Evac. level ?

[sds5150]

Well as I start most of my posts - I am an HVAC student trying to learn hands on at my factory competely on my own. (Except for you guys) I am currently working on a split AC system for a 1st story office with the condenser on the 2 stories up on the roof. The origional problem was that vibration (and someone's improper use of a coat hanger to tie up extra length of the line set) had worn a hole in the suction line at the air handler. I repaired the leak and started a evacuation. This is only the second evac. I have done and the last one went really fast and smoothly. After about 4 hours the system was down to about 700 microns, but if I valve off the vac. pump the pressure starts to increase. So, I'm thinking there is moisture in the system. The next morning I started the pump again. I still had a vac. on the system because I remember hearing the sucking sound when I connected to the schrader valves, but I don't recall the actual start reading. Anyway, today I let it run for about 11 more hours and I'm down to 295 microns. If I valve off the unit, the pressure rises quicky then very slowly starts climbing. After about 15 minutes it made it to about 700 microns. Does this sound like a moisture issue, or would you suspect a small leak? If it is moisture, at what point would you stop the evac. and CHARGE it? I am planning on starting it back up again tomorrow morning. I realize I should have charged it with nitrogen and pressure tested it, but the company has yet to purchase a kit for me. (Although I wil have one soon, especially after all this.) Thanks for the help.

[Wild Leg]

I'm impressed that you have a micron gauge.

If the pressure quit rising, then you don't have a leak.

700 microns is on the upper end of "acceptable".

Did you install a filter drier?

[bku46]

Check your hoses and all connections, I isolate my pump and see if it holds a vaccume first, then I open to my system and see if it rises, Im not to crazy about these micron meters, they dont seem to reliable.

[chilbrig]

Where is your Micron Gauge hooked up? If it is at your Manifold then you probably will see a rise in the reading if you valve out the pump. Your Gauge should be connected to a port away from the pump where it will sence the actual pressure in the system and not be affected by the Vacuum Pump. If you really are getting down to 295 Microns then I doubt that you have a leak anywhere.

[maxster]

try copper dirctly from the pump to the system(no guages)and the micron guage on a service valve or shradder.you go for the test first then reinstall your guges and repull it if you have that time.check your guages with the vac pump and micron guage also prior to system test.once your below 5000 microns the reast of the trip is moisture into the 1000 and below range if it is 300 and goes up to 750 after the vac is isolated that is just settling out.

[Edited by maxster on 05-26-2005 at 09:04 PM]

[sds5150]

I put the vac. gauge in a series directly after the vac. pump then the lines go to the center line of the manifold set, then the high and low side are open and connect accordingly. I'm glad to hear that I shouldn't have a leak. Keep the comments coming! Thanks

[sds5150]

Originally posted by bwal2
I'm impressed that you have a micron gauge.

If the pressure quit rising, then you don't have a leak.

700 microns is on the upper end of "acceptable".

Did you install a filter drier?



Thanks for the comment about the gauge. I really try to do everything right. People make comments about why things take me so long to fix, but I always double check my books to be sure I don't screw up. Thanks for making me feel like I am really doing something right.

[dgruber]

Need a job in West central Florida?

We are always loooking for good techs!

[sds5150]

You guys must really be desperate.

[pecmsg]

Sds
Take it slow at first. Don’t let anyone make you hurry-up, that’s where mistakes happen. It will come to you in time. Trust me your learning the same way we did, one job at a time. Good Luck

[sds5150]

Now it's something else!!! I finished the evac. Then I started the charging. I charged a couple pounds of liquid R-22 to the high side of the system, as I did so I noticed that the suction side pressure was going up high (about 120psi on the high and low side of the system) I started the compressor hoping it would pull it down and I would continue the charge, but nothing happened to the pressures. I am settling on the compressor being shot unless there is something else that I didn't consider. It has a low amp draw (10 A), RLA is supposed to be 17.It does seem to have a slight rattling sound instead of the nice smooth hum. Of course it did run for some time without refridgerant, so that can't be good. It seems pretty obvious, but I don't want to overlook something and order a compressor for nothing. (Bryant model:693CN030-A) Thanks

[stevehvac]

Originally posted by sds5150
Now it's something else!!! I finished the evac. Then I started the charging. I charged a couple pounds of liquid R-22 to the high side of the system, as I did so I noticed that the suction side pressure was going up high (about 120psi on the high and low side of the system) I started the compressor hoping it would pull it down and I would continue the charge, but nothing happened to the pressures. I am settling on the compressor being shot unless there is something else that I didn't consider. It has a low amp draw (10 A), RLA is supposed to be 17.It does seem to have a slight rattling sound instead of the nice smooth hum. Of course it did run for some time without refridgerant, so that can't be good. It seems pretty obvious, but I don't want to overlook something and order a compressor for nothing. (Bryant model:693CN030-A) Thanks

Is there a low pressure switch on the system? I find a lot of bad compressors are due to them running with no freon in the system. Thats what probably happened.Order the compressor I think you are correct with whats wrong.

[seaboard]

Hold on there rookie; I can think of two things that you haven't told us. First, is this a heat pump? You know that big line at the condenser is going to read the same as the high side (little line) if it's in heat mode. Hell, it should actually be higher.
Secondly if it's a scroll compressor is it turning the right way? I'm not familiar with that model number to know if your unit is single or three phase.
A lot of guys may disagree with me but if one of my guys finds a flat system before performing or quoting a leak check I want them to bump the compressor with gauges connnected. There's nothing worse than finding and repairing a leak and then finding a bad compressor that could have been determined beforehand. Word of caution. It's a good idea to meg the compressor before bumping it. If you have a very high moisture level it may not be a good idea to energize the compressor.

[beenthere]

Is it possible that you put more gas in then you think.

May be over charged now, and unable to start.

Did you weigh it in as you were charging.

How many pounds did you put in it.

[hvac-alan]

Did you close off your low side and high side at the manifold. I have done that a few times when just starting out. The high side pressure bleeds to the low side through your manifold.

I wouldn't think that it is overcharged since the amps are way under FLA.

Also--as stated earlier if you have a heat pump, make sure it is in cooling or you may be measuring two high side pressures.

Noise??? Is it a three phase motor?? If so, and you have a scroll compressor it may be trying to run backward. Just switch any two of the high voltage leads at the contactor OR a the disconnect (Your pick)

[R12rules]

Originally posted by maxster
try copper dirctly from the pump to the system(no guages)and the micron guage on a service valve or shradder.you go for the test first then reinstall your guges and repull it if you have that time.check your guages with the vac pump and micron guage also prior to system test.once your below 5000 microns the reast of the trip is moisture into the 1000 and below range if it is 300 and goes up to 750 after the vac is isolated that is just settling out.

[Edited by maxster on 05-26-2005 at 09:04 PM]


AMEN!