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#213964 - 09/14/14 10:33 PM Load control in generator start up  
ChrisCrawford  Offline
New Member
Joined: Sep 2014
Posts: 2
Molokai Hawaii USA
We installed 5 new Daikin A/C units on a large house with a back up generator and there are problems with the low voltage at generator start up messing with the A/C units (blowing fuses, etc.) Any recommendations on how to delay the power up of A/C units to after the generator stabilizes such as a time delay power relay that we could install that is available? Thanks


Chris Crawford, Space Options, Molokai Hawaii

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#213966 - 09/15/14 01:27 AM Re: Load control in generator start up [Re: ChrisCrawford]  
JoeTestingEngr  Offline
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Joined: Nov 2005
Posts: 790
Chicago, Il.
I would think it best to make sure any ATS doesn't switch until the emergency source is within frequency and voltage tolerances. Then, if I had problems with multiple compressors trying to start at the same time, I would consider TDOs on the control voltages. By time delay switching power to the control ckts, the units would just "wake up" at different times after a power outage. All high currents would be switched as they always are. This would also help on return to the normal source, and if set long enough, help prevent short cycling of the compressor(s).
Joe


#213967 - 09/15/14 02:56 AM Re: Load control in generator start up [Re: ChrisCrawford]  
gfretwell  Online Content


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Joined: Jul 2004
Posts: 9,122
Estero,Fl,usa
Most HVACs have a time delay module in them from the factory these days but they are a delay after power off deal. If the power was off for X minutes it starts immediately.
For the OP's problem you want "delay on" relays set to different times for each compressor.
Five to Ten seconds between starts should do the trick without being that noticeable to the users.

http://www.grainger.com/category/time-delay-relays/relays/electrical/ecatalog/N-8erZ1z0move


Greg Fretwell


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