Convair TRB portabale air con

[bundysnake]

Hello,

I have the above unit which the compressor kept cutting out after stripping it down i found the drain pump connections have snapped (that pump water over the condensor), i repaired these connections and the unit kept doing the same thing.

I then took temp readings of the head of the compressor and the temp was constantly rising, i then looked at the exhausty air port and found that it was partly restricted, i fixed this and the temps stayed in the mid 80deg c mark at the head of the compressor and it didn't cut out anymore.

The unit is quite old and i got it from a friend he had already welded a schrauder valve in it so i hooked up my gauges and checked the gas charge and i found that with an ambient temp of 27degrees i was only getting a 19degree S/A temp which isn't what im expecting (10deg c diff is what the manufacturer recommends) the suction pressure was around 80-85psi this seems unusually high from my experience, but i haven't worked on the smaller systems before.

Basically i want to know what you guys/gals suspect is wrong here? and how i can acheive my 10deg split.


Any help would be much appreciated.

[ozairman]

Hello,

I have the above unit which the compressor kept cutting out after stripping it down i found the drain pump connections have snapped (that pump water over the condensor), i repaired these connections and the unit kept doing the same thing.

I then took temp readings of the head of the compressor and the temp was constantly rising, i then looked at the exhausty air port and found that it was partly restricted, i fixed this and the temps stayed in the mid 80deg c mark at the head of the compressor and it didn't cut out anymore.

The unit is quite old and i got it from a friend he had already welded a schrauder valve in it so i hooked up my gauges and checked the gas charge and i found that with an ambient temp of 27degrees i was only getting a 19degree S/A temp which isn't what im expecting (10deg c diff is what the manufacturer recommends) the suction pressure was around 80-85psi this seems unusually high from my experience, but i haven't worked on the smaller systems before.

Basically i want to know what you guys/gals suspect is wrong here? and how i can acheive my 10deg split.


Any help would be much appreciated.

We cannot see the unit and so this situation is very much like a computer Garbage in = Garbage out the more information you can supply the higher quality of advice you will receive.:)

There are many things which could be wrong with the unit, here are some things to consider:

If it already has a schraeder valve fitted then you can be sure someone has messed around with the refrigerant charge or it has had a gas leak in the past.

What refrigerant is it running, a quick look on the web says R407C??? so if it has had a loss of charge then there is potential for the refrigerant blend to be out of spec which will throw temps and pressures way out. R407C is a c_o_cktail of R32/R125/R134A and once there is a leak it tends to loose more of one component gas than the others.

What is the suction superheat? If the refrigerant is R407C then 80-85 psi suction pressure indicates a 10-12°C saturated suction temp but this is no indication that the "gas charge is correct" only the evaporating temperature, which does appear high for an air conditioner. Measure the suction pipe temp and compare the difference, most of these small air conditioners operate with very low superheats ~3-5K as they try to operate the indoor coil almost fully flooded for maximum heat transfer and efficiency with as small a coil as possible.

What is the compressor amp draw versus the rated amp draw? this will assist in determining if the unit is short of gas and how efficient the compressor is.

Also measure the discharge pipe temp 4-6" up from the compressor it is more relevant than the head temperature itself.

My suggestion would be to reclaim and weigh out the charge so you can establish if the right amount was there in the first place, pressure test then add a fresh charge and take some measurements of the items above.

[momo]

My experience with these type of units is that: 1. They are very sensitive to correct charge levels. 2. If you have a test connection you may well have part of the housing open which will affect the air flows on the evaporator or condenser and the operating measurements will be off - solve this by using a temporary tape and card cover. 3. The condensate water on the condenser is part of the design parameters: it cools the condenser and then goes out with the exhaust air: this will affect the pressure levels you are getting. Although overkill I had to place a second schraeder on the high side to get one of these working spot on using R407C. Have fun!

[bundysnake]

Just reclaimed the charge and the system is holding a dry nitro charge now i will leave it for 24 hours and see what happens.

Momo - thanks for that info when i first hooked up the gauges i forgot to block off the housing and i was trying to figure out why my pressures and temps were all over the place hahaha then i bashed my head against the wall because i felt like such a dumbass.

I will keep you all informed how i go.

[ozairman]

Just reclaimed the charge and the system is holding a dry nitro charge now i will leave it for 24 hours and see what happens.

Momo - thanks for that info when i first hooked up the gauges i forgot to block off the housing and i was trying to figure out why my pressures and temps were all over the place hahaha then i bashed my head against the wall because i felt like such a dumbass.

I will keep you all informed how i go.

How much refrigerant did you pull out?