Need Advice on Thermostat

[brankin]

My refrigeration is a 110v compressor unit and cold plates. I had a generic thermostat that has failed so I am looking for advice from you ice box gurus out there. I have seen several units that will do everything short of scrubbing the bottom of the boat. This questions the need for all the bells and whistles.
One unit I am looking at is the scad sensistat refrigeration controller. I know nothing of this product and would like to hear what others are using for controllers. What is the best bang for the buck?

[djmarchand]

Rparts.com

David

[Richard Kollmann]

The most reliable full range mechanical refrigerator temperature controller thermostat for 110 volt systems is a Ranco or Danfoss both are equal in performance. WWWGrainger.com price for a Ranco is under $60 Their stock number is 1A002 Ranco P/N 010-1408. Rparts.com stocks the Danfoss at around $140.

[brankin]

Where is the end of the capillary tube need to be positioned? Attached to the return lines or in open air?

[Richard Kollmann]

Because your system is large with two holding plates the location of probe is important so before anyone can answer your question they need to know the following:

• Is this a single box area where both plates are located? or is it a single box with a divider and both plates in freezer side?
• Is this a two box system with one or two solenoids to control refrigerant flow?
• Are there two refrigerant expansion valves?
• Was there only one thermostat before?
• Is there a low pressure switch used to control compressor as well as a thermostat before?

If you are not able to answer these questions describe what you can about this unit.

[brankin]

I have 4 cold plates in the freezer side of the box. It appears that the thermal expansion valve was stuck. I tapped it with a hammer it started working again. I still need to know where the tip of the thermostat should be placed in the box.

[Richard Kollmann]

Defined as, Large box part freezer with 4 holding plates so there must be a divider if there is to be a refrigerator area. Refrigerant flow is controlled to all holding plates by one valve. Full range temperature controller allows sense tube end bulb to be placed anywhere in freezer except touching plates or box walls. Suggest bulb be clamped 1/2 inch off an open area wall but not divider if possible.

Temperature controller's differential control at time of installation should be set to minimum setting of 5 degree and never adjusted again. Box temperature setting adjusted now to zero degree F. Thermostat settings are almost never relative to actual box temperatures that is why the knob range is numerical OFF- 1 to 10 instead of degrees. In the future these degree markings are reference marks only not degrees.

Food in the freezer should not touch directly to floor of box there needs to be support rails to allow air to circulate under frozen product. The area where you most want to control box temperature is in center of space and mid way up from bottom of box. Remember these are holding plate evaporators are not as efficient as standard evaporator temperature control.

To calibrate thermostat to be accrete maintaining center of freezer I use a inexpensive thermometer setting on a cardboard box at mid point in freezer. After temperature stabilizes with controller set to zero the next day I slowly adjust controller temperature up until compressor stops running and read cardboard box thermometer. I am assuming there is a substantial divider that provides at least a 25 degree F Delta T between freezer and refrigerator. If temperature between freezer and refrigerator area is less than 25 degrees turn controller knob to increase temperature in both boxes to a point where items will not freeze in refrigerator section.

[brankin]

Thanks for the help. WhAt make and model of controller would you recommend? Also, how far off the floor of the freezer should the food be raised

[Richard Kollmann]

Thanks for the help. WhAt make and model of controller would you recommend? Also, how far off the floor of the freezer should the food be raised

Best price Ranco.

3/4 inch rails