Ecodan Zones/Wireless controller

Air Source Heat Pumps (ASHPs)

Last Post by Mars 1 year ago

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Sly5

(@sly5)

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Joined: 1 year ago

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Topic starter 07/11/2024 1:59 pm

Hi, I've recently moved into a new build which has an Ecodan PUZ-WM60VAA set up with DHW, Zone 1 > UFH, Zone 2 > rads.

There's one Heatmiser stat for the rads upstairs. UFH has stats in each room.

This is obviously setup like an old-school boiler, inefficient for a heat pump and leads to short cycling.

I purchased a couple of the wireless Mitsubishi stats and set them up, put the system into room temp mode (auto adapt?). However, I soon learned that the Heatmiser stats do actually call for heat and the system will not stop heating until it hits their limit, even when the wireless stats are showing a temp higher than the target.

I disabled 2 dip switches (SW2-1 & SW3-1) which prevents the stats controlling the heat and just act as pump control. This seems to work for the UFH however, Z2 will not heat independent of Z1 and with Z2's pump running will not put any heat into the radiators even while Z1 is flowing at 40c.

It seems the solution to this is: "For 2-zone temperature control, check DIP SW2-7 is set to ON (2-zone temperature control) and DIP SW2-6 is set to ON (With Mixing Tank)"

These are both off, I'm assuming I don't have a mixing tank and cannot just enable these?

I'm looking for a solution, maybe I need to hound the developer?

Tank image:

This topic was modified 1 year ago by Sly5

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Mars

(@editor)

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Joined: 5 years ago

Posts: 3933

22/11/2024 8:57 am

There’s quite a lot going on here, so we'll try to break it down with some unofficial insights from Mitsubishi. It sounds like your system is set up with two zones at the same design temperature rather than two zones with different temperatures. If that’s the case, SW2-6 & SW2-7 (which are for systems with a mixing tank) wouldn’t apply here. Instead, it seems SW3-6 is managing the two zones with the same temperature settings, and that’s correct for your system as it stands.

When it comes to third-party stats like Heatmiser, they usually work best when the Ecodan’s weather compensation is set up properly. The stats can then manage room temperatures and schedules. One potential tweak might be to check if the Heatmiser stats allow you to adjust the hysteresis (basically the delay between on/off signals). Widening this could help reduce short cycling. Another workaround some people use is combining zones or removing actuator heads to simplify the system and move towards an open-loop design, which can also reduce cycling.

For the Mitsubishi stats, Zone 1 should be fine in Auto Adaptive mode, but Zone 2 has to either follow the weather compensation curve or run in fixed flow mode. To get Zone 2 heating independently, you’ll probably need to look at what’s controlling its pump. It might require adjusting the signal cables or wiring, but it’s hard to say without seeing the full setup.

At this stage, it might be worth getting a heating engineer to take a closer look – they’ll be able to advise on pump controls, wiring changes or any other tweaks to get everything working smoothly. Mitsubishi’s Homeowner Helpline (0161 866 6064) could also be helpful for further advice.

Also, this video might help: