cannot get hotwater

[worrier]

hi
i cannot get the boiler to fire up when i only want hot water its ok with the heating. ive changed the 2 motorised valves, the timer switch and the pump. i have put a new thermostat on the hot water tank and even tried bridging the connection the main fuse was blown, the only way i can get hot water is to open motorised valve manually ..which is costing a bomb in gas bills, its not the new switch as i have bypassed it but still will not fire ..any ideas ...its an old system i have Baxi boiler

yours scottish gas best customer phil

 

[doitall]

and even tried bridging the connection the main fuse was blown,

yours scottish gas best customer phil

Alway thought fuses were to protect something if there was a fault

 

[DP]

Combi boiler with motorised valves and cylinder? Not unusual but rare. Very few installers will do it that way.

Would have been cheaper to get an engineer in to repair the boiler.

 

[ChrisR]

CHeck the connection between the programmer and the cylinder stat, and the cylinder stat and the motorised valve.

Wiring diagram probably this:
http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.2 S Plan.pdf

Are you sure you have a combi (fires up when you turn a tap on)?