Daikin U2 fault

[p_p]

Hi All

I have been asked to attend site on monday and look at a daikin underceiling split unit on behalf of another company.
Reported U2 error = faulty power supply voltage.
There own engineer has replaced the outdoor fan but its still the same, now he has condemmed compressor. Just wondered if there are any specific faults for this code.
Has anyone come across this fault before.

Many Thanks

PP

[Brian_UK]

Check your email for a small Daikin Book.

[p_p]

Hi Brian

Many thanks for the booklet, I hope I can return the favour one day.


Take Care

PP

[superswill]

how did you get on PP?

[p_p]

Sorted.
The engineer that attended could'nt even get the fault code correct, it was actually u1.
He had replaced the outdoor fan motor but connected the thermistor plug from the motor to an auxillary L&N output on the board. hence it was blowing the fuse.
Not bad to say that he had condemmed the compressor!!!!!!

Where do they find em?

Did you get the woman of your dreams?


Regards

PP

[paul_h]

Hey I've got that fault code on a daikin I'm looking at.
It's an RZQ90CV4A.
It runs the condenser fan for a minute, starts the compressor and runs fine for 30 sec, then the system cuts out.
Mains voltage is 230VAC (before compressor starts) and doesn't drop below 226VAC, and the outdoor is pulling only 3.9A before it shuts down.
Any ideas?

[paul_h]

Anyone? Or have all the daikin experts disappeared?

[VRVIII]

Hey I've got that fault code on a daikin I'm looking at.
It's an RZQ90CV4A.
It runs the condenser fan for a minute, starts the compressor and runs fine for 30 sec, then the system cuts out.
Mains voltage is 230VAC (before compressor starts) and doesn't drop below 226VAC, and the outdoor is pulling only 3.9A before it shuts down.
Any ideas?

Hi,

In the UK we don't have RZQ90 units, we only have
71, 100, 125 & 140 (7~14kw) available in single phase.
.
I have attached fault diagnoses sheet and would suggest you check the DC voltages when compressor is operating this should be higher than 220vdc.
RZQ_U2 error.pdf

[chill_ac]

where would i be able to get these diagnosis sheets from?
cheers

[VRVIII]

where would i be able to get these diagnosis sheets from?
cheers

The diagnosis sheets are in the service manuals that can be downloaded from daikin web site.

[chill_ac]

thanks mate

[paul_h]

The diagnosis sheets are in the service manuals that can be downloaded from daikin web site.

Don't mean to be a pain, but how?
I tried signed signing up to the extranet last year, but they never sent me a log in, and I didn't see any other downloads.

I asked daikin for the inverter PCb and they sent me the control PCB.
I thought I may as well fit that, but now the customer is calling me and saying the unit isn't working again after 2 days

[paul_h]

Is C+ anc C- supposed to always have 300V DC?

On this system, after it trips out, there's 0V DC across c+ anc c-,
then when it tried to run again, there's 299v DC on there while the fan runs for a few minutes, c+ to c- slowly drops to 280V DC while the compressor runs and then the system cuts out and there's no DC volts across c+ and c- until it tries to start the run cycle again 3 min later.

While the compressor is running the comp phases ramp up to 140 V AC between each other, or 80V ac to the neutral.
Comp windings are all 0.5 ohm to neutral, across each other they are 0.8ohm.
Comp meggers OK, above 20 Mohm.


Why does the fan run for so long before the comp even tried to start, it runs on it's own for 2 min?

[VRVIII]

Is C+ anc C- supposed to always have 300V DC?

On this system, after it trips out, there's 0V DC across c+ anc c-,
then when it tried to run again, there's 299v DC on there while the fan runs for a few minutes, c+ to c- slowly drops to 280V DC while the compressor runs and then the system cuts out and there's no DC volts across c+ and c- until it tries to start the run cycle again 3 min later.

While the compressor is running the comp phases ramp up to 140 V AC between each other, or 80V ac to the neutral.
Comp windings are all 0.5 ohm to neutral, across each other they are 0.8ohm.
Comp meggers OK, above 20 Mohm.


Why does the fan run for so long before the comp even tried to start, it runs on it's own for 2 min?

Hi Paul,
The start up fan control is normal as the unit will run the fan on high speed and open exp valve for 120sec (to allow equalization of pressures).
Does the compressor have 3 terminals U V W? the resistance should be around 0.7ohms between phases on this type of compressor.
Or do you have an additional terminal marked as N?
Do you have a ballanced ac voltage on the inverter output to compressor when it operates?
Do you have an inverter analyzer to check outputs?

[paul_h]

Hi Paul,
The start up fan control is normal as the unit will run the fan on high speed and open exp valve for 120sec (to allow equalization of pressures).
Does the compressor have 3 terminals U V W? the resistance should be around 0.7ohms between phases on this type of compressor.
Or do you have an additional terminal marked as N?
Do you have a ballanced ac voltage on the inverter output to compressor when it operates?
Do you have an inverter analyzer to check outputs?

Yeah there's U V W and N, 4 cables to the compressor.
U V W are all balanced voltages when he compressor runs, all increasing up to about 140V AC until it cuts out.
U -N, V-N, W -N all increase up to about 80V DC equally when the compressor starts up

There's about 0.8ohm between phases, and 0.5ohm to N.

I don't have an inverter analyzer sorry.

[VRVIII]

Yeah there's U V W and N, 4 cables to the compressor.
U V W are all balanced voltages when he compressor runs, all increasing up to about 140V AC until it cuts out.
U -N, V-N, W -N all increase up to about 80V DC equally when the compressor starts up

There's about 0.8ohm between phases, and 0.5ohm to N.

I don't have an inverter analyzer sorry.

As I said previously we don’t have RZQ90CV4A in the UK, all C series sky air units here have 3 wire compressors. Do you know the unit capacity?

An RZQ125B with a 4 wire compressor has a resistance of around 0.6 ohms between phases and 0.2 ohms between any phase & N, but can’t guarantee this is the same comp as your unit.
The N terminal on the compressors is a feed back signal not a neutral.

You will only have voltage on C+ anc C- when inverter circuit is charged, this should be greater than 220VDC.

Are you sure the mains AC voltage dosen't drop just as the unit trips? The compressor freq will increase after 30sec operation which will in turn draw more current, if you find the voltage is dipping check for loose connections at terminals (unit/isolator/DB) and correct cable size is installed.

Also double check all connections within the unit and closely inspect the inverter PCB for signes of damage/burning. I think the problem could be your inverter pcb.

You could try the following test but don't know if it’s applicable to your unit,
Turn off power to outdoor, disconnect compressor and switch power on
Go to indoor remote - select fan only, test operation and switch on at controller
Wait for outdoor inverter relay to click and check inverter pcb output voltages.
If you find an imbalance the inverter module is faulty the check is more accurate and easier with an inverter analyser.

[paul_h]

Thanks for all your help so far.
Mains voltage is low for this area, but still always above 226 V AC. I'm sure you know how hard it is to ever blame mains voltage anyway. It's impossible without a long history of the site to ever know if it used to be higher and there's a new mains fault that's causing problems.
I checked all the connections and boards as soon as I found out that "U2" = power supply voltage error.
I had my fluke meter (old 87vIII) on record min voltage as the unit started up, and 226V AC is the lowest that the mains dropped (228V before the compressor started)
It seems to me that the voltage is fine at the mains and at C+ C- until the unit decides to cut out on fault.

When I first changed the control PCB, to test I just pressed the pump down switch instead of turning the unit on at the controller, and the compressor ran for 2 min or more fine. Then the customer used the a/c fine for a day or two.

Then it come back with the U2 error, and now no matter how many tries or power resets it keeps tripping out. And the power/mains has been the same all along from now to when I saw it work for longer than 2 min compressor operation.

It could be the inverter board, and it annoys me that that is what I wanted all along, but didn't receive. I hate ordering parts from daikin or mits because I don't have an account or much info/manuals/online access, they always seem to screw me over in parts and service, I get the wrong parts from them a lot of the time.

[VRVIII]

Thanks for all your help so far.
Mains voltage is low for this area, but still always above 226 V AC. I'm sure you know how hard it is to ever blame mains voltage anyway. It's impossible without a long history of the site to ever know if it used to be higher and there's a new mains fault that's causing problems.
I checked all the connections and boards as soon as I found out that "U2" = power supply voltage error.
I had my fluke meter (old 87vIII) on record min voltage as the unit started up, and 226V AC is the lowest that the mains dropped (228V before the compressor started)
It seems to me that the voltage is fine at the mains and at C+ C- until the unit decides to cut out on fault.

When I first changed the control PCB, to test I just pressed the pump down switch instead of turning the unit on at the controller, and the compressor ran for 2 min or more fine. Then the customer used the a/c fine for a day or two.

Then it come back with the U2 error, and now no matter how many tries or power resets it keeps tripping out. And the power/mains has been the same all along from now to when I saw it work for longer than 2 min compressor operation.

It could be the inverter board, and it annoys me that that is what I wanted all along, but didn't receive. I hate ordering parts from daikin or mits because I don't have an account or much info/manuals/online access, they always seem to screw me over in parts and service, I get the wrong parts from them a lot of the time.

Paul,

If your ordering the pcb make sure you ask for inverter pcb wiring diagram referance A2P.

I managed to locate some additional info please see pm.

[Temprite]

G'day Paul.
Does it keep trying to restart or is it locked out on U2 fault. U2 fault may be from a previous fault situation.

Last fault I saw on one of these units was faulty suction transducer cutting out and ramping down compressor prematurly when it should have been running faster.

The machine was running incorrectly but was not generating a code.

[paul_h]

G'day Paul.
Does it keep trying to restart or is it locked out on U2 fault. U2 fault may be from a previous fault situation.

Last fault I saw on one of these units was faulty suction transducer cutting out and ramping down compressor prematurly when it should have been running faster.

The machine was running incorrectly but was not generating a code.

Seems to be locked out on U2 error. I've been there 3 times with it locked out, reset the power, test ran and it comes up U2 again after a short while. How do you clear any fault history on these to make sure?

Do these have an LP switch or a transducer? How do you bypass/test/diagnose a transducer?

[VRVIII]

Seems to be locked out on U2 error. I've been there 3 times with it locked out, reset the power, test ran and it comes up U2 again after a short while. How do you clear any fault history on these to make sure?

Do these have an LP switch or a transducer? How do you bypass/test/diagnose a transducer?

Paul,

To reset or clear a previous error from controller, press the test button once then hold down on/off button until the displayed fault code changes to 00.

When a current fault trips the unit, the controller operation light and fault code will be flashing.
If the unit is has no current fault, the controller operation light will be off or on constant. The previous error code can be viewed by pressing test button once.

you can also view the last 9 history errors in service code 40.