Walkin cooler not maintaining temperature and evaporator coil freezing up

[Rheeman]

Using penn thermostat m#a19aba-40.
What brand of thermostat a few years ago that would go bad after just a couple of months in use?

[MicahWes]

Lots of all kinds of things go bad after just a few months of use.

Is that the problem for sure?

[Rheeman]

No the main problem is that the door is bad and is left open all the time. We just change the system over from the Beacon one system to mechanical system. After I changed over to mechanical system I had to install a defrost timer to keep it from freezing up. no ice on the coil after the defrost timer was installed . I'm having a hard time getting the thermostat dialed in I don't know if its the owner changing the temperature or if its a the thermostat

[jim147]

If you don't fix the door and get them to keep it closed, you'll never win this one.

jim

[Rheeman]

You got that right!

[Rheeman]

Would a thermostat that senses the coil temp be better suited for this application?

[2sac]

You've already installed a defrost clock. IMO, no need for a coil sensing tstat. Providing the refrigeration is correct. Install an A419. The sensor line is long enough you can hide the controller and lock it out.

[Rheeman]

What is a a419

[Capz]

What is a a419

Johnson Controls A419.

I just bought one today for my problem child walk in....no defrost timer either. I think I better add that into the mix. This box has two separate condensing units and evaps that was connected to a Penn dual switch. The Penn was staying closed. I will use the 419 and a DPDT relay to control the pump down circuit along with the timer.

[xpuser357]

Links to direct purchase sites are not permitted in he open forums.

[Rheeman]

I was considering using a coil sensing stat and shorting the defrost to a minimum

[2sac]

Any mechanical stat can be used as a coil sensing stat providing you set the differential properly. The clock is already there. The a419 is similar in price, but takes a little more in the wiring install. It's going to be more accurate than a mechanical stat. If it were me, install the a419 and set the clock to defrost for 1hr at midnight and (2) 30 minute defrosts at 8hr intervals. You might even be able to get rid of the 30min defrosts. Trial and error.

[BALloyd]

I agree a A419 would be a good choice. No one will be able to figure out how to unlock the controls and mess with them without finding an install manual.

[Camiudom]

I've used the Johnson a419 for years for many more applications than you could possibly think of- an absolute staple on the truck. From water heaters to defrost- even light timers. I carry the 240/120v and a 24v and almost always can get me out of a jam.

Compact and versatile- works in a wide range of temperature and humid environments. Can be a pain to mount, can be a pain to wire, can be a pain to program, but is reliable and accurate.

[Rheeman]

I did not know that thermostat was available in 24v. I will definitely check that