Hitachi vrv blockage

[Northy303]

I visited a site today that a Hitachi vrv had tripped out on low pressure fault code 47.
It is not short of refrigerant but seems to have a blockage somewhere at the electronic exp valve. It is being used as a heat pump and is icing up into the outdoor coil. It looks like it has some sort of hot gas bypass with a small bulb on it not sure if it is a drier and another bulb before the expo valve. It also has had a new reversing valve fitted by another engineer but that seems ok.Any ideas anyone to what part I should replace by looking at photos as I am just thinking of replacing all of it

[install monkey]

i had a hitatchi set free unit fxns running but not ramping up- pulled over 12kg out of it and now its working- scroll thru the outdoor display to check if its asking for the lev to open, maybe swap a lev head over with another to see if its coil is faulty or if the valve is sticking

[Tayters]

Hi Matt.

I've emailed you a pipe diagram for the 3 pipe in case that is your version. Not got any other versions. :-(

The bulbs each side of the EEV are strainers as you say although the frost is starting at the valve itself so I'd guess the strainers at least are fine.
First off I'd try in test run cooling to see if it performs well. You can monitor lots from the outdoor PCB display to check indoor coil/air temps as well as a grope around the pipes just to see what's what.
Either you get poor cooling which would point to short of charge or cooling be fine so then try test run heating which leads onto the next chapter.

There are two 4WV and one is energised in cooling, the other in heating, so as you can see they swap over. Confirm valve operation by sticking a magnet on the valve body and watch it move when valve operated (plug is somewhere on top right of PCB but check diagram) otherwise plug it in and out and listen for the whooshing. Check you get right temperatures on 4WV pipes - discharge on the top, suction underneath in the middle then the two at the ends will go to outdoor or indoor so one hot and one cold.
This might not be your problem but should only take half hour to do and this will confirm 4WV operation which is worth doing seeing as one has been replaced. New one might have been mullered, who knows. From there follow pipes as best you can and check the larger solenoid valves which lead to the outdoor coil as operating as required.

Apart from the weak inverter boards I've seen dodgy 4WV cause good cooling and poor heating (luck of the draw on which valve packs up (and its position if stuck) will show up in heating or cooling). So I'm told the solenoid valves feeding outdoor coils can cause a similar looking fault but be 4WV wrongly condemned. Can't comment on that as not experienced it but though I'd chuck it in the mix.
Also the obvious, service valve closed, EEV initialise on power up, fans spinning, coils clear, sensors and probes read sensible values on PCB display.

Outdoor pipework looks horrendous, goes all over the shop but once you sit down and try and figure it out, take a look around it, it should start to make sense. You should find the service manual on the internet to get the details for using the outdoor PCB display for troubleshooting and DIP switch for test run on inside panel of unit.

Hope it helps,
Andy.

[install monkey]

u can do test heat.cool on dsw5 on the outdoor- look on the panel- be careful the lugs on the dipswitches dont snap

[install monkey]

cant e mail ya hitatchi vrv manuals as theyre over 30meg
just register on here and your in- the hitatchi app on ur phone is a nightmare to set up
https://www.hitachiaircon.com/argws/en/login

[Northy303]

Thanks for the replies guys, I am going back there on Monday my boss thinks it needs a new strainer drier so I am reclaiming it fitting the drier and recharging it after a good vac. I will check the 4way valve and solenoids first tho.
I am also considering fitting an extra filter drier on the liquid line or is this a bit overkill.

[Tayters]

Hi Matt.

Sure you're on the case but be worth chopping the old one apart to see if it's full of crud. Blow through EEV if possible. Might have to swap a couple of wires round then reinitialize valve to open instead of closing it. Good time to confirm gas charge and when running back up check probes and valve positions from outdoor board.

Fit extra drier? I'd say no. If oil is acidic then yes, fit a burn out drier but not easy to get oil out to check it (easily, that is). If system is dirty then other strainers would be (partially) blocked already so you're stuffed because they're are loads of them! If you are worried about moisture then perhaps, although oil could well be contaminated by now? If you do go for one make sure it is a biflow.