Posted by: @chimpy

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DIP switches were largely designed out of modern electronics back in the 1990s, yet the Mitsubishi FTC6 controller still relies heavily on them.

I have to admit that made me laugh... Hard to believe we’re still flicking DIP switches in 2026 on a controller!

I tend to disagree that DIP switches are obsolete. Surely they provide a inexpensive, clear and utterly reliable means of configuring a multi use system without having to rely on having it powered on or using a complicated software BIOS. Why is making every thing so damn complicated seen as a virtue. Whatever the cause of the OP's dissatisfaction it cannot all be laid at the door of Mitsubishi whose systems seem to be of high quality and reliable.

@chimpy 

Welcome to the forums. 

Firstly can I say that many people do have excellent experiences with Mitsubishi heat pumps and I am sure you could too, however you may have to jettison some of the assumptions you are making to achieve this.  

Its true that heat pump interfaces could be better, but that is true of boilers as well.  The problem is that houses and heating systems are very different and no manufacturer has yet worked out how to self adapt for every combination, which is anyway impossible unless they also have control of the emitters, which generally they dont.  Furthermore they are unlikely to have control of the whole system for the foreseeable future, because it would be resisted by the industry (particularly the aftermarket controls industry) and customers alike.  There is in fact a fully self adapting add on system made by Adia, that controls emitters and heat pump and works it all out, but its not that frequently installed because of the cost of replacing every TRV head.

So unfortunately some tuning is necessary unless you buy into the Adia system.  However before you do that (if you wish to) can I suggest you read this introduction to heat pumps so you have some useful background.  If you try to operate it like a boiler (which I have the impression you may be doing) you cant expect it to work well; you have to forget more or less everything you thought you know about operating boilers, much of which was wrong for boilers and is doubly wrong for heat pumps.  Don't even think about using Drayton Wiser or any other third party smart stat system btw unless its specifically designed for heat pumps, it will mess things up big time.  The only smart controllers I know specifically designed for heat pumps are Homely, Adia and Havenwise.

As I say your heat pump needs tuning to your house and also needs to be operated low and slow. The most important thing is to get the weather compensation curve adjusted.  To do that turn off smart mode, turn all your thermostats and TRVs up to full so they are effectively disabled, operate 24x7 then adjust the weather compensation curve one degree per day until the house is at the right temperature.  Start it set to something like 30C at 15 OAT and whatever the design flow temperature was (45?) at whatever your design OAT is (2?, 3?).  If you dont know what the design figures are just start at the current figures (but please tell us what they are).  Once its close you may want to change by only half a degree per day.  If rooms settle at different temperatures balance the radiators, there is an article about how to do this here.  Expect this process to take a couple of weeks.  Its best done when its cold, so depending on what the next few weeks bring you may well have to tweak next season, but once its done you can just leave it.

You may well find that, once you get it right, operating like this (ie in pure weather compensation mode) is very comfortable.  Many here do that, including me, and certainly in my case the house is way more comfortable than it ever was with a boiler and its  thermostats/TRVs.  Once you have the basic adjustment right you can set TRVs in rooms that have lots of solar gain a couple of degrees above the desired temperature, to act as limiters not controllers, and you may want to try reenabling auto adapt.  However first try running on pure WC correctly adjusted because until this is properly set up you aren't starting from the right place.

Thats a very short summary but if you read the articles I have pointed you to it will hopefully make more sense.  Feel free to ask questions, no question is silly and people here are generally very helpful.  However can I respectfully ask you to keep short and to the point and omit irrelevant detail, most people wont bother to read a very long post!

Finally please accept my apologies if you already know all of this.  Its quite difficult to tell from you post how exactly you are operating the system and it may be that you are already operating in the way I suggest and have done the recommended tuning.

@abernyte, I’d have to respectfully disagree on that one.

DIP switches certainly have their place from a reliability and cost perspective, and I understand why manufacturers historically used them. But in modern systems they can also introduce a different set of problems... they’re easy to misconfigure, difficult for homeowners or even some installers to interpret and they’re not exactly transparent unless you’ve got the manual open beside you. It's pretty old school!

Most modern controls have moved toward software-based configuration with clear menus, logging and parameter visibility, which makes commissioning, troubleshooting and optimisation much easier. With DIP switches you’re often relying on someone physically setting tiny switches correctly and then hoping they were documented somewhere. 

Just my personal opinion. 

Posted by: @chimpy

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I’ve worked in electronic design for nearly 40 years

Ecodan speaks a proprietary protocol on its connector "CN105". It's been reverse engineered and it is possible to use an ESP32 as an interface to Home Assistant for example. There are other similar projects.

It is also possible to buy the extremely expensive official Modbus interface (200€ for a MCU in a little box).

Given I am also an owner of a Mitsi Ecodan of similar vintage, I have a pretty good perspective on @chimpy’s comments. It strikes me there are several themes going on here, none of which are new and all of which resonate with previous threads here and even @editor’s podcast.

Firstly, this is yet another example of the consequences of choosing the wrong installer. @chimpy, you most certainly should’ve been given your heat loss survey and been included in the design process; an installation is a collaboration between installer and homeowner and that clearly failed here. I’m sure with hindsight you can see red flags you’d’ve preferred to pick up on earlier just as I’m sure that in an ideal world you shouldn’t’ve had to look out for them.

Secondly, whilst the design of the system doesn’t seem to have been as bad as some we’ve seen, it clearly also wasn’t stellar. There’s certainly work needed, even if it seems it’s not beyond redemption.

Thirdly, I find everything @chimpy said about Melcloud and the FTC to be bang on. It’s way behind the curve and Mitsi addons to gain connectivity beyond the in-house controller are far too expensive for what should be standard functionality. £150+ for modbus? Really? And if you do get modbus you can’t use the wifi adapter? Really? C’mon, guys, you can do better than that.

However, fourthly, whilst the heat pump itself may be a fairly pedestrian design there are far too many units out there working perfectly well to ignore. Old tech doesn’t always have to be a bad thing unless new tech is a noticeable improvement. That said, old or new, tech still needs support and it’s disappointing to hear Mitsi may have fallen short of their reputation here.

@editor I'm not so sure DIP switches are cost effective or more reliable. One byte of memory is eight switches or one package. There is no purchase cost, placement cost or reliability issues with a mechanical contact or solder joint, plus all the real estate used on a PCB for the components (switches & possibly resistors) and tracks. 🙂

@jamespa Hi, thanks for your comments.

As you say, others have a more positive outcome with an ecodan, so this gives me hope.

I feel the biggest issue with my heat pump is it's way too powerful. The minimum input power is about 1.2kw, this doesn't significantly increase until below 3 to 4°C outside. 

I've spent quite a while getting all the rooms to the desired temperature at the same time on both WC and auto adapt. I was hoping auto adapt might be more adaptable than it is.

I've read some people have had some success with quiet mode, I'll give that a go.

There is a bit of a compromise of the placement of the heat pump, (still plenty of space in front and to the side) so when it's cold and still out the air immediately around the cabinet gets 'stale'. If it was possible to move the internal thermostat, I think that would help. 

Chimpy

@majordennisbloodnok Hi, thanks for your message. 

Ignorance is bliss until it isn't. The first time for everything is always a learning experience, I know much more about what questions to ask and where to look for advice now.

Yes, as you say others with ecodans have a successful efficient installation.

I'm still amazed there is no internet based time adjustment.

Chimpy 

Posted by: @chimpy

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I feel the biggest issue with my heat pump is it's way too powerful. The minimum input power is about 1.2kw, this doesn't significantly increase until below 3 to 4°C outside. 

I think you said its an 11.2kW model and your house is a bit over 8kW.  Thats certainly a bit oversized but not unusual by any means.  In reality heat pump manufacturers mostly make two or three out of ~5kW, ~8kW, ~12kW, ~16kW (~1 ton, 2 ton and 3 ton, 4 ton in American speak) machines, with intermediate models often being firmware limited versions of the one above.  Daiklin for example make only 8 and ~16, all the others are just firmware limited versions of these.  Vaillant make ~5, ~7, ~12 (branded as 5, 7 and 12), the 10 and 3 are firmware limited.

The space between 8 and about 12 is pretty thin, I looked quite closely so I know.  Although my house has a measured loss of 7kW the self surveyed loss using MCS assumptions, which I was working to for a while during my journey, is 10.5kW.  I ended up with the Vaillant 7 (actually nearer 8) because the measurements eventually convinced me, and its just right.  Possibly you could also get away with a 7-8 but you would need a measurement not a survey to determine that; fortunately you have the measurement kit -  namely your heat pump!

This being the case with a house thats over 8, and allowing for DHW also, it would be quite normal to specify something like you have unless you, as a householder, are prepared to accept the risk that you may need supplementary heating and your installer will go along with this (most wont, some will if you insist).

I reproduce the capacity and COP tables for the R32 11.2kW machine below.  My min output power is 3.2kW and my machine bottoms out at 600W input; on the basis that your min output power is just over 4kW I would expect it to bottom out at about 900W input not 1.5kW.  You should investigate, there may be a wrong setting somewhere.  Whats your min FT set to - installers sometimes set it to 35-37 which is way too high but avoids call outs 'because the radiators aren't warm'.

Posted by: @chimpy

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I've spent quite a while getting all the rooms to the desired temperature at the same time on both WC and auto adapt. I was hoping auto adapt might be more adaptable than it is.

Auto adapt is, I understand, limited in its scope.  I suspect this is a 'control theory' problem (given you spent time in electronics you may know something about control theory, houses have vast delays in their responses, 12-24 hours, which of course isnt great for any simple, or even not so simple, feedback circuit - which is one of the reasons WC is a major advance).  Turn off autoadapt initially, get the WC right, then by all means experiment with turning it back on if it helps

Posted by: @chimpy

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There is a bit of a compromise of the placement of the heat pump, (still plenty of space in front and to the side) so when it's cold and still out the air immediately around the cabinet gets 'stale'. If it was possible to move the internal thermostat, I think that would help.

Yes I see that which may compromise performance (heat pumps after all rely on taking in ait at ambient temp, not air that they have themselves cooled).  If by the 'internal thermostat' you mean the internal (to the outdoor unit) outdoor air sensor sensor, then ideally  this should be somewhere else in the shade.  Only a few heat pump manufacturers do this however.  Often its in the input air stream (so its really an air intake sensor).  Thats probably next best so long as its shaded.

Quiet mode clamps the compressor output but wont reduce the minimum.  However it may reduce aggressive start ups that some heat pumps do, which will have a marginal effect

You might benefit from some monitoring.  Melcloud/Melpump seems liked by many but I think the interface may be an add on (as the equivalent is with my Vaillant), but perhaps first turn off auto adapt, turn up all your thermostats and TRVs and optimise WC if you haven't already done that.

Hope that helps.  Happy to answer questions, Im not a Mitsubishi expert (or indeed an anything expert, Im just an amateur) but most problems are not brand specific.