In your system do you have a 3-port changeover valve to select CH or DHW heating, or do you have two 2-port valves? I would suggest that you check that the valve or valves are operating correctly, and not supplying hot water to the heat emitters when heating the hot water cylinder.
I have been wondering if there is any link between the DHW and the UFH as I've been watching it for the past couple of days and I've had the downstairs calling for heat but left the upstairs isolated. The downstairs as warmed up despite the CH function of the ASHP not heating at all. The DHW has been heated to 53c overnight each night so not sure if the UFH is utilising any of this heating or temperature although, and here is a comment of a complete amateur, I'm assuming there is no sharing of the UFH water with the CH / tank water as the former has antifreeze within so I've always assumed they were kept separate and therefore heated separately. But I'm assuming they pipes pass through the same heating functionality within the ASHP and so could still share the heating process. Or I'm talking complete rubbish.
Anyhow, no idea on the whole 2 port v 3 port thing but I do have the Diamond Cover maintenance with Mitsuibishi and I've only ever used them for the annual maintenance so maybe I'll make use of calling them out to have a look at the problem.
If you have the Mitsubishi pre-plumbed hot water cylinder I do believe that this includes a Plate Heat Exchanger (PHE) which is used to separate the heat pump water from that going through the heating coil within the hot water cylinder.
You can of course use your Diamond Cover to call out someone to look at your system, but checking the motorised valves is quite a simple matter. Please let me know what you wish to do.
If you have the Mitsubishi pre-plumbed hot water cylinder I do believe that this includes a Plate Heat Exchanger (PHE) which is used to separate the heat pump water from that going through the heating coil within the hot water cylinder.
You can of course use your Diamond Cover to call out someone to look at your system, but checking the motorised valves is quite a simple matter. Please let me know what you wish to do.
Thanks @Derek-M for your kind offer, and apologies for my tardy response. Work has been manic and not got back on here much in recent couple of weeks. Even with expert instruction, not sure I'm confident or capable enough to be checking any valves, I'm not really trustworthy with any kind of DIY effort as I usually cause more problems than solve.
I've continued to dabble with all my settings in the recent 2 or 3 weeks and I think I have the efficiency running ok at the moment. But there are a couple of things that continue to confuse me, which isn't difficult!
I've got my weather compensation settings quite low, almost so low that I didn't think my house would heat. But weirdly, the hotter I have my flow rate, the less warm my house is. ie. if I have my weather compensation set at something like 45c flow temp at -15c outside temp down to 20c flow temp at 8c outside temp, the house heats nicely to around 21c to 22c but if I was to make it something like 45c at -15c and the other end at 25c flow temp at 15c outside, then the house struggles to get to 20c room temps! I'd have thought if I had higher flow temps (even if it means using more KwH), then the house would be warmer, or too warm. But it does the opposite. Which is a nice problem to have as it means I'm using minimal KwH as its heating far less.
The other confusion I'm having is the combination of my hot water heating and my UFH heating. Whenever I want to heat my hot water, I have to stop my UFH heating. If I don't, the Hot Water heating just chugs through the KwH but never heats the water. I heat my hot water overnight when on cheap tarrif, and pause the call for heat on the UFH during the period of doing so. Yesterday, the hot water depleted in the afternoon so the Hot Water heating kicked in. It chugged through 8 or so KwH across a couple of hours but gained not one degree increase in temperature until I turned the UFH heating off and then it went up from 38c to 50c in 20 or so mins. I can't seem to have both functions running. Its almost like they are sharing the heating process but hot water doesn't get a look in if the UFH heating is going. I've noticed all the pipes from my hot water tank go into a vertical black unit that the pipes to my UFH all go into as well. I don't know what the black box thing does.
You cannot carry out DHW heating and UFH at the same time, the two requirements are incompatible. Whilst your UFH should require a Leaving Water Temperature (LWT) probably in the range of 30C to 40C, to heat the DHW the LWT will need to be over 50C. This is why you have a diverter valve, which directs the heat pump water one way or the other.
I suspect that what you refer to as a 'vertical black unit' is in fact a buffer tank, which may cause inefficiency in a heat pump system.
Please try to draw out a schematic diagram of your system, similar to the ones shown in the manual. Also provide details of all the various settings within the controller.
I'd concur with Derek that you might need to have the three-way valve checked to see if it is faulty. The HW cycle should have the water sent through the tank, it shouldn't be able to be directed through the CH. Looking at the pics however, it is not possible to see where the return pipework from the tank goes. Is it routed through the black buffer tank before being returned to the HP? In which case the returning water, which should be getting hotter as the temperature required to heat the tank rises, is getting pulled in to the CH circuit and having its remaining heat removed which is why the HW cycle struggles to get adequately hot. When the HW cycle is running the pumps for the CH should be off, at the moment you seem to have do this manually but really there ought to be communication between the FTC and two(?) pumps to the UFH circuits. I don't know how other UFH based systems are set up in this regard - hopefully someone else will chime in. It could also be that the CH pumps can usually continue to circulate while the HW cycle is running as the return flow from the tank is completely separated from the CH circuit. But this is speculation on my part!
MelCloud will report what it thinks the system should be doing based on the signals it is giving, but if the wiring from the FTC is not connected right, or the plumbing arrangement undermines the intention of the design then the actual system may not be behaving as you think it is.
Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop 210l Mitsubishi solar tank Solar thermal 3.94kW of PV
Sliderule. mcwatson is right, the system should switch the 2 or 3-way valve(s) from heating UFH to DHW when the timer for DHW tells it to, and overrides the UFH timer. If it doesn't, the valve(s) must be wired up wrongly. It also sounds like yours is set to top up the DHW when it's temperature drops to a set level. That can be turned off if you want. Re Weather Comp, I suggest you keep the ambient settings fixed, eg. -5C and 15C, and only change the target readings, eg 45C and 30C. I have all UFH like you, and found a) I needed to have enough zones calling for heat to prevent the HP cycling on and off, and b) if WC target is too low, it will cycle, but if it's too high it will use more kW shown by my smart meter. In my experience ( this is my second Heat Pump), cycling is bad for the life of the heat pump, slows down the heating and should be minimised. I am now trying out the Advanced Auto Adaptation which I have found very good so far as kWh is low, there's no cycling and I don't have to play around with the Weather Comp. However that requires a wiring and dipswitch change and I will get a wireless controller and receiver. Are you still getting heating when you don't want it? I had that problem and in my case, it was a short circuit in my existing house wiring which caused the HP to think that heat was always being called, whenever the UFH was timed to come on. Shouldn't your installer be solving these problems for you?
Please try to draw out a schematic diagram of your system, similar to the ones shown in the manual. Also provide details of all the various settings within the controller.
Not there is much chance of me drawing out the system, I hardly know what each of the components are or what pipe is what. Appreciate this limits any advice or help you can give.
When the HW cycle is running the pumps for the CH should be off, at the moment you seem to have do this manually but really there ought to be communication between the FTC and two(?) pumps to the UFH circuits.
Yes, definitely having to do things manually. I've always had to have the programs set so that if I want DHW to happen, I have to switch of UFH heating. So I've got UFH turning off for 1.5 hrs overnight and 1.5 hrs late afternoon whilst the DHW has allocation
It also sounds like yours is set to top up the DHW when it's temperature drops to a set level. That can be turned off if you want.
I have got my DHW set to only heat if it drops to a certain temp as most days, I get through the whole day with just the overnight heat up being suffice.
I have all UFH like you, and found a) I needed to have enough zones calling for heat to prevent the HP cycling on and off, and b) if WC target is too low, it will cycle, but if it's too high it will use more kW shown by my smart meter.
I have UFH throughout the whole house, upstairs and downstairs, since moving to Weather Compensation, have all stats on max so it calls for heat always.
I am now trying out the Advanced Auto Adaptation which I have found very good so far as kWh is low, there's no cycling and I don't have to play around with the Weather Comp.
I have heatmiser stats in every room, the Ecodan thermostat is sat in the plant room so cannot be used as not a realistic temperature. I'd have to get remote sensor to try the Auto Adaption method.
Shouldn't your installer be solving these problems for you?
Long story but when I had my house built six years ago, I gave the contract to Ice Energy who designed and supplied the whole system, Ecodan, UFH, Heatmisers Water Tank etc. My builders (electricians and plumbers) then went on a course with Ice Energy to learn how to install. They did the install, then Ice Energy came along and commissioned it. Ice Energy then gave me all the certificates and paperwork, 2 days later they went bust so I can't call on them. No point asking the builder lot as they just installed as they thought so if they didn't know then, they'd probably not know now.
As I have little to no knowledge of the actual physical side of the install ie. pipes, buffer tanks, dip switches etc, I probably need to find someone local who can come and assist. But its finding someone who actually knows how to adapt the system to your house rather than just read the manual and wants to do the standard.
I would get an expert in to check over the system installation/configuration. I can recommend Mark at JMR heating who services our system and I think he has quite a bit of experience with ecodan ASHPs and he's not too far from you:
We have a 14kw Mitsubishi Ecodan ASHP with 500l using UFH downstairs and radiators upstairs with the FTC in a remote plant room. UFH is wired to zone 1 and Rads Zone 2. We also use heatmiser thermostats for the UFH and they are setup to each individually call for heat as and when they need it. The temp for zone 1 and 2 on the FTC/Melcoud app is ignored by the heat pump. It just powers up when either zone 1 or zone 2 call for heat and the DHW takes priority when the cylinder tank drops to a set temp. I believe this is how yours should be setup potentially with Zone 1 being the downstairs UFH and Zone 2 the upstairs or both downstairs and upstairs linked to zone 1.
Given you how new your property is and has UFH throughout I would try to work out what the lowest flow temp is to comfortably heat your property and just stick to that. I tried faffing about with weather compensation but found it was just easier to set the flow temp between 35-38 degrees and let the system work with your thermostats to keep the house comfortable without having to work too hard. Running the system 24/7 with all the rooms constantly heating can make it uncomfortable in certain rooms depending on their location/use/exposure to the wind. I believe the weather comp theory is based on perfect scenarios/spreadsheets/houses and in reality its quite difficult to achieve.
My installer says Mitsubishi can access your settings via your MELCloud, and hopefully eliminate any faults there, so I think you should definitely give them a call. They won't be able to correct external wiring and piping faults, and I would advise finding a local supplier with recommendations if possible, rather than paying for a "mitsubishi" person (probably a subcontractor) who might only diagnose and quote for remedial work (this happened to me) to be carried out. Whereabouts are you?
I think the silver square object with the yellow warning sign, next to the tall black box, is your 3-way valve as it looks like 3 pipes go into it, probably the horizontal pipe is your flow in, and the vertical pipes are one to the UFH and the other to the DHW. Inside would be a valve which diverts the flow up or down, but not to both directions, so it seems impossible for you to have flow to both the DHW and UFH at the same time, although it would be possible to have them reversed but you would quickly realise that. I don't know what happens inside the tall black box as I don't have one.
Although I think you should get your problems sorted before trying new systems, I am trying out Advanced Auto Adaptation with a long cable from the 2 terminals where the little FTC box is connected, to the cable from that box, and moving the little box into the living room, removing the 2 wires from IN1 (signal input), and turning SW2-1 dipswitch off. The power has to be turned off while doing that, and you may have a communication fault if you don't turn it back on within 6 minutes, and then have to re - establish it. Mitsubishi supplied a 10 metre long cable with the HP, for that purpose. When I am sure I will use AAA, I will buy a Mitsubishi wireless controller and receiver online for £167, and fit it myself, as I don't want to have a cable running round the living room. It has the disadvantage that it doesn't talk to the house thermostats at all, so you either have to have a constant house temperature all the time, or synchronize them, which I can do as I have Salus RT500 programmable thermostats (£21 at B&Q if available). Otherwise your manifold pumps will still run when your HP pauses and the HP may cycle off and on a few times before shutting down. This is something I am looking at now before finally deciding. But AAA seems to virtually eliminate cycling and keep the power low on my system, which I like.
Ps, I have seen a setting called Simultaneous Operation (on/off/ambient ). I'm not sure what it means, but maybe it is Simultaneous Operation of Heating and Hot Water. I don't even understand how that could be done, if indeed it is what I said. Maybe someone else knows. It is in Menu=Service=Operation Settings=Simultaneous Operation. I wouldn't change it unless someone can confirm what it is.
Given you how new your property is and has UFH throughout I would try to work out what the lowest flow temp is to comfortably heat your property and just stick to that. I tried faffing about with weather compensation but found it was just easier to set the flow temp between 35-38 degrees and let the system work with your thermostats to keep the house comfortable without having to work too hard.
I'm starting to come to that conclusion as well, that the weather compensation mode feels a little too much aggro. Although when I tried a few days of leaving it on a set flow rate, it seemed to just be running all the time but may need to play with it a bit more, maybe set it right low and then do the adjusting up until the house feels right.
My installer says Mitsubishi can access your settings via your MELCloud, and hopefully eliminate any faults there, so I think you should definitely give them a call.
I may give them a ring tomorrow as I emailed them a few weeks back to let them know my tank temperature had stopped recording at some point this year in MECLCLOUD, but never heard back from them. Don't know how much that info is needed for the system to do what it's supposed too but hasn't affected thinks like heating the hot water and to the right temp set on the FTC Controller.
Ps, I have seen a setting called Simultaneous Operation (on/off/ambient ). I'm not sure what it means, but maybe it is Simultaneous Operation of Heating and Hot Water. I don't even understand how that could be done, if indeed it is what I said. Maybe someone else knows. It is in Menu=Service=Operation Settings=Simultaneous Operation. I wouldn't change it unless someone can confirm what it is.
Just had a look at this on my panel, found it and its not ON. Just had a read of the function in the manual, seems to be aimed at when its very cold outside and therefore the ASHP is least efficient and struggling to cope. It seems to call on the immersion to help it out. I don't think this setting will solve my problem but good spot.
This post was modified 5 months ago by mcwatson1974
Having continued to dabble during the cold spell, I've come to the conclusion that either I haven't got a clue what I'm doing, or there is something not working or wired up correctly as behaviour of system compared to what I do just doesn't make sense.
I tried a day or two running at fixed flow temp, all it achieved was smashing through KwH's of electricity and cost but the house didn't warm up properly, 45c was the flow temp I think.
I then reverted to Weather Comp. House seems to warm up better when I run at 30c or under which makes no sense to me but I do use less KwH but ASHP does cycle much more per hour. Still struggle though to get the house to the desired 21c that I'm striving for when it drops below 5c outside. This is an example of an hour of cycling.
But the bit that is confusing me the most. Why does the UFH behaviour seem to be affected so much by my heating of the Hot Water. Currently got my HW coming on at 3am whilst on cheap tariff and heating to 52c which then usually lasts me the day. But the flow temp of the UFH system seems to 'follow' the heating of the HW. This graph is 3am to 4am.
And then once the HW has achieved the 53c, the flow temp then starts reducing. But all this time, the house isn't warming up, infact room temps start falling. This graph is 4am to 5am.
There is no cycling at all from 3am until around 9am or 10am when the flow temps have all reduced to a particular level, and then all the cycling kicks in. Personally, my objective is to get rooms to 21c and not use a zillion KwH in doing so over reducing cycling.
My instinct suggests I'm running my UFH temp too low at sub 30c, but if I whack it over that and closer to 35c or 40c, I simply use loads more KwH but without the benefit of warmer rooms.
Having continued to dabble during the cold spell, I've come to the conclusion that either I haven't got a clue what I'm doing, or there is something not working or wired up correctly as behaviour of system compared to what I do just doesn't make sense.
I tried a day or two running at fixed flow temp, all it achieved was smashing through KwH's of electricity and cost but the house didn't warm up properly, 45c was the flow temp I think.
I then reverted to Weather Comp. House seems to warm up better when I run at 30c or under which makes no sense to me but I do use less KwH but ASHP does cycle much more per hour. Still struggle though to get the house to the desired 21c that I'm striving for when it drops below 5c outside. This is an example of an hour of cycling.
But the bit that is confusing me the most. Why does the UFH behaviour seem to be affected so much by my heating of the Hot Water. Currently got my HW coming on at 3am whilst on cheap tariff and heating to 52c which then usually lasts me the day. But the flow temp of the UFH system seems to 'follow' the heating of the HW. This graph is 3am to 4am.
And then once the HW has achieved the 53c, the flow temp then starts reducing. But all this time, the house isn't warming up, infact room temps start falling. This graph is 4am to 5am.
There is no cycling at all from 3am until around 9am or 10am when the flow temps have all reduced to a particular level, and then all the cycling kicks in. Personally, my objective is to get rooms to 21c and not use a zillion KwH in doing so over reducing cycling.
My instinct suggests I'm running my UFH temp too low at sub 30c, but if I whack it over that and closer to 35c or 40c, I simply use loads more KwH but without the benefit of warmer rooms.
What are the settings of the Weather Compensation (WC) curve?
