Auto defrost on domestic fridge not working - can low gas cause icing on the evaporator coils ?

[catfood12]

Paging for a refrigeration engineer. We have a 5 year old Gaggenau fridge freezer. Mrs CFXII wanted this one in a new kitchen, and at the time it cost more than many cars I've owned. Last year the fan in the fridge started making a duff bearing noise. I bought a fan, then found the evaporator coils jammed solid with ice which had grown down into the fan. The noise was as the ice started to grow and foul the fan impeller. Once that was thawed, the thing was fine for a few weeks until the ice grew again.. rinse repeat etc... Clearly the auto defrost not working.

The fan was fine. There are two auto defrost elements, they both had continuity, as did a thermal fuse and a thermistor, which varied resistance with heat. Regrettably I had to admit defeat & call the service firm. They sent round an idiot engineer who insisted on changing the fan, unfortunately I wasn't at home during the visit. He put the thing back together and trapped wire with a screw that then kept tripping the RCD. He had several more visits changing boards etc... all to no avail.

A second engineer has now been round and spoke to 'Technical' who have said it must have low gas and he is coming back this week to re-gas. I suppose it could be this, but doubt his explanation. I'm beginning to think they share engineering principles with VW Commercial....

Is there any refrigeration engineers on here that could explain why/if low gas could cause this? I can't think of any other reason for this very annoying issue. The unit has two compressors, one each for fridge & freezer. The freezer and ice maker work faultlessly.

 

[DXX]

Not sure if the low gas would be causing external icing. A leak can allow water (moisture) into the refrigerant which can cause internal icing.
It’s pointless them re-gassing the unit unless they locate the leak, possibly using ultrasonic detection microphone and head phones.

 

[Alster]

In my opinion low gas would be unlikely to be the cause although it is possible as part of the evaporator coil’s won’t freeze meaning the rest will have to work harder causing exess ice but this would be unusual in a frost free. The most common causes are poor door sealing - this allows moist air to be pulled in which then freezes on the evaporator. A blockage in the defrost drain. Or possibly a fault with the control so it’s not defrosting (unlikely). One last thing- it takes a long time to completely defrost the airways and drain after an ice build up. I allways recommend switching off for a couple of days with the doors open to make sure all the ice has gone. One final point - if it has had a leak in the refrigeration system it’s likely to have sucked moisture into the system and compressor (modern domestic fridge systems generally work at a vacuum).so you would probably need a new compressor and the system would need a really good flush.

 

[catfood12]

Thanks both for your responses. You've clarified what I thought, it's BS then that low gas causes icing. See photos from today. I switched the fridge off for defrost last night. Ice had built up at back of evaporator only, where the sort of sump is that drains to the outside. The drain isn't blocked as we get a flood of water underneath when defrosting like this, as it overflows the tray at the back of the fridge. No sign of ice at the middle or front of the evaporator...



This was after 18 hours, as the ice had grown around the heater element. There is a second element underneath that stops condensate water freezing in the sump bit. That's reading the correct impedance for the 25W it's marked as, and I don't think that's duff as the ice is never completely filling the sump bit.

After a quick bit of help with a hairdryer the heater tray could be removed;



I'm liking the idea of duff door seals allowing moist air in. Although would expect icing over the front of the evaporator, as that's the bit that incoming air hits first....

I don't know what to say to the engineer now. He's due back on Wednesday. I'd rather he didn't just vac and recharge if it's not the cause.

 

[catfood12]

An update, as the issue has been fixed. It has been a lesson in common sense faultfinding, and checking what's actually happening, what's not working and why. An assumptive misdiagnosis, rather than just describing the fault early on by me, and the lack of validation or any further tests by the manufacturers service agent to validate or disprove what the customer stated has led to multiple visits and lots of unnecessary parts being fitted. An early idiot engineer didn't help either.

Back to the start of the fault. Ice build up on the evaporator coil in a large modern American style fridge. These fridges use a fan to circulate the cold air from the evaporator, unlike one in the olden days that just used convection. This is a top of the range Gaggenau fridge, and not a £99 Hinari. Ice began to build up over the evaporator coil and grew over the fan, initially making a noise, then jamming the fan solid. We'd defrost it for a couple of days, ice would melt. Rinse, repeat.

For some couple of years before the fault, we'd noticed that fresh fruit went off quickly, we just assumed it was modern expiry dates and ate it faster. We (nor did the engineer at any point) think to check that the temperature of the fridge was in fact 4 degrees Celsius that it was set to (first and most basic fault finding mistake here). It turned out not to be, and if anyone had checked this, it would have made the diagnosis more obvious.

I had an initial look, checked fan (induction motor, took out and connected to 240V, it span!) and defrost elements and declared the auto defrost wasn't working. I called the service agents and described this as the fault. CFXII says 'yeah, my fridge/freezer, the auto defrost is busted on the fridge, can you fix it please? Oh yeah, out of warranty, of course I'll pay'

They sent out cheery fcukwit engineer. I unfortunately wasn't at home at the time, and wifey called me after he'd been and said, it had been fixed, it was the fan. I said no it wasn't as I'd tested it. Got home that evening, RCD had tripped several times that afternoon. That's where I discover that whilst fridge/freezer was on a completely separate circuit from the DB as it was supposed to be, it was on an MCB on one of a split load RCD rather than an RCBO. A different problem, but something I'd not spotted prior.

Anyway, fcukwit had trapped some cable son re-assembly and this had caused the tripping. I took it all to bits, 11PM by now, and re-insulated the cables and re-assembled.

Fcukwit returns several times as above, swaps boards, replaces damaged loom, I explain DC blocking capacitors on induction motors, and why the fan showed open circuit when he checked with his DMM. His eyes glaze over. Fridge still ices up. Mrs CFXII starting to cry more often now. I begin to feel like a little weep too.

Then the service company offer to send a new engineer who called just before my initial post. He said that low gas can cause icing on the evaporator around the injector/capillary. I make the original post above, suspecting that this fella is an imbecile too.

He arrives, the goes on to explain, as the whole refrigeration circuit has to work longer to maintain fridge temp. Working longer with low gas then results in localised lower temp around the capillary and icing. Exactly as @Alster said above. This was the issue all along. If only someone had checked the temp of the fridge before we started, and if I'd described the issue, rather than what I thought was the fault, it would all have been sorted sooner.



Who knew R600 was just butane. That's the modern refrigerant, 60g in my fridge. Well, there is now anyway.



Now, where's that sparky with my missing RCBO.......

 

[DXX]

An update, as the issue has been fixed. It has been a lesson in common sense faultfinding, and checking what's actually happening, what's not working and why. An assumptive misdiagnosis, rather than just describing the fault early on by me, and the lack of validation or any further tests by the manufacturers service agent to validate or disprove what the customer stated has led to multiple visits and lots of unnecessary parts being fitted. An early idiot engineer didn't help either.

Back to the start of the fault. Ice build up on the evaporator coil in a large modern American style fridge. These fridges use a fan to circulate the cold air from the evaporator, unlike one in the olden days that just used convection. This is a top of the range Gaggenau fridge, and not a £99 Hinari. Ice began to build up over the evaporator coil and grew over the fan, initially making a noise, then jamming the fan solid. We'd defrost it for a couple of days, ice would melt. Rinse, repeat.

For some couple of years before the fault, we'd noticed that fresh fruit went off quickly, we just assumed it was modern expiry dates and ate it faster. We (nor did the engineer at any point) think to check that the temperature of the fridge was in fact 4 degrees Celsius that it was set to (first and most basic fault finding mistake here). It turned out not to be, and if anyone had checked this, it would have made the diagnosis more obvious.

I had an initial look, checked fan (induction motor, took out and connected to 240V, it span!) and defrost elements and declared the auto defrost wasn't working. I called the service agents and described this as the fault. CFXII says 'yeah, my fridge/freezer, the auto defrost is busted on the fridge, can you fix it please? Oh yeah, out of warranty, of course I'll pay'

They sent out cheery fcukwit engineer. I unfortunately wasn't at home at the time, and wifey called me after he'd been and said, it had been fixed, it was the fan. I said no it wasn't as I'd tested it. Got home that evening, RCD had tripped several times that afternoon. That's where I discover that whilst fridge/freezer was on a completely separate circuit from the DB as it was supposed to be, it was on an MCB on one of a split load RCD rather than an RCBO. A different problem, but something I'd not spotted prior.

Anyway, fcukwit had trapped some cable son re-assembly and this had caused the tripping. I took it all to bits, 11PM by now, and re-insulated the cables and re-assembled.

Fcukwit returns several times as above, swaps boards, replaces damaged loom, I explain DC blocking capacitors on induction motors, and why the fan showed open circuit when he checked with his DMM. His eyes glaze over. Fridge still ices up. Mrs CFXII starting to cry more often now. I begin to feel like a little weep too.

Then the service company offer to send a new engineer who called just before my initial post. He said that low gas can cause icing on the evaporator around the injector/capillary. I make the original post above, suspecting that this fella is an imbecile too.

He arrives, the goes on to explain, as the whole refrigeration circuit has to work longer to maintain fridge temp. Working longer with low gas then results in localised lower temp around the capillary and icing. Exactly as @Alster said above. This was the issue all along. If only someone had checked the temp of the fridge before we started, and if I'd described the issue, rather than what I thought was the fault, it would all have been sorted sooner.

View attachment 124058

Who knew R600 was just butane. That's the modern refrigerant, 60g in my fridge. Well, there is now anyway.

View attachment 124059

Now, where's that sparky with my missing RCBO.......

Good news, but did he make any effort to locate the leak that led to the loss of refrigerant?

 

[catfood12]

Good news, but did he make any effort to locate the leak that led to the loss of refrigerant?

Nope. His job was just to fix it, no allowance was made longer troubleshooting. I don't know how you'd go about detecting a leak of say 10g per year. This is a domestic fridge, with the pipework internal to the insulation, although I'd guess the leak is on a joint, is the compressor or condenser/evaporator. I guess I'm just into a recharge every three years or so, at least until Mrs CFXII wants another new kitchen, or the children inherit the lot.