Ice problem

[yotaman16]

I have a walk in freezer running -20degrees. Therere are 4 seprate units running in this box all on there own t-stat. They cool the space fine but one of then has now developed a small ice problem. One corner has ice on it approximatly 3/8 to 1/2 inch thick. Its not at the inlet or the outlet side. its on the oppsite side of the coil. The super heat is between 8 and 9 degrees . The system has a clear glass. All defrost heaters are working fine. What would ur recomendation be to check next.

[mdharris68]

Check your fan delay after defrost, if it has it, to see if water is being blown out of the drain pan and up on front side of coil. Thats my first thought but hard to tell since I can't see the situation first hand.

[yotaman16]

The spot where the ice is located is aprozimatly a 6 x 6 square if that helps.

[mdharris68]

Is it clear ice or frost? What about air infiltration throught the walk-in box above that end of that particular coil?

[yotaman16]

Its not clear ice. Ill keep u guys posted with more info and hopefully whats wrong... Im off to try and figure this thing out. :confused:

[james264]

Same as mdharris68 check fan termination relay also check drains and evaporator drain pain heaters ,drain heaters also be sure defrost termination relay is taking evaporator out of defrost if not it will stay in defrost longer reverting to the setting on timeclock.Had 1 last week defrost term bad would not trip defrost solenoid freezer would drip with water around evaporator.

[yotaman16]

Ok so i went today and first thing i check was the superheat and now it was in the 30s. I also noticed that the bulb on the txv was not insulated so i did that. Was very cold out so i couldnt check to see if the glass was clear because i couldnt get the head pressure up high enough it just kept bypassing the coil.. So i ordered a txv for it and should be in tommorow for me to pop in...well see i dont see what else could be up.. The system was pumping down before defrost so defrost termination was working and all heaters were working. any thoughts??? did i make the right call? Im pretty new to this i just graduated tech school in may... Trying to take all this info in..

[icemeister]

Ok so i went today and first thing i check was the superheat and now it was in the 30s. I also noticed that the bulb on the txv was not insulated so i did that. Was very cold out so i couldnt check to see if the glass was clear because i couldnt get the head pressure up high enough it just kept bypassing the coil.. So i ordered a txv for it and should be in tommorow for me to pop in...

Before you condemn any TEV you have to make sure it's getting a solid column of liquid so it can work properly. If you have 30ºF SH, the sightglass isn't clear and the HP control is bypassing it tells me that you're short on charge to flood the condenser coil at low ambients.

Add some refrigerant to clear the SG and then check your SH at the evaporator. I think you'll see a marked difference.

This may also have some bearing on the icing problem that you started this thread about.

[mark itziro]

Make sure the gas isnt flashing at the valve or that the inlet screen is clean before you swap out the valve. Low charge because of cold weather is common and will make it seem like the valve isnt feeding.

[yotaman16]

The glass is not flashing so its eather clear or empty. I used my judgment to say it was clear. I shut the unit down and the glass bubbled, so i assumed that it was not empty. Is that a bad assumption. And as i stated the weather is very cold and the refrigerant is just bypassing the condenser so i cant put a load on the condenser because its bypassing. The distributor was also all iced up apon investigating this problem today.

So what do u guys think i should do. Do u think i should change the guts or do u think its low on gas. which both or eather could and mostlikly is my icing problem.

[markettech]

One super simple way of confirming a full sight glass is to front-seat the king valve and watch the sight glass.

[mark itziro]

If your box is down to temp and only one of the four coils is starving than it is most likely a valve problem. Could be a bad power element or plugged inlet screen. But make sure you have liqiud at the valve before you change it.

Is it possible to shut off flow to the other valves? if so try that to see if it starts to feed.

[yotaman16]

the box has 4 seprate coils with there own condensing unit. To check the inlet screen i have to putt the txv anyways correct? And the box is down to temp

[markettech]

To check the TXV screen, you will need to open the system, but not pull the valve.

[yotaman16]

hey markettech can u expalin that simple way of confirming the glass is clear not empty? Thanks

[markettech]

hey markettech can u expalin that simple way of confirming the glass is clear not empty? Thanks

Front seat the valve on the outlet of the receiver. While doing this, make sure you can see the sight glass.

If the sight glass is completely full, you will see the liquid level in the sight glass slowly subside and actually be able to see the liquid boil off at the bottom of the glass as the system pumps down.

If, on the other hand, the sight glass is empty, you will see no change in the glass.

Then, open the king valve again after the system pumps down. If the system is fully charged, you will see liquid fill the glass and eventually the glass will clear.

If the system is low on charge, you will see the initial blast of liquid as it enters the sight glass and then slowly dissipate.

[markettech]

A virtually foolproof method of checking charge is to heat the receiver with a turbo torch (while the system is running) and feel for a rapid temp change on the receiver. Your liquid level in the receiver will correspond to the point where the receiver temp turns from ass kickin hot to relatively cool (depending on outside ambient and condensing unit location).

[yotaman16]

cool thanks i will check the glass using that method tommorow morning then i guess i will pull the screen and check that and if thats clean i guess i will change the guts.. unless someone thinks theres a better thing to do?

[yotaman16]

pulled the screen and it was clean, replaced the guts on the txv... went back today for a down truck and looked at the coil no ice.. said they havent had a problem...

[hvacman77]

I thinking...from what I read..Moisture. By pumping down the unit, R&R the valve and of course a new drier or cores, evacuation you solved the problem. From the symptoms you stated, being a low temp system espically.

[cracker]

Thinking out side the box, you have 4 system, blowing a lot of air, " maybe a wind storm" If your super heat Is ok and a clear sight glass, check to see if the heater is in contact, or if it is far away, when it goes into defrost, and the other units running, there may be a air flow problem, for just a little spot, some times I put a piece a bare copper wire around the heater, and over to ice spot, It would warm it up to help the spot ice melt?http://bestsmileys.com/signs10/1.gif