409 freezer

[rango]

Original symptoms: Flashing glass, low capacity.

Continuing symtoms: Low capacity and others.

Here's the numbers:

Refrigerant 409a

Suction Pressure: 2psi
Suction temp. :35*

Dis Pressure: 275psi
Discharge Temp.: 225*

Liquid line temp: 111*

Box temp: 10*

Ambient:108*

Compressor SH:47*

SC:56*

Pressure swithches set at 0 psi and 15 cut-in with 300 cutout


Got called 8pm friday nite, box is 40* with massive flashing in the glass.Clear the glass and go back Sat. Box at 15*. Find leaky discharge valve. Tighten packing nut. Attempt to adjust charge, but compresor takes a header on the 300psi switch. Subcooling and SH all wrong. Any thouhgts. Haven't worked with 409. Pressure settings right?

History: Unit has had low level leak since install 4 years ago. All lines run through 20 ft unconditioned space under black rubber roof. Compressor sits in 6 by 6 shed attached to building.

Any thoughts?

[Dad]

It is just an R12 freezer.

Is it a walk in? reach in??

TXV or cap tube??

Sounds like maybe a restriction or bad TXV

be sure this baby is clean first.. all coils... all fan blades turning correct direction

[rango]

Walkin freezer with txv. Just oicked up this account two weeks ago and cleaned coils at that time. Evap clean as a whistle as well. Its a Larkin and my flashlite shines right through the whole thing.

[rango]

Belive it or not, nobody can tell me if the darned thing ever got below 10*. Wondering about the pressure swithch setting and with 409 what kind of highs I can expect under these conditions. Also, appears to be a 12 retrofit. Personally, I'd have used 414.

[Dad]

There is nothing different here than any other walk in you may have worked on

do you have a PT chart for 409?

[Dad]

414 would be good in this situation cause 416 is not as good at low temp.

[Dad]

300 cut out is too hot...

never run a cut out at 0 or lower.. it may suck in air if you have a leak on the low side.. ect...

[rango]

yep, got the lates one from Tecumseh. Chart tells me that I may be undercharged, may have bad txv, or unit is too small. Doesn't tell me the suggested settings for the pressure swithces. Think I'm jsut missing something, but I's sill learnin every day.

[rango]

Originally posted by lusker
300 cut out is too hot...

never run a cut out at 0 or lower.. it may suck in air if you have a leak on the low side.. ect...

Agree with the low. Wondering what you mean by too hot. BTW dual switch changed out cuz it wouldn't kick out on defrost. Wonder if txv is freezing up with moisture. Moisture indicator in glass reads dry but....?

[Dad]

Originally posted by rango

Originally posted by lusker
300 cut out is too hot...

never run a cut out at 0 or lower.. it may suck in air if you have a leak on the low side.. ect...

Agree with the low. Wondering what you mean by too hot. BTW dual switch changed out cuz it wouldn't kick out on defrost. Wonder if txv is freezing up with moisture. Moisture indicator in glass reads dry but....?

300 is too high for a high pressure cut out and this switch has nothing to do with defrost.

since this box has had a leak (for the past 4 years) I would bet a dollar that you have non-condensables in the system and the fact that your low pressure switch is close to a 0 # cut out it has sucked in tons of moisture... follow me?

[rango]

This is a pumpdown system and when I was there yesterday, th unit went into defost. Pulled down to 29- and kept on going. Thats why I changed out the switch. Doesn't do that anymore.LIke you mentioned. 4 yrs. of sucking on a low side leak may have introduced moisture and noncondensibles into the system. Perhaps the condensor is packed up with air and the txv freezes up after a bit.

[Dad]

Recover and dispose

find and fix leak

change drier

pull good vacuum

recharge virgin... do not clear sight glass with 414 or 416

set your sh around 8*

[rango]

I was afraid that was where I was headed, but thought I'd throw it out to the group. Thanks . Will report back.

[self employed 1]

i agree with lusker, when in doubt pull it out.

[meltdown]

Sounds like a the txv is medium temp, and or could use you to close it down with a temp check, or a sh reading, vacuum , and weigh in the charge, check to see if insulation value is gone from box, and the txv is correct application and size for box... flare fittings, receiver cylnders- schrader valves,elctrical terminal box@ compressor/ dp ctrl capillaries or inside the ctrl itself very common leaks that get by the most busiest fastest tech's, but are are good places to look for leaks.......

[Edited by meltdown on 07-20-2005 at 01:44 AM]

[rango]

Originally posted by meltdown
Sounds like a the txv is medium temp, and or could use you to close it down with a temp check, or a sh reading, vacuum , and weigh in the charge, check to see if insulation value is gone from box, and the txv is correct application and size for box... flare fittings, receiver cylnders- schrader valves,elctrical terminal box@ compressor/ dp ctrl capillaries or inside the ctrl itself very common leaks that get by the most busiest fastest tech's, but are are good places to look for leaks.......

[Edited by meltdown on 07-20-2005 at 01:44 AM]


Spent a few hours with the beast today. Recovered, changed out high sid service valve, hit it with 150psi nitrogen and a bit of 22 and leak checked. D-tek Select found the only detectable leak other than the valve. It was under the compressor. Seems the installers couldn't make the existing heater fit the blt pattern on the oil sump so conveniently left out one pan bolt under the heater bar. Wth nitrogen on there was a steady drip of oil, do had to add oil as well. Still concerned about the 2psi suction pressure, but head is down to 225. Box down to 15 when I left. Will go back tomorrow morn and tune the charge. Still think I should have retroed the 414b. Whatsay?

[Freezeking2000]

You ahould have that baby cutting out at 5hg and in at 5 psig. If you set the L.p. to cut-in at 15 your compressor wont run till the box(low side) gets to the cut in pres/temp (about 10-15)

[rango]

Originally posted by Freezeking2000
You ahould have that baby cutting out at 5hg and in at 5 psig. If you set the L.p. to cut-in at 15 your compressor wont run till the box(low side) gets to the cut in pres/temp (about 10-15)
Fon't knoe if my screwdriver fingers are that sensitive. Diff between the two is .09 psia.

[rango]

Or am I missing something. I can be incredibly thick sometimes.