T'stat settings Reach-In Cooler

[VAV616]

Say we have a small reach-in cooler and the T'stat goes out.
I replace it with one of the Ranco digitals for $50.
Now, I push the sensor into the E-coil fins, so that it
reads the coil temp. So, where should the set point be?
most reach ins run at around 20* coil temp/pressure.
but should the set point on the t'stat be around say
33* so that when ice begins to form it shuts off
and then the differential at about 7 or 8*?

Is that about right or what do you do?

VAV

[engineerdave]

It's entirely possible that my following statement will permanently lable me as a hack..........

I'm not a big fan of the coil temp situation. When I replace temp controllers in Walk-Ins, I set 'em up to sense Return Air. For a W/ICooler I'll set it for say 34* w/ 3* swing. Seems to work out okay. So far.

That's my $0.02

[VAV616]

Well, in the case of a walk-in I agree. the sensor should be on the wall right behind the evaporator so that it reads return air temp. some set it right on the evaporator which will give you false readings especially if it freezes up.

But in this case its a small reach-in , and the original factory T'stat is embeded in the E-coil. so I put it back that way, and figure that it will shut down when ice forms and sort of air defrost that way.

[engineerdave]

Sorry man. Guess maybe I outta pay a bit more attention to the OP.

:o

[jpsmith1cm]

Say we have a small reach-in cooler and the T'stat goes out.
I replace it with one of the Ranco digitals for $50.
Now, I push the sensor into the E-coil fins, so that it
reads the coil temp. So, where should the set point be?
most reach ins run at around 20* coil temp/pressure.
but should the set point on the t'stat be around say
33* so that when ice begins to form it shuts off
and then the differential at about 7 or 8*?

Is that about right or what do you do?

VAV

You will have to play with it a little, but I think that a 33 degree setpoint will leave your box warm.

Think about it. a 33 degree coil leaves you with approx 43 degree supply air.

[nate1701]

I've never used the digital, but for the cold controls I used the cut in temp was 37*F....(coil temp)that ensured the entire coil was defrosted. As Jp mentioned the air will be warmer than the coil so the cut out can be 23-25*F, thats a diff. of 12-14. Once the coil reaches that temp it shuts off and cuts in at 37 so no need to worry about frosting.

[ckone180]

Settings depend on what your box temperature needs to be. A Ranco A12-1506/A12-700 is the most common t-stats we use in small reach-ins. They have a constant cut in of 37-39 degrees. Cut out is designed for mid range to be about 17 degrees. If you set your t-stat to cut out at 33 degrees, you will only short cycle your unit to its demise. Coil sensing is the most accurate way of controlling temp in a small box, due to the fans stay running while the doors are heavily used, i.e. cooks line prep table.

[man from trane]

I've never used the digital, but for the cold controls I used the cut in temp was 37*F....(coil temp)that ensured the entire coil was defrosted. As Jp mentioned the air will be warmer than the coil so the cut out can be 23-25*F, thats a diff. of 12-14. Once the coil reaches that temp it shuts off and cuts in at 37 so no need to worry about frosting.

This would have been great info to have last week when I charged my first reach-in to run at 35 Degrees SST to prevent freezing the coil! :o Oh well, I corrected it and it runs much better now. Thanks for posting this!

[Airmechanical]

anytime i replace a stat that was in the coil, i change it to sense airtemp



.

[KB Cool]

anytime i replace a stat that was in the coil, i change it to sense airtemp



.

And then i come along and remove it, along with your defrost timer that you had to add later because unit was now freezing up, and go back in with an A12-701. :D

[crazy eye]

And then i come along and remove it, along with your defrost timer that you had to add later because unit was now freezing up, and go back in with an A12-701. :D

That's all I use on reach-in cooler .Kbghdg how you like this nice Az weather ?

[KB Cool]

Kbghdg how you like this nice Az weather ?

2 or 3 weeks ago when it first got hot. It sucked. Sweat pouring off your body. Digital scale LCD screens going Black. Equipment panels "Hot to the touch".:eek: But, now i'm getting used to it and it's not so bad. I think this is my 7th or 8th summer doing HVAC/R in the desert.

[thermofridge]

kbghbg has it right. If you sense air temp., it will freeze up eventually without a defrost timer. Put the bulb in the coil and it is impossible to freeze it up with no defrost timer.