Daikin split short cycling after leak repaired

[Tayters]

I'm quite familiar with refrigeration units but with A/C consider myself a bit wet behind the ears so I wonder if any of you could help with this one.

I was called to a Daikin split and told the unit kept cutting out after 10mins so they had to keep turning it on and off at the remote. I found little evidence of the cassette cooling, frost right after the expansion valve and oil all around the service valves and suction flare. I recovered only 300g of refrigerant, repaired the leaks, whole system pressure tested and vacced (from both service valves)

Unit charge is 2.8Kg of R407C. After getting about half of this is in before pressures equalised, I started the unit with a view to getting the rest in through the suction port but that is where my troubles began.

System would run for a couple of minutes and I could hear a bypass valve open so suction pressure remained high (18bar - about what the liquid port also read). The valve would then close, suction pressure fell but unit would stop soon after and the process would repeat itself after about 10mins.
If I wedged the contactor in, pressures seemed fine (evap at 0*C, liquid port 40*C) but I was relectant to put any more refrigerant in at this time.

When charging the unit I got excited and charged liquid through both ports to begin with (no more than 0.5Kg went in before I twigged the manifold was still open). I wonder if there was some liquid somewhere in the unit causing a pressure switch to operate but the unit was doing this for a good 45mins so I would have thought if that was the case it would have boiled off.

The outdoor unit is a Daikin RP71L7W (R407C) running 1 cassette. Gonna press the boss to let me go back and wondered if I was missing something obvious or if my charging through the suction port caused this.

Many thanks,

Andy.

[monkey spanners]

Did you get the full charge into it?

I wouldn't worry about putting liquid into the suction pipe, they have an accumilator to catch any liquid, (in normal operation it will collect in the evap when the unit turns off and is in cooling mode, only to return to the outdoor unit when the next call call for cooling happens, so what you did is no more that what they are designed to cope with)

18bar seems very high for an expansion/suction line, was it in heating mode? where were you measuring the pressures?

Jon

[Tayters]

I got 2Kg in so 800g to go.

Pressures were measured at the service ports (not the HP port inside the unit). Unit was on cooling. First on test run, then set to 16*C to see if this made a difference.

The 18 bar suction was only there when the bypass valve was open (if that's what it was. I say bypass valve because I saw a unit overcharged once and the bypass valve would open after a bit of running and this time I recognised the same noise but not overcharged).
When the valve closed then suction would fall to an evaporating pressure of 0*C (sorry, can't remember what pressure that is but seems good in my book)

When the unit cut out again the suction pressure would rise to 17-18 bar (same as HP service port pressure).

What is the common terminology for the HP service port? I'm trying not to confuse anyone by saying HP port as obviously it's the liquid port but just after the expansion valve not the one inside the unit which is on the discharge side. Looks like I stumbled at the first hurdle!!

Thanks for the rapid reply,

Andy.

[al]

Are the condenser fans running? If you check on actual discharge schraeder head pressure would be stable at 17 to 20b, suction at 3 to 5b if indoor filters are clean and airflow is good.

It sounds as if the 4way valve is kicking in, have you tried shuttling it with a magnet in case there's something jamming it open?

Register with daikin.co.uk for manuals, they're a great help!

alec

[Tayters]

Fans running and airflow, coils and filters all good.
Had to leave to pick my son up from the nursery so didn't get a chance to check as much as I would have liked unfortunatley.

Now I'm not so sure if this was an original fault and the leak was another really.

Still waiting for the Daikin registration to come through. Looks like they don't work weekends...

[al]

Pm me, i have a service manual for rp71, may not be your generation though.

alec

[Tayters]

Done!

Many Thanks.

[al]

Ok, first time doing this so bear with me...



alec

[al]

Ok this seems to work better....

http://www.mediafire.com/?dkyqjzjzdlz

alec

[marc5180]

First things i would check would be why the condensing fans aren't coming on at 18bar and also the 4 way reversing valve is it stuck and dumping hot gas straight into the suction causing your high suction pressures.

Also Daikin suggest to recover refrigerant/pressure test and especially vac out from the internal schrader points once the system has been running for a while.

This happened to me a while back as i pressure tested the system and vacced it out just as you did from the suction and liquid portts (on cooling) but found that somehow i had nitrogen trapped inside the system causing the system to go off on head pressure.

Just something to be aware of.

[Tayters]

Right chaps, case solved.

Went back today and first off measured the standing pressure which equated to 40*C. Looks like some of the OFN found it's way inside the unit and didn't come out.

I recovered 2.6Kg (only got 2Kg in on friday) from both service ports and the discharge schrader then vacced and charged.
The unit now runs fine and I've learnt something along the way - if there's a port, stick a hose on it!

Many thanks to Jon, Al and Marc for your time, it is very much apprieciated.

Cheers,

Andy.

[al]

No worries andy, didn't realise this could happen on a Daikin!

Alec

[tradybrad]

r407c is a blend is it not it should be added to the system as a liquid so the blend goes in correctly.correct me if im wrong but vapour charging this system with r407c would give you abnormal running pressures due to incorrect blend of refrigerant.

[moondawn]

yes r407c should be charged as a liquid sounds like this is what he was doing but for a short while was putting it in to the low side. and then was worrying about starting the system with liquid in the suction pipework heading back to the compressor.

cheers lee

[frank]

Just come across this thread - don't know how I missed it before.

Tayters, quite a lot of the new A/C systems have the electronic expansion valve on the outdoor unit (VRV/VRF excepted) so the 2 service valves are both on the evaporator side. When you do any refrigerant recovery/charging or evacuating you always need to have your gauges connected each side of this eev as you dont know if it is open or closed.

Seems like you learned this the hard way. Good you though for sorting it.

[Tayters]

r407c is a blend is it not it should be added to the system as a liquid so the blend goes in correctly.correct me if im wrong but vapour charging this system with r407c would give you abnormal running pressures due to incorrect blend of refrigerant.

High pressures turned out to be OFN. Not sure which way pressures would go if charged as vapour. I've been told too high but if you consider Daltons Law O' Partial Pressures (Total pressure is sum of individual pressures) I would have thought the pressure would be too low because you are missing an individual pressure.

yes r407c should be charged as a liquid sounds like this is what he was doing but for a short while was putting it in to the low side. and then was worrying about starting the system with liquid in the suction pipework heading back to the compressor.

cheers lee

Was charged as a liquid. Initially I thought I did a Frank Spencer and got too much liquid in the suction side causing some safety mechanism to work. Knew there was a suction accumulator but after 30 mins of running was pretty sure the liquid charge wouldn't make a difference but at the time began to doubt my thinking.

Just come across this thread - don't know how I missed it before.

Tayters, quite a lot of the new A/C systems have the electronic expansion valve on the outdoor unit (VRV/VRF excepted) so the 2 service valves are both on the evaporator side. When you do any refrigerant recovery/charging or evacuating you always need to have your gauges connected each side of this eev as you dont know if it is open or closed.

Seems like you learned this the hard way. Good you though for sorting it.

Cheers Frank. Drawn a picture of it and now see that if the EEV is closed, OFN will go in through the suction port, through compressor, non return valve (sure there is one of these there somewhere on the compressor) and condensor to other side of EEV. When letting the OFN go and evacuating OFN is now trapped between EEV and NRV. Only way out is by opening the EEV or a schrader between EEV and NRV.

Clear as mud.

[fridgy_1]

Hello
does any one have the foults code for Daikin?! F4 F3 ... etc.