@old_scientist I have never cleaned the mag filter myself either but, if I had to, I think it is a case of isolating with the two valves, having a bucket or suitable container then using that large plastic spanner that should be hanging close by. Regards, Toodles.

@heat-pump-newbie Yes you need F Gas engineers like us if a split or monoblock system. Otherwise they just service the heating side of things.

@old_scientist my Daikin ran for nearly 2 years following the cat-astrophic refrigerant leak, but with no error code. Once I'd persuaded the installer that something was wrong they removed and weighed the refrigerant and it only contained 55% of what should have been there. Since refilling with the correct amount the COP has improved no end !!!

Posted by: @heat-pump-newbie

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@old_scientist my Daikin ran for nearly 2 years following the cat-astrophic refrigerant leak, but with no error code. Once I'd persuaded the installer that something was wrong they removed and weighed the refrigerant and it only contained 55% of what should have been there. Since refilling with the correct amount the COP has improved no end !!!

@heat-pump-newbie as I suspected. I measure/monitor my COP daily, so I think I'd notice pretty quickly unless it was a very slow prolonged leak where performance gradually tailed off.

Having bit the bullet and paid £250 for a service, our service engineer came today so I thought I'd report on the experience.

We'd paid for the ASHP and tank service, and the service engineer was great - very happy to show me what he was doing and seem genuinely pleased I was interested and engaged.

Outside he stripped the casing and thoroughly cleaned. We talked about the vibration from the compressor which I thought was a little noisy. We briefly fired up the unit for him to hear, and we agreed it was at the top end of normal. He's asked me to record a video when it's running hard for him to send to Samsung. The compressor is mounted on rubber feet, and just moving the compressor slightly reduced the vibrations, so we will see how things go.

Due to vibrations, he explained that cable connections can work loose over time, so tightened all the screw down cable clamps to ensure they were tight and had not worked loose.

He examined cabling for signs of burning and explained some cables can sometimes start to brown, so just visually checking all the cabling looked good and no signs of electrical faults.

He showed me where to check for refrigerant leaks. He mentioned the circulating refrigerant gas contains a small amount of oil so you can feel if the joints have leaked. He showed me the common failure points to check and all looked good. He did not otherwise check refrigerant levels.

Inside I am happy with all the controller settings, so we skipped checking those at my request.

We did have an issue with our immersion heater cutting out too early to complete the legionella cycle (cuts out at ~57C). He had a spare thermostat for the immersion, so swapped that and just quickly checked it powered up without tripping anything - I didn't want to fully test the cut off temp of the new thermostat as we were on peak rate by then, so I'll test that later.

We cleaned the Y strainer and the mag filter. I'd already cleaned the Y strainer a couple months after installation, but I now know how to clean a mag filter, so that's good. Checked pressure relief valves and expansion tanks.

Overall I'm pleased we did the service. The engineer was great but I do feel the price is a bit steep (part of the issue will be the amount of travelling these guys are doing to service nationally, so I expect he's done more travelling than servicing in a day). I've learned quite a bit and know more things to keep an eye on and check. Of course the main issue is the warranty. Next year I think I'll be happy to maybe just pay for the ASHP service, and take care of the tank side myself.