mpo257
Newbie hoping for expert advice on proper sizing for stand-by power. From July 2010 to August 2011 I used 33,605 KWH with a daily average of 90.2. Peak period was July-August 138.3/8853 and May-June 103.4/6618. I want to power the whole house and have a pair of 150 Amp panels. There's no NG in my neighbor hood and I'd like to avoid more "stuff" in getting propane tanks. Diesel would really be best. I'm located in Long Island, NY. Thanks much, Jim
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Skip Douglas SkipD
Daily average power consumption isn't enough to calculate the required generator capacity. You need to do some calculations to arrive at the total load possible with everything that would be automatically connected to a stand-by generator.

I'd suggest that you contact a generator installer in your area to help with the application. They can help you do the calculations to satisfy all of the applicable codes in your area.

For some reason, I could not get a response on Generac's dealer search page. You can call Kelly Myers at Ziller Electric (number at the top of this page) and he can help you find a reputable installer.
Skip Douglas
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mpo257
What other calculations are you talking about? I'm fairly handy and have access to those who are better than me. Before I get involved with a generator contractor, I want to do as much "homework" as I can on my own. Thanks!
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ceb58
Go back to the power company and find the maximum demand in over a one year period. You can then use this to size the generator. 220.87 (2008) NEC
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mpo257
ceb58;10241 wrote:
Go back to the power company and find the maximum demand in over a one year period. You can then use this to size the generator. 220.87 (2008) NEC


Is that a link for the calculation or a reference manual to get? Thanks
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Skip Douglas SkipD
mpo257;10244 wrote:
Is that a link for the calculation or a reference manual to get? Thanks
What ceb58 gave you was a reference to the National Electrical Code. The current version is 2011, but that does not mean that the government in your area has adopted the NEC 2011 yet. The previous version is 2008.
Skip Douglas
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mpo257
SkipD;10245 wrote:
What ceb58 gave you was a reference to the National Electrical Code. The current version is 2011, but that does not mean that the government in your area has adopted the NEC 2011 yet. The previous version is 2008.


Right now my local utility, LIPA, is up to their necks in turmoil from TS Irene. I was out 5 days and my 30kW diesel unit from China, POS that it is, failed me in multiple ways mostly due to electronic/ATS issues. It has maybe 10 hours and generates power just fine. The rest is a long story, so unless someone asks I won't list my problems. I decided to scrap the whole thing and start over. I just want to make sure this time, I do the right thing instead of being mislead by an unscrupulous salesman who vanished. Penny-wise and pound-foolish got me nowhere.
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rico567
I have been in the process of attempting to size a generator to my house since I began the whole project in the Spring. So far, I've got the pad constructed, but sizing a generator is definitely one of those "depends who you ask" things, and please spare me the NEC chapter and verse, up front, since it's already been quoted to me.

The NEC has two criteria for standby generator size; the first is apparently "sky's the limit," wherein every single watt that any load in your panel could ever pull must be matched by current from the generator. The second is far more equivocal, and allows for "load management" such that the generator need only be as large as the load that the "load management" allows it to see.

What I know is that every time I enter what I want to run on emergency power into one of the online emergency power estimator things (most manufacturers have them), it tells me that I only need one of the smallest (usually about 7KW) units. This makes me nervous for several reasons, which I won't expatiate on at this point.

Every time I talk with someone who's selling generators about my needs, the conversation always ends up with me considering something that could provide backup if the Three Gorges Dam in China ever goes down. I understand why this is happening, and I reject it without discussing it, as above.

Having estimated my emergency power needs and tacked on a nice amount of overhead so that the generator is never running close to capacity, I think my actual needs run somewhere in between 7KW and 20KW. So.......14KW it is. I think that 6051 unit or equivalent that has the load-shedding ATS, so that I'm protected both ways.....
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mastr
mpo257;10286 wrote:
...my 30kW diesel unit from China, POS that it is...has maybe 10 hours and generates power just fine...


If I had that to start with, I would think strongly about fitting it with a good controller such as a Deep Sea DSE7110 and then installing a decent automatic transfer switch like an ASCO 185.
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mpo257
mastr;10317 wrote:
If I had that to start with, I would think strongly about fitting it with a good controller such as a Deep Sea DSE7110 and then installing a decent automatic transfer switch like an ASCO 185.


RICO567: I hear you and ended up with the 30 initially for the reasons you say. I was told that it's not good to "oversize" too much in that the generator never gets to work near it's capacity. My house has incredible variation, with 11 tons of AC possible in extreme heat (would NEVER allow that in stand-by), pool pumps, hot tub, multiple ovens/electric cooktops, etc. In early spring, fall or similar, I'm sure my demand isn't great. Makes it hard to be truly comfortable with ATS vs. MTS.

MASTR: I'd love to break the thing down and eliminate ALL the crappy electronics, but truth-be-told, I've had cold-start issues in winter and some other problems unrelated to electronics. This unit would be perfect for someone as a project to make it into a trailer-portable or warmer climate stand-by. I plan to give it away just for someone to come and take it.
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Skip Douglas SkipD
mpo257;10340 wrote:
I plan to give it away just for someone to come and take it.
Look up your local emergency management director who can then get you in touch with amateur radio operators in the area. They can often use a large portable generator for emergency communication operations coupled with a shelter operation.
Skip Douglas
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rico567
Oh, yes, if you're looking to donate the generator, an amateur radio club that does field day or is into emergency services would snap it right up. If they happen to be set up properly as a nonprofit, you could get a tax deduction on the donation, too.
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mpo257
rico567;10354 wrote:
Oh, yes, if you're looking to donate the generator, an amateur radio club that does field day or is into emergency services would snap it right up. If they happen to be set up properly as a nonprofit, you could get a tax deduction on the donation, too.


Thanks for the advice, I will try that first.
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