wood backboiler (water not getting hot enough)

[gra26264]

Hi,
I have just fitted a woodburner (20 kw) with back boiler(12kw) on an existing system,pump was knackered so replaced,when the pump is turned on manually,when hot water circuit has reached 45 degrees, the hot water seems to be pumped too quickly through the boiler and the temperature drops away,radiators not getting very hot,is it possible to restrict the flow from the boiler to heat the water for longer,

 

[REDSAW]

welcome to the forum

 

[oldplumber]

Have a look at the instructions first and I hate to say this, if your not a plumber/heating engineer get one in who knows what they are doing, solid fuel heating can be inherently dangerous as it is an uncontrolled heat source and the idea that you manually turn on the pump when water temp reaches 45 degrees is not what I would expect to have to do for this sort of system. omho but given what you have said thus far, things dont seem quite right.

 

[themorgatron]

Have you tried turning the pump speed down. It's normally better to turn the speed down on a solid fuel back boiler.

 

[gra26264]

pump is at the lowest setting,switching is now though a stat on hot water return pipe,when pump kicks in boiler loses heat very quickly as if flow is too fast to build up heat

 

[oldplumber]

boiler will lose heat quickly as its taking in cold, so i would think it will take a while to bring back the temp as the system settles again. you could check that the rads have their lockshields turn down to ensure the system is balanced properly to allow your boiler to keep up with the flowrate.

 

[ecowarm]

Make sure you use dry seasoned hard wood as green wood has a low heat output and will also tar up the boiler and flue.
It does make a big difference.
You could possibly only getting 3-4kw out with the wrong fuel.

 

[justlead1]

Hi. As eco says. When pulling heat off for rads, you need to burn at a rate and calorific value that at least matches the demand. Not unusual with solid fuel as client want to save money by reducing fuel spend. Stick a nob of coal on, open the bottom and away you go. Good Luck

 

[gra26264]

Hi, using fairly well seasoned wood,,still think flowrate could be a problem,it is an old system that used to be fed by an open fireplace with a back boiler,that worked fine until boiler rotted through and had to replace,rads seemto have valve at one end.pipe fit straight to rad at other end,still tinkering with rads to decrease flow rate,one rad valve stuck fully open at present

update,
after regulating the rads,but with i rad stuck fully open we have been able to maintain a much higher temperature thoughout the system,going to try to deal with that next and see what happens,