Heating Won't Turn Off

NickyK

Hi there,

So, tonight I noticed it was uncomfortably hot in the house. Wife switched off the heating and 30 mins later the oil boiler is still running. Turned the thermostat down to zero, boiler still running. Switched electricity to controller off, heating went off.

We have a Horstmann Channelplus H37XL controlling the upstairs and downstairs heating plus the water. We never use the water. It was installed almost 15 years ago

The heating is normally at 21°c.

If I turn the power to the Horstmann back on the boiler comes on. Upstairs at our hot press there's a low humming sound. There's a small white Myson box switched to AUTOMATIC. If I switch this to manual the humming stops. I've switched back and forth with boiler running but moving to manual doesn't turn it off.

Any ideas? I'm not great with DIY and am even unsure if it's a plumber or electrician I need.

Thanks in advance,

Nicky

dathi

https://www.screwfix.ie/p/eph-controls-v221p-2-port-motorized-valve-compression/227HP?gclid=CjwKCAiAlrSPBhBaEiwAuLSDUPXzh54IeitCjiCvAgKeURDYGRlOuUgRxRDhwyE7te5TpKTDQ_i7mRoCZQUQAvD_BwE&gclsrc=aw.ds

something like above ? sounds like your motorized valve is broken and needs replacement, if they can no longer close they will call for heat continuously.

maestroamado

Did you turn down the stat that is on the actual boiler....

893bet

https://www.boards.ie/discussion/comment/118520350#Comment_118520350

If you can find where these are they can be manually closed usually.

Wearb

As per 1st answer, this is often caused by welded contacts on the end switch of a motorised valve.

Electrician or plumber would replace it. The whole valve doesn't need to be removed, just the head.

NickyK

Hi,

Thanks for your responses.

I turned back on the power this morning and same thing happened (downstairs rads piping hot even though thermostat @ zero and Horstmann in off position) so I went upstairs to investigate.

There's two motorised valves, I presume one for up and one for downstairs. I turned heating on and off upstairs and rads functioning as normal.

Again thanks for your help. I'll give electrician a call tomorrow.

Nicky

Charles Babbage

I've had this problem. The valve head could be malfunctioning and your electrician can fix it, I just changed the valve head myself. However, the valve itself could be sticking and that needs a plumber, which appears to be the problem in my case.

maestroamado

I am assuming its traditional boiler and if it is there is a stat that will only allow the temp to go so high... i expect the reason the other rads are hotter is only 50% being heated.... If you want to reduce the heat in these turn the stat down abit...

youtheman

Normally on a zoned system the only thing that turns your boiler on is any zone valve confirmed open (by the respective valve limit switch). All the zone valve switches are wired in parallel such that any switch activated will turn the boiler on. So if you turn all your thermostats down and the boiler is still 'on' then it indicates that one of the switches is stuck (in the 'on' position).

maestroamado

https://www.boards.ie/discussion/comment/118536815#Comment_118536815

Does not the boiler stat determine the max temp... what i cannot understand is why the rads are getting way hotter... i assumed valve in off position so heat only goin to half rads...

youtheman

No. You have 'internal controls' on a boiler (boilers stat) and 'external controls' (room stat). Ideally the room stat (the external control) controls the system (i.e. turns the boiler off) before the boiler stat kick in. The boiler stat is really just a 'high-high' safety system. For example you turn all your radiators off, and turn your boiler on. The boiler pumps out hot water around the system, but there are no radiators on to take the heat out of the system. The room temperature is not going to rise because the radiator is off, so the room stat is never going to reach its 'set point'. So the water returns 'hot' to the boiler only to be reheated again. And so on and so forth. Eventually the water could reach boiling point. This is what you have a boiler stat on the return pipework to tell the boiler 'hey, this is not right, there is too much heat in the system, so it will shut off). So the room stat is your 'normal control# and you boiler stat is just a control for an 'upset or abnormal' situation.

maestroamado

https://www.boards.ie/discussion/comment/118538716#Comment_118538716

I have to sat my experience of boilers is limited to Grant and a few others that are more or less the same, all the heat boilers hat a stat cut-off at about 70 and boil is about 95... are you saying thjere are boilers on the market that have not a built-in stat ant temp controlled by remote stat...

seems unlikely...

youtheman

I'm saying all boilers come with an 'internal' stat and the provision for an 'external' stat. They system should normally run such that the on/off function is provided by the 'external stat' (i.e. the wall mounted room stat and/or the cylinder stat). The 'internal' stat should not normally be called into action, and only when the boiler senses that the return water temperature is getting too hot. This could be due to failure of the room/cylinder stat, failure of the zone valves, all radiators being turned off etc.

smuggler.ie

Actuators have lever to set valve into "permanent open" for system servicing purpose. This in turn(if power present) kicks the heating ON irrelevant of controller settings and could explain why one zone is blasting and not the other. Worth checking if it was not set by mistake or accidentally.

Edit: All actuators should be on "Auto" so if downstairs blasting - check actuator serving that zone.

maestroamado

I expect its sorted...

sundodger5

Not a plumber but i have had the batteries in the wall controller go flat or at least low enough not to work and the heat stays on despite the display showing off.