Daikin VRV K series Issues

[troymedhurst]

Good Evening All

Been having some problems with a RSXY10K7W1

Main Issue is fan control and dropping discharge and suction pressures.
After monitoring system, I noticed that MF1 high speed relay was not working, so MF2 was cutting in, but then dropping head pressure to 7.8 bar before cutting out. This was causing a suction pressure drop, which was then backing off internal units. I also noticed that voltage on HP transducer was reading 2 bar higher than it actually was.

I changed A1P board and HP transducer and ensured that ambient sensor was correct.

Now when system starts fans both start etc... then MF1 is on Low when pressure reaches about 16 bar MF1 High then comes on, which is fine, but it is not cutting out when it should ! according to Daikin they say MF1 High should cut out at 15.7 bar, but it doesn't and the pressure sits about 13 bar with the inverter not really ramping up fully, even though there is plenty of load.

Now I have read in the manual about Low ambient Cooling, but the manual doesn't make sense! even to the point that daikin Tech didn't understand it either. It almost seems like the control logic is back to front and it tries to keep head pessure low? I was supposed to get a call back from their VRV specialist, but no joy yet. ( probably busy).

Notes:
Gas charge is correct.
Daikin state that MF2 should'nt cut in until 21.6 bar actually cutting in at around 19 bar and should cut out at 16.1 bar, does'nt cut out until around 7.8 bar

If anyone has any ideas? or could read the manual about Low ambient cooling and can make sense of it?

I would be most grateful for any input.

[install monkey]

http://www.mediafire.com/view/cnmnp6...ies%20407c.pdf
service manual- have you checked the dc voltage on the transducers,wash condenser coil to ensure it aint operating outside its limits. in setting modes on outdoor unit u can change the discharge temp from normal to low, also check ur liq inj solonoid is working

[r.bartlett]

disconnect one of the fans off the board and let it run. Then see how the pressures are. In this climate unless the condenser is blocked it should be running on one fan only

[troymedhurst]

Yep checked voltage, as old transducer was out of range, I replaced HP transducer and now reading correct.

I did change outdoor setting to run at high Tc setting, but made no difference.

hot gas solenoid is not required, as suction is not going that low.

I did remove MF2 plug and also switched high and low speed wires, in order to run the system with just low speed fan. This was ok, as temp solution. the discharge was up around 45 degrees, but the inverter would'nt ramp up due to discharge.

I have now replaced parts and put back as normal.
I agree that only MF1 should be running, but its staying on high speed and not cutting back to low speed when it should.

Thanks for you input

[troymedhurst]

Just read manual, regarding low ambient cooling and it states that it will be High speed MF1 on, until it is less that 12 bar! ( Which contradicts what Daikin told me!) As my discharge seems to now be sitting about 12.5 bar (31 degrees), its keeping head a little lower than I would like. Hey-Ho.

[r.bartlett]

are you sure the condenser is clean as we had a lot of issues which went away after we pressure washed what we thought were clean coils. because they are two together the front face is clean but half way through is where the dirt builds up. hose them out in any case unless you personally know it's been done within the last year.