Transfer Switch: prewird vs. Whole House/Subpanel

[Ignoramus13229]

As some of you might remember, I own a well working Onan DJE generator, 7kW continuous.

I will soon start working on setting up a proper transfer switch. I am now deciding which one.

SOME BACKGROUND:

3400 sq ft house plus finished full basement, 200A service, almost all slots in the panel taken. A lot of little circuits. (which has its advantages). Many of these circuits power very small equipment like lights, phones etc.

The generator will be installed behind the house, very close to the panel. It will still be on its carriage.

My objective is to do work that can be UNdone if I want to sell the house. Hence, I would prefer to not do any service entrance type work.

I have, logically, two alternatives.

1. Buy a prewired transfer switch.

1. Add a large subpanel, move all breakers that I want to be on a generator, there, and insert a transfer switch between subpanel and main panel.

Note that this would involve also making wire connections in the main box, since the circuits are terminated in the main box, obviously, but the breakers will be in the subpanel box. Because of this, I am not sure if choice 2 is even legal.

Assuming it is, I see some advantages of 2) over 1).

1. Being able to add more circuits due to having an extra subpanel.

1. Being able to power more circuits in case of an outage, and being able to choose which ones to turn on and off, with breakers.

Any thoughts on this will be appreciated.

i

[zxcvbob]

You might consider hiring an electrician to install a 200A DPDT switch between your electric meter and your service entrance panel. Hardwire the generator to the switch with appropriately big service entrance cable. When you move, you can disconnect the generator (to take it with you) and leave the switch -- it will function as a disconnect for the house, and the new owners can use it to hook up their generator.

I don't know if this will require any modifications at your service panel (installing a ground bus and seperating the grounds and neutrals, etc.)

You don't want to do this yourself. I *might* try it myself if I got permission from the utility company to pull the meter and reinstall it when I was done.

This is one of those jobs where you really should get a permit.

Best regards, Bob

[Ignoramus13229]

Bob, do you have an idea how much it could cost (beside the cost of the switch). I have no clue.

i

[zxcvbob]

No idea. Probably a couple of hundred dollars just for the enclosed switch. I'm not an electrician, and I've never had occasion to wire a transfer switch. There are a lot of subtleties to a job like this -- whether the switch should be fused or not, solid neutral vs. switched neutral, etc. -- the whole thing needs to be planned out before you start, otherwise you will cause a lot of complications later, mostly dealing with proper grounding of the panels and the generator.

You need to get your garage subpanel fixed before you start worrying about a generator transfer switch.

Bob

[Steve Spence]

[Ignoramus13229]

Thank you Steve. In my case, I need a lot more on the utility side.

Also, I am a little surprised as I thought that your unit was rated

12.5 kW, which comes to 50+ amps per leg, not 30 as you noted. i

[Steve Spence]

[Ignoramus5713]

Oh, I see. Thanks.

i

[Dave Morrison]

Iggy I am in process of putting in a whole house auto transfer switch. I brought in a licensed electrician Friday to mount the switch under my main disconnect. Took six hours, my man got $70.00 per hour (Az.a right to work state YVMV). You might go to the ASCO transfer switch sight and download all the pdf files on the 165 series switches. Those files will answer most of your questions. If you want to go manual switch there are a lot of used ones on Ebay. Dave

[Ron Rosenfeld]

In a situation where I wanted power backup when I was living on the grid in another home, I installed a whole house manual transfer switch. This did involve work at the service entrance and the cost of having it done, including the switch and running cable to the generator location, was about $1500. All code compliant.

Knowing a bit more, if your generator is capable of autostart, I would suggest an automatic whole house transfer switch. These units can automatically start the generator when grid power goes out; and also exercise the generator at preset intervals.

-- ron (off the grid in Downeast Maine)

[Ignoramus5713]

My generator is Onan DJE, 26 years old, and I doubt that it is capable of autostart. I can probably jury rig something, but, honestly, I would like to be next to it when it is starting.

Here it is, my little pride.

i

[Ron Rosenfeld]

Oh, yes. I recall looking at it now when you first posted about some problems with it. Glad you got it working. The newer Onan home units can be autostarted, but I sure don't know about the one you have.

-- ron (off the grid in Downeast Maine)

[Ignoramus5713]

It works beautifully, starts every time. Load tests very good also. I am very happy, thanks not the least to members of these newsgroups. I know that I can buy a starting relay for it from FW Murphy (with preheat and all), but, to me, it is all not worth it. I would have to spend $1,500 on an autostarting transfer switch, plus extra for relay, etc. All for what? For not taking my ass out of the house in the rare event of loss of power? Nah. I can walk out for 3 minutes, preheat the engine and start it.

Besides, I want to store the batteries in the garage and also close off the fuel valves when not in use. So, a walk outside is necessary.

I would rather spend $329 or so on a whole house transfer switch like

maybe $100 on a subpanel, and have it working. That is provided it is not illegal to put a subpanel on a transfer switch. Which is equivalent to making my own analog of a pre-wired TS.

i

[Ignoramus5713]

Thanks. An ATS does not fit my needs (see my response to Ron Rosenfeld), and also would be too expensive. My genset is not autostartable, unless I add a starting relay. See its picture at

I want to store batteries in the garage, have fuel valves shut when not in use, etc. I do not mind spending 5 minutes outside if power goes out.

i

[Ron Rosenfeld]

One advantage of an automatic transfer switch is that you don't have to be home to start the generator when the power goes out. Since we take winter vacations, and live where it's cold, that would be an issue for us.

But they are expensive, and not for all situations.

One advantage of a whole house transfer switch (manual DPDT like I had installed at my previous home) is that you don't have to decide in advance which circuits are critical during the blackout. For example, in our last home, we could have run one burner on the electric stove, whereas with the smaller, then available sub units, we would not have had that option.

You just need to take care to not overload your generator.

Again, even the whole house manual transfer switch may be more expensive than what you want to pay, but it would be something to check on, as I believe prices have come down.

-- ron (off the grid in Downeast Maine)

[Ignoramus22481]

I would be uncomfortable with the thought of a generator running without me for a week. I would rather take my chances. Also, usually, someone is home when we leave for vacation (wuthout going into details).

Definitely a huge advantage for me as well.

Yep.

Check out that Harbor Freight transfer switch, made by Cutler Hammer.

i

[Dave Morrison]

Check those Asco files anyway, the 165 series is available in auto or manual start. They have a series of installations illustrated. Price wise you can due better on a used manual transfer switch on Ebay. Dave

[Ignoramus22481]

Thanks, I will read them, yes.

i

[Ron Rosenfeld]

It sure looks like a good price. Add to that the wire from the switch to your generator, and electrician charges, and I'd guess you're looking at under $1000 for everything installed.

That's less than I had to pay 7 or 8 years ago and, if I were wanting a manual solution, I'd go for that before a limited panel solution.

-- ron (off the grid in Downeast Maine)

[Ignoramus22481]

Thanks. You are talkin gabout installing this switch at the service entrance, is that correct?

I am sorry, what do you mean by a limited panel solution?

Thanks Ron.

i