On Sep 8, 3:40 pm, "Karl Townsend"
wrote:
Each of the evaporators in the apple cooler has a thermostat like item C on
page 603 ofhttp://www.mcmaster.com/ They are mounted on the 13' ceiling in
the dark area behind the evaporator. I have to climb to the top of a 10 foot
step ladder to adjust them and they need several adjustments per season. My
old tired eyes almost can't see the dial anymore, trying to look through
bifocals to the ceiling while holding a flashlight and leaning over a stack
of apple boxes just ain't fun.

So, I'm looking for a better thermostat. First I looked at an electronic
thermostat - item E on the same Mcmaster page 603. I could move it about
four foot down the wall as it has a longer bulb length. That would put it
9-10' high on the wall. easier to see but still need a ladder.

Then I noticed item 331K21 on page 544. If I could lengthen the cables from
3' to 30', the control unit could be placed near the cooler walk door at eye
level - no more ladder. It says the sensor is a thermistor probe with a 3.5'
cable. So, can a thermistor probe cable be lengthened?

Or, any other good suggestions? I'd really like to adjust cooler set point
without a ladder and at the front of the room if at all possible. The back
evaporator often gets stacked in. FWIW, any thermostat just energizes a 220
VAC solenoid to let the refrigerant flow.

Karl

Make sure you're dealing with a thermistor, not a thermocouple.
Thermistors are "thermal resistors" and can use regular copper wire
for hook up. Thermocouples use two different types of materials and
require the same pairing for hookup wire. One causes a varying
voltage drop to an applied voltage, the other generates a (small)
varying voltage. Temperature controls can be designed to use one or
the other, but they don't substitute types without some redesign. With
a thermistor, you may have to adjust for the voltage drop of the
additional wire, the temperature control may think it's cooler(or
warmer) than it really is because of the additional resistance,
depends on the coefficient of the thermistor, positive or negative.

Stan