indoor coil freezing when system is not running

[andymccc]

Hello everyone i'm having trouble with a daikin R407c vrv system (2 pipe). unfortunatly i cant tell you the model as the name plate as been weathered and unable to read.
Anyway a client of mine is complaining about two of the units that are fed from this system whats happining is the indoor coil is freezing over and leaking, having first checked the filters which were fine then checking system pressure which again is fine i'm at a loss as to why!
Any over fault ie stat would send a fault signal to the remote.
Then speaking to the client, she then told me both indoor units where not even switched on when this happened, which as you can imagine brought a blank expression to my face.
Can this happen??????
I wouldn't have thought so but if there is anyone out there that can shed a bit of light over this matter it would be very much appreciated.
This is my first thread so look forward to what you guys have to say.
Regards Andy

[frank]

How did you manage to check the system pressures and confirm that they were OK?

I would suspect that the 2 fan coils showing signs of freezing up may have faulty eev's

[martinw58]

you have faulty eevs try changing the heads over with a unit that is working it is userly the head not the hole valve

[install monkey]

is the contactor welded on the condenser?
isolate condenser the power up the compressor shouldnt start straight away-usually a 3-5 min delay

[Mentallist]

This does sound like an EEv issue. If a VRV indoor unit in cooling reaches set point - 1 degree, expansion valves closes, so does not allow refrigerant to flow into coil. Failure of the valve is apparent if the units are off, but freeze up occurs, expansion valve will also remain fully closed. You can reset the expansion valve heads by powering the unit down and swapping the yellow and blues wires in the plug, then power up the unit for 5 seconds, power off again, then back up for a further 5 seconds. Power down and then swap the yellow and blue wires back to original position. Swapping these cables will fully back seat the pin in the valve coil, so when the unit is powered back up, the software will fully close the valve (+ 50 pulses to ensure closure). Operate the system with the units off and see if refrigerant still passes into them, if it does, then you will need to change them.

[andymccc]

Thanks for that guys, will give it a whirl.

Thanks again

[Royal241]

I read it too fast, but seems like a leaking solenoid valve, not sure if your system has one, but if it does...replace it.

[Grizzly]

This does sound like an EEv issue. If a VRV indoor unit in cooling reaches set point - 1 degree, expansion valves closes, so does not allow refrigerant to flow into coil. Failure of the valve is apparent if the units are off, but freeze up occurs, expansion valve will also remain fully closed. You can reset the expansion valve heads by powering the unit down and swapping the yellow and blues wires in the plug, then power up the unit for 5 seconds, power off again, then back up for a further 5 seconds. Power down and then swap the yellow and blue wires back to original position. Swapping these cables will fully back seat the pin in the valve coil, so when the unit is powered back up, the software will fully close the valve (+ 50 pulses to ensure closure). Operate the system with the units off and see if refrigerant still passes into them, if it does, then you will need to change them.

Very good and informative post.
Many thanks Grizzly.
Rep points added.

[brunstar]

yeah definitely an EEV body jammed.