Stanley twin burner cooker.The cooker works ok the central heating works ok. BUT when the change over switch is put to hot water on we do not get hot water??????? Have fitted new stat fitted but problem not fixed

Combi-boiler-turn hot water tap on/off and the heating stops for ...

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Combi-boiler-turn hot water tap on/off and the heating stops for 20secs ... hot watertakes priority over central heating so when you run the hot tap, heating is ... Yeah onmy worcester combi there is a diverter valve - it feeds either the heating or ...

My central heating works but I have no hot water - 24'7 ...

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Diverter valves switch heat between the hot water and the central heating. When youturn your hot tap on, the diverter valve temporarily shuts off the water supply ...

Does your boiler keep switching itself off? Here's why ...

www.dhs-uk.com/does-your-boiler-keep-switching-itself-off-heres-why/

Jul 7, 2015 - ... Bathroom Suites, - Showers, - Wet Rooms, - Taps and Accessories, Information and ... Low water pressure can cause your boiler to turn itself off. ... boiler is not turning off, you aren't getting the amount of hot water you require. ... If there is air in your central heating system, then your boiler may shut down.

The water isn't maintained hot (unless the central heating is on) in a combi boiler. you will, therefore have to turn the water on, which activates the burner. The burner will then have to heat up the heat-exchanger which then supplies the hot water through cold pipes. Once the pipes are warm, you will receive hot water.

Sounds like you have a valve sticking or a safety switch causing it to shut down. Does this unit exhaust first then the burner ignites that might be your issue

If when you turn power off you wait a while it is probably not the central system coming on. You have a triple aquastat that maintains a temperature level needed to provide hot water. but you are not getting the thermostat to operate the central heating. The thermostat is a switch that operates by temperature. if you have tried raising the thermostat and the system did nor kick in. try jumping the thermostat terminals in the aquastat . if that works then the problem is either in the thermostat or the wiring to the thermostat. also with a electrical tester." while the thermostat is jumped" test the c1 and c2 terminals to see if power is going to the circulator. If not then you need a new aquastat. if you have power and the pump is not moving water replace it.

over heat limit stat on central heating circuit ? if hot water is ok and hot to temp when run for 5 minutes the expansion vessel is doing its job.remember hot water is the maximum demand for any boiler ,,heating is secondry?once you establish hot water at maximum rate then the only real problem is on you demand for heating??

you dont say but i presume you have an early model 1996-2000. these had the most horrid burners ever. its wasnt untill later when the ecoflam burners were used that problems that you describe were elimanated as a standard every day problem. better still was the much later 800 series ecoflam twin burn as fitted in the rayburn 800 series this is the aga company that closed down the alpha and now produce the same cooker with better burners.
www.topoftherangeltd.co.uk who can suply used and new burners for you

my stanley oil fired range fires up then cuts out

if it is wick burner it will not work. if it is a single pj a gas oil burner can be fitted that will work. if a twin pj then it will work if you turn up the fuel pressure to 12 bar

There are 2 Heat Exchangers and 2 Water Pumps on a Combi, at least the one I had when I lived in the UK did.
There is a Thermal Cut Out on both. They look like a Disc, that is Soldered [with provision for connecting the wiring] onto the Hot Water Outlet from the Exchanger to the Pump, to Supply either the Domestic Hot Water, or on the other Exchanger, Central Heating.
If 1 of these fails, the System will start up and when the temp reaches a certain point will trip out the Burner, and continue to Run the Pump until the Temperature drops, and then Stop.
The type I had, had Pumps with a Black front facind nut, this unscrews anti clockwise to release that center, that could be pulled slightly, and used as a Key to turn the Pump Impeller, in the event that lack of use would make it stick, when powered up.
There shouId be a Diagram, inside of the Front Panel, that shows the layout for the whole Internal Water flow, Pipes, Pumps, Safety devices etc. I hope this has helped you.
Regards,DT
Nevada, USA

I'm from Oklahoma, & we have'nt seen that type of heating system!