I upgraded to a York 15 SEER 4 ton 2 stage AC (DNX024-048) I also have a Generac 20kw natural gas generator. My previous 4 ton 10SEER AC (with a much higher LRA) started just fine on generator power. The new unit's compressor won't start on generator power. The fan will run and it will attempt to start but all it does is make our ceiling fans hum and dim the lights slightly. I am being told by YORK it doesn't recognize the generator's sine wave as a correct sine wave and treats that as low power and therefore won't start. I'm being told by Generac that I just need a Line Conditioner. Is there a way to determine what the issue is and then what the solution needs to be?

Someone could do a power quality analysis. Some UPS systems are frequency sensitive, but the compressor has me slightly baffled.

A couple of thing to look at:

Turn the AC off. Go on generator power. Wait 5 minutes. Turn on AC. Does the AC start within 10 minutes?

I'd make sure that guidelines for the install of compressor heaters and hard-start kits are followed.

I'd add a hard start kit. Here is one for 5 ton. Hard Start Kit,5.0 Ton A/C Units {Dayton 1BAF1}[1BAF1] (http://www.kvmtools.com/product_info.php?products_id=24281&language=en&cPath=25)

HOME AC | HVAC replacement systems | HVAC repair systems | HVAC parts: a/c motor repair parts condenser (http://www.home-ac.com/products/COMPRESSOR_HARD_START_KIT-129-16.html)

Check the grounds. Although this should be more of a heating issue.

There is a cheaper way to use a starting kit

Kickstart®Hard Start Devices - Home Owner FAQ's (http://www.kickstartoem.com/faqs/homeowner.html)

Thank you for your responses. A hard start kit was my initial direction as I had one on my previous unit just to help if the generator had a heavier load than normal. I was told by an AC professional that a hard start kit would not help a scroll compressor type unit. Your information along with looking at the links you provided tells me that the original simple cure of using a hard start kit is exactly the correct answer. It appears that the torque is the issue and the Kickstart Hard Start Device will solve that problem. Thanks for your responses and your time.

Thank you for your responses. A hard start kit was my initial direction as I had one on my previous unit just to help if the generator had a heavier load than normal. I was told by an AC professional that a hard start kit would not help a scroll compressor type unit. Your information along with looking at the links you provided tells me that the original simple cure of using a hard start kit is exactly the correct answer. It appears that the torque is the issue and the Kickstart Hard Start Device will solve that problem. Thanks for your responses and your time.

Not all hard start kits are the same. A potentail relay and a cap should only be used.

See:

YouTube - Hard Start Test! Not all Hard Start Kits are the same! (http://www.youtube.com/watch?v=jFFRpxFkpcM)