Rads on when not supposed to be

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We had a new boiler fitted last July through our builder. Guys who did initial install were great and nice tidy work. They put in a Vaillant system boiler, Instinct cylinder and the Vaillant sensoHome control.

We had issues straight away with the radiators coming on when it was hot weather and should only have been hot water. Guys kept saying it was the controller but Vaillant said it wasn't. Installers came out and changed some pipe work around that initially seemed to fix it. This was ongoing until colder weather and then they said rads just needed balancing (builders son did this by just turning up flow on all that we felt were too cold) and they told us issue was fixed.

Now it's warmer weather and rads are on even though we have set required room temp to 17 and the thermostat is reading 23.5 due to rads being hot! Not all rads are on. The downstairs ones and the loft ones are but the first floor aren't. Currently we are having to manually turn them on and off with TRV or set whole heating to off on control. That's fine in really hot weather but sometimes you need the chill taken off in morning/evening.

Any thoughts on what this is? Anything we can check ourselves? Otherwise will get someone out but not original installers as they don't seem to be able to fix it.
 
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How many zones do you have controls for? Can you take some pics of the valve gear around the boiler and/or cylinder to give a clue as to what you've got
 
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BoilerPic.jpg
Its an Ecotec 630
 
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CBW

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Good evening,
  • Is the job finished?
  • I would suspect a 24v link has been left in at the boiler
  • Was this install a replacement to a previous setup?
  • Where is the boiler located?
  • One of the motorised valves doesn’t appear to be wired to anything
 

CBW

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I’m guessing that’s the finished job? Some of the Gas pipes isn’t 25mm away from other services either.
 
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Good evening,
  • Is the job finished?
  • I would suspect a 24v link has been left in at the boiler
  • Was this install a replacement to a previous setup?
  • Where is the boiler located?
  • One of the motorised valves doesn’t appear to be wired to anything

Hello. Sorry the first photo was not fully up to date so second boiler photo is taken today as the others were. Yes it replaced a previous combi boiler but was moved to corner of room, although same wall as previous boiler. We were told we had to have system boiler for loft conversion. Builder also did mains pipe upgrade as part of it. The boiler is in the kitchen in the dining area section.
 
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CBW

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I’m guessing that’s the finished job? Some of the Gas pipes isn’t 25mm away from other services either.
This might have crossed over (eg when you replied same time).

I would suspect then the link has been left in at the boiler, or a wiring fault.
 
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Ok, the 2 motorised valves (the 2 shiny boxes just below the boiler, left hand side). The bottom one looks as if it is driving the heating circuit.
Just below where the cable enters the valve there is a small lever.
First experiment for you- when the controller is set to hot water only (heating off) move that lever upwards- you should feel some spring resistance, when you let the lever go it should spring back.
Second experiment- set controller for heating on, set thermostat so it is calling for heat (set it to 30 or something like), move that lever again, see if it feels the same (it should move more easily with very little spring resistance).
Third experiment- set thermostat to 5 degrees (or cooler than the room), again try that lever (should feel spring resistance).
These experiments will tell us whether the controller is sending the right signals to the valve.
 
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Ok, the 2 motorised valves (the 2 shiny boxes just below the boiler, left hand side). The bottom one looks as if it is driving the heating circuit.
Just below where the cable enters the valve there is a small lever.
First experiment for you- when the controller is set to hot water only (heating off) move that lever upwards- you should feel some spring resistance, when you let the lever go it should spring back.
Second experiment- set controller for heating on, set thermostat so it is calling for heat (set it to 30 or something like), move that lever again, see if it feels the same (it should move more easily with very little spring resistance).
Third experiment- set thermostat to 5 degrees (or cooler than the room), again try that lever (should feel spring resistance).
These experiments will tell us whether the controller is sending the right signals to the valve.

First experiment for you- when the controller is set to hot water only (heating off) move that lever upwards- you should feel some spring resistance, when you let the lever go it should spring back. YES SOME RESISTANCE AND DOES SPRING BACK BUT VERY SLOWLY AND NOT RIGHT BACK TO BOTTOM


Second experiment- set controller for heating on, set thermostat so it is calling for heat (set it to 30 or something like), move that lever again, see if it feels the same (it should move more easily with very little spring resistance). YES NO RESISTANCE AND STAYS UP


Third experiment- set thermostat to 5 degrees (or cooler than the room), again try that lever (should feel spring resistance).
NO RESISTANCE AT ALL. ALSO BOILER ISN’T TURNING OFF AFTER EXPERIMENT TWO AND THERMOSTAT SET TO 5 DEGREES. WAITED TEN MINUTES BUT BOILER STILL HEATING.

We have also now discovered that even with the heating set to fully off the rads are still coming on. Need to get this fixed before the weather gets really hot!
 
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Ok, ta for that lot. So during experiment one the rads were heating up even tho the motorised valve was closed? That has to be a reverse circulation problem, to confirm that you'd need to draw up a schematic of the flow and return pipework (doesn't have to be to scale or anything, just has to show what joins to those 2 tubes and in what order.
So shelve that problem for now, solving it involves plumbing.
Is there a thermostat on the hot water cylinder? If yes, does it do anything (ie if the hot water is cool, boiler is running heating water only (in theory) does turning the stat down to 15 or so cause the boiler to switch off?
Final Q for now- exactly which Sensohome controller do you have?
 

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