How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Andrew Smith Your Own Question
Andrew Smith
Andrew Smith, Engineer
Category: UK Plumbing
Satisfied Customers: 3629
Experience:  Domestic Gas, Commercial Gas, LPG, Unvented Hot Water, Part P Electrical, Commercial Catering
Type Your UK Plumbing Question Here...
Andrew Smith is online now
A new question is answered every 9 seconds

Can I link a back boiler heating system to my existing hot

This answer was rated:

Can I link a back boiler heating system to my existing hot water radiator system to get an increased heat output to the radiator and underfloor systems?


Will I need to add another expansion pipe for the wood burner circulation or will the existing system one suffice?


I am looking at fitting gate valves to the wood burner flow & return pipes in order to be able to shut that circuit down when fire is not in use.

Hi my name is XXXXX XXXXX lets see if we can get you sorted in the shortest possible time.
Yes you can, but extra controls would be needed.
You cannot put two valves on the wood burner, it is an explosive risk if they were closed.
You can put one on the return to stop the flow of water but leave the vent open in case the heat becomes uncontrolled.
Customer: replied 3 years ago.

Customer: replied 3 years ago.

Hi Andrew

thanks for reply.


You say extra controls needed, what do you suggest,

currently apart from circulating pumps for the radiators and underfloor heating the only other control is a temperature control on the hot flow pipe linked to the underfloor heating pump which turns the pump off if the inlet temp. is too high.


I take your point on explosive risk if both flow and return are fitted with valves. It was only to stop the flow if the wood burner was not in use so one will be fine. Does this assume I have a separate expansion tank for the wood burner?


Because our chalet bungalow does not have a loft as such, space and height is limited for tanks etc. which is why I want to use the existing expansion tank and pipe on the AGA circuit for both when the wood burner and an additional radiator are linked in.



You can run from the same tank if you wish, but you will need a separate expansion pipe directly from the flow of the wood burner.
There should be a thermostat on the flow pipe (like a cylinder thermostat) from the wood burner that could open a 2 port valve on the return, to create circulation only when the heat source is on, this valve would then run a small pump on that circuit to feed the heating.
The flow pipe must be one continuous pipe up and over the tank, no valves!
You can then tee off this pipe before the tank through the pump and into your heating circuit via a non-return valve.
There MUST be somewhere for the heat to go, so no thermostats on radiators with at least the same output as the wood burner (eg 12kW)
Customer: replied 3 years ago.

Thanks Andrew, one final question.


If the existing pump on my aga system is powerful enough to circulate both systems. On the wood burner side if I tee off the expansion pipe from the wood burner and just fit the non-return valve before connecting into the heating circuit ,would this be o.k ?

Yes, you would soon know if it was not powerful enough if you were not getting complete circulation.
You may need a valve on the return from the Aga to throttle down and balance them
Andrew Smith and other UK Plumbing Specialists are ready to help you