Wood burning stove with back boiler problem

[Zaffy]

Not sure if this is a plumbing question or a wood burning stove question.  Anyhow, this winter, lit the fire.  When the stove was hot, the water cylinder became very noisy, swooshing, kettling etc. and hot water rose up into the expansion tank.  I  was told back boilers can be repaired but not replaced.  Not had any joy ringing around.  Any ideas, thanks.  

[GarethM]

Are you sure you didn't just boil the hot water cylinder?.

[Squaredy]

54 minutes ago, Zaffy said:

Not sure if this is a plumbing question or a wood burning stove question.  Anyhow, this winter, lit the fire.  When the stove was hot, the water cylinder became very noisy, swooshing, kettling etc. and hot water rose up into the expansion tank.  I  was told back boilers can be repaired but not replaced.  Not had any joy ringing around.  Any ideas, thanks.  

Yes, you have managed to get the water too hot.  Does it heat radiators as well?

 

 If it does not you will have to manage the wood burner very carefully to avoid letting the water boil.  I would have thought the system would have some radiators in the system to help dissipate heat.

 

 More details of your setup are needed please.

[Zaffy]

You may have cracked it.  Thanks.  I shut off a couple of radiators.  

[Honda]

Seems as though your water pump is not working.  

[GarethM]

Unlikely you've cracked it, but valuable lesson for you all the same.

 

Still probably needs a bigger tank and or better fire control as you should never shut down a gravity radiator system, yes it can boil over but it's also a big grenade without knowing how to use it safely.

[Zaffy]

17 minutes ago, Squaredy said:

 More details of your setup are needed please.

So complicated, for me at least.

Warmflow oil boiler.  Heats water and upstairs rads.

Wood burning stove, heats water and should heat downstairs rads but doesn't seem to do it very well.  All are patchy luke warm.  I shutthem off and hoped wood burner would at least warm the towel rail and the laundry room rads. 

The immersion heats the water cylinder and I have it on at the moment and it is heating the water and the towel rail and the laundry room rad.

Since your reply, I am thinking that the towel rail and the laundry room rad are heated by the hot water cylinder and not by the back boiler and when I turned off the two large rads, heat had nowhere to go.

Please ignore if my answer is not clear.  I am, as you guess, not a plumber.

 

17 minutes ago, Squaredy said:

 

 

[GarethM]

You're oil boiler does the job when it's on tho doesn't it ?.

 

As a low tech solution, rewire the pump to always be on regardless of the heating.

 

There are more elegant solutions, but that's a simple way, as you don't want it boiling again if the timer turns the boiler off when your in bed 🙂.

Edited January 4 by GarethM

[Doug Tait]

I'm not a plumber either but patchy heat from a radiator would make me think the radiator had problems rather than the heat source.

 

If I remember correctly, hot at the top but cold at bottom is a sludge build up, cold at the top but hot at the bottom is trapped air, and a uniform too cold or hot across the radiator indicates it isn't balanced right.

[Rob_the_Sparky]

Cold at top hot at bottom yes is air, there is no water at the top so no heat at the top.

 

Hot at top and cold at bottom is low flow, water is cooling in the rad faster than it is flowing through.  Could be a number of causes for that and it is not necessarily a problem.

 

Hot top and bottom (equal temp) is high flow rate.  Again not necessarily a problem but could mean you have not enough flow elsewhere.  Some rads like this and some hot at top and cold at bottom (or just cold) and you  most likely have a balance issue.

 

No I'm not a plumber, just an engineer with crappy plumbing so been looking at the problem for a while!