Time clocks on w/i coolers

[lennoxman]

My service manager always says to put a time clock on for air defrost when we start having ice up problems.It seems to be a great fix and less midnight calls. I know people in and out and warm/hot product will cause ice up, but what else will cause it out of nowhere. Charge good, s/h good all ideal conditions from a troubleshooting standpoint. (A couple locations I am thinking of.) Human Factor? The clocks work but I don't want to be a lazy hack if I am overlooking somethig. Any thoughts?

[chiller mekanik]

With your service mngr. I don't work on refrigeration much but I remember when I did on a regular basis & the pit falls on walk in coolers that did not have them.

a. The beer guy shows up & has the door open for an hour while he loads everything.

b. The store clerk is doing inventory & turns the evap fans off so he/she doesn't get cold.

c. Some do-gooder decides to crank the t-stat down to 30 so they can have the "coldest beer in town".

I could go on & on. I suppose in a perfect world someone could make a case for not having to have a defrost timer if everything is working right & some people might say that "if you have to put on a timer you're just trying to mask some symptons, be a tech, fix the problem"!!!

I learned along time ago, its not a perfect world.

[t527ed]

Originally posted by chiller mekanik


I learned along time ago, its not a perfect world.

this is the reason we have NEVER installed a walk-in cooler without a clock. have added clocks to many over the years.
always use the defrost o matic clocks to have multiple short defrosts, not some cheap clock that has one long defrost.

[R12rules]

Originally posted by t527ed

Originally posted by chiller mekanik


I learned along time ago, its not a perfect world.

this is the reason we have NEVER installed a walk-in cooler without a clock. have added clocks to many over the years.
always use the defrost o matic clocks to have multiple short defrosts, not some cheap clock that has one long defrost.

I agree.

[Dad]

R-22 walk in's.... clocks are a must

[pecmsg]

Originally posted by lusker
R-22 walk in's.... clocks are a must

A pressure control or Constant Cut In Stat still works better then a time clock. I’m not saying all but most.

[t527ed]

Originally posted by pecmsg

Originally posted by lusker
R-22 walk in's.... clocks are a must

A pressure control or Constant Cut In Stat still works better then a time clock. I’m not saying all but most.

pressure control useless except for pump down or loss of charge if unit is outdoors. never ever ever ever saw a constant cut in thermostat on a real walk-in cooler.

[lennoxman]

So the clock seems to be the right answer. Thanks guys. I just want to be a good honest tech.

[smilies]

Originally posted by t527ed

Originally posted by pecmsg

Originally posted by lusker
R-22 walk in's.... clocks are a must

A pressure control or Constant Cut In Stat still works better then a time clock. I’m not saying all but most.

pressure control useless except for pump down or loss of charge if unit is outdoors. never ever ever ever saw a constant cut in thermostat on a real walk-in cooler.

True that. Those may work on a fractional horse unit, not on walk ins

[K_Neil]

Had a walk-in freezer with a door switch that shut only the fans off. Disconnected it after numerous freeze up calls. Another one is store workers sneaking in there for their breaks on a hot day. The store is in a mall and A/C's are maintained by mall maintenance crew and I get lots of calls caused by high humidity/heat in the store. Store manager keeps calling anyhow. The last call was a walk-in meat cooler closing time panic running too warm. Got there and the evap fan switch was off.

[condenseddave]

Originally posted by lennoxman
My service manager always says to put a time clock on for air defrost when we start having ice up problems.It seems to be a great fix and less midnight calls. I know people in and out and warm/hot product will cause ice up, but what else will cause it out of nowhere. Charge good, s/h good all ideal conditions from a troubleshooting standpoint. (A couple locations I am thinking of.) Human Factor? The clocks work but I don't want to be a lazy hack if I am overlooking somethig. Any thoughts?

Two things cause ice ups:

A coil temp below 32 degrees.

A coil surface above dewpoint.

Both conditions exist in almost EVERY walkin cooler.

[kerndt]

Pecmsg I agree, old time refrigeration guys never used and off cycle timers for defrost. We rarely used thermostats; we used pressure controls to set temperature and to maintain a clear coil. Now with these blends, I find it harder to set up a pressure control to do both.

Dixell makes a controller that has multiple sensors, which allows you to maintain prefect box temperature, without off cycle timer interruptions. It uses one sensor in the air for controlling temperature, a second sensor inside the evaporator coil for controlling defrost, and an optional third sensor that you can put inside a bottle of glycol for displaying a balanced box temperature and alarm monitoring. You set the control up to air defrost every hour or two etc…. but have it terminate on the evaporator sensor, this eliminates excess off cycling. This takes the guess work on figuring out how long to set the off cycle on the mechanical timer.

This is an all in one controller, and it’s cheap, about half the price of a Pargon timer.

[pecmsg]

Its not that I never use them, I just try to avoid it whenever possible. I agree with the blends not as forgiving as R-12.

Thanks for the Drexell information. Looks interesting. Will have to check it out further.

Paul