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Richard Stephen
24-03-2008, 04:45 PM
I have 2 split units as described above. They were installed by a dealer. Since installation I have found that sometimes the compressors come on even when the units have been switched off with the remote control. When this happens the flap on the indoor unit remains closed and the indoor fan does not run. The indoor coil gets either very hot or freezes up. The current draw rises steadily and in one case tripped the breaker. This renders the units essentially useless. I have had 2 visits from a service company but the fault could not be duplicated during these visits. Any ideas?

Thanks in advance

nike123
24-03-2008, 05:03 PM
And that is happening on each one of them simultaneously or independently?
Are they are on same circuit breaker!

Richard Stephen
24-03-2008, 05:10 PM
Independently. Each is on a dedicated circuit breaker.

nike123
24-03-2008, 05:15 PM
Independently. Each is on a dedicated circuit breaker.

Are their pipes and cables, in any part, has been layout alongside each other?

SteinarN
24-03-2008, 07:15 PM
My shot from the hip:
The pipe and the cable from one outdoor unit is conected to different indor units.

Richard Stephen
24-03-2008, 09:57 PM
The units are in opposite ends of the residence. There is no shared pathway.

RWS

nike123
24-03-2008, 10:39 PM
The units are in opposite ends of the residence. There is no shared pathway.

RWS

Have you got any device that use bus comunication or comunicate thru power supply? Any bluetooth or computer WLAN device?

Richard Stephen
24-03-2008, 11:27 PM
Nothing like that Nike. Only an infra red remote. Be advised that the power LED is off when this happens. Thanks for your help so far.

nike123
24-03-2008, 11:38 PM
Nothing like that Nike. Only an infra red remote. Be advised that the power LED is off when this happens. Thanks for your help so far.

Disconnect one of them from power and see if that is happening again on other unit!

Richard Stephen
25-03-2008, 01:46 AM
It is. That's to say that disconnecting one unit has no effect on the other.

paul_h
25-03-2008, 04:21 AM
I'd say sticking compressor relays or faulty PCBs.
I haven't seen the compressors running by themselves a lot, but this problem with the condenser fans constantly running due to faulty relays is very common on small panasonics. They use tiny solid state relays with a switched neutral to the outdoor.

nike123
25-03-2008, 09:36 AM
I'd say sticking compressor relays or faulty PCBs.
I haven't seen the compressors running by themselves a lot, but this problem with the condenser fans constantly running due to faulty relays is very common on small panasonics. They use tiny solid state relays with a switched neutral to the outdoor.

If it is sticky relay, that couldn't happened randomly on his own, it would happened after turning off the unit by remote.
If it is faulty PCB then only thing what comes to my mind is that some electrical noise or surge has damaged both units after they are commissioned on site.
Because two units are behaving similar we need to search for common cause of error outside of units, or it is (really odd) possibility that two different models having same factory mistake in their PCBs.

paul_h
25-03-2008, 12:00 PM
True, I understand why you are looking for a common cause since both have the same problem. But panasonic does have a big problem with relays and PCBs in the smaller non inverters.

I guess I'd make sure the wiring isn't crossed and the active and neutral are wired the right way around from the mains and on the interconnecting cables.
Also make sure that the mains does not go to the outdoor terminals. The mains goes to the indoor, and the indoor relays feed the outdoor when it wants the compressor to run. If the installers have wired mains to the outdoor, then of course the outdoor is going to always run.

paul_h
25-03-2008, 01:11 PM
If it is sticky relay, that couldn't happened randomly on his own, it would happened after turning off the unit by remote.
If it is faulty PCB then only thing what comes to my mind is that some electrical noise or surge has damaged both units after they are commissioned on site.
Because two units are behaving similar we need to search for common cause of error outside of units, or it is (really odd) possibility that two different models having same factory mistake in their PCBs.
Actually after re reading, I'm still even more convinced it's a relay/pcb problem. I've seen this problem so many times in the small relays that panasonic and fujitsu use, ie the relay sometimes stucks, but doesn't every time

The story is it sometimes happens, and it's never happened with the service guys have been there.
It could be the system only faults due to a relay PCB problem after x amount of hours running.

The service guys must of checked everything else, and the only possible wiring faults I could think of would mean it fails every time, not occasionally like a relay could. The relay might be powered up by solid states, which fail in interesting ways, unlike a mechanical relay which just normally sticks when trying to open circuit.

edit: I know you'd be surprised, but relays in panasonics give a lot of problems, so I am not suprised at the likelihood of two in one house failing. I've even had defective replacement new ones!
The problem only exists in the small conventional units that switch mains to power outdoor compressor and fan. The larger units and the inverters that only have a comms cable and don't switch mains to the outdoor are trouble free

nike123
25-03-2008, 01:38 PM
Actually after re reading, I'm still even more convinced it's a relay/pcb problem. I've seen this problem so many times in the small relays that panasonic and fujitsu use, ie the relay sometimes stucks, but doesn't every time

The story is it sometimes happens, and it's never happened with the service guys have been there.
It could be the system only faults due to a relay PCB problem after x amount of hours running.

The service guys must of checked everything else, and the only possible wiring faults I could think of would mean it fails every time, not occasionally like a relay could. The relay might be powered up by solid states, which fail in interesting ways, unlike a mechanical relay which just normally sticks when trying to open circuit.

Only logical thing I could came up with this is next scenario:
The contacts distance of compressors relays is to small and power supply voltage fluctuates enough to create steady flow of current thru contacts of relay even they are not acted by PCB. When current flow is established it is easy to maintain flow even voltage drop somewhat. That mean that compressor have steady power supply and works till circuit breaker trips.

Common to these two units are possibly same craped relays and voltage fluctuations of same power supply.

Occurrence of these failures differ at each unit because different cable lengths and small difference in relays and all other factors involved to fulfill this scenario.

Richard Stephen
25-03-2008, 05:01 PM
Power is connected to the outdoor units as given in the installation instructions. This does not appear to be a sticking effect as the compressor starts up on its own long after being shut down by the remote control. It seems that the fault occurrs at outdoor temperatures at or just below freezing but I am not absolutely certain of this.

paul_h
25-03-2008, 05:28 PM
Hey, you sure about that?
I don't have anything on the cu-a12ckp6 as I left them a while ago, and of course I'm in australia with 220v mains power, the last service manual I have is a cu-a12ckp5.
But nearly every a/c at that capacity no matter what brand, always comes with a standard gpo lead and plug on the indoor unit, as they are only a 1.5hp compressor and draw 5amps or less on 220v mains. Therefore power should go to the indoor unit. Some istallers cut the plug off to hardwire it to an outdoor isolator, but mains should only be going to the indoor unit.

nike123
25-03-2008, 05:40 PM
Power is connected to the outdoor units as given in the installation instructions. This does not appear to be a sticking effect as the compressor starts up on its own long after being shut down by the remote control. It seems that the fault occurrs at outdoor temperatures at or just below freezing but I am not absolutely certain of this.

If it is power fed to outdoor unit then relative humidity in the cold air (could be very high to 100%) and water condensation could be cause for that error. And that is also common possible cause for both units.

Richard Stephen
25-03-2008, 05:51 PM
Installation instructions are very clear. Power goes to outdoor unit. There is a 6 conductor cable from outdoor to indoor unit that provides power to indoor unit. Incidentally, I was told that terminal 5 on indoor unit controlled the (outdoor) compressor. In normal operation this line is at 120VAC when compressor is running and at 0V when compressor is off. Under fault conditions this terminal is not energized and compressor runs.

paul_h
25-03-2008, 05:59 PM
No problems, I made it clear that it may be different for you as we have 220v mains, so a/cs of that size are normally connected to the indoor unit via GPO instead.
the first non mains terminal will be for the compressor, 4-5 condenser fan motor, terminal 6 reversing valve for heating operation. It all depends on how many wires. If six terminals, 1 and two will be mains, 3 compresor, 4-5 fan motor (high and low speed), 6 will by r/v.
But panasonics have an outdoor control pcb that controls defrost operations, so the indoor unit doesn't always sends mains voltage to start a compressor, just closes a neutral. So sometimes it's hard to diagnose a panasonic by measuring voltage at the outdoor terminals.

Richard Stephen
25-03-2008, 06:11 PM
Indoor unit sends 120VAC to outdoor via terminal 5 to run compresssor I think. There is no terminal 6. 1 is mains hot, 2 is mains neutral.

Edited to say that terminal 5 does not send compressor current, only a control voltage presumably to actuate a relay or contactor.

Richard Stephen
17-04-2008, 05:42 PM
Paul H or anyone,

Any further thoughts? Problems still exist.

paul_h
17-04-2008, 06:59 PM
Well like I said, panasonic has big solid state relay problems, always had. The inverters are good stuff, but the conventional units always had frequent relay problems.
Though I'm pretty sure now after looking it up, they don't use solid state relay for compressors, but mechanical ones, and while not perfect they didn't have a lot of problems.
When the compressors run, are they going into heating mode (meaning some PCB logic circuits are being used to start operation) or just running in cooling mode (simple mechincal relay just activating)?
If cooling mode, maybe problem with relay sticking. If heating mode, maybe outdoor defrost logic circuit fault.
I can't say for sure because symptoms like this demand the presence of a tech to test where the power is coming from. Ie. tracing power to a relay, then seeing if the relay coil has power (control problem) or if it doesn't (relay problem)
Most of the time a simple relay playing up problem can be shown by running the system for an hour of two before the techs get there. Let them switch it off and see if it keeps running etc. Or if you think the unit starts up on it's own when the ambient is low, get the techs to put the outdoor sensors in a cup of ice.
There's tricks I can do as a tech, but I can't diagnose your system from here as it's obviously different to the ones I used to repair based on your description and the lower mains voltage and the outdoor unit getting mains power instead of the indoor unit like australia does.
edit: some panasonics of that size had an outdoor PCB, just to control defrosts etc, some just had a few mechanical contactors and relays. It all depends on the a/c capacity and vintage, as the basic wiring is different to what I know here, I can't say what's in there. Running it for a few hours before the techs you call come, or getting them to put the sensors in icy water, is about the only things I can suggest to try at the moment based on your descriptions.

nike123
17-04-2008, 10:02 PM
You need to find out if control voltage for compressor is present at moment when compressor works with shut down indoor unit.
If that is the case, you have PCB of indoor unit fault.
If not, then maybe someone with required skills and qualification need to change compressor relays with other type (higher contacts distance).
Also, try to find schematic diagram of outdoor unit (could be at inside of panels) and take picture and post here.
It could be helpful to diagnose that problem.
Also make notes about humidity and temperatures at which these error occurs for diagnosing purpose.

philfridge
17-04-2008, 10:09 PM
Yes basically you got it wired up incorrectly from what you have said.

Richard Stephen
18-04-2008, 03:19 PM
Nike

Compressor control (Connection 5) is not energized when the unwanted behaviour happens. I have noticed the problem with the indoor coil hot. I have also noticed an indoor coil cold and indeed iced up. Both times the unit had been in heating mode when last used. The connections from indoor units to outdoor are correct.

nike123
18-04-2008, 04:45 PM
Nike

Compressor control (Connection 5) is not energized when the unwanted behaviour happens. I have noticed the problem with the indoor coil hot. I have also noticed an indoor coil cold and indeed iced up. Both times the unit had been in heating mode when last used. The connections from indoor units to outdoor are correct.

Then change relays, as I described (at least at one unit for test purpose of this teory). Before, I would love to see schematic diagram of outdoor unit to be sure in need for this step.
So, if you found diagram at outdoor unit, make a picture and send it here. Or, if someone here have el.diagram of outdoor unit, please send it.

Chunk
18-04-2008, 08:44 PM
I found the manual online but cant get the wiring diagram off of it as my computor wont let me.

If someone wants to read it and post the diagram,be warned it is an 8mb pdf file.

http://www.panasonic.com/consumer_electronics/bp_split_ac/pdf/csu_a912ckpg_sm.pdf

Unless you want to wait for a photo.:D

nike123
18-04-2008, 09:55 PM
There is block diagram! Thanks to chunky munkey!
http://farm3.static.flickr.com/2348/2423930336_019e93396e_b_d.jpg

From this diagram, it is obvious that, if voltage is not present between terminal 2 and 5, that compressor relay should not be closed and neutral should not be supplied to compressor main winding terminal and compressor condenser terminal.
First I would change wiring (or check insulation with megaohm tester between all wires) betwen indoor and outdoor unit and make check of conection terminals insulation.
Then, if that is OK, it is necessary to change relay, and I would find other relay type with contacts who are more apart.
But first, I would triple check that there is no any voltage at compressor relay coil in moment when compressor exhibits this behavior.
Also, before anything, I would disconnect terminals 1,3,4,5 at outdoor unit and wait few days to see if that make any changes.
If, after that, compressor doesn't work on his own like before, than it is Indoor unit PCB fault.

Richard Stephen
19-04-2008, 03:12 PM
Many thanks Chunky and Nike!

RWS

Richard Stephen
11-03-2009, 05:36 PM
Had a unit running for a while on heat. I shut it off (using the remote control) because OAT went below the operating limit. It seems that during the night the compressor came on by itself in cool mode. The inside fan didn't start so the inside coil froze. Still no better off than I was a year ago.

nike123
12-03-2009, 06:36 PM
Had a unit running for a while on heat. I shut it off (using the remote control) because OAT went below the operating limit. It seems that during the night the compressor came on by itself in cool mode. The inside fan didn't start so the inside coil froze. Still no better off than I was a year ago.


High humidity or condensation problem.

Richard Stephen
12-03-2009, 07:23 PM
Yeahbut...

The thing was turned off at the time!

nike123
12-03-2009, 08:14 PM
Yeahbut...

The thing was turned off at the time!


So what? Power supply is fed to outdoor unit.
It is possible that some contact is made where it should not be, because of humidity/condensed water at outdoor unit electrics.

Indicative is that you don't have that problems during summer. Therefore, it is probably weather related.

Richard Stephen
12-03-2009, 09:29 PM
Outdoor stuff looks clean, no moisture. Present temperature outdoors is -5C. At this moment I cannot duplicate the fault.