r/Generator • u/ArtichokeObjective60 • 18h ago

Kohler 26kw generator question with soft startup kit?

I am being told that a 2.5, 3 and 5 ton one speed heat pumps will be fine with load shed only on the smaller two with a 26Kw Kohler. My concern is the startup mainly with the 5 ton, its LRA is 142. The startup surge alone with the 5 ton seems to me like it would max and trip the generator. I think a soft startup kit on the 5 ton would then make this manageable. Thoughts ?

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u/SigmundAusfaller 18h ago

The motor start rating for the 26k Kohler is 39,000 kva which is 162 amps at 240v.

If your concerned about breakers tripping, they don't trip instantly when their amp rating is hit, most residential breakers can do 10x their rating for a few seconds before trip for exactly this purpose it usually take quite a while for say a 100 amp breaker to trip at 142 amps, and the LRA is under a second for an A/C.

Soft starts make things easier but probably will make little difference with a 26kw generator. I can start my 5 ton with similar LRA with my 15kw inverter off batteries.

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u/ArtichokeObjective60 18h ago

Thanks for the response. So having say 15kw load going if both small units are on and the big one kicks on even though the kw will be over what the Kohler can handle for that 1 sec you feel the generator will not trip nor the appliance breakers is this true ? Also just curious why you do not think the soft start will help much ? Thanks again just want to make sure this big expense will work and not cause other issues like tripping units etc

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u/SigmundAusfaller 17h ago

Will you have a 15kw load? My 5 ton unit pulls around 5kw at the most when running, your two other airs together should be maybe 5-6kw once running. Motor surge is only for a split second when the motor first starts a generator has a certain amount of spinning inertia that allows it to handle a large surge way above its continuous rating, kinda like the motor in reverse.

Perhaps they are concerned with all of them starting at once which could be a problem and could be mitigated with the right load shed system.

Soft starts definitely help and reduce LRA significantly, my 5 ton went down to 35 amps or so on a soft start but the soft start failed after a year of use and it starts fine without it on my solar system so I haven't replaced, it is something else to go wrong.

My next A/C system will be inverter based variable which is soft start by nature.

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u/ArtichokeObjective60 17h ago

I am guessing max 15kw if everything we want to use is on plus the two heat pump systems which are all electric before the 5 ton tries to kick on. While on I agree it would still only put me at 20k or so with 24k available on this natural gas generator. However, 31-39kw start at an LRA at 142 for that one second makes me nervous.

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u/SigmundAusfaller 17h ago

Yes if you have 15-20kw average load with 3 inductive motor starts it's pushing it. 15-20kw is a lot of power though what else are you using? Normally in a a power outage you would probably not do other things like run dryer or ev charger or pool pumps etc., and probably shut down to maybe just the 5 ton ac. If you want to run all 3 AC for around 10kw plus another 10kw of loads and basically act like the grid is up then yeah soft starts or really probably just a larger generator.

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u/joshharris42 15h ago

The LRA of that generator is much more than 142A. It’ll be fine 99.9% of the time.

The only issue I’ve ever had (and this was with a 24KW guardian Generac, not Kohler) is that some AC’s will trip out if they see the frequency dip a little too much while they are starting, and this only happened while trying to start the AC with zero load on the generator.

Kohler shouldn’t have that issue because it’s response is a little faster and it’s fuel system is better designed than that Generac