HIGH SUCTION LINE SURFACE TEMP WITH R22 @ 60psig

[TRASH101]

Greetings to one and all ,this is my first post and probabley the start of many more.

I recently charged a DX system (R22) ,twin comp in parallel, got full glass; liquid 225 psig; suction 60 psig only to find suction temp 18 c at the evap. Unfortunately only got someones word for vac and better still there could be a 1/2 litre of endoflush contaminating the system (system charge 48 Kg). One other factor is that the head pressure control seemed to be driving the fans rather fast for the ambient (about 9 c). The expansion device is rated ok as far as the C.U. goes but no details exist for the evap. Hi side temp @exp is 18 c low side is 8 c lack of schraeders so no pressures to help.

If anybody has any idea whats going on with this system please respond or it means I'm spending a week on an unholy roof to far from the ground to be healthy.

[Brian_UK]

Hi Trash and welcome to the forum.

You say that someone else did the evacuation but you recharged it.

Why was the system degassed in the first place? What work has been done it and what was the vacuum reading before you charged it?

Also, what type of system is it serving?

[TRASH101]

thank you Brian for your prompt response

the reason for the recharge is that both comps died got stripped out left open to the elements( condenser and evap.) the fridge was a R22 drop in dont know which as i dont have the job details with me.

As for the vac and pressure test ......I was dropped in at the end to finnish someone elses job (as is oft the case) with assurances that a valid test had been accomplished and a vac of sub 1 torr had been achieved and kept for 24 hrs. He left a holding charge of 25Kg in the system (again unverified). The endoflush only came to light after i remarked that the charge was reacting as if contaminated but i need to feel more confident that i have eliminated all options before pointing any fingers.

I cant rule out oil locking either as there are 4 traps in a vertical rise and no real guarantee that the evap was flushed

any help would be appreciated

[TRASH101]

sorry almost forgot system is a DX serving an ahu running mainly on recirc. Fresh air used as free cool
but only 10% (for air changes) on the day. Air on was 21 c air velocity less than 2.5 m/s at coil face.

thanks again.

[goodguy]

Trash 101, I think if you can find the reason for the first compressor failures you will be set. A r-22 drop in replacement may not have the right capabilities to bring your oil back to the compressors, especially if you have a vertical rise with 4 traps. Is the oil compatible? do both compressors run together all the time and if they don't is the piping correct to maintain proper velocity. As for as the condenser fan, it sounds like it is trying to maintain 100f on the liquid line and that seems normal to me. Does this system have a receiver? If not maybe it should be charged by sub cooling. Hopefully something I mentioned will be of some help to you, I'd like to see what anyone else has to say.
Good luck.

[Gary]

Your evaporator is picking up far less than a normal heat load with the TEV underfeeding, and yet the head pressure/temperature is way above ambient.

Given the low evaporator load and the low ambient temp, the head pressure control should easily drop the head pressure and shut off the fan(s).

Sounds like contamination to me. You can confirm this by closing the liquid line valve, pumping down and shutting off the system, and seeing if the high side pressure matches the ambient temperature.

I would be leery of evacuating one end of a split system with a very long run and 4 traps in between. I would install shraeders at the AHU and evacuate from both ends simultaneously.

[TRASH101]

Thanks Gary

I am going to do that ASAP plus climate centre have offered to send a sample to A-gas for component analysis (for a small fee of course).

Could I also impinge on yourself and all @ RE for guidance on oil compensation for the traps. I have calculated an amount based on (1/2 circumf. X vol. of pipe)/ 2 for each trap (just about a sump ) I hope I haven't over egged!!!!

Thanks again to you all and any more advice/ criticisms will be greatly appreciated.

[TRASH101]

by the way Brian your quote is excellent
I earned my nickname from taking it as an ethic