T 49 Ref.

[olivero]

Could be the thermometer/temperature probe. I have had those get wacky before.

 

Did you know that a frozen pellegrino glass bottle can explode if its frozen? Well, it does when your fridge’s probes go bad and it keeps cooling till everything’s frozen.

 

The probes have a set resistance which is what the temp controller bases all of its temperatures from, so one thing you can do Is call the manufacturer, ask them for the resistance readings in the probe and then go ohm it out yourself, that will tell you if its bad.

 

If the resistance is different, the reading at the temp control will be different than the actual temperature in the cavity.

[alnelson]

The temperature control senses the cooling coil temperature and not the air temperature, so if there’s a refrigeration problem (low on refrigerant or restriction) the coil will cool unevenly and not get cold enough in certain spots to satisfy the temperature control.

 

There may also be a relay mounted behind the electrical box next the the condensing unit that could be sticking on.

[olivero]

Then what is measuring the cavity temperature? The temperature of the evap coil is pretty insignificant in the big picture as long as the unit cools down to its set point, the evap coil is cold enough.

[alnelson]

Olivero have you ever worked on a cooler with a coil sensing temperature control? They are very common.

 

ECtofix did a nice write up about them on here.

[olivero]

Can’t say that I have, at least not when I knew that’s what it was, does Delfield make any like that?

[alnelson]

I think Delfield may use coil sensing temperature controls on a few models.

 

It’s only on medium temp coolers, not freezers.

 

You can tell because the thermostat sensing bulb/tube mounts on/in the evaporator coil.

 

Since its sensing the coil temperature, a refrigeration problem can cause the control to not sense/work properly.

 

They use a coil sensing control because it will control temperature and also provide a means for defrost. They are a “constant cut-in” control, which means the control knob only adjusts the temperature they cut-out at.

 

Since the temperature control senses the coil temperature and always cut in at a fixed setting (usually 37 to 41 degrees), it provides a means of defrost because when the coil gets cold the refrigeration will shut off and won’t come back on until all the ice has melted off the coil.

[ectofix]

Here’s the link to my latest posting regarding coil sensing thermostats:

 

http://techtown.partstown.com/thread/1457