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Thread: Cold Controls

  1. #1
    Join Date
    Jul 2001
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    Detroit
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    15
    Is it common practice to put a cold control sensing bulb in the evaporator? And if it is turned to the coldest setting are you at risk of an ice up?

  2. #2
    Join Date
    Nov 2003
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    501
    I've seen it before on smaller applications. I don't know if it'll cause it to freeze because the smaller cold controls come in so many different temperature ranges, it could or it couldn't.

    In my opinion, the best place to put them is in the return air stream so it senses the warmest air.

  3. #3
    Join Date
    Nov 2001
    Location
    Seattle, WA
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    7,774
    The majority of the OEM cold controls are located in the evap to allow the coil to defrost should it ice up during an off cycle.

    The off set point is typically below freezing as the evap coil is below freezing in order to chill the box to set point -- say 38 degrees. So those OEM controls can not be used for return air sensing.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  4. #4
    Join Date
    Sep 2001
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    East Stroudsburg, PA
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    13,215
    Originally posted by dorrmann
    I've seen it before on smaller applications. I don't know if it'll cause it to freeze because the smaller cold controls come in so many different temperature ranges, it could or it couldn't.

    In my opinion, the best place to put them is in the return air stream so it senses the warmest air.
    Delta is right.

    Placing the bulb of a cold control in a small self-contained case will result in case ice ups, unless something else is done to defrost the evaporator.

    Most cold controls (OEM) are designed within a range of evaporator temperatures approximately 10 degrees below the desired box temp. (IE, If you want a box to hold 36 degrees, the coil will need to be run down to 26 degrees.) Now, the majority of these controls are also "constant cutin", which means that they will always cut in at a factory set evap temp, like 41 degrees. That way, all frost is removed from the coil before the next refrigeration cycle begins.

    On larger, remoted boxes, walkins, etc., the temperature control (NOT "cold control" at that point.) should be mounted in the center of the inlet of the evaporator coil. (Returns are on air conditioners...)

    On these larger boxes, a defrost timer can, and should be, IMO, employed to defrost the coil(s) at certain intervals, usually every 8 hours. Sometimes, pressure controls are cobbled into this service, by having their cutins set high.

    Pressure controls should be used as safeties only, and temperature controls and defrost controls applied as operating controls.

    There are other ways, but when you're talking small cap tube self-contained cases, the constant cutin cold control is the single best way to control temp.

  5. #5
    Originally posted by JEFF36
    Is it common practice to put a cold control sensing bulb in the evaporator? And if it is turned to the coldest setting are you at risk of an ice up?
    Very common, that is how they work and are normally set to operate at colder temps. On coolers, they have a preset cut-in above freezing.
    Hey cockroach, don't bug me!

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  6. #6
    Join Date
    Sep 2001
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    East Stroudsburg, PA
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    13,215
    Originally posted by Diceman
    Originally posted by JEFF36
    Is it common practice to put a cold control sensing bulb in the evaporator? And if it is turned to the coldest setting are you at risk of an ice up?
    Very common, that is how they work and are normally set to operate at colder temps. On coolers, they have a preset cut-in above freezing.
    Isn't that what I said???

    Admit it, if there is no photoshopped up copy of one of your pictures, you don't even read what I write...

  7. #7
    Ranco makes a constant cut in cold control that I have used for many years.
    A12-701 is one of them. Another is the a12-1506. Johnstone has them in their catalog listing their temps.

    Make sure if the customer doesnt want a high cut in, you dont give them a replacement control which cuts back in real high.

    I choose the one which cuts back in at the lowest I feel will overcome any light icing which may be occuring during "normal" ops. Say like a 38 degree cut in.


    If the customer has had repeated problems with his box icing up ... make sure you find out why it's icing before just replacing the control.

    A dirty condensor is one reason on those little systems. Another is the door being propped open for extended periods.
    Another is a bad cold control. Or the control bulb is mounted in the wrong area.

    Or ... the charge is off slightly.
    Now this may be the case due to the last tech, or the one before him ... not getting the charge correct.

    It's a snowball affect.

    If you have exhausted every other possibility mentioned, consider doing the charge.


  8. #8
    Originally posted by condenseddave
    Originally posted by Diceman
    Originally posted by JEFF36
    Is it common practice to put a cold control sensing bulb in the evaporator? And if it is turned to the coldest setting are you at risk of an ice up?
    Very common, that is how they work and are normally set to operate at colder temps. On coolers, they have a preset cut-in above freezing.
    Isn't that what I said???

    Admit it, if there is no photoshopped up copy of one of your pictures, you don't even read what I write...
    I didn't read your whole post, too confusing. I just answered him in one sentence. Is Dow rubbing off on you?
    Hey cockroach, don't bug me!

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  9. #9
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,774

    And worn out door gaskets too! Check them carefully. I think a few guys on this board have a couple of blown gaskets from time to time. And the gaskets are easy to replace, easy to get and fairly good money. I bet 72.3% of all the samall door gaskets in every restaruant and every convenient store are worn out or broken.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  10. #10
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by Diceman
    Originally posted by condenseddave
    Originally posted by Diceman
    Originally posted by JEFF36
    Is it common practice to put a cold control sensing bulb in the evaporator? And if it is turned to the coldest setting are you at risk of an ice up?
    Very common, that is how they work and are normally set to operate at colder temps. On coolers, they have a preset cut-in above freezing.
    Isn't that what I said???

    Admit it, if there is no photoshopped up copy of one of your pictures, you don't even read what I write...
    I didn't read your whole post, too confusing. I just answered him in one sentence. Is Dow rubbing off on you?
    Oh. And I thought it would be OK because I didn't tell him to check the superheat.

    You're beginning to get to be high maintenance, in your senility.

  11. #11

    Talking

    What is this superheat stuff about?
    Hey cockroach, don't bug me!

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  12. #12
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by Diceman
    What is this superheat stuff about?
    Here's a picture, ta make ya feel better.


  13. #13

    Talking

    That,s my Monday morning look.
    By Friday afternoon I am almost human again.
    You sure are getting your dough out of that photoshop software.
    Hey cockroach, don't bug me!

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

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