Open Dairy / Deli case freezing up

[EugeneTheJeep]

Open air cases will sometimes ice up at irregular intervals, based on when nearby HVAC Supply Air Ducts are 'washing out' the case air curtain. Especially when the HVAC is Calling for Heating. It's possible you don't have a Refrigeration problem.

Right, no sense in over analyzing this, it is a one time thing, and the coil defrosts just fine. Of course when you question was the door open the day of the freeze up, you just get a big NO? The customer is a great guy to work with, and he is all cool with it may be a fluke, and may happen again. Plus I get the sale of the night curtains on a 48', 12', and 36' case. So that will be some good money$$$$$$$$$$

[jklondike]

Check insulation on your suction line

[koolkahuna]

[QUOTE=EugeneTheJeep;14760341
Drains run clear, verified by hot water defrost.[/QUOTE]

Did you confirm the P-trap is full of water and not allowing the influx of moisture laden air into the bottom of the case?
I have seen cracked P-traps leak out into the transit or underneath the case not visible unless you look behind the kickplate. Defrost water fills trap, trap leaks out in 30 minutes, reverse airflow from drain water venting pulls moisture into case
Some traps have a drainplug/cap on the bottom for cleanout. They can also leak there if not tight.


Just something extra to check...

[ddalberto]

If there is no problem with the refrigeration I.e. leak, bad heaters etc. I would try a ke2 controller. Much better defrost. http://www.ke2therm.com/

[Snapperhead]

This more than likely has a head master .... are you familiar with charging this kind of setup in winter ?

If someone worked on this unit during summer, and charged it by " sight glass " it would run fine all summer , but they didnt charge it properly for winter.

[EugeneTheJeep]

Did you confirm the P-trap is full of water and not allowing the influx of moisture laden air into the bottom of the case?
I have seen cracked P-traps leak out into the transit or underneath the case not visible unless you look behind the kickplate. Defrost water fills trap, trap leaks out in 30 minutes, reverse airflow from drain water venting pulls moisture into case
Some traps have a drainplug/cap on the bottom for cleanout. They can also leak there if not tight.


Just something extra to check...

That sounds like a good idea, however the case still is running fine. But it is something I will check next time. It only froze up that one balmy fall couple of days where it rained heavy?

This more than likely has a head master .... are you familiar with charging this kind of setup in winter ?

If someone worked on this unit during summer, and charged it by " sight glass " it would run fine all summer , but they didnt charge it properly for winter.

Been working in cold climate for 30 years, so it is not my first. The unit is charged to receiver capacity.

[jpsmith1cm]

Been working in cold climate for 30 years, so it is not my first. The unit is charged to receiver capacity.

That's not necessarily the correct way to charge a headmaster.

http://www.sporlanonline.com/90-30-1.htm

[EugeneTheJeep]

That's not necessarily the correct way to charge a headmaster.

http://www.sporlanonline.com/90-30-1.htm

The system has been charged this way for 5 years, I was the last one to recharge it over the summer, when the HP capillary snapped, it dumped its entire charge, and it is charged per Trenton specs.

[Snapperhead]

Im interested in hearing 30 years of experience , new ways of doing things , tricks of the trade , so how do You charge your systems with head masters in the summer ?

[heresjohnnyb]

defrost termination? possibly the cause of a freeze-up every now and again. does it have one? what style if so. I have had a few run-ins with these irregular nuisance calls with frozen coils. Also, when you say frozen coil, what type of frozen, if you get my drift. Block of ice, or the kind of ice you wanna make a snow cone with while it defrosts.

[EugeneTheJeep]

Im interested in hearing 30 years of experience , new ways of doing things , tricks of the trade , so how do You charge your systems with head masters in the summer ?

I charge it till I get a full site glass, then I add about 20% extra based on receiver size. I then do a pump down to make sure I am not over charged, and it does not raise the head pressure. I learned this by installing a unit years ago that recommended this method of additional charge on the receiver, I do not recall what brand it was? I never get a winter call back.

[ryan1088]

I charge it till I get a full site glass, then I add about 20% extra based on receiver size. I then do a pump down to make sure I am not over charged, and it does not raise the head pressure. I learned this by installing a unit years ago that recommended this method of additional charge on the receiver, I do not recall what brand it was? I never get a winter call back.

I'd be interested to see the Sporlan calculation vs your method and see if you come close to what is needed from doing the math.

[EugeneTheJeep]

Well guys, it froze up again, on a very cold day in the teens, driving over I thought it has to be a headmaster charge problem, now that you had me over analyzing it , now I am going to have to eat crow at HVAC Talk! So I defrosted it, as I was hosing it down, strange enough the txv started hissing with the solenoid switch off? I thought maybe the solenoid is leaking by, but that stopped and it was late, I thought maybe just a pump down as the coils were thawing? System was running fine so I put it back together as it was late and dark on the roof. Follow up in the AM.

Customer left a message over night that the alarm company called about the dairy case temp. I arrived in the morning, 2 degrees outside, and the case was running at 20 degrees, so it was a low temp alarm. So it is starting to look like solenoid or cold control. Of course by the time I get a ladder out and get to the solenoid, every thing is back to normal. So I pulled apart the solenoid (sporlan) and I could swear the small orifice towards the edge of the disc is partially clogged. So I blew it out, it looked better. Since they had product pulled from the case, I also changed the cold control.

Now lets get to the charge on a 2 degree day, I had about 200 PSI high side and a clear site, so no problem with headmaster or charge.

Wish me luck guys, cause ironically I got this customer 5 or 6 years ago, when the dairy case was giving him a problem at the old store, it was a night call, and his former service company would not call him back after multiple repeat calls and call backs. It was tripping out on low oil, and I fixed it by changing out crappy old TXVs, and became his hero.

[Snapperhead]

I assume you have checked the evap fans

maybe a fan blade on upside down ....

you want the cup of the blade facing the direction of air flow

[EugeneTheJeep]

..

you want the cup of the blade facing the direction of air flow

Really??????????

[steve wright]

Better to eat crow with us than the customer! They make you eat the feathers too.

Your doing what you should staying with the problem, I bet they will understand

[Capz]

I never worked or troubleshooted an open air case but I see plenty of older coolers and the like. When I find an issue with freezing evaporator, after checking the obvious, fan motors, blades, SH, I always test the thermostat using my Fluke 52 to see that the t-stat is accurately triggering on and off. I usually end up replacing those old Ranco's with the ETC-111 or the A-419. Both are very precise.

[Snapperhead]

Really??????????

dude you'd be surprised how many people i worked with didnt know which way the friggin dip goes , or why it matters

[EugeneTheJeep]

dude you'd be surprised how many people i worked with didnt know which way the friggin dip goes , or why it matters

Same here, I saw a lot of those fans going backwards in my day. I had a tech trying to sell another customer on a defrost timer for a sandwich unit with LP operation, it had worked this way since the early 70s, turns out he had one fan blowing in, and one out. Air was going in one fan, and out the other, never going through the coil.

[koolkahuna]

Update?