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  1. #1
    Join Date
    Dec 2006
    Location
    Tulsa, OK
    Posts
    80

    Question Condenser Fan Cycle switch question

    We recently had a Copeland scroll compressor fail in a commercial unit at a broadcast transmitter site that needs cooling almost year around due to the heat load. Both units at the site have fan cycle switches on the condensers due to the low outdoor temps we receive in the winter.

    The technician that came out to replace the unit believes the failure was caused because he says the fan cycle switch was no longer working, which is possible.

    However, the thing that got me is he said because the unit uses a scroll compressor instead of conventional compressor a fan cycle switch is not required.

    I have at least another 1/2 dozen commercial units that came with factory installed fan cycle switches and some with variable speed controls on the condenser fans and everyone of them has a Copeland scroll in it, I've been looking all morning to find a definitive answer to this question but can't find one, can someone help me with this?

    I need to know whether to get the guy back out to finish the job or maybe I need to find someone else to finish it.

    Thanks

  2. #2
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    4,847
    All condensing units need some type of head pressure control during low ambient operation, fan cycling is just one.

    Posting the Make & Model # of the unit would be a big help. Copeland only made the compressor not the unit.

    In the mean time I’d look for another tech.

  3. #3
    Join Date
    Dec 2006
    Location
    Tulsa, OK
    Posts
    80
    Having overseen the maintenance of HVAC equipment for almost 20 years I thought this guy was incorrect, but I could tell he was was very much convinced of what he was telling me so that's why I asked the question. Prior to this guy I had always been told to specify fan cycle switches on new system purchases due to the units likely running during winter months but never did someone tell me that if the unit employed a Scroll compressor that some kind of fan control was not needed.

    The unit is a Goodman 5 ton unit, split system, I thought I had the model number with me but I don't.
    Last edited by LightGuy48; 02-21-2010 at 10:40 AM. Reason: Typo

  4. #4
    Join Date
    Mar 2008
    Location
    wi
    Posts
    282
    Agree all units need a fan cycle control of some sort. But I would give the guy benifit of doubt he might be a A/C guy thats pretty good but all hes seen is resd units without low ambient controls, one thing about hvac/r is that its a diverse field and theres no way that every tech can know everything. Also in my opinion the comp should have a crankcase, I know some people think they don't need one, but I'm a fan of them, maybe thats what the guy was refering to. If I remember right I read somewere that all comp scroll como over 6 hp should have crankcase heaters.

  5. #5
    Join Date
    Dec 2009
    Location
    Southern US
    Posts
    504
    When your next tech comes out you might ask about a free cooling option to go along with a head pressure control.

    Curious as to the techs explanation as to why you would not need a pressure control on a scroll?
    I'm good at making things cold...You can ask my first two wives!

  6. #6
    Join Date
    Dec 2006
    Location
    Tulsa, OK
    Posts
    80
    Most of our units have heaters on them, I never really got any explanation out of the guy as to the basis of his belief that no switch was needed other than Scrolls didn't need them and the only thing necessary for cold weather operation was a heater.

  7. #7
    Join Date
    Mar 2007
    Location
    State of Confusion
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    1,210
    When your "next" guy comes out,have him install the modulating type of controller. ICM makes a good one. Switches wear out and their not consistant enough for head pressure/temp. control. Just my opinion.

  8. #8
    Join Date
    Dec 2006
    Location
    Tulsa, OK
    Posts
    80
    Are they better than the Honeywell units? We have a number of Honeywell fan controls on our DataAire units, the triacs they use have a tendancy to fail. We repair them in-house but it's a pain to pull them apart and work on them.

    The triac is only a 20amp device in a TO220 case so there's not a lot of heat dissipation so any problem with the fan motor tends to take the triac with it.

    Which model of ICM is it? I was looking at the ICM326, it appears it doesn't even need a connection to high side pressure? It just uses a thermister? I kind of like that, less chance of leaks, but is it reliable?

  9. #9
    Join Date
    Mar 2007
    Location
    State of Confusion
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    1,210
    Next time you go to your supply house,ask them. Then you can choose the one you like. United refrigeration sell's them in my neck of the woods. It is a thermistor. I dont know the m/n of the control. If you do use switches, install them on the neutral side. Good luck!

  10. #10
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    4,847
    ICM senses the line temperature. I’ve used them on smaller applications.

    The Penn P-66 Control operates on pressure and is designed for larger loads.

  11. #11
    Join Date
    Mar 2007
    Location
    State of Confusion
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    1,210
    I'm guessing these are small "Bard" units...?

  12. #12
    Join Date
    Dec 2006
    Location
    Tulsa, OK
    Posts
    80
    We've got a mix of units, some Bard wall mount packages, some Goodman package units, and some Goodman split units

  13. #13
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,284
    Quote Originally Posted by maxpower View Post
    If you do use switches, install them on the neutral side. Good luck!
    That sounds like bad advice. The last I checked 120v and 277v are the only voltages with neutral legs. And you don't want any safety switches on your neutral leg. If a switch shorts to ground you want it to blow a fuse or trip a breaker.

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