Rads on when not supposed to be

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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?

Yes there is a thermostat and yes it appears to work as we have adjusted it due to tap water being too hot. I need to try to check it switches the boiler off though but didn't catch the boiler this morning before it heated the water.

The SensoHome is the wired in one VRT380.
 
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A) Reverse circulation (cylinder needs to be last tee on return).
B) mcv letting by
C) wiring issue

Check all the above.
 
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A) Reverse circulation (cylinder needs to be last tee on return).
B) mcv letting by
C) wiring issue

Check all the above.
I give advice on reverse circulation, then I thought **** it I get paid to deal with situations like this to sort out. Then mr big *******s takes my idea and get recognition for it. Ps not you I’m having a go at dilalio. I like you
 
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Bejeezus!

Did the installer of this boiler know feck all about elecktrikery?
Did they assume that their boiler would never ever leak?

Placing a boiler directly over the incoming supply like that (a supply that cannot be turned off) is IMHO only asking for trouble.

Build a shelf/cover that will protect the supply below from any water soonest!
 
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Really hoping it isn't reverse circulation as all new boiler pipework was done by removing our kitchen ceiling which has since been replaced and skimmed. I do remember the installers coming out and mentioning something that I'm sure was reverse circulation and they changed pipework and moved things around. However the builders son also did plumbing and made a lot of mistakes so he could have done something afterwards.

How can I check mcv letting by or wiring?
 
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Get the builder back to investigate.
You paid the builder, and if he paid the plumber, it's down to them to sort.
 
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Get the builder back to investigate.
You paid the builder, and if he paid the plumber, it's down to them to sort.

To be honest the builder was pretty dire and he made us pay each trade he hired directly. The initial installers of the boiler seemed good and knowledgeable but then the builder stopped them coming back in favour of his son (newly qualified and very inexperienced). The son has made so, so many mistakes with the plumbing and doesn't seem to know how to fix this at all. The builder ripped our kitchen ceiling down to do boiler so I'm concerned this will all mean it has to come down again too.
 

CBW

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Regardless of who installed it, the contract will be between yourself and the builder. If he refuses, or the problem isn’t rectified, withhold some payment if you can, or take him to a small claims court?
 
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If builder's son adjusted the plumbing after the installers then he's the last man in.
Get him back through his dad and if it turns out the fault was there, before he interfered then he can call the original guys and tell them what it is he thinks they've got wrong (unlikely).
More likely is that he has installed a towel rail in a bathroom and has teed this into the return after the cylinder. It's a common mistake made by bathroom fitters, who are often* plumbers only because they know how to join pushfit together!

* edit: added "often" as many bathroom fitters are proper plumbers :oops: xx.
 
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That's a very likely scenario for the backflow. The control problem is more interesting.
That controller uses ebus for its signalling (low voltage digital signal, might be the same as Opentherm and might not be), main point is there is a 2 core cable between boiler and controller and nowt else.
Hot water appears to be working so it's connected ok.
Do you have a copy of the installation manual for the Sensohome controller (if not you can get one here https://www.vaillant.co.uk/for-installers/products/vrt-350-350f-4160.html

You could try going into Installer mode (the manual tells you how) then check that Room Control Mod is set to Active or Expanded.
 
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That's a very likely scenario for the backflow. The control problem is more interesting.
That controller uses ebus for its signalling (low voltage digital signal, might be the same as Opentherm and might not be), main point is there is a 2 core cable between boiler and controller and nowt else.
Hot water appears to be working so it's connected ok.
Do you have a copy of the installation manual for the Sensohome controller (if not you can get one here https://www.vaillant.co.uk/for-installers/products/vrt-350-350f-4160.html

You could try going into Installer mode (the manual tells you how) then check that Room Control Mod is set to Active or Expanded.


I've gone into the installer mode but can't see the Room Control Mod you mention. Is it under another name?
 
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If builder's son adjusted the plumbing after the installers then he's the last man in.
Get him back through his dad and if it turns out the fault was there, before he interfered then he can call the original guys and tell them what it is he thinks they've got wrong (unlikely).
More likely is that he has installed a towel rail in a bathroom and has teed this into the return after the cylinder. It's a common mistake made by bathroom fitters, who are often* plumbers only because they know how to join pushfit together!

* edit: added "often" as many bathroom fitters are proper plumbers :oops: xx.

Yes I will have to contact the son as he made so many mistakes this wouldn't surprise me. I spoke to our friends who used him for their conversion at the same time and they said the son had caused them a problem with their underfloor heating coming on with hot water and he came back and changed a pipe.
 
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