Carrier Container-High Head Pressure

[dag3xxx]

Hi All,
I work in Iraq as a civilian contractor and I've just recently been transfered to a new base where I inherated a new job; "Reefer Tech" and about 20 assorted reefers in various levels of disrepair. I've been doing HVAC all of my life but I'm new to container reefers. I've notice something rather troubling since I've been here, all of the Carrier 69NT40-444-8 and 464-1 units have there HPS disconnected! On further inspection most of the units are running a very high head pressure (250 300psi).
I've tried everything I can think of (cleaned the condenser, removed the charge and pulled a good vacume, removed, cleaned and inspected the TXV, SSV and Quench Valve) but I cant get the pressures under 225. The area where we keep these units is littered with old burnt out compressors, I'm really trying not to contribute to that collection! I'm starting to think that maybe theres in the condenser coils.....If anyone can give me any suggestions I'd greatly appreciate it, cause I'm drawing a blank right now.

[cadwaladr]

take the coils out check the condition,if any doubt change it

[Brian_UK]

Do the condensers have any 'sand' etc stuck in the hidden fins or that potential problem.

Maybe the coils aren't big enough for the ambient?

By the way, welcome to the forum and good luck with your new 'role'.

[abbsnowman]

I don't do allot of "can" units but more truck and trailer but depending on ambient, is that really that un-common? (Pressures)
We see that kind of pressure all the time.

[djbe]

Hi All,
I work in Iraq as a civilian contractor and I've just recently been transfered to a new base where I inherated a new job; "Reefer Tech" and about 20 assorted reefers in various levels of disrepair. I've been doing HVAC all of my life but I'm new to container reefers. I've notice something rather troubling since I've been here, all of the Carrier 69NT40-444-8 and 464-1 units have there HPS disconnected! On further inspection most of the units are running a very high head pressure (250 300psi).
I've tried everything I can think of (cleaned the condenser, removed the charge and pulled a good vacume, removed, cleaned and inspected the TXV, SSV and Quench Valve) but I cant get the pressures under 225. The area where we keep these units is littered with old burnt out compressors, I'm really trying not to contribute to that collection! I'm starting to think that maybe theres in the condenser coils.....If anyone can give me any suggestions I'd greatly appreciate it, cause I'm drawing a blank right now.





What refrigerant are the units runnings on and what is the ambient and cargo temperature?

[Reeferman27]

Hi All,
I work in Iraq as a civilian contractor and I've just recently been transfered to a new base where I inherated a new job; "Reefer Tech" and about 20 assorted reefers in various levels of disrepair. I've been doing HVAC all of my life but I'm new to container reefers. I've notice something rather troubling since I've been here, all of the Carrier 69NT40-444-8 and 464-1 units have there HPS disconnected! On further inspection most of the units are running a very high head pressure (250 300psi).
I've tried everything I can think of (cleaned the condenser, removed the charge and pulled a good vacume, removed, cleaned and inspected the TXV, SSV and Quench Valve) but I cant get the pressures under 225. The area where we keep these units is littered with old burnt out compressors, I'm really trying not to contribute to that collection! I'm starting to think that maybe theres in the condenser coils.....If anyone can give me any suggestions I'd greatly appreciate it, cause I'm drawing a blank right now.

Good day to you.

I've been there and know the problems.

The 444 unit has either R22 or has been retrofitted from R12 to R409a (FX56) as the 464 should have been. Some were not fitted with a higher rated HPS. Some of those reefers were local purchase?????? but most were shipped over from here and were old when we retrofitted them 15 years ago, I found one of my old service stickers on one.

I was there 2004-2007 as Reefer workshop supervisor, at least its cool at the moment wait till summer +65C :confused:

[tspgr]

with those temps
I dont know if you ever going to see hp under 300 psi .
But for the unit with R22 or any other mixture of this type (with boiling point under -39 C ) its a normal hp until 350-370 psi with such temp outside

[jasperreefers]

Check out the current limiter settings (should be 21amps) and modulation valve (7.2ohms) this should be controlling the compressor current draw at frozen temps and keep the head pressure down to reasonable pressures. I get a load of this equipment from Iraq and Afghanistan for off hire in the UK, here are a list of problems I come across
1. Mix of refrigerant ie r22,r12,r134a all in the same system
2. Blocked/corroded condensers
3. 41cfm compressors in R12 units so the condenser venturi and CF blade too small (need to be 17.5 ") not the 16.5" (makes a big difference )
4. receiver chopped out and unit over charged (if r409a the charge needs to be 85% of plate rating. This applies to r413a as well
5 CF blade poorly positioned in venturi, it needs to be in line
6. Condenser cover damaged allowing short circuit of air flow

If you need parts i can put you in contact with a good company in Sharzha (English guy) who can help you.

These, in my 30 years experience of reefers are all the items I would check, Condensers should be WASHED with water if practical as opposed to blowing out with compressed air.and if you have a good clean condenser,good air flow, the correct refrigerant at the right charge and a working modulation coil/valve and the current limiter your problems should be resolved

Best regards

Geoff Wooler

the Units are designed to work in high ambeints

[bruisermac]

nice post jasper. good accurate info!!

[Magoo]

Good posting Jasper.
They would have been as sea for twenty years and fin corrosion is highly likely at contact between tube and aluminium fins.