York oil return system

[r404a]

York Types:

Wanted to get a little knowledge from you guys on Yorks oil return system on a YT. I recently worked on a “G” design series, R123, YT machine. The machine experienced oil loss, and after I inspected this unit, I found one of the oil return eductors plugged up. I cleaned both eductors and bench tested them. When I had the eductors on the bench, I put 10 psig nitrogen on the motive force connection and a vacuum gauge on the pickup line showed 6.6” vacuum on a new eductor and on an old one, wth the eductor that was fouled at 4.5” vacuum. I could not find a different part number for these eductors, so I asssume that both are the same eductor. Got them cleaned and got great oil returen, pulling the oil out that I added to get it online, watched discharge temps come up and evap approach get tighter.
Incidentally, the eductor in question was the upper eductor that pulls from the "suction cover"(Trane term, sorry).
This leads to my first question. This oil port at the impeller inlet, is it at a pressure that is vented DIRECTLY to the impeller inlet, in that case, being at the lowest system pressure possible, or is it vented to the pressure before the PRV’s, thus being not as low as inlet pressure at full PRV closed state?
Next question. This is a YT and looking at an overhaul guide I see what is listed as a “High Pressure Seal”, consisting of 3 parts: an oil seal retaining ring, a flat washer, and a seal ring. Does this assembly do the same job, effectively, as a balance piston assembly on a YK machine, and a Lab seal, on a CVH trane machine, that is, minimize oil sump pressurization?
This unit is not experiencing an over pressurized sump, and I have verified the vent solenoid operation. For you York techs, what pressure would you gauge the sump pressure against other than evap pressure? I noticed on this machine, and others I have overhauled in the past, an allen plug up on the compressor case, in this unit, opposite the vent valve piping. Do you guys ever use this port for trouble shooting?
What pressure limit can the eductors effectively return oil against? Thanks for the replies.

R404a

[klove]

Lot's o' questions.....

1) Port is at impeller inlet pressure, between vanes and imp eye
2) High pressure seal and balance piston seal are the same thing
3) Nothing to gauge sump pressure against other than evap.
4) 1/4" angle valve in that pipe plug hole works great for what you want to do
5) Hard to say about pressure limits. I'm sure there are some engineering numbers, but generally, to get good oil return, I've found that the sump pressure needs to be > 2" below evap pressure. Closer than that under normal operating conditions, and things start getting marginal to non-existent, depending on differential. Because loading and vane position and comp speed with vsd's have such a direct effect on this sub-system, you're really shooting at a moving target with the numbers. E.G.: what is lost by equalizing pressure when opening vanes may be offset by slightly higher hot gas line pressure.

[r404a]

Thank you for your insight, Klove.

r404a

[heavymetaldad]

great questions 404. what on earth made you check an eductor? never thought about it, have to investigate that sometime
great answers klove

[r404a]

heavy

hope you are doing well. I had a little forewarning on this particular system in that I knew from past inspections that I had got some small pieces of debris in the liquid pick up for the purge feed, mesh material that seems to be from an eliminator. also, this machine had been running fine, even earlier in the day of the same day that it went down. At the same time, the weather got much milder and I felt that it had to be something drastic to go from a full sup to an empty sump. Luckily the vent valve checked good and the eductor was a next best guess.
Klove always is a wealth of york info, as is Yorktek and so many others.

R404a

[heavymetaldad]

i mean bench test an eductor - or - a 'jet pump'.
and it's great we have this forum to communicate. the gents here have a wealth of knowledge and skills
as far as me, thank you for your concerns. not anticipating tomorrow's festivities too well

[Randy S.]

What effect would a malfunctioning "equalizer" or "vent line" solenoid have on the YT oil return?

[r404a]

sump would pressurize, thus oil would not enter the sump, especially if said sump pressure was too high.


r404a

[yorktek37]

first of all If I remember right the vent line is at wheel inlet pressure. I don't thing there is any opening to the other side of the PRV's. When the vanes are closed the sump is at a lower pressure. That is why there is a delay when opening to minimize foaming. It almost sounds like your balance piston is leaking. Can you get me the operating info at different loads with oil levels and send then to me. My e-mail is screwed up but I can furnish you with a different one or a fax number that you can send it to. Just let me know. I will forward this info to Denny Deitz and see what he says.

[r404a]

thanks for the input, yorktek


r404a

[Randy S.]

Thanks for the info, guys.

I have one that makes me wonder about the back side wheel seal, too.