hot water problem

i have a baxi solo boiler, lately the boiler wud switch on for 2 mins and go off then the pilot light wud try igniting but to no hope. plumber came round said it was the gas valve on boiler changed that and heating seems fine. all heaters warm up and the house heats up but there is no hot water in taps. called plumber round agn and he said my mid position zone valve was faulty got that changed no luck still no different any help. i tried pluging the imersion heater on its own in a socket and it warms the water for the taps no probs. any ideas plumb phone is switched off cant get hold of him.
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Make sure that the thermostat strapped to the hot tank hasn't accidentally been turned down.
Also, there may be an adjustable gate valve in one of the pipes going to the indirect coil in the hot cylinder (to balance hot water vs heating when both are on). Make sure that this hasn't been turned right off - which would stop any flow going to the coil.
Roger
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The following items could cause hot water not to be heated in no particular order.
1. Programmer electrical fault 2. Programmer programming fault (i.e. you haven't turned the hot water on) 3. Cylinder thermostat fault 4. Wiring design fault (not if it has worked before and not been modified since). 5. Wiring fault 6. Zone valve failure 7. Pump failure (depending on the design, you may find that the heating works slightly with gravity circulation, masking the problem). Alternatively, there may be two pumps, one for heating, one for water. 8. Manual hot water circuit valve turned off. 9. Bypass open too much, giving easier path for circulating water than the cylinder coil. 10. Failed automatic bypass valve.
Don't disregard the possibility of zone valve failure. The "bathtub" reliability curve means that newly fitted components must be regarded with extra suspicion.
Christian.
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