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  1. #1
    Join Date
    Jun 2001

    Freeqing the condenser

    I see a lot of new technology via my fabulous lot in life.

    I was on a new store today, big chain, and doing some work and seen the condensers being freeq driven, no big deal but also seen them fan cycled too. I seen in the e2 that there is this choice you have to combine freeq drive with fan cycle.

    I think this is stupid. I have commisioned some, and I have worked on a lot and I never seen the reason to do this and since I was on the roof working today on a particular condenser driven like this, it occured to me how stupid this set up is. You got fans running at low percent, not nearly fast enough to be doing any effective work, and yet as the program worked, fans were cycling via the outputs and contactors. I think it's rough on the contactors. Premature deteiroation for needless cycling.

    So I thought the commisioning was all horked up. As I found out this is mandated by engineering for this chain.

    How stupid. 1 fan running 200 rpm or all, still not moving any air over condenser. None. Yet, the wind blows, the drop leg temp drops a tad, were shutting fans on and off.

    Even on the top end, your never gonna get it so tight you have the need for fan cycling. Just ramp up and down.

    How come everyone is not as smart as I am?

  2. #2
    Join Date
    Aug 2002
    Orange County CA
    I've heard of this .....the energy saving specs are getting silly.
    I'd rather set a low minimum(8-10HZ) and let the fans cruise until the stategy calls to ramp again. I set the low limit at about 65*
    I usually set the condenser start/stop in sensor control or an outside task just for that reason. Like cut in 66..cut out at 64 for 2min.
    The condenser task will want to cycle the cond fans on/off way too much.
    The only thing I have the cond task do is the A.O.(0-10v)

    Then again , where you live low are the "droplegs" getting.

  3. #3
    Join Date
    Sep 2005
    Just wait until you have to replace one of them motors they are fan blade and motor combo both have to be replaced as a unit at about well lets just say its not cheap.
    I love the smell of phosgene first thing in the morning:

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  4. #4
    Join Date
    Sep 2008
    Western PA
    We have both setups.

    An RC-2000 controlled condenser that starts at 10%, stages up all the fans, then begins to ramp up.

    In 10 years, I have not seen a contactor replaced on this store, except for the odd coil burnout. Points are still in good shape.

    Other end is an AK controlled condenser that has individually controllable motors (hardware is actually ahead of the software) Each bank (right and left) operate as a unit. No contactors in used, only a pair of relays. All fans start at 10% speed and ramp from there.

    That one is a remodel in progress, so i'll give an update if I get reliability and performance data.

  5. #5
    Join Date
    Jun 2001
    the fan cycle is needless. Even in fast recovery. Even in a tight target in a say 40 to 60 degree ambient when she's splitting and unsplitting. You just never see the need when using freeq.

    I never seen the manipulation needed. Just ramp all up and down.

    I can not for the life of me understand why an engineer is specifying this.

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