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.

[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.

[2sac]

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

Why not?

[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.

[ryan1088]

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.

This would work on a non pumpdown system. Otherwise you'll short cycle the compressor and be in worse shape than a frozen coil. I still have 3 coolers that operate this way and haven't had any trouble with them in the 3 years I've been doing refer work here.

[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

[J_Bridge]

I have been doing this for over 13 years and my company for over 35 years and we have never had a tstat in the coil on a WIC. But let me clarify what I am calling off cycle defrost. We always recomend and install pump down systems and install defrost time clocks. As I stated earlier the defrost is 4 x 30min, sometimes we might go to 6 x 30min if it is a high traffic box or they are putting hot product in it. We set and mark the tstat to cut out near 32 degrees on return air temp. If your super heat is set properly 10-12 degrees, and you can go lower as long as your superheat at the compressor isn't below 20 degreees during the busy time(this ensures that during the low load at night you still have superheat at your compressor). This will prevent the coil from freezing up. This all being said you need to be checking the size of the system and the box size. I always do tis when it is a job site we don't normally service or if we have had multiple issues on the system.
Back to the bulb in the coil, none of the manufactures put their bulbs in their coils on WIC's. Their bulbs are always in the return air, Their is a reason the factories don't put them in the coils.

[2sac]

I believe a manufacturer like ICS for example who drops their boxes complete, minus plumbing and power, off a trailer won't put a bulb in a coil for a number of reasons. The first on being someones going to mess with it. Improper startup procedures, lack of knowledgeable techs, possible breakage during shipping to name a few. If I set my CI between 38-40 and set my CO appropiately it will not freeze up. Fast food restaurants are notorious for proping doors open. With the bulb in the coil as soon as the coil temp reaches the CO setpoint the compressor shuts down and will not come back on until the coil temp reaches the CI setpoint not allowing the coil to freeze. With a door propped open and the bulb in the return air the compressor will run forever.

Neither way is incorrect. There is just more than one way to skin a cat.

[Snapperhead]

Bridge ..... lets take a refrigerator with the bulb hanging in the airflow , and its suddenly packed with warm product and the box temperature shoots up to 60°F. The compressor starts, but it has a long journey before the box temperature drops all of that warm product to 40°F. The coil begins to frost, blocking airflow and heat transfer. Because the frost is insulating the coil from the warm boxes temperature , the evap temp continues to fall eventually forming ice. This Air sensing stat keeps the compressor running because it still senses 60 degree product, adding to the frost problems .... however if the bulb was indeed mounted in the coil fins, the stat would shut down the compressor when the evap dropped to the cutout temp of 25. Then while the compressor was off the Fans would be steadily running circulating the warm box temp air over the evap melting the frost ,and when the coil defrosts to the point of ultimately raising the coil temp to 40 deg cut in , the compressor comes back on. This cycle continues back and fourth until both product and box are at same temp.

Like 2sac said , both work , but the air sensing one needs a time clock which is alot more wiring and more crap to go bad.

[ETC1]

In my world units are undersized Boxes are poorly insulate with leaks,loaded with hot steaming food etc. On Indoor condensing unit temp was frequently controlled by the LP switch. I have placed t'stat bulbin the evaporator coil on outdoor units too allow proper defrost as it mimics the action of the LP switch. If you set the cut in to box cut in and adjust cut out according to appropriate coil temp drop box maintains temp based on coil temp.

[timebuilder]

I believe a manufacturer like ICS for example who drops their boxes complete, minus plumbing and power, off a trailer won't put a bulb in a coil for a number of reasons. The first on being someones going to mess with it. Improper startup procedures, lack of knowledgeable techs, possible breakage during shipping to name a few. If I set my CI between 38-40 and set my CO appropiately it will not freeze up. Fast food restaurants are notorious for proping doors open. With the bulb in the coil as soon as the coil temp reaches the CO setpoint the compressor shuts down and will not come back on until the coil temp reaches the CI setpoint not allowing the coil to freeze. With a door propped open and the bulb in the return air the compressor will run forever.

Neither way is incorrect. There is just more than one way to skin a cat.

One of our guys called ICS with a question, and he said they don't actually make the equipment, they just put their name on it. Any idea who actually makes the stuff?

[carmon]

out of all the coolers I service maybe 1% have a defrost clock....... you usually don't require one.....