Hitachi pressures off the scale!

[ianybeany]

Hi there
Came to a hitachi unit today (raso9ch1), small wall mount split R22. Unit had operating temps of 19C air on 14C off on cool and 33C on heat, so decided to stick a gauge on it as the temps were poor.
Cooling - 5.5 Bar
Heating - >34Bar !!!!! , the only reason it was at 34 bar and not further was the fact the pointer had gone all the way around the gauge!

Immediatly shut down the system and told the customer that it looks like it is severly overcharged, or possibly wrong gas I plan to weigh it out, but anyone ever see pressures as crazy as this on a similar sytem?

[coolments]

Hi There

I think its more like none condensables in the system, i would re-charge with new refrigerant after a triple evacuation, also take an oil sample and check it as this will most likley need changing also.

[marc5180]

Hi Ian Beany. I had a similar problem like this a few weeks back with a Hitatch unit. checked absoloutley everything i could think of. I recovered the refrigerant and weighed it back in and it worked for a few days then it happened again so i checked th reversing valve the condensor fan the compressor. Eventually after hours of scratching my head i decided to check the indoor fan. Upon further inspection the fan would run on medium and high setting but when it was set on auto fan the fan just woulnt work at all causing increased head pressure. changed the indoor PCB and problem solved...
Hope this helps
Cheers

[cool#9]

HI
As marc says the problem is probably from the indoor unit.
In heating mode on indoor side the pressure reach 34b( r22 !! )and if it's not inverter drive the only way to decrease it is to reduce the outdoor fan.
This is usually done by a sensor on the indoor coil that cut or reduce outdoor fan control via the main pcb. So check this thermistor first (resistance value, etc...) before the remplacement of the pcb.
In addition in cooling the pressure is -5.5b :impossible or maybe -5.5°c...or a defective low pressure gauge...Maybe the indoor coil is dirty or the air flow rate too low.
It'll be interesting to have more information about supply / return air of both indoor / outdoor side to check for example if the system takes too much calories in heating mode from the outdoor coil this will justify the regulation i described above...
Good luck
cool#9

[DEVIL]

heh, whas on a Daikin duct, 2 years ago or and new that before me, there whar 3 engineers on it, and didn't manage to make it work, so ... after 15 minutes, i discoverd that the compressor whas fluded with refrigerent, after 2 hours of dumping refrigerent out, all my tools whar frusted over, and got the sistem runing, it whas a 10 KW unit , that as i rememberd had les then 3 Kg of refrigerent from factory, and took out, more then 15 Kg of refrigerent, and whas so amased how could a engineer, do somth so stupid

And aferwhords took me 1 hour to get to the duct filter, and found the problem they all missed.

[ianybeany]

Yea, cowboys at work again!
Pulled out 2.3 kg of 22 the correct charge was 850g !!! After vacing it out and recharging , pressures and temperatures were fine!

[cool#9]

Thanks for this good new and after my finest explanation dated 22/04/2007 i want to say : we sould go back to basics first !!!
cool#9

[The MG Pony]

Thanks for this good new and after my finest explanation dated 22/04/2007 i want to say : we should go back to basics first !!!
cool#9

RE: Your sig, there is a blind fellow who rebuilds diesel injector pumps! I think he wins the Buddha of building award lol, I hope to get a dead scroll just so I can try and tear it down and rebuild it, be a neat project I think, educational at the very least

[cool#9]

I MGP
My signature shows an inverter horizontal scroll type i've open last year.. it's a bit different from vertical type due to oil pump.
I know a firm in Israel which open hermetic Bristol compressor to repair them...
For me it's far from business, just for fun and understanding.
Kind regards
cool#9

[The MG Pony]

Thats what it would be for my self fun and learning.

Iany here we call them trailer park engineers