# Timer on a walk in cooler



## leland (Dec 28, 2007)

What are you timing? Lights?


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## Chris1971 (Dec 27, 2010)

Senad said:


> Anyone ever install one? Can you install a regular timer or does it have to be a defrost timer?


The only timer ive seen on a walk in cooler was factory installed with the cooling equipment. The refrigeration company set it.


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## Senad (May 25, 2011)

He wants it to shut off for an hour every night.. So it doesn't create frost, so defrosting it..


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## Chris1971 (Dec 27, 2010)

Senad said:


> He wants it to shut off for an hour every night.. So it doesn't create frost, so defrosting it..



Is it an older unit? A good person to ask would be BBQ. Send him a pm.


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## Senad (May 25, 2011)

It's about 10 yrs old..


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## mgraw (Jan 14, 2011)

I usually use paragon clocks. 40 minutes around 2-3 am. Just break the refrigeration unit, leave the evaporator fan motors running if it is a cooler.


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## Chris1971 (Dec 27, 2010)

mgraw said:


> I usually use paragon clocks. 40 minutes around 2-3 am. Just break the refrigeration unit, leave the evaporator fan motors running if it is a cooler.



That's exactly like the factory installed timer does. I couldn't remember. Thanks.


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## Senad (May 25, 2011)

Thank you


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## KayJay (Jan 20, 2008)

Senad said:


> He wants it to shut off for an hour every night.. So it doesn't create frost, so defrosting it..


As far as I know, you shouldn’t need a forced defrost cycle on a walk-in _cooler_ if the equipment is operating correctly. Any frost that forms on the evaporator will melt quickly during the compressor off cycle since the air being continuously blown over it is at the box temp, which is always warmer than the coil temp. A walk-in freezer would be a different situation though.


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## mgraw (Jan 14, 2011)

KayJay said:


> As far as I know, you shouldn't need a forced defrost cycle on a walk-in _cooler_ if the equipment is operating correctly. Any frost that forms on the evaporator will melt quickly during the compressor off cycle since the air being continuously blown over it is at the box temp, which is always warmer than the coil temp. A walk-in freezer would be a different situation though.


_I agree in theory you should not need a defrost timer. But in reality cooler doors are left open, evaporator fans are turned off, t-stats are set too low, etc. Sometimes it is easier and cheaper to add a defrost timer. I always put them on walk-in coolers._


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## MechanicalDVR (Dec 29, 2007)

Chris1971 said:


> That's exactly like the factory installed timer does. I couldn't remember. Thanks.


 
Ahh yeah no, factory installed timers shut off the compressor and turn on the defrost heaters in the evaporator and a defrost termination thermostat in the evap coil turn the compressor back on. A typical defrost clock has two sets of no contacts and a set of nc contacts many have more sets.


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## MechanicalDVR (Dec 29, 2007)

KayJay said:


> As far as I know, you shouldn’t need a forced defrost cycle on a walk-in _cooler_ if the equipment is operating correctly. Any frost that forms on the evaporator will melt quickly during the compressor off cycle since the air being continuously blown over it is at the box temp, which is always warmer than the coil temp. A walk-in freezer would be a different situation though.


 
Here on earth that is NEVER the case.


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## MechanicalDVR (Dec 29, 2007)

Reading some of the statements some guys on this forum say about refrigeration and air conditioning amazes me.


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## MechanicalDVR (Dec 29, 2007)

Here's a couple common ones:


http://www.uri.com/is-bin/INTERSHOP...egoryID=LJEKFgIKktIAAAE00iIOJMg9&OnlineFlag=1


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## mgraw (Jan 14, 2011)

MechanicalDVR said:


> Reading some of the statements some guys on this forum say about refrigeration and air conditioning amazes me.


 I come to this forum to learn about things I don't know. I don't have a problem when someone ask a question. I will try to help them if I know the answer. That is how we all learn and grow in our fields. Many times the information given as fact is totally wrong. Changing settings and speeds, adding relays, etc. when they don't know what they are doing makes me shutter. When you give a different answer many times you get personally attacked. At times I chose not to respond to wrong answers because I don't want to deal with the garbage that comes when you disagree with some on this forum.


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## MechanicalDVR (Dec 29, 2007)

mgraw said:


> I come to this forum to learn about things I don't know. I don't have a problem when someone ask a question. I will try to help them if I know the answer. That is how we all learn and grow in our fields. Many times the information given as fact is totally wrong. Changing settings and speeds, adding relays, etc. when they don't know what they are doing makes me shutter. When you give a different answer many times you get personally attacked. At times I chose not to respond to wrong answers because I don't want to deal with the garbage that comes when you disagree with some on this forum.


 
I hear that but I wonder what would happen if the PO actually took the advise stated in a factual matter sometimes that is dead wrong. I get some flak fairly often but, put my answer often anyway. The biggest problem I have most often is getting the answer out there in a way that someone who has no clue will understand it without writting a book.


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## KayJay (Jan 20, 2008)

MechanicalDVR said:


> Here on earth that is NEVER the case.


I suppose. I'm sure there are some reefer techs out there that could set the LPC and differential to prevent frost buildup on a WIC coil without the need for a timer.


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## MechanicalDVR (Dec 29, 2007)

KayJay said:


> I suppose. I'm sure there are some reefer techs out there that could set the LPC and differential to prevent frost buildup on a WIC coil without the need for a timer.


 
Wouldn't help you a bit if the door was propped open for a delivery on a humid day. I have been around hvacr for more years than I'd care to admit and have as of yet seen a box without sometype of defrost. It has a whole lot more to do with than just coil temp and or refrigerant pressure. Ever hear of a psychometric chart, latent humidity, or dew point ????


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## mgraw (Jan 14, 2011)

KayJay said:


> I suppose. I'm sure there are some reefer techs out there that could set the LPC and differential to prevent frost buildup on a WIC coil without the need for a timer.


 That setup would probably work on a self contained indoor system. It would not work with a remote condenser outside very well. I would say my worst service calls were at 2:00 am 100 miles from home watching ice melt for a few hours. If I can eliminate a few of those by installing a defrost clock I will install them.


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## joemerican (Feb 28, 2012)

Walk in coolers do not have defrost timers because when they cycle off the evaporator becomes ambient temperature. Freezers however do not creating the need for such a device. If the evaporator is freezing up, it is due to lack of refrigerant charge(temp = pressure). A defrost timer normally operates a hot gas bypass melting condensate off the evaporator. This would be a waste of money and a bandaid.


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## joemerican (Feb 28, 2012)

Defrost timers are meant to activate hot gas bypass solenoids on walk in freezers. Don't bandaid it, charge it with refrigerant(temp=pressure) make the customer happy


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## nick.pei (Jun 15, 2009)

http://www.intermatic.com/en/Products/TimeSwitches/Electromechanical_Switches/DefrostTimer.aspx

Here's one. Have one on the wife's stores walkin but I'll have to check model #


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## KayJay (Jan 20, 2008)

MechanicalDVR said:


> Wouldn't help you a bit if the door was propped open for a delivery on a humid day. I have been around hvacr for more years than I'd care to admit and have as of yet seen a box without sometype of defrost. It has a whole lot more to do with than just coil temp and or refrigerant pressure. Ever hear of a psychometric chart, latent humidity, or dew point ????


I’ve seen many walk-in coolers with no forced defrost that work just as designed. Can't say I've heard the term _latent humidity_ used in HVACR before though.


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## MechanicalDVR (Dec 29, 2007)

KayJay said:


> I’ve seen many walk-in coolers with no forced defrost that work just as designed. Can't say I've heard the term _latent humidity_ used in HVACR before though.


So they had no hot gas bypass or any type of defrost at all?


Most buildings condition a combination of outside (ventilation) makeup air and recirculated (return) air. Latent (humidity) loads are typically handled by cooling the air below the dew point to reduce humidity and then re-heating it to reach the desired air temperature. A highly integrated, high-efficiency HVAC system for commercial buildings can be at least 30% more efficient than conventional approaches.


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## mgraw (Jan 14, 2011)

joemerican said:


> Defrost timers are meant to activate hot gas bypass solenoids on walk in freezers. Don't bandaid it, charge it with refrigerant(temp=pressure) make the customer happy


 
If your solution is to add refrigerant to a unit just because it froze up without finding the cause I guess you over charge alot of units.


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## MechanicalDVR (Dec 29, 2007)

joemerican said:


> Walk in coolers do not have defrost timers because when they cycle off the evaporator becomes ambient temperature. Freezers however do not creating the need for such a device. If the evaporator is freezing up, it is due to lack of refrigerant charge(temp = pressure). A defrost timer normally operates a hot gas bypass melting condensate off the evaporator. This would be a waste of money and a bandaid.


I hate to break this to you but there is more than one reason a coil will freeze up and charge is just one reason. And while we are on the subject hot gas bypass is just one type of defrost, more modern evaps have electric heaters in the coil than hot gas bypass which costs more up front.


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## BBQ (Nov 16, 2010)

Lets just all agree that there are as many variations in cooler freezer controls as there are freezer cooler manufacturers.

I spend a great deal of my time working in large supermarkets. We work for at least four large chains and each chain has their own ideas about how they want things controled.

Some common points

Most all coolers and freezers will have defrost times at least a couple of times a day. Likely four times a day.

Some may simply be 'off time' which means the cooling circuit is held closed for a period of time

Others may be reverse or hot gas defrost cycles and others may be electric defrost.

Some are entirely self contained and others may be connected to a large rack of compressors with other coolers. 

Some will have controls in the racks, others with have an entire stand alone control system

Some will re-route the hot gas from the condensers to water heaters or furnaces to reclaim the heat instead of tossing it to the atmosphere.

Some will use glycol as the cooling medium and all the refrigerant stays in a mechanical room and chills the glycol via a heat exchanger.

And on and on and on....

There are a million ways to do it.


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## MechanicalDVR (Dec 29, 2007)

BBQ said:


> Lets just all agree that there are as many variations in cooler freezer controls as there are freezer cooler manufacturers.
> 
> I spend a great deal of my time working in large supermarkets. We work for at least four large chains and each chain has their own ideas about how they want things controled.
> 
> ...


 
Very true and good way of making the point. Sometimes we get hung up on the specific answers given and get myopic. 

Do you get to play with Danfoss electronic expansion valves?


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## Toronto Sparky (Apr 12, 2009)

Why not like a regular frost free fridge? Timer shuts off compressor and turns on heating element for 20-40 minutes to clear frost from coil. Running down a tube to a (so called) rust free pan so the heat of the compressor can evaporate it back into the air so it can once again work its way back to the coil and freeze.. Come to think of it that's not very efficient is it :no:


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## KayJay (Jan 20, 2008)

MechanicalDVR said:


> So they had no hot gas bypass or any type of defrost at all?
> 
> 
> Most buildings condition a combination of outside (ventilation) makeup air and recirculated (return) air. Latent (humidity) loads are typically handled by cooling the air below the dew point to reduce humidity and then re-heating it to reach the desired air temperature. A highly integrated, high-efficiency HVAC system for commercial buildings can be at least 30% more efficient than conventional approaches.


 
No, just off cycle air defrost.
Not sure exactly why the quote was included, but the author is apparently referring to humidity control using reheat in commercial comfort cooling applications.


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