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  1. #1
    Join Date
    Sep 2002
    Posts
    12,568

    Tell me how to wire fan delays -

    This is a used custom-built process-refrigeration tunnel with two five HP R-404 condensing units. One does nothing. The other is piped to two Bohn evaps. Tunnel was cut in half, relocated, and sort of re-piped towards the condensing units.

    "OK; we're ready"

    So I get there today and the liquid and suction lines are twenty feet short, nothing is insulated. No lines are mounted. Joints look they were done with a 1" rosebud tip, and the fitters said:

    "Nitrogen?"

    Also the electricians pulled out nine conductors and pulled in seven. No one seems to know why. <g>

    But never mind all that; I want to use one condensing unit and they kept the section with the two evaps. Each evap has defrost heaters and so a temperature fan delay. Should the delays be paralleled? Series-ed? Or one used and the other not used?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  2. #2
    Join Date
    Jun 2005
    Location
    Las Vegas NV
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    1,152
    Quote Originally Posted by Poodle Head Mikey View Post

    But never mind all that; I want to use one condensing unit and they kept the section with the two evaps. Each evap has defrost heaters and so a temperature fan delay. Should the delays be paralleled? Series-ed? Or one used and the other not used?
    phm,

    Check out this link to Heatcrafts IOM manual. Page 40 starts the wiring diagrams. Page 41 shows the wiring for multiple evaps.

    powell

    http://www.hvacrinfo.com/compressor_data.htm

  3. #3
    Join Date
    Sep 2005
    Location
    florida
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    5,512
    Dang powell you beat me to it. Ya old fart.
    I love the smell of phosgene first thing in the morning:

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  4. #4
    Join Date
    Sep 2002
    Posts
    12,568

    That shows them wired in series

    So either delay open will keep all the evap fans off.

    I'll have to look tomorow but I don't think they gave me enough conductors to do that. <g>
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  5. #5
    Join Date
    Sep 2005
    Location
    florida
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    5,512
    PHM why not just put one on each evap?Just break the fan wires?
    I love the smell of phosgene first thing in the morning:

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  6. #6
    Join Date
    Sep 2002
    Posts
    12,568

    There is one on each evap - they came that way

    The previous wire-er ran a wire to apparently parallel the fan delays. That means that either fan delay making will bring on all the fans on both evaps.

    That didn't make sense to me.

    So then I pondered the whole issue, in my very-tired way, in the 110 degree heat, and finally thought to ask you all about it.

    If the TD's are in series - then both fan delays will have to make before any of the fans run.

    My basic thought agrees with you - let each evap cool and bring on it's own fans on - independent of that it's neighbor evap is doing.

    On the other hand; what the hell do I know? <g>
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  7. #7
    Join Date
    Sep 2005
    Location
    florida
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    5,512
    Quote Originally Posted by Poodle Head Mikey View Post
    The previous wire-er ran a wire to apparently parallel the fan delays. That means that either fan delay making will bring on all the fans on both evaps.

    That didn't make sense to me.

    So then I pondered the whole issue, in my very-tired way, in the 110 degree heat, and finally thought to ask you all about it.

    If the TD's are in series - then both fan delays will have to make before any of the fans run.

    My basic thought agrees with you - let each evap cool and bring on it's own fans on - independent of that it's neighbor evap is doing.

    On the other hand; what the hell do I know? <g>
    I have lot's of store's set up to come on one at a time works for me and with
    no iceing issues.
    I love the smell of phosgene first thing in the morning:

    To apply for professional membership click here


    Educational forums are open.

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  8. #8
    Join Date
    Apr 2004
    Posts
    18
    Possibly a termination wired in there some were???

  9. #9
    Join Date
    Jan 2006
    Location
    DFW Metroplex
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    4,910
    Why couldn't you wire it just as it shows in the wiring diagram on page 41 of the Heatcraft manual (diagram 3) with the following modifications:
    1. Remove the jumper between "F1" on Unit "A" and Unit "B"
    2. Remove the fan delay wire from "F1" on Unit "B" and cap it
    3. Run a wire from "N" to "F1" on Unit "B" terminal block and install a separate thermostat (possibly a Honeywell T6031A1029) in series between "N" and "F1"
    You'd have the best of all worlds then - you wouldn't need extra wires pulled, you could still have the defrost terminations wired in series so each coil would defrost as long as needed............and the fans on each unit would come on independently.

  10. #10
    Join Date
    Aug 2002
    Location
    Orange County CA
    Posts
    1,084
    To bring each fan coil on with it's own control ,yet still have "series" term would be ideal.

    Unless there is a fan contactor/contactors involved ,that's the way I'd go.

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