Fujitsu R32 ducted system fault - A1.1

[stephenM]

Hi all,

I've got a frustrating problem with my Fujitsu R32 7.5kw ducted air conditioner (ARXG18KLLAP), and am hoping for some guidance.

The system ran flawlessly for the first 8 weeks, providing heating for 12-18 hours per day. It then began showing an A1.1 error, which relates to a high discharge temperature. It worked intermittently for a couple of weeks, sometimes would go into A1.1 error within 10-15 minutes, but other times would work for 12 hours. It now won't work at all, showing the A1.1 error within 10-15 minutes.

Our AC engineers initially checked the discharge probe to ensure the sensor wasn't faulty - it was correct, and >100c was being observed from the compressor. Too hot.

The R32 was then recovered and weighed, and came in at 900 grams when it should have been 1022g. The pipe run is fairly short - around 10m, and the AC engineers don't believe a loss of ~10% refrigerant is significant enough to cause the fault.

We then pressure tested the system (4 weeks due to coronavirus!) with nitrogen, and it held 36 bar without any loss.

The system has been installed as a joint effort between myself and the AC engineers - I did the basic work (holes through walls, pipe runs, brackets, etc) and the AC installer then connected and commissioned the system. Therefore, I don't really have an installer per se, so the cost of diagnosis / repair falls to me.

Our AC engineers believe the fault could lie with the 3-way valve in the outdoor unit. However, as I'm having to foot the labour bill, any repair work on the outdoor unit (diagnosis to date hasn't been cheap!) would be without any guarantee of success. I think I'd be better off just replacing the outdoor unit.

However, since the system has passed the pressure test, and worked flawlessly for the first 8 weeks, I'm tempted to pay for a re-gas and give it a second chance. That's not free, and could be a waste of time, but a new outdoor unit will be a lot more expensive!

Any advice would be gratefully received.

Thanks!

[frank]

If it's faulting on high pressure while in heating mode then I would look at the indoor unit and check that 1) the filter is 100% clean and 2) that the indoor fan is fully operational.

In heating mode it is the indoor unit that acts as the condenser and the fan speed should control the HP.

What are the pipe temperatures at the indoor unit before it fails on HP fault?

As it is a ducted unit, can you try running it with some or all of the installed ductwork disconnected?

If the gas charge is OK then it may be a restriction on the ductwork side causing the total air flow across the coil to be outside of the operating envelope

[stephenM]

Hi Frank,

Thanks for replying.

During initial investigations, the AC engineers did wonder about the ductwork restricting the airflow so we removed the plenums and re-tested. The result was the same unfortunately.

I'm not sure about the indoor refrigerant pipe temperature because I don't think it was checked (no gas in system to check at present), but the AC engineer did say the heat output from the indoor unit was a little weaker than he would have expected.

[frank]

Have the pipe thermisters been checked against the resistance table?

[stephenM]

We haven't checked the thermistor resistance, but I don't think the thermistor is faulty because the discharge pipe was checked with a laser thermometer and showed >100c, consistent with what the probe was reading.

[al]

Any chance you have nitrogen in the system from the pressure test? I would tend towards recovering charge, recharge with fresh gas. Can you put the system in test mode cool, is it faulting in this condition? If not, as Frank has said, issue is with indoor.

[RANGER1]

Hi all,

I've got a frustrating problem with my Fujitsu R32 7.5kw ducted air conditioner (ARXG18KLLAP), and am hoping for some guidance.

The system ran flawlessly for the first 8 weeks, providing heating for 12-18 hours per day. It then began showing an A1.1 error, which relates to a high discharge temperature. It worked intermittently for a couple of weeks, sometimes would go into A1.1 error within 10-15 minutes, but other times would work for 12 hours. It now won't work at all, showing the A1.1 error within 10-15 minutes.

Our AC engineers initially checked the discharge probe to ensure the sensor wasn't faulty - it was correct, and >100c was being observed from the compressor. Too hot.

The R32 was then recovered and weighed, and came in at 900 grams when it should have been 1022g. The pipe run is fairly short - around 10m, and the AC engineers don't believe a loss of ~10% refrigerant is significant enough to cause the fault.

We then pressure tested the system (4 weeks due to coronavirus!) with nitrogen, and it held 36 bar without any loss.

The system has been installed as a joint effort between myself and the AC engineers - I did the basic work (holes through walls, pipe runs, brackets, etc) and the AC installer then connected and commissioned the system. Therefore, I don't really have an installer per se, so the cost of diagnosis / repair falls to me.

Our AC engineers believe the fault could lie with the 3-way valve in the outdoor unit. However, as I'm having to foot the labour bill, any repair work on the outdoor unit (diagnosis to date hasn't been cheap!) would be without any guarantee of success. I think I'd be better off just replacing the outdoor unit.

However, since the system has passed the pressure test, and worked flawlessly for the first 8 weeks, I'm tempted to pay for a re-gas and give it a second chance. That's not free, and could be a waste of time, but a new outdoor unit will be a lot more expensive!

Any advice would be gratefully received.

Thanks!

I disagree that the AC installer has no guarantee of some description.
He should have some type of guarantee that he installed & commissioned as per manufacture recommendations.
If you have that paperwork then call supplier of equipment for warranty.
If he is not a registered & accredited engineer then all bets are off.
I’m assuming equipment is newish, as you mention run okay for a period

Warranties should be minimum a few years

[frank]

We haven't checked the thermistor resistance, but I don't think the thermistor is faulty because the discharge pipe was checked with a laser thermometer and showed >100c, consistent with what the probe was reading.

In heating mode you need to be looking at the indoor pipe thermistor
The compressor discharge thermistor is only used to protect the compressor

[martinw58]

have you tried running the unit in cooling to see if it works correctly

[stephenM]

Hi all,

Thanks for everyone's replies, and apologies for not updating you sooner.

Since I last updated you, we've re-gassed the system, but the original fault persisted. Further diagnostics revealed that the expansion valve's electromagnet was faulty, as one of the 4 positions was reading 0 ohms. I didn't get any cooperation from the retailer (they promised a replacement, then stopped responding), so ordered a new one myself from a wholesaler as it was only £20.

Although this corrected the 0 ohm electromagnet fault, the original problem remained - the machine's heating/cooling output was lacklustre at best, and the pipes quickly develop frost. Given that the system has been proven to hold a refrigerant charge, this indicates refrigerant starvation.

Further investigation has revealed that the new electromagnet is permanently warm/hot, because one of the 4 electromagnet positions has a permanent 12v supply from the main PCB, even when the AC is powered down. This suggests that the main PCB is faulty, as the electromagnet should surely only be powered momentarily when a change of valve position is required?

In all likelihood, the permanent 12v will have been the cause of the first electromagnet's failure. It also explains why the system is being starved of refrigerant, as the expansion valve isn't actuating successfully.

I am therefore now pursuing the retailer for a replacement main PCB for the outdoor unit. Although I overlooked having to buy an electromagnet costing £20, I'm not going to let them off a PCB costing £200-300!

Am I on the right track in diagnosing the main PCB as faulty?

Thanks

[RANGER1]

Stephen,
I don't know how warranty works in your part of the world, but the retailer would usually advise you of contact details of manufacturers warranty, or it is in instruction book.
They would then come out & fix it, no charge unless installed incorrectly.
Maybe I'm a broken record