MorganP

Yeah, the house has UFH, zoned with stats connected to a wireless UH8-RF V2 unit (attached). When the HP isn't tripped into immersion mode, the heating is fine. Zones call for heat, the HP kicks in etc. I have the Heating switched off at the mo, and it hasn't cut out in a few days. I wonder if it's an issue specifically to do with the heating. Maybe the HP can't generate enough heat so calls for the immersion to kick in, and then everything cuts out. Does that sound likely? Water temp is set to 50° / auto adaptive. Regarding original Installers. Hmm. Competent installers but abysmal aftercare. Very quick to charge (whether they fix your problem or not).

Thanks again for the feedback. There's no fault showing but your point does flag two things that aren't necessarily related. Firstly: I think the immersion may be faulty as it doesn't get over 20 degrees. I can't see a specific immersion temperature setting. I assume the Ecodan controller would try and use the immersion heater to get to the regular tank temp of 50°. If so then it's not working properly. If anyone knows how it's meant to work I'm all ears! Secondly: Even if true, I can't see how the above issue wouldn't be the reason it trips into immersion mode in the first place. @Dillsue - following this comment I'm trying to isolate the issue. For now I've switched off the heating all together on the controller. I did think that auto adaptive mode would use the stats though. There are three modes - fixed flow, compensation curve and auto adaptive. I assumed all three would still need the stats to call no?

This is correct, thanks Rick. The heating and hot water work well when the ASHP is running. The issue is that the ASHP randomly cuts out and flips into immersion mode. Given that immersion mode never gets above 20 degrees, it's effectively useless at that point. It kicks back in after I restart the system. The installer annoyingly put the main controller in the garage next to the tank - always fun being out in my dressing gown first thing in the morning So my Ecodan set up should (I think) have the water on permanently. It's set to heat to 50°. It then has a 10° drop off before kicking back in, and presumably going back up to 50. That seems correct because when it's working, the water is rarely below 40° according to the MelCloud (Mitsubishi) app. I'm not sure how to manually check the diverter valve but I'm pretty sure that's fine too as the heating works well when the ASHP is running. Hmm, so very frustrating.

Thanks John. Our Heat Pump does both heating and hot water but I'm not sure what immersion mode is trying to do when it kicks in. Maybe just supply the domestic hot water. Either way, it doesn't work as it never gets above 20° I'll have a proper look through the settings and report back.

Morning hive mind - really hope you can help. We have a Ecodan r32 installed about 3 years ago. Not long after, it would occasionally flip into immersion mode and need restarting. Since then it has gradually got worse and is now happening every day or two. Some details - no faults showing - legionella mode set to 30 days - Heating is auto adaptive mode - House has rads upstairs, UFH down - Stats run through wireless UH8-RF V2 - Seems worse when stats are calling for heat. When all stats are off then it doesn't happen so often - immersion mode doesn't seem to heat the water either - only around 18 degrees We've spent hundreds on not getting it fixed so need a different route! Original installers not very helpful; charge for call out but don't fix issues. We have a decent freelancer who does the annual service but he doesn't seem able to fix it either. My wife is now threatening to take the kids to live in a hotter country (again).

This is invaluable, thank you @Nickfromwales - there is a beer and a giant Toblerone waiting for you all if we should ever meet 👍 I do have one last question if I may. Would it be worth getting the whole setup repiped with a new manifold? Something like this which already has the pump and AAV included >> It also has a better looking mixing valve set up (mine is dropping 5+ degrees even when fully opened).

Re. AAVs - does the system need to be drained first? And can any heating engineer do it? I'm near Newark, Notts and failing to get a good, local UFH engineer. Re. this: "3 lpm flow rate on the 12mm pipe is not too shabby tbh, and if the pump was zooted you’d not even have that. How old is the pump? Is it noisy?" I'm trying to get 3 lpm but failing! Two are slightly over 2 lpm but the rest are 2 or under. The pump is likely as old as the system - circa 2004. It's not noisy. Would it be worth changing at the same time as fitting the AAVs?

My best guess is 12mm and 15mm - there are two different sizes. There are photos in this earlier post:

Seems to only have 3 settings. Would a newer pump help do you think? And is the system pressure a factor do you think?

I did think of that but it seems to be on full already - turned all the way up to 3 bars.

Hello all - @Nickfromwales @JohnMo @John Carroll Now the temperature is finally dropping outside, I've been able to do some proper testing. I've hit two issues which I'm hoping you can help with. Firstly, my system doesn't have an option to turn the flow gauges. It seems I have to use a key to adjust under the actuators - see image. Let me know if I'm missing something. Secondly, I've adjusted under each actuator - turning counter clockwise - but it wont go much above 2 LPM for most loops. From John Carroll's earlier post I was hoping to get about 3. Is that a water pressure issue or something? The system was flushed of air last winter.

Good point. The sink next to it already has hot water from the cylinder so this should be an easy option 👍

Thank you for the suggestion @MikeSharp01 - I've just ordered one. The wooden flooring is the same as before so I'm going to wait for the IR gun to arrive and then change flow rates to see what works. This is the reason we're no longer using them. They also miscalculated the energy load which meant the electrician on the day disabled our shower to bring it within acceptable levels! Another job on our list is to have the electricity upgraded to get our shower back.

Thank you all for pitching in. I'll increase the loop flow and post back. Any further ideas in the meantime will be much appreciated.

Thanks again @JohnMo - and @John Carroll This is very true. The flooring is 12mm oak laminate but we have a tiled utility room which is the warmest room downstairs! All zone stats are set at 20º during day / 17º at night. As the rooms rarely hit temp when it's cold, the ASHP runs all day - and often all night (racking up the leccy cost!). Not tried to measure temp but will have a go 👍 We had no issues at all when on oil - lovely and toasty with the kids frequently basking around on the floor enjoying the heat - good times! I never clocked the flow temp when on oil but I suspect they were a good deal higher - the mixing valve seem near fully open so I'm guessing around 40º - 45º. The setting on each flow meter hasn't changed since we installed the ASHP so I'll try increasing the loop flow to see if that helps - that seems the conclusion from @John Carroll post I'm assuming. May I ask how you bypassed it? Back to my original question - could I do this by removing the mixing valve?