I have Baxi Boiler (model unknown at this precise moment in time) which British Gas have fixed up to a seperate control panel (see image - not our actual panel, image from Google!). enter image description here

The problem is that even with the Central Heating set to off, when we want hot water, either via the timer or setting it manually to "on", all the radiators heat up.

Is an easy to fix problem? Has the control panel been set up incorrectly, or is this a problem with the boiler?

  • This might help you identify your boiler and find the manual: baxi.co.uk/products/combi_boilers.htm . If I may make a wild guess, either its plumbed wrong or the boiler doesn't support having two zones. It sees a need for hot water and pushes hot water out to both the radiators and the faucet when it should only be pushing water to one. Are there two outputs from the boiler? One output with a T fitting to both the faucets and radiators?
    – Freiheit
    Commented Aug 21, 2012 at 15:10
  • Is that to say then that having the control panel for heatin and water is pointless as they do the same thing? Commented Aug 21, 2012 at 15:15
  • Sort of. As @bcworkz says below, it depends on your installation. Does the heater itself have one output for hot water or two?
    – Freiheit
    Commented Aug 21, 2012 at 21:49

2 Answers 2


It could be:

  • an electronic problem, does the radiator heats up when you don't "ask" for hot water (with the winter setting)
  • a deficient 3-way valve, you should have two distinct pipes for the hot water output, and they are wired on a 3-way valve that distributes hot water in the two circuits. If the valve does not work, then you may have what you experience, or you may need the winter setting to be on in order to have hot water, or you may not have hot water at all. This is a rather common problem.
  • a plumbing problem: someone forgot that there is a need for two distinct circuit. This problem is highly unlikely if the plumbing has been done by a pro.

It's extremely difficult to answer you questions accurately without examining the installation. It could be as simple as replacing a defective solenoid valve, or even just correcting the wiring. If your system is actually a single zone setup, it would still be possible to modify it to separate the domestic water from the radiators by installing some solenoid valves and some basic control wiring so the valves open and close appropriately based on the various operating conditions.

Heating your house in the summer every time you need hot water out of a tap is very inefficient. It's worth getting this sorted, a correctly operating system should pay for the modifications in a few years of saved energy costs.

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