Not a Refer guy.

[3E151]

I have had some limited experience in refrigeration (commercial) but not a lot and all the stuff I learned in school is lost in the abyss.

Here is the problem. I have an APEX walk-in cooler and the evap coil is freezing from the bottom first then slowly creeping up. It is a fairly new system.

First I checked the pitch of the drain pan. Everything is fine, it drains to a secondary drain pan that the high side runs through to evaporate it.

Both fans are working correctly and the pressure is fine. I adjusted the defrost parameters so that the drip time after defrost is longer to facilitate proper drainage.

I am going back to check it first thing Monday morning. I suspect the TXV, however I don't remember what I am looking for. Am I barking up the wrong tree, or have I fixed the problem already?

Help, I HATE repeat calls. If the answer is already posted somewhere else let me know?

[iceetech]

need more info!!!!!!!!!!!!!!!!!!!!!!!
heres a start: low on charge, dirty evap coil, door left open, tstat set too low, bad tstat.

hope this helps

[hvaccop]

more info is needed. Air defrost? Electric? walk in cooler not freezer

[3E151]

Walk in Cooler, NOT freezer. Coil is freezing from bottom up, and charge is good. Air Defrost. Not door, evap coil clean as a whistle. T-stat is fine, not too low or bad.

[t527ed]

has a defrost timer, is it running??

[3E151]

has a defrost timer, is it running??
yup.

[whec720]

What's your superheat?

[the mojo]

Tap the equilizer line on Monday. From now and into Monday refresh yourself on Superheat and its effects on a coil how it feeds when starved, flooded and running normal.;)

[push 2 reset]

also make sure you have a drain trap,just curious what gas is it

[icemeister]

An accumulation of ice starting from the bottom of the evaporator coil that slowly builds over time is an indication that the coil is either not completely defrosting and/or not completely shedding the drip water during each defrost cycle.

Normally the coil gets a thin layer of frost fairly even distributed over its surface and during an off cycle defrost period the frost melts and the remaining water droplets fall to the bottom and drip off into the pan. In you case it appears that the drip water may be beading up on the lower finned surface due to surface tension and refreezing into ice. Subsequent defrost cycles may be sufficient to melt new frost but not long enough to melt off the ice formation.

Try spraying the coil with Rain-X. This often does the trick to get that water completely off the coil.

[whec720]

Rain X, good idea. Thanks for the trade secret.

[3E151]

Rain X, good idea. Thanks for the trade secret.

Yeah, I would have never thought about that. Thanks.

[3E151]

also make sure you have a drain trap,just curious what gas is it

It has a trap. Also it is 22.

[mdharris68]

Clear ice? or white frost? I tend to find drainage problems associated with clear ice and refrigerant feed problems with coils frosting up from the bottom.

Since it's a med temp, are they trying to run the box temp consistently below 35*? If so that will cause alot more frost to build than if it runs 35 and above. What about air infiltration? Could that be an issue? Just my 2 cents worth.

[push 2 reset]

It has a trap. Also it is 22.

anytime I had a med. temp. coil ice from the bottom up it has been a coil that uses r-22 they all seem to start this way then with any other gas or so it seems.I worked for a company that serviced all the 7-11 stores all along the garden state parkway and southland corp. wanted all beverage w/ins to bottom out at 35f no exceptions.more product gets sold that way.this meant for a long off cycle defrost generally in the wee hours of the morn.now it so be noted that the coils were in prestine condition,my point is anytime you run the temp down to 35f you may actually be running colder before the unit cycles off and when that happens as in the case with lets say fresh meat storage box 32f to say 34f you needsome supplemental defrost this can happen with any gas not just with r22 as I stated earlier........ hope this helps

[hvaccop]

I would most definitely check your defrost clock and verify 100% sure that it is working properly. Also watch the cooler satisfy and see what temp it satisfies and what temp it cycles back on to make sure it is within proper range. One of these two will most likely solve your problem

[frozensolid]

I would check to see if the evap distributor has a orifice installed, it sounds like a classic case of no orifice in distributor.

[hvaccop]

I would check to see if the evap distributor has a orifice installed, it sounds like a classic case of no orifice in distributor.

Didnt think of that but you may have hit the nail on the head

[3E151]

Thanks for all the help. I think it is entirely a defrost drip time issue. I will know soon enough.

[itsiceman]

Are the evap. fans running while in defrost? If they are the cut out on the t-stat might be too cold.

[3E151]

Well, I was right, and technically I fixed it Friday. No ice, unit running fine pulling down to 38 just like it should. Thanks for all the help!