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frozen ocean
21-11-2005, 12:05 AM
why should we trap discharge lines on racks.from what i've been told it was there when the power goes out so you don't oil log your comp.please explain

US Iceman
21-11-2005, 01:08 AM
There may be a couple of reasons for traps in the discharge line.

If the condenser is higher than the compressor:

a) during reduced capacity the gas velocity decreases in the discharge line, so the trap may be for oil (you might also see two discharge lines going up to the condenser; the trap is used to collect the oil. When the trap fills with oil, the refrigerant vapor is forced to travel up the smaller vertical riser to maintain a velocity to carry the oil up the riser).

b) the trap may be used to collect refrigerant that can condense in the discharge lines during off cycles (cold weather conditions). Better to have the liquid collect in a trap, than on top of the compressor discharge valves.

Peter_1
11-12-2005, 12:51 PM
If there is a need for a trap in the discharge line, then it only can be for the 2 reasons you mentioned US Iceman.

As long as the system is running, miscibility in a discharge line is that high that oil is carried together with the discharge gasses without many problems.

It's not because you install 6 of it that oil return will be better. It's only do be sure that the oil is pushed upward to the condenser where it then can flow mixed with the refrigerant to the evaporators.

The main reason for me is always liquid refrigerant build up at the compressor discharge valves.

But with a pack in a supermarket where there is never an complete standstill for longer periods, this is also not a problem. So, my advise with the 6 siphons in the discharge line was: install one just after the compressor and on the roof,make that the discharge lines are inclined toward the condenser.

Especially because the discharge line was not straight up but there were 3 small horizontal deviations which could serve as an oil trap if the lines were inclined down with the flow.

So no oil siphons at all were necesarry at this site, especially where in this particular case they had toi be installed in a technical shaft of 6 x 6 ft where the tech was hanging on a safety rope while soldering. Temperature in the shaft was +/- 35C.

I said that they didn't understand their basics but who am I. That was also the vision of BESC5240.

US Iceman
11-12-2005, 04:11 PM
install one just after the compressor and on the roof..

I completely agree with you on all points. The trap at the compressors should be deep enough to collect liquid refrigerant from getting back on to the compressor discharge valves.

In some circumstances, the trap will collect a small quantity of oil when the compressors are off. The main reason for this trap (in my opinion) is to collect liquid refrigerant that has condensed.

The trap at the inlet to the condenser is an inverted trap, to prevent refrigerant from running down the discharge line.


Especially because the discharge line was not straight up but there were 3 small horizontal deviations which could serve as an oil trap if the lines were inclined down with the flow.

The horizontal incline is the trap... I agree.

The basics of piping is much more than soldering pipe.

US Iceman
11-12-2005, 04:29 PM
It's not because you install 6 of it that oil return will be better. It's only do be sure that the oil is pushed upward to the condenser where it then can flow mixed with the refrigerant to the evaporators.

You are right. When I wrote "oil return", a better use of words would have been... for better control of oil flow.

A large part of when to use traps is based on the location of the condenser and compressors, and if the system has capacity modulation for the compressors.

The other reason is control the flow of oil, or refrigerant.

I need to watch my use of words so that I do not confuse anyone. :o