Noise issue

[lostndebox]

I got a service call to a store with a Trane Voyager series rooftop package unit. The call was for a very loud squeeling noise coming from the unit. I was called out last year for this same problem and after some troubleshooting and some calls to some other service techs, decided that the valves for the number 2 circuit compressor were shot. Unfortunately, I was not the one sent out to replace the compressor. However, the noise stopped after the new compressor was installed. That was last year around june.
Well, I got called out again for noise comming from the same unit. I get on site, make a wild guess that it is the circuit two compressor again, and bam! I've located the noise. Sure enough, it's the circuit two compressor. Crap. I know it is the compressor because I shut everything else off to locate the noise - the cond. fan, the blower fan, the circuit one compressor. The noise starts just as the compressor pressures get up towards 125 discharge. Then it keeps getting louder and louder until you can hear it in the parking lot.
Now, while I'm looking at the compressor, I look back and see that the liquid line filter does not appear to be new. In fact, it still has the trane paint on it and I can't think of one of our techs that has that paint on their truck. I was trying to look at the label to see if it was new or not so I had to stick my head in over the compressors but under the control box. Hidden up behind that is a suction line filter on circuit two. (brazed in, not replaceable core type) and for some reason, it looks brand spankin new.
After a little research, I find out that back in 2004, we had replaced the compressor due to a burnout, and no one had ever followed up with acid tests or removed the suction filter.
I also find out that the tech that replaced this compressor last year for some reason changed the suction filter, but not the liquid line filter.
I know I should've found that suction line filter last year, and that's on me. However, that bastard was hidden pretty damn well. My question is whether or not that suction filter could've been the problem all along. The pressures don't really reflect it, and I haven't been able to find my notes from last year, but here is what I've got this year.
Trane model # YCD150C4HBB , serial # R25104819D, 460 volts, 3 phase.
With both stages running, blower on, and condenser fan running, here are details.
Circ 1, comp amps 6.7, 7.9, 7.6 (10.6 max), press 65/225, ret air 72, sup air 56, superheat at compressor 21 degrees, no subcooling possible
circ 2, comp amps 7.3, 8.2, 7.4 (10.6 max), press 67/240, ret air 72, sup air 46, superheat at compressor 24 degrees, no subcooling possible
I took the supply air readings 15 minutes after stage one on and ten minutes after stage two on (noise was unbearable)
Blower fan and condenser fan rotating correct and amp draws and voltages ok. Voltage for unit is 494, 496, 494

[jayguy]

according to "Service Facts: YC*150-SF-4D"

if your outdoor air temp was about 63F, with about 50% RH then 21F superheat is ok, however, your pressures indicate about 83F outdoor air.

at 83F OAT, 50% RH: you should have about 9F superheat

get the above service bulletin and check your pressures and temps.

good luck.

[bc guy]

Are these scrolls?I know you mentioned valves but i've only seen scrolls in my Voyagers.
I know if they run down to low pressures they will scream,maybe suction drier is blocked,where are you taking suction pressure readings,before or after drier,and is the low psi switch before drier?

[Tool-Slinger]

That is as strange as anything I have ever heard of.

The only idea leaking out of my ear is that it may have something to do with the high-velocity gas in the dis-charge line. I would look there for anything wierd with the piping, or perhaps a vibration associated with the noise to help isolate it? Sounds like quite a puzzle, and I'll bet your custromer will not buy into the banshee explanation.... Good luck.

[lostndebox]

BC Guy. As embarrassing as this is, I just assumed that these were recips. They looked like recips. I'm not absolutely sure now that you ask, but I will look. I hope to god they are now that we changed one out. If they are scrolls, what could be causing that kind of noise inside the compressor? And will you be hiring soon? I may need a job if they are scrolls. lol. I'm taking the suction pressure after the suction filter and after the low press. sensor, but before the compressor.

[lostndebox]

I noticed that there is also some noise comming from the unit when you are standing under it in the space. That noise is more like the noise you get when there is no vibration isolation on the unit. However, that noise and the noise comming from the compressor are quite different. They might be connected though, and we are already considering a fix for that. There doesn't seem to be any irregularities in the discharge piping. And we're going to do a vibration analysis on it this week.

[lostndebox]

I have looked everywhere for that service bulletin and I can't find it. Do you have a link I could use?

[Tool-Slinger]

I noticed that there is also some noise comming from the unit when you are standing under it in the space. That noise is more like the noise you get when there is no vibration isolation on the unit. However, that noise and the noise comming from the compressor are quite different. They might be connected though, and we are already considering a fix for that. There doesn't seem to be any irregularities in the discharge piping. And we're going to do a vibration analysis on it this week.
Let us know the outcome, in any case, I am dying to find-out.
BC guy seemed to have the only actual experience reference, and with your dryer issues,.... I guess I would make sure I checked the pressures ON the compressor for sure. My tranes only have access there, so I had earlier dismissed the concept.

Very strange.

[jayguy]

"yc150-sf-4d" file is too big to post...email me.

the pressures and temperatures that i mentioned are for "0 pressure drop" across any LL and SL F/D obviously.

when you change out the compressor and filter-driers...add taps. you may have something in the condensor that true pressure drop may be able to solve.

good luck.

[lostndebox]

haven't been able to find your e-mail address. And I made absolutely sure that those were recips also.

[jayguy]

jayguy@engineer.com

[indianajones]

i had one that's pretty close to what you are describing,it turns out that the LL drier was partially clogged and causing the comp to blow it's internal pressure relief.but mine had no access on the discharge line and a port after the drier.it's scream was deafening.

[Shophound]

Just a SWAG, but does this Voyager have cap tubes or TXV's for metering devices on the circuits. The cap tubes on some Voyagers have a history of restrictions...just ask Payson...maybe yours is just slight at this time but enough to prevent good oil return to the compressor, hence it screams? Plugged filter-driers could also hinder oil return...suction line driers can act like oil traps if piped improperly.

[lostndebox]

We are going to change the liquid line dryer any way we go since it wasn't done when they changed the compressor out. I also forgot to call the tech that installed the new compressor last year and ask him why his report says he changed the suction dryer but not the liquid line dryer. The scream didn't have that gas hiss to it like most internal relief's, but that couldv'e just been because I was deafened. It's also got cap tubes so I will be checking them out also. So far, we haven't had time to go back out, and since they have one stage of cooling, we don't have this on the priority list. I will make sure to tell ya'll what we find.

[drrtu]

We had a few odd noise issues with the 12 ½ and 15 ton voyager CV gas / electric units. The sound was the fan and compressor flexing the base of the machine. The noise was very loud directly below the RTU. We now only cut the deck 1” larger than the drops. We had been cutting out the complete area between the supply and return. We now fill in the curb with wall board and roof foam in alternating layers with offset seams. The units are still noisy but quieter in space.