Heating Controller Being overridden (UK)

[Tony P]

Hi hope someone can help me, it’s a bit of a long story so sorry in advance.

Around 10 months ago we had a power cut and when the power was restored, we got a bit of a surge. Didn’t realise that it had impacted on our central heating until we woke up in the middle of the night with the water and heating going full blast and the controller showing no on lights. Only way to turn it off was to turn it off at the mains.

I call Dryton who said this could happen due to the micro switch being damaged in the surge. They said take the controller off give it a bang and see if that helps the micro switch.

All fine for a few weeks and it happened again, seemed to happen after we had used the advance switch. Next step was to replace the controller, bought another Drayton (LP522) and within a week it had happened again. Phoned Drayton who said it must be the actuator, change it. I called my regular plumber who said can’t be that as the actuator wasn’t powered so can’t override anything! He said he had come across a similar problem and to change the controller to a different make, that sorted it before. So I changed the controller to a Honeywell (ST9400C). All has been good for 6 weeks and then last night even though the heating and hot water timings had gone off, the hot water was getting hotter and he radiators were piping hot, no lights on the controller and the thermostat was not working as no power to it. Only way to stop was again to turn off at the mains.

Anyone come across something like this before, if so what was the solution.

Any help much appreciated, Happy New Year



Tony P

 

[baldelectrician]

I would suggest a SPD as a start

Seems to coincidental, 2 things failing within a short time

As a short term measure you could change the timer to a 2 gang switch and see if all the valves and stats work as they should (saves frying another timer)

 

[ImpededLoop]

The fact that the thermostat had no light on it makes me suspect that something else is causing this, perhaps the microswitch on the actuator.

If you reinstate the power and make sure there are no lights on the programmer, does the boiler still fire? If so, see if you can manually open and close the valve actuator a few times. Does this stop the boiler running?

Beyond this, you'd need to do some live testing which I'd recommend is done by an electrician.

 

[brianmoooore]

S plan or Y plan? (Do your control valves have two pipes or three)?
Do all radiators that are turned on at their valves get hot?

 

[Tony P]

The fact that the thermostat had no light on it makes me suspect that something else is causing this, perhaps the microswitch on the actuator.

If you reinstate the power and make sure there are no lights on the programmer, does the boiler still fire? If so, see if you can manually open and close the valve actuator a few times. Does this stop the boiler running?

Beyond this, you'd need to do some live testing which I'd recommend is done by an electrician.

Thanks for getting back, once power is reinstated then it operates as normal, till the next time it doesn't. If the heating and hot water should be off when power is reinstated then the boiler doesn't start up. Can the actuator has a fault could it make the heating/hot water come on even if the control panel says it should be off?

 

[ImpededLoop]

Thanks for getting back, once power is reinstated then it operates as normal, till the next time it doesn't. If the heating and hot water should be off when power is reinstated then the boiler doesn't start up. Can the actuator has a fault could it make the heating/hot water come on even if the control panel says it should be off?

Easiest way to find out would be to manually open the valve and see if the boiler then starts whilst the programmer is off.

 

[brianmoooore]

Easiest way to find out would be to manually open the valve and see if the boiler then starts whilst the programmer is off.

Most, but not all, valves operate the internal microswitch, when the valve is manually operated.
Need answers to my last question!

 

[Tony P]

Easiest way to find out would be to manually open the valve and see if the boiler then starts whilst the programmer is off.

Sorry, not sure how to open the valve manually!

 

[ImpededLoop]

Sorry, not sure how to open the valve manually!

There's often a spring loaded metal lever on the side which you push across and hook under a lip to keep it open.

 

[Tony P]

S plan or Y plan? (Do your control valves have two pipes or three)?
Do all radiators that are turned on at their valves get hot?

Sorry just seen this, 3 pipes, its an MA1 mid position actuator

 

[Tony P]

There's often a spring loaded metal lever on the side which you push across and hook under a lip to keep it open.

Hi, just taken actuator off and it has a small plastic leaver on the side and another on the back marked W M H, with hot water & heating controller both set to off I couldn't move either leaver/switch

 

[Tony P]

I would suggest a SPD as a start

Seems to coincidental, 2 things failing within a short time

As a short term measure you could change the timer to a 2 gang switch and see if all the valves and stats work as they should (saves frying another timer)

Hi, thanks for getting back, what is a SPD & a 2 gang switch please?

 

[ImpededLoop]

I'm not familiar with that particular actuator. W M H stands for Water, Mid position and Heating. Best to look up the instructions for that actuator to see how to manually operate it.

 

[Tony P]

I'm not familiar with that particular actuator. W M H stands for Water, Mid position and Heating. Best to look up the instructions for that actuator to see how to manually operate it.

Cheers will do
Tony P

 

[UNG]

When the heating and hot water are off the MA1 will still be energised to the hot water position

When you turn the heating on does the lever move to the other position

Do you have a meter so you can check what incoming voltage you have

I thinking this problem may be down to an intermittent incoming mains issue

 

[Tony P]

When the heating and hot water are off the MA1 will still be energised to the hot water position

When you turn the heating on does the lever move to the other position

Do you have a meter so you can check what incoming voltage you have

I thinking this problem may be down to an intermittent incoming mains issue

Thanks, I will check the heating control, I don't have a voltage meter so will get a plumber/ heating engineer to check for me. Do you thing the intermittent mains issue could be the micro switch inside the actuator? Thanks for your help Tony P

 

[brianmoooore]

Your system is a Y plan , unfortunately, which makes fault finding more difficult, and I'm also unfamiliar with your model of valve, in spite of having been installing heating systems for 40 years.
Y plan is more complicated because the boiler is only sometimes operated by the valve's switch, whereas with S plan it is always operated by the valves' microswitch.
A further complication is if you have a boiler which has frost protection. An externally positioned (to the boiler and airing cupboard) thermostat then fires up the boiler in cold weather, and, of course, this can become faulty.
Getting back to your original question, yes, a faulty microswitch in the valve can cause what you describe. It's happening with my own heating system at the moment. About every two weeks or so, we find the towel rails in the house to be permanently hot, and although the valves are closed (towel rails don't go through valves), the pump and boiler are on. Thumping the hot water 2 port valve provides a cure for the next couple of weeks.

 

[Tony P]

Your system is a Y plan , unfortunately, which makes fault finding more difficult, and I'm also unfamiliar with your model of valve, in spite of having been installing heating systems for 40 years.
Y plan is more complicated because the boiler is only sometimes operated by the valve's switch, whereas with S plan it is always operated by the valves' microswitch.
A further complication is if you have a boiler which has frost protection. An externally positioned (to the boiler and airing cupboard) thermostat then fires up the boiler in cold weather, and, of course, this can become faulty.
Getting back to your original question, yes, a faulty microswitch in the valve can cause what you describe. It's happening with my own heating system at the moment. About every two weeks or so, we find the towel rails in the house to be permanently hot, and although the valves are closed (towel rails don't go through valves), the pump and boiler are on. Thumping the hot water 2 port valve provides a cure for the next couple of weeks.

Thanks Brian, couple of more questions if I may, if I replace the actuator do you feel it is OK to use a junction box rather than change the wiring behind the control panel, is it better to bite the bullet and change the type of actuator? If so does that mean changing all the pipe work? Thanks again for all your help

 

[UNG]

Thanks Brian, couple of more questions if I may, if I replace the actuator do you feel it is OK to use a junction box rather than change the wiring behind the control panel, is it better to bite the bullet and change the type of actuator? If so does that mean changing all the pipe work? Thanks again for all your help

If your MA1 actuator is not the quick release type then you will have to change the valve as well

 

[Tony P]

If your MA1 actuator is not the quick release type then you will have to change the valve as well

It is quick release, thanks again Tony P