daikin RZQ71

[r.bartlett]

Chaps

Got an RZQ71 which is icing up solid. It seems that the unit goes on defrost and the fan stops but it stays on heting and hence doesn't defrost the coil.

When i turn it to cool it works normally so isn't a stuck faulty valve etc


Any clues??

Richard

[RusBuka]

How much you wait when defrost is on?

[r.bartlett]

How much you wait when defrost is on?

15 minutes with the unit remaining on heat but condenser fan not running

9854

It's the furthest unit

[jonjon]

what temp was it outside ? what air was you getting on the indoor in heat/cool

[Brian_UK]

Can't remember the model number but I had something like that a few years back.

It turned out that the indoor PCB was corroded, marine environment,; replaced that and it worked OK after that.

Would suggest checking the sensors anyway but might be worth a visual inspection of the PCBs.

[install monkey]

http://www.mediafire.com/view/?fbkn16dqvik9kmf page 48 defrost

[r.bartlett]

Didn't realise you could force a defrost on these unit :-)

Will give that a go this morning

Ta :-)

[r.bartlett]

Tried the forced defrost same thing. Won't swap over. tried disconnecting the sol and it clicks and there is a slight change of the refrigerant which indicates something is happening but still not defrosting the coil.

What I don't understand is why it works ok on cooling though??

[frank]

You need to be taking temperatures on the pipes into and out of the 4way valve in both modes to see if the valve is sticking

[r.bartlett]

You need to be taking temperatures on the pipes into and out of the 4way valve in both modes to see if the valve is sticking

There is something weird. On heating it works fine , on cooling it works fine, on defrost it won't defrost either normally or when forced. The valve is energised but won't swoosh over and start defrosting. the suction pipe remains hot and condenser is icing.. Yet when I put it on cool it defrosts the condenser and the suction goes cold...

[frank]

The valve is energised but won't swoosh over

A problem with the valve then.

When you choose either heating or cooling mode, the system will shut down, pressures drop and the valve changes over.
During defrost, the compressor keeps running, so higher pressures when the valve tries to change...listen to the compressor ramp down and the valve change (or try to) over.

Then listen to the compressor when you change mode. See the difference?

[r.bartlett]

I am pretty much at the same conclusion. I am going to have to break the news gently they need a new outdoor unit as the present one was installed in 05 (even they refer to it as 'the new unit' :-) and I can never see the point in repairing a unit when the cost will almost be the same..

[Tayters]

The valve works on a pressure differential so wouldn't this argument mean a higher differential therefore more force to slide the widget across?
Or do you mean it's this higher pressure difference which is causing the fault somehow?

Of course if the valve is energised in heating and de-energised during defrost then it counts out a PCB / electrical fault and the only real culprit the 4WV but like Mr B I can't fully convince myself.

[Scooby]

Hi,
From the picture it looks like you have 2 badly iced up outdoor units,
Are you sure the interconnecting cables are going to the correct indoors, i had a similar problem a few weeks ago when the install idiot didnt commission individually and handed the job over as complete.
Simply fix but did have me scratching my head for 10 mins.
cheers

[r.bartlett]

Hi,
From the picture it looks like you have 2 badly iced up outdoor units,
Are you sure the interconnecting cables are going to the correct indoors, i had a similar problem a few weeks ago when the install idiot didnt commission individually and handed the job over as complete.
Simply fix but did have me scratching my head for 10 mins.
cheers

I had a couple of installers who whilst they thought they were the best in the world were actually a couple of idiots they did this twice on two jobs and the second one cost the compressor.

However on this particular job these systems were installed 6 years apart...(2005 +2011)