Cant have hot water and central heating at the same time

Is there anything I can do before calling in a heating engineer? For some reason I can't have the hot water on and the central heating at the same time. I always used to be able to, though it did mean the radiators didnt get quite as hot until the water heating was off.
 
I have a worcester bosch condensing boiler

you got a combi boiler
 

no mate condensing boiler

I don't know anything about boilers but we had the opposite problem last summer - couldn't have hot water without the heating trying to come on. Had the heating guy out and he said some valve or other between the boiler and the pump was knackered, he changed that out and it was okay afterwards.
 
Sorry I can't be more specific, I know bugger all about plumbing but it might be a DIY job if you know what you're doing I suppose.
 

not sure then m8. 
 
iv got a problem with the combi there a nytmare. 
 
example if you were to run the hot water in the kitchen and in a shower or w.e then it would turn cold. heating could be on and the suddenly turns of. 

do you have a traditional hot water storage tank? 
 
If so then you almost certainly will have a motorised valve:
 
Input from the boiler, then accroding to what you have asked and the thermostats (room & tank) then the water will go out to heating, water or both via the three port valve. 
 
Sounds to me like the motorised valve is broken. If you can find it - its often beside the pump, then there is usually a manual overide/lockoff which you can activate to put it in the mid position which is heating&water
 
 

to add, depending on the age and mak/model of the valve the head is often replaceable on its own, meaning that you can change that part (which is most likely to be at fault) without draining down the heating circuit.

Yeah i have a hot water tank that has the 2 motorised valves connected to it. The valves are both ok at the min as can have one running ok sepearately. Its when I have the hot water heating on and the central heating tries to kick in it won't actually heat the radiators.  The valve does turn on, have checked that. 

Hmm, how are you checking that the valve is working?
 
If there is heat at the input pipe to the valve, if the valve is actually working then you should near instantly feel the heat on the output pipe that feeds the rads, no heat and the head of the valve may turn but the body of it may be stuck.

 
could be the time control. As a 2 port zone valve is basically a switch and it works when you ask for heating alone and hot water alone so the clock is the most likely culprit. Unless you are confident using a voltage tester and following a wiring diagramme then i would call an engineer in.
 
In the mean time you should be able to open the valve with the manual lever.

snoopy101


 
could be the time control. As a 2 port zone valve is basically a switch and it works when you ask for heating alone and hot water alone so the clock is the most likely culprit. Unless you are confident using a voltage tester and following a wiring diagramme then i would call an engineer in.

In the mean time you should be able to open the valve with the manual lever.

 
Good call, it could well be the controls too. 
 
I am still not sure how he 'tested' the valve though, if he seen it moving then I still think its the valve, if it doesnt move at all then it could be either the valve or the control and would need diagnosis with a meter and diagram as you say. 
 
I recently saved myself the cost of a new 3-port valve with the use of the multimeter - one of the microswitches in the board was faulty. An £80 valve fixed with an £0.98 part out of RS!!

The valve for the central heating has a light on it that comes on when it turns on. the heat gets to radiators shortly after the valve for the hot water turns off tho.
 
will call an enginneer, im prob not describing the problem well enough 

Do your valves look something like this?
 

The valve for the hot water is a danfold and the one for the central heating is a sauter detatch.
 
the sauter was put on last year and he had to bleed the system before doing that. might it be some sort of balance issue?

The valve for the hot water is a danfold and the one for the central heating is a sauter detatch.
 
the sauter was put on last year and he had to bleed the system before doing that. might it be some sort of balance issue?

Sorry, my link didnt take:
 
http://www.screwfix.com/c...ynnDDRw2vT!-1495008777
 
is it like one of those roughly?

the one for the hot water is a plain white one.  the one for the central heating is one of these 
 
http://solarproducts.ie/sauter-motorised-valve/

Hot water always gets priority on any system and as you have a s plan heating system it may be that the stat for the cylinder isn't telling it that its hot and continues to give cylinder heat instead of closing off and going to CH or your valve on the heating side is gobed up and or your whole ch side is mucky and its easter for water to go hw

Thats not really what I mean. I mean that when im heating water i usually can have the central heating on at the same time but lately the central heating hasn't kicked in until the hour the water heating is on for is over. i only heat the water for an hr a day as there is only me in the house and I dont need any more than that

engineer time, let us know out of interest what the problem turns out to be.