looking at gen just for hurricane in houston power outage :
these are loads.

fish tank=1500watts
(2)fridges total=1700watts
(3) small ac window units total 2800watts
computers = 1500watts
tv , lights, misc= 1500 watts

so total 9kw for the above .

so i could put this on 10kw genset , on natural gas ,,, so 9kw ?

also going to get the trans switch ,,,

also if need be i could get a DLM module to drop a load one of the loads if required ?

with small loads no big start up currents i think ,, would this run on 10 kw gen set ?

other things pushing small gen set ...

have existing 1 inch electrical conduit from exist panel on house to a exist panel on garage ... 60feet long dist ... ( not using garage panel any longer)

i wanted to just use the 1 " cond for the main power feed from gen to house panel ( gen located at garage )

but maybe better just go to the 14kw ?

any comments on things i am not considering ?

thanks, joe
Skip Douglas SkipD
I would never plan to fully load a generator when sizing it. For that matter, I never plan to load [U]anything[/U] to its rated limit.

For one thing, you've totally overlooked the starting current required by the motors in your lineup - the refrigerators and air conditioners being the heaviest draw. They can easily draw twice the rated current on startup. Look on the appliances for a LRA (Locked Rotor Amps) rating which will tell you the what the maximum starting draw might be.

I have a fairly small normal load in our house, but even our 16 kW generator (the rating on natural gas) output dips momentarily - but noticeably - when either our air conditioning or my (240 VAC) table saw are starting up.

I would suggest that you consider a generator with about 50% over-rating from what you think you'd need by adding up the loads that you'll be automatically connecting it to. Even with that, you may want some accessories that would prevent everything from starting at the same time after the generator starts.
Skip Douglas
ok, ... .. sigh ...


for some reson i have been fighting going conseravative design calcs on this ...

but you hit it hit right on ,,,, i never push the calcs right up to the limit on anything else. -- because it comes back to bite ...

so 14kw it is not 10kw

thanks for getting me back on track

I'm really not sure about some of your numbers above. I could see fish tanks needing that much if you are using heaters. However, I have 2 fridge/freezer combos and one freezer, and [I]all three [/I]together only use 88 watts-hr. Same goes for A/C window units and computers. Maybe you posted instantaneous useage?

You should also look into as many conservation methods as you can, first, which will always be cheaper than buying a bigger genset (plus gas). After buying my genset I switched over to all CFLs, replaced one of my fridges and my freezer and did other things and now I could get by with half as much genset.
I can not recall a situation where I thought-"this generator is too large", but I have been in the reverse many times.

Genset capacity is like money in your wallet, it is generally better to have it and not need it, than to need it and not have it.
well after reviewing gen set sizing with this forum users and with kelly and jeff from ziller's office ...

i reviewed my bare min choice = 10 kw gen set , 9kw natural gas rating x .8 rule of thumb loading , so 7.2 kw "was my design max".

with 7.2 kw max load, i was right at max with my present connected load.. and using load shedding ...

so allowing for some spare capicity that everyone suggested when using gen sets .... went up one size gen set ... so purchased the 14 kw, natural gas .

gen set should be arriving today purchased from ziller's office.

thanks again EVERYONE for all the input to help selecting the gen set !!

have a great day .
more is better. It's like a gun, bigger is better. Figure you're married, your wife will thank you many times over.
More isn't always better, a larger genset means burning more gas over the lifetime of the genset. Its better to spend some money to reduce your loads first, then size the genset accordingly (I did the opposite :( ), which saves money on the genset [I]and [/I]then gas.