thermoelectric actuators on CH and DHW

6 May 2024
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United Kingdom
hello all,

I recently moved into a new place and it has a system boiler with 4 zones: 3 x CH and 1 x DHW (to an unvented cylinder). Each zone has a thermoelectric actuator on 15mm, reducing from 22mm down to 15mm through the actuator valve and then back to 22mm going off to rads etc:


I need to replace one of the valves and actuators on a CH zone as the actuator is not working and the valve is worn and leaking when the pin is depressed. I have ordered this for the valve and this for the actuator.

a few questions:
1) Will the above replacement parts work? I think I need DN15 for 15mm pipe and I can get a couple of nuts and olives to install
2) Is this an unusual/non-standard set up? Would it be better to go with something like this?
3) Should I be concerned that the valve has a 4mm stroke, yet the actuator is 3mm? There is a 3mm version of the valve but it's not available for a couple of weeks and would prefer not to wait.

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Are you sure it’s thermoelectric? Looks like a trv imo
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What you have is similar to this idea, including a 4 wire actuator with an end switch:

You should be able to adapt with 1/2" female threaded fittings rather than nuts and olives - it doesn't look like there's a chamfer on that valve to accept an olive. In the picture on link above, you'll see the brass fitting on the left hand side - you'll need 2 of those.

Or to connect to 22mm:

Edit: Looking at the datasheet for the valve, it may be 3/4", so you'd need to change the adaptors accordingly...
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Look at Honeywell Evohome or Tado smart TRV heads

The spindle that is leaking, can be changed or o rings replaced. ( done that )
Thanks for the replies.

I might try to change the spindle first. Can’t find the replacement part online but not sure really what to search for. Any ideas? Or would I get a new valve and swap just the spindle out?

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