Heating downstairs only works if upstairs is called.

24 Jan 2018
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United Kingdom
I've got 2 thermostats, upstairs and downstairs.

Downstairs thermostat was calling for heat but boiler did not react. Then I called for upstairs and boiler got the signal and the rads upstairs started heating (downstairs not calling for heat).

Swapped the thermostats, issue remained (so possibly not the thermostats).

Something peculiar, I called downstairs, nothing, then I called both up and down and the downstairs rads started working as well.

But as soon as upstairs is off, it's off again, regardless of downstairs calling for heat or not.

I have removed the thermostat and connected live and switched live directly with downstairs only and it still isn't calling for heat. Any ideas?
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Sorry, wouldn't it be the downstairs one? As the upstairs one is working fine?

Thought I'd add:

Up: On / Down: On = Rad Up: Hot, Down: Hot

Up: Off / Down: On = Rad Up: Cold, Down: Cold

Up: On / Down: Off = Rad Up: Hot, Down: Cold

I mean it's odd that even though the call for heat downstairs isn't activating the boiler, it is opening a valve that's allowing hot to circulate downstairs.
We concur then. I know only a part costing a few pence has failed, but I have tried opening the actuator, and although not impossible, not an easy job to replace the micro switch.
Agree completely, it is possible to replace the micro switch but depending on the make thay can be a complete ball ache
Ok thanks guys, I will get the Mrs to empty the entire cupboard to have a look. JW video helped to understand what a micro switch was. Maybe the plastic bit has just snapped off and I can just get a replacement. Is there a good supplier for these things?
Ok thanks guys, I will get the Mrs to empty the entire cupboard to have a look. JW video helped to understand what a micro switch was. Maybe the plastic bit has just snapped off and I can just get a replacement. Is there a good supplier for these things?
No you need a new actuator
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Could have, but repair isn't usually possible as the heat makes the plastic brittle, and any repair just breaks again.
The plastic bit is a simple indicator, it serves no part in the operation of the valve , they break off and only time that becomes a problem is when the broken part can get stuck in the gear for the synchron motor
Personally I see little point having the home split into upper and lower floors in most cases, OK with my own house where the lower floor only used for guests, we only use the upper two floors, but those two floors are used during the day, and at night the heating goes into Eco mode both upper and lower.

I have in the upper two floors 8 zones, and each is controlled by TRV's, the hall/landing is the master zone, which also has a wall thermostat in it. And the TRV in the hall/landing is set to match the wall thermostat. Then all rooms have their own programmable TRV's. Splitting those TRV's into master zones is simply pointless.

If in your place likely I would combine the two zones, then one micro switch not working would not matter.

Not all thermostats are on/off, EPH do master/slave thermostats designed for multi zone valves, the thermostat has two outputs, one to motorised valve, and one to the boiler, to which it connects using OpenTherm, so the micro switches in the motorised valves are not used.

It seems county councils have published documents stating they feel TRV's form zones, but it seems many builders feel they do not, and think they must fit hard wired zone valves, I can to a point see the argument that years ago when TRV's first came out, programmable versions were not available, but when I moved into this house (2019), I fitted programmable TRV heads for £15 each, not linked to master wall thermostat, but still means I can stop heating rooms not in use, if I could get my wife to shut internal doors.

In my case with an oil fired boiler it does not really matter having multi wall thermostats, but with gas boilers normally modulate (turn down) so only reason for wall thermostat is to turn off boiler in warm weather, to stop it cycling, control needs to by with the TRV's so the boiler can modulate correctly, whole idea is it does not turn off/on, but up/down, so other than to stop cycling on/off wall thermostats do very little. In last house with gas, the wall thermostat switched between Eco and Comfort and Eco was basic same as frost stat.

There are exceptions, did once live in an open plan house, where one thermostat in centre of house would control all, and did once live in a house with hot air central heating, again one thermostat did all, but it does seem systems for heating are not designed, but fitted this way as that's the way we always do it, and no thought as to if appropriate for the home it is installed in.
In my house once the day begins, we spend most of our time downstairs so it makes sense. The cost benefit as it stands, I cannot justify replacing it all with smart TRV.

Only need upstairs closer to night time.

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