Boiling and banging pipes

[saveasteading]

I think it is called kettling?

 

Lots of banging and it will be spluttering into the header tank.

 

It's not all the time though.

Does this need a heating engineer? Can I turn something down for now?

[G and J]

When troubles come they come not as single spies but in battalions….
 

I’m guessing you’ve a vented hot water cylinder and a gas or oil boiler which indirectly heats the water?

 

If so you should have a stat on your cylinder, which you could turn down to stop the water in the cylinder boiling, assuming no valve or control faults.
 

However I think it also means your flow temp must be rather high.

[ProDave]

I really don't think it would be the boiler heating the hot tank that hot, much more likely the immersion heater is turned on and the thermostat has failed.

 

Immediately find and turn off the immersion heater switch.

 

Boiling water venting to a plastic header tank has been the cause of more than one very unpleasant death and why the law was changed for a secondary thermostat in immersion heaters.  Don't ignore it, act NOW before even replying to this thread.

 

I would add, turn off the boiler as well, and run a hot tap to run off some of the boiling water out of the tank.

[G and J]

13 minutes ago, ProDave said:

I really don't think it would be the boiler heating the hot tank that hot, much more likely the immersion heater is turned on and the thermostat has failed.

 

Immediately find and turn off the immersion heater switch.

 

Boiling water venting to a plastic header tank has been the cause of more than one very unpleasant death and why the law was changed for a secondary thermostat in immersion heaters.  Don't ignore it, act NOW before even replying to this thread.

 

I would add, turn off the boiler as well, and run a hot tap to run off some of the boiling water out of the tank.

Good point, I didn’t think of the immersion heater.

 

We had a holiday rental where one of the guests helpfully turned up the stat on the tank as they wanted more hot water.  It boiled over and made a big mess of the landing ceiling.   This brought back memories.

[saveasteading]

Thanks. Not the immersion. It wasn't on: never is.

It is an oil burner.

I vaguely remember this happening before, and the little thermostat on the tank was an option...and that it's just in round number clicks.

The  boiler temperature is an uncalibrated knob, currently at mid point.

U haven't twiddled them yet. Should I do one rather than the other?

 

I've turned the CH back on and left the water off, for domestic harmony.

No banging yet.

 

[ProDave]

Well one of the thermostats is dud.  I would say boiler thermostat.  The water exiting the boiler should never be near boiling, so even a failed cylinder stat should not cause that.  I bet the radiators are scalding hot to touch.

 

Until you get it sorted, do not leave the boiler on at all over night, or while out of the house, and watch it like a hawk when in, first sign of boiling or banging turn boiler off. 

[saveasteading]

In case its relevant: The header tank recently had issues which I resolved. The balcock valve was leaking so I changed the whole thing.

 

But along with the leak, it was coming through the ceiling which is why we noticed it.  So I found that the overflow was not sealed, and never had been....that was put in 30 years ago. I've sorted that too.

 

I think I may have been overcautious in setting the balcock float so the level could be an inch higher, if that might reduce the temperature. I also removed the insulation, because that seems unnecessary in the SE. I topped up the additive but rather a guess.

[joe90]

2 hours ago, ProDave said:

much more likely the immersion heater is turned on and the thermostat has failed.

I know you have proved this is not your case but years ago I had the same problem, came home from work to find the header tank (plastic) was so hot it was about to give way and flood the house, it started out square but ended up round. The immersion thermostat failed and boiled the water. With yours  A thermastst somewhere has failed by the sound of it. 

Edited Friday at 12:32 by joe90

[Marvin]

Kettling is usually caused by water in the system not passing quick enough out of the heating element in the boiler, causing the heat to 'Boil' the water. The water expands with the steam and looking for somewhere to get out pushes up to the header tank.

 

Either the flow is restricted by gunge, thermostatic valves closing too many radiatiors, or pump not working properly.

 

[Timedout]

Is the heating and hot water controlled by thermostats and two port valves? If it is there is another potential cause. This has happened to me twice, both times with Danfoss two port valves heads. The valve head had jammed in the open position which means the boiler keeps on running when it ought to stopped either by the programmer of the thermostats. It was the electrical part of the valve head not the brass paddle valve bit. Giving the valve head a sharp bash made it release but it would jam again on the next cycle. New valve head fixed it both times. It should not happen but it does and you will find other people on web forums (or fora if you prefer) with exactly the same fault. It is always Danfoss valves.
 

Your oil boiler will have two stats. An adjustable one like that one with the knob you described and another upper limit stat. That upper limit is high though, probably around 90. When mine was in that fault mode I found the flow temperature hit 92. That is far too hot for anything to be safe. Turn down your adjustable boiler stat. I have mine set to run at 70C flow. 

[saveasteading]

1 hour ago, Timedout said:

Is the heating and hot water controlled by thermostats and two port valves?

Radiators all have thermostats plus there are room controllers in 2 distinct circuits, each with a hot water tank.

Port valves? I don't know.

 

On further investigation, I half recall that the radiator nearest to the boiler is on its own loop, for some reason of keeping a circuit open during maintenance????? may be wrong.

That was the hot one. Others seem to be on and off without issues.

Since my first post and turning the room heating (only) back on it has been working nicely. I haven't touched the controls.

I will continue this for completeness and only turn the water heating on when necessary and then after a decent test period.