Trane TTA240B400BC

[monkeyman#1]

Ok, I'll try and make this as brief and concise as I am able. No cooling call, first floor of a 4 story bldg. Each floor with its own split system. Condensers located at ground level. Bubbles in sight glass at txv, 150# head 75# suction (strange), 3 deg. SC, 78 deg.OA. Ok, figure she is low on gas, charge to a 10 deg.SC. Head pressure only comes up to 165#, Lo 77#, 30deg. SH , suddenly comp. drops out. IOL is open. End of day so I tell customer I'll be back in the morn, let second stage handle cooling load.
Return this AM. Remove 6# of gas, just until sight glass begins bubbling then charged to full sight glass. Here are my findings.
OA 64 deg
return temp 72 deg
supply 64 deg 8 deg TD evap
lo press 69# SLT 67 deg = 27 deg SH
hi press 165# LLT 85 deg = 4 deg SC * panel removed to prevent
fan cycling*
DLT 206 deg
cond inlet temp 65 deg
cond outler temp 79 deg = 14 deg TD cond.
comp rated at 13.6 A Pulling 13 A
L1 - L2 481V L1 - L3 480V L2 - L3 485V

I have pumped down the compressor, pulled down to 3psi Trane pumpkin style scroll. According to trane, this is ok. I am thinking maybe a mixed charge? Plan on returning Mon. and pulling charge, weighing in proper charge and seeing what happens. Your thoughts?

[pipefitter636]

I am thinking maybe a mixed charge? Plan on returning Mon. and pulling charge, weighing in proper charge and seeing what happens. Your thoughts?

Each TTA unit ships with a holding charge of dry nitrogen. The nitrogen should be removed and
the entire system evacuated (at the proper time) to avoid possible contamination. http://www.trane.com/webcache/un/spl...n_11012006.pdf

[monkeyman#1]

Each TTA unit ships with a holding charge of dry nitrogen. The nitrogen should be removed and
the entire system evacuated (at the proper time) to avoid possible contamination. http://www.trane.com/webcache/un/spl...n_11012006.pdf

These units are vintage 1996, am thinking maybe some dumb a$$ mistakenly added the wrong refrigerant? We just recently took this bldg over and I dont have any history of this unit. I know it is a long shot but ........

[brooklyntech]

1996 you say? Could be compressor starting to die. But itr sounds like u might have a restriction in ur condenser. Ddid u try bumping up head pressure by covering barrel type condenser? Or maybe stop cond fan? I know that Trane ships condensers with a factory liquid line drier. U might have blockage!! But ur hypothesis on wrong refer might be correct. @ ambient temp with unit off- whats ur pressure? Good old P/T chart should tell u if u have a HFC(r22) or if some shoemaker has created a blend for u to ruin ur day !!!!! And remember kids have fun!!!!

[brooklyntech]

itr & Ddid- time for beddy by

[monkeyman#1]

1996 you say? Could be compressor starting to die. But itr sounds like u might have a restriction in ur condenser. Ddid u try bumping up head pressure by covering barrel type condenser? Or maybe stop cond fan? I know that Trane ships condensers with a factory liquid line drier. U might have blockage!! But ur hypothesis on wrong refer might be correct. @ ambient temp with unit off- whats ur pressure? Good old P/T chart should tell u if u have a HFC(r22) or if some shoemaker has created a blend for u to ruin ur day !!!!! And remember kids have fun!!!!

Checked TD across drier .5 deg - nothing wrong there. Went out today to recover and got rained out. Looks like Wed. might be the best day this week.

[monkeyman#1]

Ok, so I finally get back to this building, and to make a long story short, end up condeming the compressor. Get to talking to the maintenance guy who informs me that they just had a compressor replace on the third floor unit, hmmmmmm? Start lookin at the other unit (3 total on site) and discover that it had a compressor replacement in May of this year, WTF?
I go inside to the mechanical room and start lookin around. Then it dawns on me (I'm a little slow) the air handler is a multi-zone, vfd drive and these condensers have no HGBP! Same set up on all floors. Geez I wonder what happens as the load in the building comes down? Perhaps some liquid slugging?
Further investigation and I find that the LL is 3/4 inch and Trane requires 1/2 inch LL. 46 foot run for first floor, second and third floors set up the same way. All the piping is hidden behind sheet metal, so I am going back next week to insure that all piping is correct. Also am meeting with building tenant, my boss and the owner of the company that we were doing the subcontract work for. May have some control issues as well. How does all of this get missed for 13 years (units are vintage 1996)?
I suspect that original condensing units had HGBP but were replaced at some point. Indoor units are Lennox, outdoor units are Trane.