Off-line Mitsi VRF leaks!

[sinewave]

Site has 5 Misti VRF R22 units feeding 35 cassettes.


One set of six cassettes has a 2502 (Drain up fault) which knocks off the other 5 cassettes.

Usual procedure is to re-boot the condensor after a deft flick of SW2 so the condensor now only 'sees' 5 units and can carry on operating whilst parts are odered for the faulty unit.

However in the mean time the off-line unit has dumped pints of water over a desk and soaked a laptop! :eek:

On investigation it seems that even though this unit is 'off-line' that Refrigerant is still evaporating through it's coil and freezing it up and then it's melting all over the place! :(

Unit which is 'off-line' is No' 2 of 6 in the run.


Not come across this before chaps, any comments? :confused:

[aeb200]

probably a leaking lev (linear expansion valve)

when unit is off refrigerant lets by thus freezing coil and causing a water leak when it thaws out

the lev is in essence an orifice with a pin inside -that throttles refrigerant flow to unit. It is driven open and closed by a stepper motor attached to a worm drive(they can sometimes loose position and stick open).

you can try and reset the valve to the minimum position by turning off outdoor unit (or disconnect m-net connection from indoor board - mauve wires and blue plug) .then power the indoor unit off/ on for thirty secs (you may need to do this several times) you should head the valve driving closed to minimum postion. Then plug m-net connection back in or turn outdoor unit on.

I have found that this only usually works in the short term it is best to try and replace valve which can be quite tricky as the valves come with very short stubs
cheers aeb200

[sinewave]

Cheers aeb200 :)

[Thermatech]

Sinewave

Impressed with your 'deft flick' ploy. They say its all in the wrist action.

Carrying out 'virgin start' with SW2 procedure will only work if you disconnect the indoor unit from the M-net communication wiring to outdoor unit.
Remember 30v d/c is generated at outdoor unit & it can see all units even if no 240v power is connected at indoor units.
Just turning off 240v power to indoor unit will not take indoor unit 'off line' after an SW2 virgin start.

Is the system R2 heat recovery system or Y series heat pump ?

aeb200 has remembered the old LEV reset procedure ploy very well. But if the system is R22 then it has been running for at least 5 years or more & LEV valves dont last forever.
If the system is Y series PUY or PUHY then if the LEV valve on this unit has failed in any open possition no mater if you have taken the unit off line or not , all the time outdoor unit is running in cool mode refrigerant will flow through this unit ,,, frost up the coil if fan off & flood drain pan next time the outdoor unit happens to stop.
First get the indoor unit back on line & test to see if refrigerant is passing through when this unit when switched off & LEV valve should be shut.
In thisis the case there may be no problem with drain sensor or drain pump.
If LEV valve is suspect then try fitting only the LEV valve motor head followed by the LEV valve reset procedure.
If this does not stop refrigerant flowing through the coil at indoor unit off then you will have to remove refrigerant from system ( pump down to outdoor unit as much as you can first ) & replace valve body.

If the system is R2 heat recovery PURY then the liquid line is always live but gas line will shut at B/C box suction gas solenoid valve(on the port connected to this indoor unit). In this case if the indoor unit LEV valve has failed in open possition the the indoor unit coil will fill up with liquid if the indoor unit is turned off & LEV valve should be shut because the B/C suction solenoid valve for this unit port will be shut. Indoor unit coil & gas tube back to B/C will just fill up with liquid,,, this will tend to make the system look short of refrigerant because this unit will trap a large volume of refrigerant.

Keep up the dip switch flicking ,,,,,,,,,,,, remember practice makes perfect.

[sinewave]

The unit in question is a Mitsi PLFY-P20 VLMD 3.6kW

The procedure followed to remove an individulal AH from the sight of the supplying condensor is as follows.......


After removing the electrical supply from the affected Air-handler disconnect the signal wire from the unit and reconnect the loop to the other units.

Daisy chain wiring BROWN - RED
BLUE - WHITE

On the supplying outdoor unit, do the following

Ø Set Dip SW-2 to ON
Ø Set Dip SW-2 to OFF
Ø Turn main isolator OFF
Ø Set Dip-SW-2 to ON
Ø Turn main isolator back ON
Ø Let the unit go through it’s reboot procedure
Ø Turn main isolator OFF
Ø Set Dip SW-2 to OFF (Unit won’t run with DP-2 set to ON!)
Ø Turn main isolator back ON


System will run without 'seeing' the faulty Air-handler.

[Thermatech]

Sinewave

So long as you have removed the indoor unit from the 30v d/c daisey chain & then carried out the virgin start as described then you have removed the indoor unit from the system.

The model you have given is the indoor unit but what is it connected too?
Is the outdoor unit PUH (cooling only), PUHY (heat pump) or PURY heat recovery with a B/C distribution box?
How you proceed with trouble shoot procedure depends on which type of system the indoor unit is connected too.

[sinewave]

Outdor unit is a Cooling only PUY-200YMF-B :)

[Thermatech]

Ok so the unit is cooling only two pipe multi split. In some respects similar to Daikin two pipe system in that all units are connected to common suction & liquid tubes from outdoor unit.
This meens that suction & liquid are live to the unit all the time & if the LEV valve does not shut completely then refrigerant bypass through this unit all the time outdoor unit comp running. This makes poor cooling performance at the other indoor units.
Options are limited on this one compared with R2 heat recovery system with B/C box.
Best replace the LEV valve head ( same as Daikin LEV valves)
The needle shaft screw thread in the valve head is what usually fails & so you can usually resolve this problem by taking off the valve head & fitting new one & so no need to replace valve body which would need refrigerant recovery,vac & recharge.


good luck

[sinewave]

Cheers Thermatech! :D