Walk in cooler without defrost

[cajunhvac75]

I went on my first solo refrigeration service call today and it was stuck in defrost. I turned the wheel until it finally clicked on, took out the timer screws and let it run. Called boss and told him what was up and he said to just let it run without defrost until we get to it next week (probably not until Wednesday). I'm sure I should have gone and gotten a new defrost timer and put it in, but I'm still just a noob doing what I'm told. Is it OK to leave it running without defrost for 5 days?

[crazzycajun]

What was the t stat set to, was it a beer box is the box in decent shape (door seals etc).Now the varibles you cant control do the store idiots leave door open go in and out 3000 times an hour. But just for refernce a lot of 35f-40f wi dont have defrost clocks

[cajunhvac75]

Stat set to 35. It is actually a walk in cooler in a restaurant that has a small walk in freezer inside of it...seems to be in fairly good shape. Crazy, are you a wayward cajun that found your way to Kansas?

[local 392]

If it is a cooler it should not need defrost.

[ryan1088]

Now you have what's called off cycle defrost. As long as you don't have leaking doors, open doors, or an excessive load this time of year you should be fine. I like to have timers on my bigger boxes .

[2sac]

Is it OK to leave it running without defrost for 5 days?

Worst thing that will happen is the coil will freeze. In my experience, clocks are a necessity on keg coolers and chicken coolers. The problem with many restaurants is the employees prop doors open. There are a number of other factors, that are less relevant. Many manufacturers have begun putting defrost clocks in their condensing units because they have realized the issues. A properly set HW or WR mechanical temp control with the sensing bulb inserted in the coil will accomplish the off cycle defrost with no possibility of freezing, providing the system is set up and charged properly.

[J_Bridge]

Stick a tstat of a walk in cooler in the coil? What? You should never do that! Return air is where the bulb should be at, t-stat set to cut out at 32 degres in ice water(calibrate). The numbers don't always match up. Super heat at 10-12 degrees with 4 x 30min defrost. The lowee cutout will ensure proper food temp coming out of the w/i/c. These defrost are needed in the south, with the warner air and high humidity situations. This is an off cycle defrost. You should be good, but if they call back with a warm box. Take the timer and be done with the call.

[Snapperhead]

Stick a tstat of a walk in cooler in the coil? What? You should never do that! Return air is where the bulb should be at.

depends on the stat you choose. There are 2 types of bulbs , one needs to be on coil , one hanging in air.

[2sac]

Stick a tstat of a walk in cooler in the coil? What? You should never do that! .

Why not?

[timebuilder]

The problem with merely sensing air temp when using off-cycle defrost is that the air can be warm enough to keep the compressor running, while the coil is already frosted, making the frosting worse, and unable to cool the air. When you have the sensing part embedded in the evap coil, you will trigger the compressor to cycle off, clearing the frost, and then when it comes back on, you are actually getting the air-cooling job done. In the case of using an air temperature thermostat, you MUST have a timer to force a defrost once in a while, for the reason I gave, above.

[NedFlanders]

Low pressure controls save lives....Compressor lives

You can get by in setting the Low Pressure control to a higher cut in temp. If you "cut in" at 38*- 40* (converted coil temp estimated) and "cut out" at 18*- 20* (converted coil temp estimated), you'd be surprised how long and how well it will run like that. The warmer "cut in" will defrost it every time it off cycles. Not to mention , you can mellow out comp cycle starts at the same time. You have to play with the numbers , but it works almost all the time.
The pressure control will run a system (if set up correctly), better than a t-stat most of the time.

Most knuckleheads bury a Med Temp system LP control to cut out at 3-5 #. Every time it pumps down, you drag the coil temp into the toilet. There is no need for that.

[2sac]

Low pressure controls save lives....Compressor lives

You can get by in setting the Low Pressure control to a higher cut in temp. If you "cut in" at 38*- 40* (converted coil temp estimated) and "cut out" at 18*- 20* (converted coil temp estimated), you'd be surprised how long and how well it will run like that. The warmer "cut in" will defrost it every time it off cycles. Not to mention , you can mellow out comp cycle starts at the same time. You have to play with the numbers , but it works almost all the time.
The pressure control will run a system (if set up correctly), better than a t-stat most of the time.

Most knuckleheads bury a Med Temp system LP control to cut out at 3-5 #. Every time it pumps down, you drag the coil temp into the toilet. There is no need for that.

That may work in California, but it does not work where low ambient temps exist. If the outdoor temp is lower than the space temp, the refrigerant will stay in the receiver unless the receiver is wrapped in heat tape and insulated. This used to be a regular practice with R12

[NedFlanders]

That may work in California, but it does not work where low ambient temps exist. If the outdoor temp is lower than the space temp, the refrigerant will stay in the receiver unless the receiver is wrapped in heat tape and insulated. This used to be a regular practice with R12

true...good point