# ?s on portable generator & existing generator sub-panel



## Phantomfyre (Jul 1, 2004)

After spending 24+ hours without electricity from Monday nightâs storms, DH is on the âWe-need-a-generatorâ warpath. *Sigh* (The only reason Iâm not vetoing this in favor of putting this money towards a solar setup is that Iâm thinking this thing might be handy even when we do get solar, and have a stretch of bad weather and no sun.)

So he found one for sale at what I guess is an excellent price, but if weâre going to get a generator, I want to be sure it'll serve our needs and work with what weâve already got. When we bought the house, we found that the previous owners had wired in a generator sub-panel. In the sub-panel are 30 amps' worth of breakers, but a note written in marker on the inside of the panel says - "East side by meter, 50 amp, twist lock." 

Here are the specs on the unit DH is looking at:
Briggs & Stratton Vanguard VTwin 18hp LP gas Generator with key start.
120/208v 3phase 22amp with 50 ft 3ph plug, also has 4 120v outlets.

Now to the questions:
1. Itâs a portable unit, so weâd have to store it and hook it up (to the sub-panel and the house propane) as needed - is that doable? Or do we need one of those huge, premanent, $$$$$ outdoor gennies? 

2. If I'm right on the amps in the sub-panel, this won't run everything at once, but maybe, if this thing is a good enough price, we could be careful to only run 2 breakers' worth of stuff at a time? In the summertime, we wouldn't need the furnace blower, but we'd need the fridge, for example, so I don't think it'd be hard to play musical breakers to stay under 22 amps...

3. How much propane would this thing burn? (Our neighbors said their 6HP gasoline generator used 1 Â½ - 2 gallons running all day yesterday, which isnât bad.)

4. Would a propane backup generator be a good idea with a solar system? Or should I still put the kibosh on this plan because it's overkill?

I think that's it... for now, anyhow. 

Thanks in advance!


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## Jim-mi (May 15, 2002)

. . . .120/208 3phase . . . . .
Yes you did type that.

That would be fine for your *work shop tools*

But is your *home* 3phase . . . .??? . . .I highly dough that.

Taking power off 1 or 2 legs of a 3phase is not a good plan.
And you would not have 220 for what ever needs it in your home.

Might be wise to have a qualified electrician go over that sub panel.
If the panel is not wired right, and you have a generator running and the grid comes back on.......you will have instant Fire and smoke . . . . .


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## Phantomfyre (Jul 1, 2004)

Jim-mi said:


> . . . .120/208 3phase . . . . .
> Yes you did type that.


Er, well, actually, I copied and pasted it directly from the listing for the generator... It did seem a little weird to me, but I'm not very fluent in electrical.



Jim-mi said:


> Might be wise to have a qualified electrician go over that sub panel. If the panel is not wired right, and you have a generator running and the grid comes back on.......you will have instant Fire and smoke . . . . .


I agree. I do think it was professionally installed, but still a good idea to have things looked over. 

There's a switch inside the sub-panel to switch the power supply to the breakers in there from grid to generator power. Then there's the box outside the house where the generator gets plugged in that is one of those big 3-pronged outlets like a dryer uses. (240v, right?) So it looks like a person just fires up the *proper* generator, plugs it in to that outside box, and flips the switch in the sub-panel, and has power to those breakers...?

But like I said, I have very little electrical knowledge, so I could be totally wrong... on that, too.


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## Gary in ohio (May 11, 2002)

22amps is small but typical of portable generators. The issue your going to have is wiring safely into your home. Your going to need a transfer switch to be legal, Just plugging it into a sub panel is dangerous. WIth that size generator you can run pretty much a typical house except A/C, Except electric driver or stove. You may not be able to drive a well pump. Keep in mind, 1 outlet is 15 or 20 amps. YOur basically getting one outlet worth of power out of the unit.


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## Windy in Kansas (Jun 16, 2002)

You should probably read this Wikipedia entry as to number of wire conductors, etc. 

http://en.wikipedia.org/wiki/Three-phase_electric_power

As Jim-mi pointed out single phase is what is normally used. You would need to change the hookup outside and probably inside too. 

Personally I would shy away from the 3 phase unit, however I question whether the generator actually has 3 phase output. 

When determining watt needs remember that some motors as they initially kick on require nearly double the rating for start up. Will you need to power a water source pump of some sort?

Just go in with both eyes open which is what you have already started doing by asking questions.


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## Jim-mi (May 15, 2002)

From what your describing, perhaps you do have a "transfer switch" . . . . ????
Then that 'plug' outside would then have been intended for conventional single phase generators . . . .NOT 3phase.

That gen you describe is not for you.

That gen would be for some ones shop backup supply.

I've got one out in the barn (3phase) that I picked up real cheap . . . . . . never have used it.

OH Ya . . . . . PLEASE do not end up buying one of those El Cheapo $199 buck pieces of junk 'generators'.
You would eventually regret it.


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