Compressor not pumping?

[theyelk]

Hi guys got a new site with a Mitsubishi PUMY-P140 YHMA multi split with 6 indoors. The system has terrible performance and in test heating i only achieved 27 celcius at the indoor coil and in test cooling 10 celcius. Ok so reclaimed gas and only recovered 7 kg of R410a, with it meant to be 8.5kg up to 50 metres i thought i would find a leak and all would be clear. Pressure tested and found no leak even pumped her up to 40 bar for an hour still no leak... Was told by previous engineer that a compressor had been fitted two years ago so could only assume that maybe it wasnt charged back up properly?? Anyway recharged with 8.5kg and hardly any change in performance! Performed an LEV reset which improved things a little or it seemed it did. Checked indoors again in test mode, turned off half of the units, all to no effect. Spoke to technical and they said sounds like compressor not pumping, also the model number of comp doesnt match the one they have on their system. Spoke to previous engineer again who it turns out fitted the comp and said they ordered it through Mitsubishi so no probs there.
My concern is that as the guys on this firm are fridge they are 'scared' of A/C so they may not have checked to see why the comp broke in first place, ie moisture in system or acid?? I haven't done that much on Mitsy stuff so this is going to be a learning curve. When the system is in test mode and i shut the liquid service valve and the unit doesnt pump down and pressures dont change is it gospel that the comp is not pumping and is knackered? Tech said with it in test mode comp should run regardless and by shutting service valves you can determine whether comp is knackered and not pumping. The client says that the system worked fine until october last year, so sounds like the compressor worked until then
Any advice is appreciated guys as i have only been in this company two weeks and already ordered a compressor:eek:
Cheers Kelly

[monkey spanners]

Could it be a reversing valve problem?

[theyelk]

I ran it in heating and cooling test modes and traced the hot gas/ cold gas through reversing valve all way past service valve so didnt think that was problem, plus when had gauges on only obtained 15 to 16 bar high pressure and 11 bar low pressure and also in test cooling i shut the liquid valve with no effect

[joe-ice]

i am also a fridge guy ,systems are systems ac or not .is this an inverter compressor,things to look for are faulty 4 way valve ,also most of these systems have a solenoid to bleed the high side to the low side during changeover,rule these out and narrow the field.

[r.bartlett]

i am also a fridge guy ,systems are systems ac or not .is this an inverter compressor,things to look for are faulty 4 way valve ,also most of these systems have a solenoid to bleed the high side to the low side during changeover,rule these out and narrow the field.


pound for pound, a good fridge man is a better engineer than a good a/c man

[joe-ice]

people seem to forget that all split type air con was originally done by fridge companies ,a lot of companies still do both.

[theyelk]

Are you refering to me? I know that fridge and AC is the same but these guys are mostly supermarket fridgies and have said to me they hate working on air con coz they don't really understand it give them a pack or coldroom/ display case any day. The reason i said they may not have investigated why the comp broke originally was coz the engineer who did it was a bit vague

[theyelk]

I know a fridge man is better than A/C which is why i changed jobs and am now working for a fridge firm as an improver who has A/C bias

[jiminajam]

Check your indoor unit index plus outdoor base charge, sounds short of gas to me. Windies V Frosties bring it on:D

[Peter_1]

Are you sure compressor is speeding up to its max speed? If at max speed, compressor is faulty.
You could check this with the small VFD checker - forgot the right type -you can buy at Mitsubishi, connecting it to the outdoor PCB.

[Neddy]

If the compressor is at full speed check the running amps. If the running amps are low your compressor isn't pumping. It may be possible to check the frequency of the compressor if the PCB has a Display by changing a dip switch.

[Peter_1]

http://www.mitsubishipro.com/media/318886/pumy-p36-48nhmu_techservice_oc366f_12-10.pdf this will help you. You can check some temperatures via the LCD control on the outdoor unit

[theyelk]

Arrived on site early this morning, checked resistance of 4 way valve and bypass valve all ok so ran it in test heating at full speed it seemed the compressor only pulled 5 amps and 18 bar high pressure, also when I shut the gas stop valve it only rose to 25 bar so I'm certain it's the compressor under pumping

[Neddy]

When you close the gas valve the discharge pressure should have increased very quickly and the compressor amps should also have increased .Sounds like the compressor is faulty.

[theyelk]

It did increase but stopped around 25 bar and the amps increased to 7 amps

[r.bartlett]

No we were talking generally..Sounds like you work for ARCUS?

[theyelk]

Ok sorry for confusion R Bartlett, I appreciate everyone's input thanks again as said previously I reckon it's comp under pumping so ordered one and will update once fitted... I take it if it is the comp then it's died of natural causes...?

[RusBuka]

1. Bypass valve can be locked in open position.
2. Restriction of maximum frequency of inverter can be enable.

What DIPs is ON or Off on SW-6?
What was SH, SC and SHT, how many impulses was on EEV of every indoor unit? Did you have M-net checker?

And the last question, you make pressure test in 1 pipe or in 2?

[Neddy]

Where are you checking the run amps from the terminal block or the compressor? It is a single phase condenser?

[theyelk]

I was checking from terminal block its a 3 phase unit

[Neddy]

7 to 8 amps is about right for a 3 phase outdoor. When you checked the bypass valve was it hot on one side? Is the discharge pipe leaving the compressor getting hot ? Is the compressor body getting hot to touch? What pressure are you getting at the gas ball valve?

[monkey spanners]

i m also facing the same problem but i got the solution from snipped


it is a very good company they help alot

I bet they ripped it all out and fitted an old fashioned ducted system with gas furnace!

[Neddy]

Or a new window rattler!

[theyelk]

Only got 7 amps when i shut the gas stop valve in test heating otherwise it was 5 amps at full tilt and between 1 and 4 amps all the rest of time it was on test mode

[theyelk]

Getting the impression that nobody believes it could be the compressor under pumping except me...
Ok so far
-checked gas charge reclaimed and weighed correct amount back in so not gas issue.
-checked capacity of indoors to outdoor including liquid pipe length all ok.
-checked test heating and cooling, only obtained 30 degrees coil temp in heating and 10 degrees in cooling. Which in heating was 16 bar high pressure and 9 bar low pressure
-closed gas stop valve in test heating and pressure only rose to 25 bar and Amps rose from 5 Amps to 7 Amps, if compressor was running normally it would achieve 30 Bar in heating HP with gas stop valve open and then if it was closed would shoot up to 40 bar + which would then trip out the HP safety
-checked resistance of 4 way valve and bypass soleniod and both were around 1.4 kohms which is within range
-closed liquid line with unit in test cooling to try and pump unit down, unable to pump down as compressor was under pumping

Pretty sure i have covered everything now

[monkey spanners]

Think we are all just trying to cover all the possibilities. When you change it, cut the old one open and see what went wrong in it, can help stopping the new one going the same way as i'm sure you know. Pictures or a vid would be interesting if you do cut the old compressor open.

[theyelk]

So an under pumping comp is the cause of something or natural causes wear and tear... If it was a burnout or something like that which was caused by something then its obviously not from wear and tear sorry for all questions i have been this deep in troubleshooting before (good learning curve)
Cheers

[install monkey]

set dip switches on sw1 on outdoor to see comp freq output- discharge pressure is limited and controlled so freq will drop down if head pressure increases due to shut service valve, is there another unit u can compare it to?

[theyelk]

sadly not, dont forget tho when i shut the service valve the pressure only just rose to 25 bar from 18 so not really enough to cause a reduction in freq dont you think? Then when opened valve back up the pressure dropped back to 18

[install monkey]

http://www.mediafire.com/view/?6g5tc3v1bi42xx5
did you carry out the correct method for additional charge- ie not 30grm per mtr- measure each pipe length,size and allow for refnet branches etc??

[monkey spanners]

Wonder if a faulty pressure sensor would limit the compressor speed?

We had a duff discharge themisitor (value jumped about) that made the inverter comp sound like the crazy frog on a mitsi vrf.

[theyelk]

Yep gas charge done properly measured pipe run and gave all info to technical ( pipe lengths, how many refnets, pipe sizes and all indoor model numbers ) to which they said we are well within the chargeless length of 50m. Whilst tech was on phone we configured SW1 to read discharge pressure which corresponded to what gauges read and indoor coil temp read too think it was 260 or 200 psi

[theyelk]

Another thing which makes me think compressor is when I re gassed the system with correct charge I had unit in test cooling to try to meter last bit into suction as the vac only took 5kg out of 8.5kg. The comp wouldn't suck properly it would suck let's say 100 grammes then the sight glass in gauges would fill back up with liquid so I had to keep resetting the test cooling function to get more in??

[Neddy]

You checked the resistance of the four way valve and bypass valve. Did you measure the discharge and suction temperatures in and out of the four way valve. Did you measure the temperatures across the bypass valve? Was one side hot and the other side colder? When you had your one of your gauges connected to the gas valve service port, did the pressure change in cooling/heating?

[theyelk]

Traced the gas through 4 way valve by touch, pressures not much different in heat and cool, didn't check bypass valve temp is it supposed to be cold one side in test heating? Would that have an effect on comp suction in cooling when I was unable to suck additional charge in?

[theyelk]

Might be popping back to site today should I try removing bypass valve coil? And see if it has any effect?

[bigor_2]

Imho 4-way valve is defective and needs replacing at an additional cost!

[monkey spanners]

With the reversing valve, if the shuttle doesn't fully move from one end to the other (or seals fubared) on change over, some of the discharge gas bleeds back into the suction, this give low head and high suction pressure. Not sure on the bypass valve plumbing but it may do the same thing if fault mechaniacally.

I have done this on fridge stuff where i've dumped the gas back in but forgot to shut the high and low taps on the gauges...

To confirm the rv valve is ok you need to measure and compare hot gas in and out temps and suction in and out temps in cooling, and then in heating also.

http://www.youtube.com/watch?v=3D7GxezgPd0

[Neddy]

At the gas valve service port in heating you should have discharge vapour. In cooling you should have suction vapour. You should have different pressures. Put your gauge on the gas valve service port and run the system in test heat. Let the pressure rise. Remove the solenoid coil on the four way valve and you should hear a gas noise and the pressure should drop. This proves the valve is moving but does not prove its by passing internally. With the bypass valve one side should be hot and the other colder. If both sides are hot the valve may be mechanically stuck open or the solenoid coil may be energised keeping it open. If this is the case the system is pumping discharge gas into the suction so your pressures will never get to target.you can prove it works by placing a mag valve on it and you should feel a temperature change.

[joe-ice]

With the reversing valve, if the shuttle doesn't fully move from one end to the other (or seals fubared) on change over, some of the discharge gas bleeds back into the suction, this give low head and high suction pressure. Not sure on the bypass valve plumbing but it may do the same thing if fault mechaniacally.

I have done this on fridge stuff where i've dumped the gas back in but forgot to shut the high and low taps on the gauges...

To confirm the rv valve is ok you need to measure and compare hot gas in and out temps and suction in and out temps in cooling, and then in heating also.

http://www.youtube.com/watch?v=3D7GxezgPd0

Bypass valve dumps discharge directly into suction

[frank]

pound for pound, a good fridge man is a better engineer than a good a/c man
Where did that come from???? Each to their own I say.

[RusBuka]

I don't agree. All familiar fridge man VRF systems avoid like the plague.
Actually the problem in this case is discovered quickly and easily. When already do it. Without Maintenance Tool longer. I am lazy to sit with the translator)

[r.bartlett]

Where did that come from???? Each to their own I say.

A good fridgeman knows how to fix refrigerating systems. A good air con man knows how to use a mobile phone...:D

[install monkey]

thought fridgies- top up and leggit:D

[theyelk]

Going back to site in morning so will update

[Neddy]

Any update?

[theyelk]

Compressor is on site and waiting to be fitted should be doing it Saturday will let you guys know the outcome... If it was a faulty comp ie not pumping then I don't need to worry about just fitting a new one is that right? Because it wasn't killed due to improper use it died on its own

[RusBuka]

Take a look at oil...How many oil was in under-dome, and what the color.

[Neddy]

Carry out an acid test to prove the compressor oil is not acidic.

[joe-ice]

Depends on age of system,An old one would suggest wear an tear,a newer system the biggest culprit would be liquid carryover or excess oil ,I would imagine lack of oil would do alot more damage.Just give the system a good long test on all modes when you have it back up and running.Hate calls like these real headwreckers,

[theyelk]

Update!

Replaced compressor today and its now all working fine! Phew! I am so happy and relieved that it was the comp :-)
I got an acid test kit but was unable to get any oil out of old comp to test it... Never done it before so not sure what the procedure is so any advice is welcome.
Ran system in heating and got discharge up at 30 bar with nice 50 degrees air off indoor unit so client is over the moon, got 5 degrees air off in cooling too.
Thanks for your help guys I would've struggled even more without your input!
Kelly

[Gary]

Air off temps are meaningless without air on temps, we need to know the air on and air off temps for both coils in both modes... and compressors almost never die of natural causes.