DIY Doctor

Main navigation

Underfloor heating stopped calling for heat

Postby A1cap0ne » Tue Nov 17, 2020 5:25 pm

I’ve had wet ufh working fine on timers in my extension for nearly 2 yrs then last week it stopped working.

It is a single zone, with manifold, heatmiser digital thermostat, and 2 port zone mechanical valve connected to a comi boiler setup.

The CH side is working fine, it has a nest thermostat and a 2 port zone mech valve.

Now when the ufh comes on, the pump works but there is no independent call for heat to the boiler and the mech value does not switch on. Like I said this was working fine until last week. No changes have been made.

I can turn the mech value manually and the ufh will work when the CH is on. If CH is not on it just pumps around normal water.

what could the issue be? From what I’ve read up on, if it was just the valve not working I assume it would be the motor at fault? But why is is now not calling for heat from the boiler? I’d appreciate any help before I call anyone out. TIA
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Tue Nov 17, 2020 5:19 pm


Simply Build It

Postby ericmark » Sun Dec 06, 2020 12:43 pm

Sorry for late reply, UFH uses many methods, and hard to know which yours uses, however the micro switches in motorised valves do fail, and so most likely is the motorised valve head or motor, theory you can change micro switches, but in practice normal to change whole head.
Rank: Project Manager
Posts: 2659
Joined: Fri Oct 02, 2009 8:49 pm
Location: Llanfair Caereinion, Mid Wales.

Postby B4Less » Thu Dec 10, 2020 9:52 am

If the valve is not turning on then it is very likely that it is also then not calling for heat. The transition from closed to open is what then calls the boiler to come on due to a relay on the motorised valve or fuse board. I would suggest replacing your motorised valve and everything should be back up and running also.
Rank: Ganger
Progress to next rank:
Posts: 64
Joined: Thu Apr 04, 2019 12:36 pm
Location: 3rd Floor, 207 Regent Street, London, W1B 3HH

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics