In addition to my reply on Buildhub. Have you considered dumping all the third party rubbish and then you have no need for the FTC2BR.

I doubt you need any of the third party stuff, just set to weather compensation and leave the heat pump to get on with it. If you have a thermostat that stops things you are flowing to hot and impacting CoP.

Hi, yes, planning to use the stats as safety limits, ditto mixer on manifold as safety limit to avoid floor over heating, and run the ashp on weather compensation. I’ll use manually set zone valves for trimming.

But as I understand it, this is what the FTC2BR does (controlling the heat pump flow temp and therefore weather compensation ) so I don’t understand your suggestion of getting rid of it?

@biggles welcome to the forums, and thanks for sharing your experience with us. It sounds like you’ve had quite a journey with your installation.

I reached out to Mitsubishi on your behalf to get some clarity.

Basically, the FTC2BR is specifically designed to work with a Building Management System (BMS) and isn’t a standalone controller like the FTC6. Essentially, it relays commands from the BMS to the heat pump but can’t control the heat pump on its own without third-party BMS inputs. Mitsubishi mentioned that this should have been clear to whoever sold the system to you, which suggests it may not have been purchased directly through them.

While I understand it’s frustrating to be advised to upgrade to the FTC6, Mitsubishi confirmed there’s a valid reason for it, given the limitations of the FTC2BR in a non-BMS setup.

I know this probably isn’t the news you wanted, but if you have any more questions or need further advice, feel free to ask - there’s a lot of knowledge in this community, and we’re here to help! Hopefully, we can get you pointed in the right direction.

Posted by: @biggles

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Hi, yes, planning to use the stats as safety limits, ditto mixer on manifold as safety limit to avoid floor over heating, and run the ashp on weather compensation. I’ll use manually set zone valves for trimming.

But as I understand it, this is what the FTC2BR does (controlling the heat pump flow temp and therefore weather compensation ) so I don’t understand your suggestion of getting rid of it?

Maybe not the most efficient way to run your heat pump. Your trimming is just done by balancing the loops. Instead of off or on commands from the thermostat.

If you want to protect the floor just use a pipe stat, then you are not running the heat pump hotter than is really needed and you can ensure the system has an always open flow path.

Deleting the FTC2BR as explained above by Mars. It is just an interface not a controller. Basically a fancy relay box.

Posted by: @biggles

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safety limit to avoid floor over heating

Just to show you what occurs when you switch from DHW heating - max flow temp 60 degs.

Within about 40 secs the flow temperature drops from 60 to 30 degs. Has a slight bounce back up 33 after a few minutes. My piping length to diverter valve is 10 to 12m each way, so quite long.