Worried my back boiler going to explode

[LovemePal]

Appreciate any advice on this!
We have a 1970s house with an open fire and back boiler that heats the hot water. We recently had the top of our chimney rebuilt and since then when we light the fire the hot water gets CRAZY hot, the hot press cupboard gets so hot that the door handle is too hot to touch. Also the hot water runs a little brown. Clearly something is wrong. Have only lit the fire a couple of times, second time was to see if it happened again. Could something have damaged the system when rebuilding the chimney? Who do we call about this sort of thing? Do plumbers work with open fire back boilers? Are we in danger of it exploding?
Many thanks for your time!
Catherine

 

[Jackrae]

If you look up inside the fire above the throat you should find a slide or a lever. This controls the damper which opens a channel that "sucks" the fire under and behind your back boiler. In all probability the damper is open. Simply close it and less heat will be drawn around the boiler so reducing the amount of hot water it generates.

There's a bit of a diagram on this site http://www.coaladvisoryservice.com/resources/files/howtogetthebestresultsfromyouropenfire.pdf

The browning will simply be residue in the hot water tank that has been stirred up by the boiling action.

As kids (back in the 50s !!) we used to have to run off boiling water from our domestic system because it worked so well.

 

[LovemePal]

Thanks Jackrae, we've tried closing the damper already and it gets that hot even with the main heat coming back into the room or up the chimney. Can't imagine how hot it would get if we sent it back into the boiler! So I'm not to worry about the brown water? Thought it might be a sign that something had cracked somewhere? Hence why it was overheating?

 

[LovemePal]

Also the water is that hot that from one fire it is still roasting hot water the next evening

 

[Norcon]

What system do you have?
Can you post a diagram?

How many rads?
Heat leak rad fitted?

If a door handle getting hot in the hot press is to be believed then the cylinder must obviously be getting hot.
I assume you have hot water?

The chimney being built will not affect the hydronics. That was just a coincidence and allows you to blame someone in your quest for answers.

It might just be a pump stopped working and the gravity to the cylinder still operational with no heat leak rad fitted.

 

[Burnerman]

Is your loft full of steam, Catherine, and does the back boiler circulate water to the radiators too?
John

 

[LovemePal]

Not sure what brand system, we bought the house last winter with no info on the back boiler, but is pure gravity fed, we have no pump to turn on/off, just the damper above the hearth. The boiler doesn't heat any of the rads, so I assume no heat leak rad fitted. I haven't checked if the loft is full of steam, can light a fire and do that today - what would it signify? Thanks for the replies - much appreciated!

 

[Norcon]

How many radiators are there in total?

 

[LovemePal]

Have never noticed any of the rads getting hot before so I don't believe the system has changed. I guess my question is why is it suddenly making the water SO hot? What could have happened? Last winter when we were lighting the fire the hot water was a good temperature but this is scalding hot now, lasting for a couple of days, and yes the hot press gets that hot the door handle is too hot to touch.

 

[LovemePal]

7 radiators and a towel rail in the bathroom - thanks Norcon

 

[Norcon]

Are you sure no pump is fitted?

Sometimes they were concealed behind panels at the side of the chimney breast.
And a manual switch on the wall near the fire to turn it on.

 

[LovemePal]

well, not sure honestly, we don't have any info on it. But there's definately no switch and it worked comfortably last winter heating the hot water nicely even with the damper closed.

 

[LovemePal]

we've been advised that these houses were built without the back boilers connected to radiators, not big enough system

 

[Burnerman]

What system is used to heat your rads, then - if not the back boiler?
John

 

[LovemePal]

oil boiler outside heats rads and hot water too - but we're careful not to have it on at same time as fire. We're the only house on the block still to have open fire and back boiler, so can't ask anyone else how their's works...