walk in cooler EVAPORATOR coil icing up

[kurt854]

walk in cooler is kept at aound 38 degrees F. ....

clean evap. coil every year, and every year after running for 6 or 8 months i go back and check it and the ball of ice is slowly getting bigger and bigger.

its been doing this for few years now.

its running on mp-39 or (r-401a) refrigerant.

checked psi on suction line and its running at about 15psi. witch i belive is to cold, way below freezing.

so evap. coil is clean, it must be low on
mp-39 refrigerant ?????????????? any guesses?

[taz24]

walk in cooler is kept at aound 38 degrees F. ....

clean evap. coil every year, and every year after running for 6 or 8 months i go back and check it and the ball of ice is slowly getting bigger and bigger.

its been doing this for few years now.

its running on mp-39 or (r-401a) refrigerant.

checked psi on suction line and its running at about 15psi. witch i belive is to cold, way below freezing.

so evap. coil is clean, it must be low on
mp-39 refrigerant ?????????????? any gue

R401a has temps very similar to R12 so the back pressure is not excessivly low.
Does the thing have a sight glass?
Every six or eight months is ok!!!
Just adjust the defrost so it defrosts longer or hoter?

taz.

[kurt854]

thanks for the idea taz, it is a walk in cooler, not a freezer.... so do you think defrost is needed just for evaporator coil than? is that a normal aplication? it seems to run fine other than the slow icing of coil.

[US Iceman]

If you have ice or frost forming on the coil, then the coil temperature is below freezing. Say, you have a room at 40°F (4.4°C). The coil temperature may be operating at 30°F (-1.1°C). Over a long period of time this could slowly accumulate frost/ice (especially during the summer).

An application similar to what I have described above is a candidate for an air defrost cycle. In this instance, the a defrost timer would lock out the compressor for say 30-40 minutes twice a day to allow the frost/ice to melt. The evaporator fans would still be running during this defrost cycle to help melt the frost.

One thing to remember, frost is easy melt but once the frost melts and re-freezes on the coil it becomes ice. Ice takes a lot longer to defrost because it has a higher density that frost.

[Peter_1]

Are the fans running all the time?
When is it frosting up: in winter or summer?
Or the old trick, 2 thermostats.
The room thermostat with the bulb located in the room is set to the desired room temperature and controls the fan (DT set to 1 K)
A second thermostat is placed with its bulb in the coil and controls the compressor, set at start 2°C (see, if you're not used to work with °F, then this is difficult to read a post in IP units) and a DT of 10K.
Your coil will never frost again.

You repleid to Taz "it's a cooler not a freezer" Well, even a cooler needs defrosting from time to time

[US Iceman]

(see, if you're not used to work with °F, then this is difficult to read a post in IP units)


Sorry Peter.:o I fell back on old habits again. I'll try to remember not to do this the next time.;)