R-22 Walk in cooler

[serviceguy]

sorry to post another walk-in cooler problem here,but hoping for some help here...
keep in mind i mostly do residential work

outdoor condensing unit:copeland model#F3AH-A100-CAV-001
indoor evap. unit:BOHN model#adt070ak
indoor txv:Sporlan KT 43 VC
76.4 F outdoor temp
38 F inside cooler temp
suction pressure:49 psi head pressure:200 psi
suction saturation temp:25 head saturation temp:100
suction line temp:47.3 head line temp:91.4
**unit uses a thermostat set at 36 F**
problem is, as you can tell the superheat is way high and over a period of a week the indoor coil is frozen up solid. I've tried adjusting the txv in both directions from factory settings and the best I can achieve is 20-22 superheat. Tried to adjust it by adding and taking away freon (oh yea i forgot to mention it's a R-22 system), finaly got frustrated and recovered all freon from system and recharged until site glass just was clear and then tried to adjust the superheat yet again by the txv with the same results. Any help with this situation would be greatly appreciated. If I have left out any needed info. please let me know.

[frozensolid]

You gave us the powerhead of the valve but not the size. Sounds like it may be to small, or your strainer is clogging. Is the valve body icing?

[serviceguy]

srry...should have wrote it like this
BOHN (heatcraft) model #ADT070AK

[serviceguy]

no the valve body is not icing. i start seeing frost at the distributer and the first 2 loops of the evaporator.

it doesnt seem to go any further while im there, but if i come back in a few days its frosted at least the whole coil and frozen up solid within a week

[frozensolid]

That’s the coil size, what’s the valve size (Tonnage).

[serviceguy]

not sure...we didnt install the unit and the #'s i gave are the only ones i could find on the valve...is there another way to tell?¿?¿

[frozensolid]

If its not on the powerhead, it should be stamped on the valve body. If it's a Q body there may be a silver tag on the cap tube.

[serviceguy]

the valve is in a position that is very easy to see all sides of it and there are no other visible #'s on it or around it and there is no trace of any silver tags

[coyote]

Where are you reading your suction line temperature and your pressure reading. You should have 6°to 10°superheat at the expansion valve bulb but if you are reading the suction line temp at the compressor copelands recommendation is 20° at the compressor

[serviceguy]

i was told 12 degrees at the compressor by our supplier, but i suppose they may be wrong...were did you find ur info at¿

[ahc&r]

40 degree suction line temop at compressor, or max of 240 degree? within 6 inches of discharge. Hermetic or semi? 12degree superheat at txv, possibly down to 4 degree depending on line length. add for pressure drop. Sporlan and alco will be stamped with tonage. Recommend, Depending on location of stat bulb, running box too cold. Insall a stat that read evap temp,say 37 degree constant cut in with specific differincial or install a time clock to shut down system for 1 to 11/2 hour each night.

[ahc&r]

I'm new so a response would be appreciated

[psmurf]

take out tstat and replace with lo press control. set it at 37#to 40# cut in and about 61# cut outto start. then measure box temp to fine tune press control. be sure to set cut in high enough to defrost coil. this takes some time but it works. i have done this many times with great sucess

good luck

[ahc&r]

Unless condeser is in an ambient cotrolled ambient out doors, a low preessure control will not give adequet results.

[prestiege]

Originally posted by psmurf
take out tstat and replace with lo press control. set it at 37#to 40# cut in and about 61# cut outto start. then measure box temp to fine tune press control. be sure to set cut in high enough to defrost coil. this takes some time but it works. i have done this many times with great sucess

good luck

i asked in the topic i started about the LPC settings i have it at 32CO and 64CI, that i got from a frefrigerant table the yellow laminated card by alco controls, why did someone say to set the cutout at 5 and cut in at 25, maybe he didnt see it was R22

but did you take the discharge line off of the txv and inspect the screen when you evacuated the system

[ahc&r]

Unless condeser is in an ambient cotrolled ambient out doors, a low preessure control will not give adequet results.

[ahc&r]

Post 9: backward but OK if condenser is indoors, otherwise, is there pump down?

[Dad]

prestiege

i asked in the topic i started about the LPC settings i have it at 32CO and 64CI, that i got from a frefrigerant table the yellow laminated card by alco controls, why did someone say to set the cutout at 5 and cut in at 25, maybe he didnt see it was R22

LPC set at 5lbs in and 25lb out is for LLV (pump down, not temp/pressure control)

I think you were peeking at another post

32lbs cut out w/ R-22 = 10* too low!

[ahc&r]

powt 14 Info comes from copeland engeneering manuals,basic refri( not trying to be ruud), Maintain minimum superhaet to maintain minimum discharge temp, to be > ? temp. Can't rem exactt #

[serviceguy]

i believe i misled you when i stated i had removed the freon...what i meant is i blew it back into a recover cylinder straight from manifold until i began to see the sight glass half empty. then i began adding freon until the sight glass just was full. i do apoligise for my misleading u to what i had done...i also failed to mention that the unti also has a lpc however i did not pay attention to what they were set at(i was trying to figure out why i felt as if i could not get the superheat right) i was taking my line temp readings from 6" away from the compressor as recommended by copeland in their faq section; here is there exact quote from that page (Superheat at the compressor should be checked at the compressor only. Take the suction pressure at the service valve and convert it to saturation temperature. Compare this to the actual temperature obtained approximately six inches out on the suction line.)

i will check the lpc settings and once again see if i can find anymore #'s on the txv, tomorrow when i return to finish
However going by the method that copeland says for checking the superheat i still do not understand why i cant get the superheat down anymore?¿

on another note:i found this particular and very useful site while looking for answers to my dilemma that may be helpful to everyone if you havent already seen it
http://www.brainerdcompressor.com/tech_data.htm