Generator question (household wiring to be more accurate)

[Richard]

I saw a comment in another thread regarding a 100 amp service panel and adding some 220V items....

Got me wondering.

My main panel is 200A.

I have (if I recall correctly) an 8-3 wire going .... let's call it 40 feet to a second panel in the garage.

On this second panel, I have a couple 20 amp circuits going to the downstairs HT setup. The rest of it will be used for some garage lights and circuits.

This second panel is on a 50A breaker in the main box.

Brings me to a generator question. We needed one a year ago and the brother in law happened to have a 10KW diesel unit he could bring over. We were able to hobble along for the week and keep things working as long as we rotated them.

If I were to buy a generator, I'm wanting a larger one than the 10Kw because I'd like to have the ability to keep the well pump on as well as the water heater!

So, if I were to get (what size?) a 20-30 Kw generator.... what I'd like to do is take another run of that wire (which again, I believe to be 8-3 or, was it 8-2 with ground....I get that third wire confuse sometimes!)

Anyways, what I envision is running an outlet to the outside of house. Being able to then, plug the generator into that outlet to it feed the second panel and then let that panel feed the primary panel.

Ultimately, my question is, with a 50 amp breaker serving the second panel, what might that restrict me to with regard to a generator?

(I'm aware that need some kind of control panel to prevent back-feeding to the electric company, that is independent of what size generator might be too big for that 50 amp circuit)

 

[davesl708]

You need to get a licensed electrician involved. You are treading in dangerous territory with your plan. NEC and local code will not permit what you are trying to do. The results could be a disaster.

Get an Electrician.

 

[Travelover]

While I agree that you should consult an electrician, you are installing an awfully huge generator just to run the water heater. I run my 220 volt well pump off a 4000 watt continuous / 5000 watt surge generator. Water heaters have two elements and you can temporarily turn off one to ease the load on the generator. You will still have hot water but the recovery will be slower.

Having a huge generator is not only expensive to buy, but expensive to run, especially if fuel is in short supply.

There are also devices that will shed loads selectively so, for example, the water heater would be disconnected when ever the pump is running.

 

[PILOON]

As to water heaters, I discovered during a 5 day outage that (in desperation) that I was able to enjoy a decent shower days later as long as I did not add any cold to the mix. Not scalding hot, but quite comfortable.
Modern hot water tanks really hold the heat for much longer than we think.
Another option is a kettle and sponge baths.
\
On the other hand if you have a household of teenage daughters you do need that huge gen set.

 

[LittleBill21]

electric water heater only uses 4500 watts, and only 1 element is on at a time, what size is your well pump? i run my electric water heater and well pump off a HF 7000watt generator, it grunts but does it fine

 

[Licklog]

I have run a generator for the last 13 years as a backup for power outages. Ten years ago I converted it to propane to minimize the gasoline problems and it has worked beautifully It was a Generac SuperBoss with a self installed propane kit. Rated at 7500w surge. It handled all of my power needs except air conditioning and water heater. I have propane heat and two fireplaces with propane logs so that is not an issue. It runs all the lighting, fans, tvs, well pump, refrigerators, freezer, etc.

This year I sold the Generac and replaced it with a Home Deport 7000w propane unit with electric start (wife could not use the pull start). Have used it twice this season for extended times (4-5 hrs) with no issues. They were/are both 120/240 units and the setup is similar to what you are suggesting. Power coming in from the generator to a 220 breaker in the control panel. Turn off the main power, water heater and air conditioner circuits; plug in the generator to the outside outlet, crank up the generator and when it is up to speed, flip the breaker.

 

[Pipestone Kid]

If you are hooking up you whole house, check this out. <http://www.interlockkit.com/?gclid=CPPrv6K79K8CFbMEQAodrCALVg>

 

[Richard]

We're getting a bit into the weeds.

My brother in law happens to be an electrician. I am always running to him for this & that so I'm trying to get some education without bothering him.

(which is also why I mentioned that I know I need a transfer switch)

So, back to my question...

If I have two wires (I only have one but I don't recall if it's 6 or maybe 8 gauge. It's a heavy bugger)

If I have a 6-2 w/g going from the second panel to a 50 amp in the main panel, how large of a generator might work on that line?

If I have an 8-2 w/g going from the second panel to a 50 amp breaker in the main panel, how large of a generator might work on that?


Our main breaker is in the basement. It would be nice to have something that would power the "whole" house. Meaning I'd like it to be big enough to run the water heater and pump at same time (more if possible) so that we don't have to do the endless run downstairs and play musical switches to get the various items working.

It's not like we're having a party when the power goes out and maximizing our hot water use....while at same time burning all the lights while at the same time turning the A/C system on.....

It would however, be nice if the generator had enough oomph to allow some overlap of above items without triggering breakers somewhere.

wifes, and for that matter, electrician brother in law have a niece who's in a wheelchair. When she visited last time it happened right at the beginning of an ice storm and we were without power for a week. We rigged (correction, "HE" rigged) his generator to the second panel and backfed the main panel (main breaker was off) It was during this week of daily use that I felt the 10Kw unit was underpowered. It "worked" in that we could do some things but there was an issue if some of them overlapped so I'd like to look at a larger unit so I don't feel everything is so stressed.

I know it would cost more.

I'm just presuming that if the idea works (at all), then the limiting factor is this wire going from the second panel to the main panel.

 

[Travelover]

I think the issue is that you want to back feed off the sub panel. Normally, a transfer switch is located at the main service box so the outside power is disconnected there and generator power is substituted. I don't see an easy way to do that via the remote sub panel.

 

[Richard]

I think the issue is that you want to back feed off the sub panel. Normally, a transfer switch is located at the main service box so the outside power is disconnected there and generator power is substituted. I don't see an easy way to do that via the remote sub panel.

I can see how that might be an issue (a killer issue)

I just checked and the wire I have is (copper) 6 Gauge 3 wire with ground.