Multistove burher with backboiler

[cooket3]

Hi

I have a multistove burner with a back boiler. I think I may have a problem with the back boiler absorbing heat from the fire.

If the fire is roaring the central heating does get nice and hot, very hot in some cases, which is nice and fine.

However when I do an over night burn or even burn the stove at a lower temperature the back boiler doesnt seem to absorb any heat. I did an overnight burn the other day, when I came down to look the stove was still nice and warm, too hot to touch. However when I felt the pipe coming off the back boiler it was cold.

Does this mean I have an air lock or something?

Thank You

 

[Agile]

It sounds like a gravity circulation and not pumped.

Sometimes they do not work properly if the fire is not on high output.

Tony

 

[cooket3]

forgot to ask and add. I believe my stove is an Evergreen ST1017

On the night I did the overnight burn I did have the pump on, hoping the radiators would be warm downstarrs.

From what ive read many people can acheive this

The central heating was drained before I moved in.

Another thing. With the fire really hot and hot radiators, I turn off the pump and the colder water from upstaris seems to flow back down into the back boiler as the pipe gets cold and the back boiler begins to bang, at this point I crap myself and turn the pump back on, which makes an even louder bang for a second or two then goes to normal. Is this normal or an issue with my pump not being strong enough to pump the hot water everywhere.

I am hoping to get someone out to look at this but want to make sure its not normal first

Thank You

 

[Norcon]

The system should have a gravity rad. Usually fitted above the appliance.

If all electrics fail then this rad should prevent any banging.
Usually needs the air supply shut off though.

When the electric returns, Hi - Lo stats that should be fitted, take over and control the pump.
The gravity loop through the heat leak rad or the cylinder is important to ensure the correct operation of the Hi-Lo stat set up.

It very simple but requires some logical thinking at the same time.
Basically the hydronics and electrics have to be comapatible with each other.
Manual pump control is a real bad idea.

My gut feeling on these stoves was "china". And sure enough that's where they hail from.
You'll probably have to refer to a UK manual to find out how to properly fit them. Or hire a plumber who knows what he's doing.

 

[Corgigrouch]

Much as it pains me to agree with Norcon, but he is right.. If you just leave te pump on then you will have cold water returning to the boiler which will cause condensation inside the stove resulting in the boiler corroding and leaking prematurely... If your rads give off heat at a greater rate than the slumbering stove can provide, then you will end up with cold water returning to your boiler..

 

[Nige F]

Problem is the old plumbers who can install a gravity circuit are few and far between

 

[Biggles..]

There's plenty of young uns that can do it.

 

[cooket3]

Thanks for your replies.

The banging is only when I have the fire on full and not on slumber.

The main issue Id like to resolve is the poor heat transfer from the slumbering fire to the back boiler to heat my radiators and if there is an explanation to why this is.

The back boiler is an inverted L and the flue is on the top of the fire and not the back.

I probably should have had the whole system checked before I got the rooms plaster boarded and carpets upstairs!

 

[Norcon]

I run my boiler stove flat out on aga anthracite and some logs. It's a Stanley so I'm confident it can run like a steam train. I keep the LO stat adjusted as high as possible to keep the firebox as hot as possible.
Also the rad circuit is purposefully undersized slightly. It all performs beyond my expectations.

The anthracite will glow orange and keep that state for a few hours with the flow temp a steady 70c.
I wouldn't expect it to heat rads whilst slumbering. Cold water from the rad circuit being allowed to freely flow through the boiler will lower its efficiency.
And low temperature smouldering of wood results in more tar formation and higher usage of fuel.

If you want to slumber your stove then change over to a dry model.

 

[Corgigrouch]

The main issue Id like to resolve is the poor heat transfer from the slumbering fire to the back boiler to heat my radiators and if there is an explanation to why this is.

!

Please read what you have been told.... It isn't a case of poor heat transfer. If you leave the pump running overnight, then the heat is being removed and dispersed before the heat exchanger can heat up...A situation that can lead to problems eventually...Over night you should turn off the pump and allow the reduced heat in your boiler to heat the heat leak radiator and possibly the hot water cylinder.... You ain't gonna heat the whole house with the boiler slumbering overnight..

 

[cooket3]

Thanks for your replies. Im off to a stove centre today, to get some ideas if i need a new stove or add thermostats etc. And a plumbers coming to check out my system to see if i can have a thermal store added. This will allow me to give the radiators some heat before i wake up and my house isnt freezing, then top it up with a new fire at night

 

[Norcon]

Before you go spending a few £k.00 on new stoves and thermal stores and probably another few grand to control/install it and still end up with an abortion, have the current system set up correctly with the right control.
And piped properly which means the gravity circuit must work unrestricted.

A few hundred quid might sort it out.

Study page 17 of this link...
http://www.woodwarmstoves.co.uk/_assets/manuals/new instructions fireview march 2010.pdf

And study the diagrams. This is how your system should be piped.

Thermal storage has to be massive just to supply a few rads for a short while.
1000/l minimum and slumbering a small stove against that will be like pizzing against the wind.

 

[cooket3]

Thanks. I am planning to have all the central heating pipes sorted and done correctly before proceeding with a new boiler.

The people I have had out mentioned a flue damper and a flue liner would stop the heat escaping rapidly up the chimney and therefore increase efficiency of the heat transfer from the stove to the back boiler.

Is this correct?

If these will help I will do these first as they are a much cheaper option!

Thanks again