Problem with a multi-split Daikin inverter

[ccarmock]

I have a Daikin multisplit inverter installed at home. The external unit is a 3MX unit with connections 1 & 2 only in use and 2 x FTXS35G2V1B internal units. It is a heating & cooling system

All was working well after installation.

I had a need for the pipework to be disconnected about a year ago so the maintenance enginner did that and reconnected for me. Again all seemed well though unit number 2 seemed less powerful in cooling.

Then unit number 2 stopped cooling altogether and tripped out flashing a UX error. A power cycle reset it and it worked again.

This repeated. The engineer visited again and found that the re conenction of the pipes had one crossed with the other so corrected that.

No 2 indoor unit seemed more powerful now. But has started to have intermittent cooling failures again.

When the system works correctly all seems very normal. BUT in failure mode when number 2 unit only is on I find that the pipes that feed no 1 unti get cold and indeed the coil inside no 1 indoor unit gets very cold.

So refrigerant is going to the non operating internal unit.

I have checked cabling which matches the units correctly.

A power cycle sometimes makes them work again, but I have tried no 1 only no. 2 only and both running and often no 2 will not cool.

What I also notice on the external unit in failure conditions - the upper two pipes for no 1 unit both get cold and the THINNER of the second set of pipes gets cold but not the thicker.

I have an engineer calling next week, but wondered what people felt might be the issue here. Could there be a valve failed that means no 2 gets no refrigerant and when that happens it's forced into no 1?

When no 2 works the fan coil in no 1 does not cool so it is a weird fault.

Any advice much appreciated

[ccarmock]

Just a little more information. Both indoor units seem to run fine in heat mode.

[install monkey]

http://www.mediafire.com/download/5v...m219-50663.pdf
click on link above, look at page 2 for checking indoors for fault code, could be going out on freeze protect, but appear ok in heating mode

[ccarmock]

http://www.mediafire.com/download/5v...m219-50663.pdf
click on link above, look at page 2 for checking indoors for fault code, could be going out on freeze protect, but appear ok in heating mode

Thanks - I get a 00 code returned on both indoor units right now indicating no fault. Yet still indoor Unit 1 works fine in both heat & cool mode

Unit 2 will heat but in cool mode no refrigerant runs to unit 2 instead the coil in unit 1 (not even switched on) gets very cold. Every so often it will run fine in cool mode and then the coil in unit 1 remains at room temperature.

So I think the piping is correct. Wiring is also correct. Stuck valve maybe? I don't think it's a thermostat problem as if the indoor unit 2 had a broken thermostat it woudn't call for cooling and thus there would be no refrigerant flow to Unit 1 in error? and in that case I'd expect the compressor to shut down and idle.

[Slim R410a]

Replace the valve coil first - If symptoms are the same looks like the valve body may have to be replaced?

I had the same last year - No fault code (00 code), Room A had little or no ref. passing through whereas Room B worked fine. Just replaced the coil on Room A that worked however have had to change both coil and body on other multi splits and splits.

Apparently there was an extended warranty on some of these that run out this year...not much to buy but might be worth checking anyway against your outdoor's serial number.

Just noticed you have a 3MXS unit - If you find you need to replace the body you would be best just to pump down and re-pipe/wire onto the spare port? (Room 3)