iced evaporator

[coolerman]

hey guys,i got a little problem.its the 4th time ive gone to service beer coolers w/frozen evaporators,i found out that everytime the bar owners change the thermostat settings and the box was running 29-30 degrees.once i de-iced the evaporator,put the gages in and the pressures were fine.sub-cooling was fine but the on cycle its always alot longer than normal.usually i get about 3-4 minutes on an empty box but on these cases it takes over 15 minutes to bring the box from 45 degrees to 35 degrees.its 134A freon with a cap tube with a 1/3 hp compressor.any ideas on whats the problem? thanx

[Dad]

You have a cap tube system? Suggest using superheat at the evaporator not subcooling.

R134 is heck on cap tubes. If everything is equal and the system coils are clean, I mean really clean condenser coil then you may have a restricted cap tube which is caused by over heating the POE oil and the varnishing of the cap tube interior. You may want to pull the refrigerant and install a new cap tube with a cap drier such as a Sporlan 032S-CAPT. When you use a substitute drier like this one you must compensate for the larger liquid storage area. Most will take 1.5 to 3.0 oz more charge.

Make sure your drier is pointed down for a good liquid seal and charge it to superheat. I would even suggest recharging the box with R-416 instead of R134 to reduce your condenser temp if the condenser system is in a low or no air flow area.

If your compressor has flooded back that many times (freezing of the evap coil)and depending on how old these boxes are there is no telling how much oil in is the evaporator as well. This too will cause an increase in pull time.

[Edited by lusker on 07-14-2004 at 09:00 PM]

[coolerman]

the first time that happened, i recover,change the dryer,vacuum and charge the system with the 8 oz the manufacture recommend. low 17 psi,high 135 psi,10 deg condensor subcooling and about 10" of the return really cold and a bit frost.compressor superheat 75 degrees.
still was taken over 15 minutes

[sparks]

I agree with lusker, overheat 134a/poe oil one time and it's problematic in a cap system.Gums up the inside of the cap line. When I run into these I try to get the customer to change out the compressor and cap. I've expierenced nothing but headaches and problems with this crap.

Superheat is way too high bro.

[Dad]

If they want an explanation of why they need thi$ done... tell them if they would keep the conden$or coil$ clean and leave the thermostat$ alone it would not freeze up and co$t them $o much to fix.

Most boxes will run for a very long time until they are turned into a hot rod or ignored.


Like a car you buy for your son, you know he is going to race it. You know if he does, some one will have to pay.

[jackmm1]

If you plan on replacing the metering device, change it over to a TXV. Make sure you have a hard start kit (Pot relay and start capacitor)installed.

[R12rules]

Originally posted by jackmm1
If you plan on replacing the metering device, change it over to a TXV. Make sure you have a hard start kit (Pot relay and start capacitor)installed.

Hi Jack. I would agree with you if this were a factory package or "kit" they gave you.
But when you have to experiment around with the system in order to get the bugs worked out once you have changed it from cap tube to TXV, who is going to pay for all this time and materials?

If it were my own system, and not for a customer, I would consider doing the retrofit yo mentioned. But only for my own personal pleasure.
There is a reason cap tubes are popular. When tuned correctly, they simply work.


What I might suggest here is replacing the current T-stat with a Ranco A12-701 constant cut in control.
AND making sure the condensor is spotless.

And bury that bulb inside the evaporator coil, securely!



Just my two cents worth.

[Freezeking2000]

A-12 701 t-stat will do the trick, that stat is n.g ill bet!

[coolerman]

Originally posted by lusker
You have a cap tube system? Suggest using superheat at the evaporator not subcooling.

R134 is heck on cap tubes. If everything is equal and the system coils are clean, I mean really clean condenser coil then you may have a restricted cap tube which is caused by over heating the POE oil and the varnishing of the cap tube interior. You may want to pull the refrigerant and install a new cap tube with a cap drier such as a Sporlan 032S-CAPT. When you use a substitute drier like this one you must compensate for the larger liquid storage area. Most will take 1.5 to 3.0 oz more charge.

Make sure your drier is pointed down for a good liquid seal and charge it to superheat. I would even suggest recharging the box with R-416 instead of R134 to reduce your condenser temp if the condenser system is in a low or no air flow area.

If your compressor has flooded back that many times (freezing of the evap coil)and depending on how old these boxes are there is no telling how much oil in is the evaporator as well. This too will cause an increase in pull time.

[Edited by lusker on 07-14-2004 at 09:00 PM]


Hey lusker do you think the evaporator will get the same varnishing as the cap tube and lose efficiency?
is there any way to clean them?

[Dad]

The evaporator will see some varnish but it will be in the thousandths of an inch, remember your cab tube will be from .032 to .050 “ diameter. Your coil will be 3/8” so there is nothing to worry about.

Pull that cap and install a 032-capt drier. Charge to superheat between 6 to 10* and you will be fine.

[melxiv]

4th time of de-icing? how about you install a defrost timer and set it to air defrost during night time?