In my mums house we have a glowworn hideaway boiler with a gravity fed hot water system and on the heating system there is a tank in the loft to keep the radiators topped up. The system was put in in abbout 1991 and has allways worked fine. This morning i woke to here like the sound of thunder in the loft and when i looked the tank has really hot/boiling water in it and the upstairs radiators are really hot aswell. There dont seem to be any thurmostats in the system we just switch the heating on and off from the control box next to boiler. Has anyone any ideas what might be causing this?
Help.
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First of all, it's most important you turn the system OFF straight away and don't use it again until it's fixed.
Boiling water entering a plastic water tank can cause it to burst spilling scalding water through the ceiling onto anyone below. There was a case of a child being killed in his bed due to this a while ago.
Now you have turned it off and come back to continue reading the reply, I think the most likely cause is the boiler's inbuilt thermostat has failed.
With a gravity hot water system, there are no controls on the hot water tank temperature, so the hot water tank just heats up to the boilers water temperature. That is regulated by a thermostat that turns the boilers burner on and off to maintain a set temperature.
Since you appear to have near boiling water it sounds like the boiler thermostat is not working and the boilers burner is running continuously making the water hotter and hotter until it boils.
You need a heating engineer capable of servicing your particular boiler to fix it, and like I say, I advise not using it at all until it's fixed.
Boiling water entering a plastic water tank can cause it to burst spilling scalding water through the ceiling onto anyone below. There was a case of a child being killed in his bed due to this a while ago.
Now you have turned it off and come back to continue reading the reply, I think the most likely cause is the boiler's inbuilt thermostat has failed.
With a gravity hot water system, there are no controls on the hot water tank temperature, so the hot water tank just heats up to the boilers water temperature. That is regulated by a thermostat that turns the boilers burner on and off to maintain a set temperature.
Since you appear to have near boiling water it sounds like the boiler thermostat is not working and the boilers burner is running continuously making the water hotter and hotter until it boils.
You need a heating engineer capable of servicing your particular boiler to fix it, and like I say, I advise not using it at all until it's fixed.
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Technician
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IIRC there are two thermostats for the water temperature control.
There is the control stat that controls the temp. in the heating
circuit and the other is a limit stat on the water outlet from the
boiler. This is controlling the temperature of the primary circuit
that circulates the radiators.
Check the pump and ensure that it is running when the control stat
calls for heat. The primary circuit is overheating and needs the
water circulating to keep the temp down. The limit stat on the boiler
outlet may also need to be checked.
Edit from above post; this is potentially dangerous.
There is the control stat that controls the temp. in the heating
circuit and the other is a limit stat on the water outlet from the
boiler. This is controlling the temperature of the primary circuit
that circulates the radiators.
Check the pump and ensure that it is running when the control stat
calls for heat. The primary circuit is overheating and needs the
water circulating to keep the temp down. The limit stat on the boiler
outlet may also need to be checked.
Edit from above post; this is potentially dangerous.
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?? :C
A gravity fed HW system can still have a tank thermostat to fire the boiler...
Consider a sundial C plan system...
(typical wiring info can be found on the Honeywell site...)
So it could be just the thermostat at the cylinder needing replacement..
:|
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It's rare (but not impossible) to have controls on a gravity HW system.
But even if there is a tank stat, and it has failed, the water in the tank will just heat up to boiler output temperature, which should be nowhere near boiling.
As the water is boiling, it can only be a failure in the boiler causing the boiler output temperature to be too high.
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Could it also be a blockage in the pipework and no bye-pass, so discharges into header tank.
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Not that rare, 'C plan' is not that obscure....
Is it boiling? or just very hot though??
Hi guys, i have been off today so ive had a look at the system. What seems to be happening is when you have the gravity fed hot water on the radiators upstairs come on and get really hot and the vent pipe that goes into the central heating header tank in the loft also gets really hot and starts to make the funny noise like its exhausting steam or something. Any ideas what this could be?
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Blockage somewhere.
Probably piped with a common return for HW and heating (never a good idea) and due to a blockage normal circulation isn't happening so it's overheating, building up pressure and flowing the only way it can, the wrong way.
Do please get someone to look at it before it all ends in tears.
Probably piped with a common return for HW and heating (never a good idea) and due to a blockage normal circulation isn't happening so it's overheating, building up pressure and flowing the only way it can, the wrong way.
Do please get someone to look at it before it all ends in tears.
Thanks i have a man coming monday so he can service it at the same time. The plumber that put it in was a cowboy ive never been able to find the stop cock where it comes in the house, probably plastered behind a wall somewhere. I will leave it off and get this chap ive phoned to try and fix it. Thanks for your help.
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Its possible the feed pipe from the expansion tank is blocked and there is a shortage of water in the system but really you are going to need to know what you are doing to put this right. To be safe you need to switch system of until it is fixed. As Dave says its possible the expansion tank could fail and put a lot of boiling water through the ceiling. A this will cost a lot of money to put right and B somebody could be injured.
A power flush would sort it out and not a bad thing to have done anyway.
Its possible the last time it was drained down, sludge from the header tank may have been pulled down into the pipework.
It may not be a blockage so as said above don't use until you get the system checked over or it could get worse and be costly.
Its possible the last time it was drained down, sludge from the header tank may have been pulled down into the pipework.
It may not be a blockage so as said above don't use until you get the system checked over or it could get worse and be costly.
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that happend to mine, the air seperator blocked so the system could not refill and the pump was running dry.
the feed pipe is only 15mm which does not help
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