back boiler boiling

[Coly Loughlin]

Hi there i have a problem with a new woodburning stove with backboiler. It is on a gravity fed system but it doesnt seem to be working as it should. It will boil and release itself up to the header tank then repeat.There was an air lock in the circuit but i let it off at the hot water cylindar and this seemed to let heat all way round. however the boiler still seems to be boiling up
would there be a problem in the circuit that it isnt flowing properly ie airlock or pipe run or would it need to be pumped as the circuit is quite long about 30m thereand back over 2 floors. If an airlock how do you flush out
any help grtefully recieved

 

[dontknowitall]

Ideally it should be pumped.

One way you can do this is to put a pipe stat on the pipe and link it to the pump so when it reaches a certain temperature it turns the pump on automatically. (A customer of mine has a pump but has to turn it on when they light the fire which, to me, seems a bit of a chore but then I'm lazy!)

PS - have you bled the radiators and presumably there are no parts of the pipework that go up and down without a vent on the up part? (For example if you've bent some pipe over a joist, the highest point will need to be vented.)

 

[Gray0689]

Hi there i have a problem with a new woodburning stove with backboiler. It is on a gravity fed system but it doesnt seem to be working as it should. It will boil and release itself up to the header tank then repeat.There was an air lock in the circuit but i let it off at the hot water cylindar and this seemed to let heat all way round. however the boiler still seems to be boiling up
would there be a problem in the circuit that it isnt flowing properly ie airlock or pipe run or would it need to be pumped as the circuit is quite long about 30m thereand back over 2 floors. If an airlock how do you flush out
any help grtefully recieved

30m is crazy for a gravity circuit
Who instaled it?

 

[Coly Loughlin]

did it myself after advice from a plumber mate.Its a big house selfbuild and the stove is at the opposite end of house from cylindar. The circuit is vented ot the header in the roofspace which is at the top of the run which is rising from the boiler. it then falls from here through the hw cylindar on the ist floor down to the ground floor and over to the boiler

 

[dontknowitall]

Presumably you've a permanent vent for the fire to prevent carbon monoxide poisoning? I think you're meant to be HETAS registered to install these. Sorry to be a doom monger but these health and safety and building regs people are everywhere !!

 

[Gray0689]

Don't need hetas as I think your in northern Ireland
But 30m is crazy never going to gravity that far
Dontknowitall was right you will need it pumped with a pipe stat to kick it on
But will have to watch it may start to pump over if vent to low

 

[dontknowitall]

Those bloomin' regulations and where they apply - always my weak spot!!

 

[buffy27]

30 meters is not ideal but will work as long as u have a gradual rise on the flow ..there would be considerable friction over such a long run and the pipework would need to be 1 "......u should really vent directly above the boiler and t off to the rads on the gravity loop to the coil ..as was stated already a pipe stat and pump pulling from the rads on the return pipe to the boiler...most important thing is to tie in the feed [cold feed to system] after the pump..1/2 inch will do fine ...

 

[Coly Loughlin]

there is 1 spot where it saddles another pipe so ill vent here and see if that helps. Failing that i think a pump may be the answer. Thanks all for the help ill let you know what happens.By the way i am in NI and the pipe is 28mm

 

[Gray0689]

You need to vent from highest point or water will take point of least resistence (ie do up vent at this point)
Put a pump on will be best option
I'm in NI to mate