Sizing a backup generator? Install costs?

[Phil Thien]

I shifted to working from home end of April of this year.

Since then, we've had two blackouts. Basically, it rains kinda hard. As soon as rain moves out, power goes with it.

I have battery backups on important stuff, and this time power was only out about 30-45 minutes. But last time it was several hours.

I have a small lot and never thought I had room for a backup generator, but recently saw some compact, air-cool Rheem models, like this one:

http://www.comfortup.com/rheem-seregen-1...tor-system

I have a small house with a 2-ton central A/C (on 20-amp breaker). Would also like to power furnace (for the blower to make A/C work, and of course if it is winter, I'd like heat), fairly typical refrigerator, and maybe several hundred watts of computer gear. Anything else can go dark. I don't care about the washing machine or dryer or even the range or microwave.

That page I linked said the generator can power TWO 4-ton A/C units. I'm a bit surprised by that because A/C can draw quite a bit at startup.

Do generators handle that okay?

Think I could accomplish what I'd like with 10 KW?

Any estimates of installation costs? I'd need a transfer switch, right? Any pitfalls to be concerned with?

[blackhat]

10 kw is the smallest unit i would consider for your application.  Consider a unit made by someone that has a dealer with qualified techs and parts close by.  Not dissing the unit you linked, never seen them before.  Cost, between 5 and 0 thousand
.  The amount of wiring and gas line involved can shoot costs all over the place as well as local permitting etc.  Personally, I like a setup with a critical circuits sub panel, or an integrated switch and subpanel.

[frule]

I have an 8kW Generac with a transfer switch which has 10  circuits. I run a 1 1/2hp well pump (big pump in a 900ft deep well) and the generator really surges as the pump kicks on. It cost about $4500 installed. I had existing propane lines to the generator, so that saved money.

I run a computer station, my 65" TV, a freezer, a refrigerator, lights in several rooms, plugs in several rooms, a gas furnace, microwave (1200w) a commercial coffee maker (1700W), the well pump, etc. I never considered putting my heatpump (5-ton) on this generator as it would never start up. But I use ceiling fans when the power is off in the summer. And the LP furnace in the winter.

Two 4 ton units sounds like way too much for a 10kW generator. Of course, it's all about start-up power. I've never heard of this Rheem unit, either. Good service and installation is paramount. Check out dealers rather than brand. Many HVAC companies now install generators. I'd get a really good explanation of how it will do with your AC units-probably OK.

Fred

[rwe2156]

I would be skeptical that's going to power one 4 ton ac, much less 2.  I have a friend with a 10KW backup at his house.  Not hooked to AC they told him he needed at least 15KW, 20 better.

Keep in mind most generators are rated "surge" vs. "continuous output". Check that first.

I would check with an electrician or someone knowledgeable other than a forum.

[fredhargis]

I'm getting quote on a standby generator right now. While I think a 10KW is really small for what you want, the quotes I've got on them run $5-6K. A 22 KW (which is what I'll install) is $8K. Consider those ballpark numbers since they will vary somewhat.

[Snipe Hunter]

Phil,
I have a 15kw (running) 22kw (start up) which ran a well pump, 4 ton heat-pump and an electric water heater. It fed the main service panel. That tapped it out. That seems like an awfully small unit.

[Phil Thien]

I just don't think I have the physical space for anything much larger.  And if I had to drop the A/C from the list, I could (but would rather not).

The Rheem units indicate they use Briggs and Stratton engines, so that is somewhat encouraging (I think).

I'm going to get a list of dealers in my area and see if I can find anyone installing them in any quantity.  I don't want to be the only guy with one of these in Milwaukee.

Thanks for all the feedback.

[Admiral]

I got a Kohler 20kw, with the extra load manager add on unit for whole house coverage, had a bit of a cable run from the install location to the main panel, but all circuits in the house are connected and the load manager balances all this (don't ask me how but it does); I also have a well and central a/c; total all in $12k installed including natural gas hookup by plumber and site prep, about 18 months ago.  Cost now likely less as installers were very busy.  I preferred the Kohler engine over B&S.  So far, had several short outages (max 12 hours) and it works like a charm.  Here on the east coast, lost power for 10 days from Irene, and the very next year 15 days from Sandy, and decided I was NOT going thru that ever again.  Cost was less than a good used pickup, I'd do it again in a heartbeat.

[blackhat]

You do know that Generac is in Waukesha county right?

[RichK]

Phil, my backup generator takes about 30 seconds to kick-in.  I ended up buying a battery backup ($75) that sits under my desk so that my PC does not shut off when the main power goes out.  I learned that the hard way.