open dairy half coil freezing

[Capz]

Regarding the defrost, are there electric elements or is this air defrost? If electric, I'd be testing that circuit right after I thawed the ice. Hell with taking apart a TXV until I knew if the unit was defrosting correctly.

[jpsmith1cm]

Yes I did in post #24. And JP if you remove the TXV and service it and even change power head why not just replace it? For the cost of time to sweat it out ( even better if they are flare), re- install, vacuum, etc and just a couple hundred more to replace. I've replace a few that had leaks in the body already in my short career.

Why remove it?

Just take it apart in place. No need to unsweat most TEVs to service them.

If you've got to take it out, then replace it.

[jpsmith1cm]

depends .... if its a customer who always complains " dat bill too spensive " its getting cleaned.

If they pay their bills without question , give them a shiny new Txv if the supply house is near by

Sporlan makes a kit that you can carry on your truck and build a TEV right out of the box.

Saves those trips to the supply house.

[KickedGinger]

A motor up top too? Really hey? Haven't seen that yet. Yes one TXV. I never looked at the sight glass when I was on the roof as I just opened the electrical panel.
Monday will have to get their staff to remove product and get the back panel off to check for another motor and see if any obstruction. dont think these have another motor. then also check if evidence of a leak starting from condenser.

We recently had a problem at a grocery store where half of the coil would freeze up. We found that the filter for the ambient air curtain was plugged solid. The cold air would drop to the floor, freeze the water in the drain line and ice up half the coil. We cleaned the filters and have not had a problem since.

[K_Neil]

If drain pan doesn't clear fast enough you will see ice on the cold side of the case. Open cases (headaches) are the garbage collectors where the grape seeds,gum,etc. wind up. The case drain flushed ok? A long time back when the same thing was happening to me on a new case I finally got mad enuf to empty the whole case and found an air drill under the fan shroud. The cold side of the case will ice up first even if all is clear on that side.

[TempcoDog]

That's interesting Neil. Yes lots of crap collects and the adjoining case had a plugged drain last week. But my case in question has been good. Once I took panels Nd shelves off I discovered a very large build up of ice on back side of coil. Spent some time defrosting it

[BDOLIN]

Shouldn't there be a divider (plastic wall) between the two cases to prevent what happens in one to affect the other?

[jpsmith1cm]

Shouldn't there be a divider (plastic wall) between the two cases to prevent what happens in one to affect the other?

This is common on frozen foods cases with defrost that require additional heat.

Open air cases with off-time defrosts don't typically have dividers.

[K_Neil]

Abnormal moisture will always find a way to plug things up

[BDOLIN]

This is common on frozen foods cases with defrost that require additional heat.

Open air cases with off-time defrosts don't typically have dividers.

Of course you are right, cases in supermarkets with common suction groups would not be divided. Since these two cases are on separate condensing units, I wonder if the warmer air from one case in defrost (even just off cycle) could affect the thermostat of the other case and cause it to overcool.
Just a thought.

[jpsmith1cm]

Of course you are right, cases in supermarkets with common suction groups would not be divided. Since these two cases are on separate condensing units, I wonder if the warmer air from one case in defrost (even just off cycle) could affect the thermostat of the other case and cause it to overcool.
Just a thought.

Even open-air cases on different suction groups don't have dividers that I've ever seen.

[icemeister]

I'm going back a bit here, but about 30 years ago Hussmann (I believe) required dividers between gas & electric defrost cases on different circuits or systems and recommended them for all others.

I haven't found any current requirements...but that doesn't mean there aren't any.

[Kool Tech]

Assuming I understand your description it sounds like you are saying the coil has one copper tube that runs the length of the unit, then it returns to the other and so forth. Is this correct? If it is and you are getting frost on one side of the unit instead of the first half of the coil where it enters the evaporator. The your problem is not a refrigerant charge but an airflow issue. If it is the first half of the evaporator then and only then is it a low charge.

Now assuming you have a airflow problem, I would look into if maybe the fans have been replaced. I would look into their specs for horsepower, rotation, fan blade direction, is it where it belongs inside the opening where the metal shrouds around it. Also look at the back of the coil it is possible that it may be restricted from dirt or some food has been placed too high blocking the vents that circulate the air. Remember that the open air units are really closed, not by a housing but by an air curtain. This is void if food is stacked up too high. Ask the employees to show you how they usually stock food on a normal basis & ask them what do they do if they they have a large load of food.

Another thing I would look at is are the vents clogged with dust from inside. Is the plenum blocked or no longer secure against the wall as designed to be. Someone may have worked on it prior & not installed it back as it should be.