DAIKEN RZQ71KCV4A Ducted System

[gbc.heat]

Hi All ,

Got called out to a reverse cycle ducted Daiken RZQ71KCV4A AC unit today not cooling or heating !

Switched it to cooling and checked air temps at outlets , pumping out around 27 C , near enough the same temp at the intake filter , checked and cleaned filter , replaced .

Went to outdoor unit checked / cleaned then tested all the intake , coil , discharge etc thermisters reading about 20k ohms , checked low pressure and high pressure switch for continuity all good . Checked windings in the compressor all good . Capacitors all good !

Put on my gauges after unit was running about 10 mins and seen that discharge was 890 kpa / 6 c and the outlet line was 15 c with clamp on thermometer . Suction was 800 kpa / 3 c and 30 on the line .

So at first I thought the reverse valve might not be seating properly and cross flowing due to suction / discharge pressures being so similar so checked temp differential across inlets / outlets and same temps noted !

So I always thought the suction line should be about 5-6 c and not 30 c . What temp should I look for normally on the superheat in C ?

If it was low on refrigerant surely the discharge would still be a lot higher after it has went through the condenser then out on the liquid line at the 2 way valve ? Weird thing was the liquid line was sweating leaving the unit going to the Evaporator then coming back at 30 C.

Could it simply be low on gas or is it more sinister like a faulty expansion valve or solenoid stuck open ?

please help a rookie out !:rolleyes:

[Brian_UK]

Is your high side pressure taken at the external service valve or the high pressure access port inside the casing?

Also monitor the compressor discharge temperature. If it continues to rise then, with your high superheat, you could have a shortage of gas.

What is the refrigerant btw?

[gbc.heat]

Is your high side pressure taken at the external service valve or the high pressure access port inside the casing?

Also monitor the compressor discharge temperature. If it continues to rise then, with your high superheat, you could have a shortage of gas.

What is the refrigerant btw?

Hi Brian ,

It's R410A , yeah I took pressure reading at the service valve not the valve inside the unit !

I did notice that the high side pipe was sweating at the service valve leaving the unit going out to the evaporator in the ducted unit inside the house .

I did think it was low on gas but you never can tell with these inverter systems ! I added about 100 grams over 5 minutes throttling the valve to charge it as a vapour but it never had any effect on the temps . Seemed to increase the pressure slightly on the suction but nothing on the discharge side .

I always thought if it was low on gas it would be low pressure on the suction side and high side . I am getting 800 kpa and 890 kpa respectively .

Thanks

[gzhjb]

Based on what info you mentioned, I'll say it's short of gas. When you recover the remaining gas back to cylinder, you will soon notice that.

[Brian_UK]

Hi Brian ,

It's R410A , yeah I took pressure reading at the service valve not the valve inside the unit !

I did notice that the high side pipe was sweating at the service valve leaving the unit going out to the evaporator in the ducted unit inside the house .

I did think it was low on gas but you never can tell with these inverter systems ! I added about 100 grams over 5 minutes throttling the valve to charge it as a vapour but it never had any effect on the temps . Seemed to increase the pressure slightly on the suction but nothing on the discharge side .

I always thought if it was low on gas it would be low pressure on the suction side and high side . I am getting 800 kpa and 890 kpa respectively .

ThanksWhat you are calling the high side is downstream of the expansion valve so is the inlet to the evaporator and nothing to do with the 'high side' at all.

[gbc.heat]

What you are calling the high side is downstream of the expansion valve so is the inlet to the evaporator and nothing to do with the 'high side' at all.

Ok thanks for that , makes sense now that I have re-read my college books lol

I'm going back on Tuesday so I will stick my gauges on the discharge side inside the unit .

I will recover the refrigerant inside the unit to a bottle and check against the data plate to see whether it's short on gas !

Thanks for your help !