no hot water/ boiler cutting out, but heating working fine
Is the boiler only cutting out when you are trying to heat the hot water only or does it also cut out when you have the central heating on?
They recommended "acid power wash of entire system" quoting about £800.00 because thought system probably "sludged up"
If it was sludged up, the central heating would not work properly.
They said they checked boiler, system, 3 way valve, thermostat and pump and everything works fine
They would say that - they want you to spend £800.
Do you live in a hard water area?
If yes; how old is the hot water cylinder?
When you are calling for hot water only, is the pipe between the 3 way valve and the boiler warm?
Some simple system checks
Turn the power off (this resets the mid position valve)
Set your CH and HW timers to off.
Turn CH and HW thermostats down.
Turn power on (relight boiler if necessary)
Turn HW on at timer
Turn HW thermostat up to max.
The boiler should light and the pipe from 3 -way valve to HW cylinder get hot.
Check the return pipe from the HW cylinder is hot.
Turn CH on at timer
Turn CH stat up to max.
The boiler should continue to run.
You should hear the 3-way valve move to mid position (get help if necessary) and the pipe from 3-way valve to rad should get hot.
Turn the HW thermostat down.
The valve should move over to CH only position and the boiler continue to run.
Turn HW stat up to max so the valve returns to mid position
The boiler should stay alight and both pipes from 3-way valve get hot
Turn HW OFF at timer
The valve should go to CH only position.
Just the CH pipe from 3-way valve will be hot.
If the Return pipe from the HW cylinder is cold when the feed from the 3-port valve to the cylinder is hot, you have a blockage in the cylinder coil. But if it is hot, or slightly cooler than the feed, the coil in the cylinder is furred up so none of the heat is reaching the water.
