Gas Boiler Running Continuously

VonLuck

This is a strange one. I have my gas boiler set to a schedule for both separate hot water and heating. Yesterday I noticed that the water temperature was low, so I checked the boiler and the pressure was almost at zero. I topped up the water so that pressure was at about 1.5 bar.

This morning the water seemed to be okay, but then about two hours later it was scalding hot and just figured that it was running more efficiently. Another couple hours later it was still extremely hot when normally it would have cooled down by then. I checked the thermostat/controller and it was off. Then I decided to check the boiler itself and could hear it running and vapour coming out of the flue. It seems to be continually turning itself on and off to maintain hot water.

I have a Hive thermostat and controller but the app, thermostat controller and manual controller are all off so I've no idea why it's turning on. And it seems to be just the water. Radiators are turning on as per the schedule.

Any idea what could cause this to happen? I've had to turn off the boiler itself to stop gas wastage now.

VonLuck

I may have figured out the cause of the problem. There is an actuator valve beside the hot water tank which I may have hit last night putting something into storage. It may have been dislodge and I was able to click this back into position just now.

Would this likely to cause the boiler to continuously turn on to heat the water?

Lenar3556

Possibly, on a motorised valve. It is possible that the auxiliary switch was manually engaged. The fact that the timeclock was switched off may suggest the manner the auxiliary switch is wired is incorrect and this should be checked by your electrician when the opportunity allows. It should be simple to correct.

Another thing which may give rise to the symptoms you describe at the present time would be activation of a frost stat. Less likely to be a factor if you have an indoor boiler.

VonLuck

Lenar3556 wrote: »

Possibly, on a motorised valve. It is possible that the auxiliary switch was manually engaged. The fact that the timeclock was switched off may suggest the manner the auxiliary switch is wired is incorrect and this should be checked by your electrician when the opportunity allows. It should be simple to correct.

Another thing which may give rise to the symptoms you describe at the present time would be activation of a frost stat. Less likely to be a factor if you have an indoor boiler.

I don't think the manual switch had been engaged as it was in the 'automatic' position when I looked at it. I think the entire unit had come away from the valve. It's a demountable motorised valve which seems relatively easy to remove.

Would I be right in assuming that if this isn't fully engaged with the valve that it effectively would run continuously to maintain hot water?

Lenar3556

VonLuck wrote: »

Would I be right in assuming that if this isn't fully engaged with the valve that it effectively would run continuously to maintain hot water?

Not quite. Typically the actuator is controlled by a thermostat and/or timeclock. When a call for heat is received, the actuator typically does two jobs - (1)opens the mechanical valve, (2)closes an auxiliary switch within the actuator to send power or a start signal to the boiler.

An actuator which has come away from the valve body may fail to perform (1) but would still do (2). It could still be a defective actuator that is the cause of your issue.

VonLuck

Well pushing the actuator back in place seems to have fixed it. Thanks for the help.

By the way, is there a good resource for understanding the basics of plumbing systems? Have learned a fair bit from trying to fix problems as they arise but I'd be interested in knowing more.