer switch. It all depends where you meter is and the panel.

On my build the Gen and propane tank have to be out behind an outbuilding. It's 100' away form the main house where the service connects and main panel. I mounted the transfer switch inside next to the panel and ran conduit (x2) to the generator (2" and 1"). This way the load relays are inside as well --next to the panel. Makes running the electric stove and one of the AC units easy through the relay -- also low volt to the TS is there from relay to transfer switch

If the gen is on the other side of the garage from the panel and you are removing the sheetrock. You can just run regular wire to a box mounted outside -- like you do for an AC unit. You can also run the low volt the same way ... 120 as well if your code demands. That's how my beach house is done.

The Transfer Switch the load relays are surface mount -- so keep that in mind as often in a garage with drywall -- the main panel is recessed.

In some situations I have seen splice boxes placed between the meter and the panel -- they are designed just for future connections ..my memory is it has to be a disconnect as well. The do this on new builds: This box is outside next to the meter and the panel is recessed inside on the other side of the wall in the garage sheetrock. Down the line the home owner can have the generator line spliced into this box -- since it's all there there is little to to. The disconnect in the box allows the power to be cut off. In and out connection to TS and on to gen.

 

[TheEquineFencer]

I'd run a panel/circuit for your future air compressor as big as you think it will be. You can always de-rate the circuit with a smaller breaker. same with anything you plan or think you might need in the future.

Unless your Meter for the shop runs the house, the issue of the generator is a mute point. If you're renovating the house too...I'd put a disconnect between the meter and the house. If you did that, you could buy a Manual Transfer Switch and put it there, it'd serve two purposes. It's a disconnect for when you install the ATS in the future yourself and also and extra connection for when you run out of propane and need to tie another Garage Journal member's portable Harbor Freight Generator in.

 

[SGKent]

run conduit now as suggested and wait until you buy the compressor and generator to add wiring. Otherwise you may have to do it again. Also when you run the conduit make sure it is sized for the largest wires you might be running.

 

[wyliesdiesels]

That was my back up plan, but thought it would be easier to pull the wire now. What size conduit would you guys recommend?

Wont be easier if you pull the wrong size wire

1” should be more than enough.

 

[yeldogt]

Wont be easier if you pull the wrong size wire

1” should be more than enough.

The feed out to my 22 generator is 1.5 at least .... it may be 2".

The second conduit is 1"


Frankly - since he running this inside his walls .... doing conduit makes no sense to me -- unless it's a very simple run.

Just run the wire needed for the 22kw to a box on the outside of the building.