Plumber powerflushed through the CH system (removed lots of gunk) and it now works fine....
- however HW now does not!
HW pipes in cupboard get very hot - and leading up to the HW cylinder they start hot when we first switch HW on...but then as they reach the cylinder they irregularly turn hot / tepid / cold / tepid again.
Have checked thermostat on side of cylinder. Boiler is up to max and is firing fine. Have CH turned off to encourage HW to work. Have released any air from sump radiator and valve on hot water pipe leading into the cylinder.....
At a total loss as to what is going wrong inside the cylinder.
Some plumber!!! He just seems to be making things worse.
Re. the possible airlock in the cylinder coil. Do you know where the Feed & Expansion tank for your CH system is? If you have an indirect system as it seems from your posts, there should be two cold water storage tanks, possibly in the loft. The bigger one is to replace water in your cylinder when drawn from hot taps and the smaller one is the Feed & Expansion tank (or Central Heating Top-up Tank).
If you can easily access the smaller tank, fit a hosepipe onto the vent pipe that goes over the top of the tank with the other end attached to a mains water fed cold water tank. Then get an assistant to gradually open the cold tap whilst you look inside the tank. If any air bubbles come up through the bottom keep the cold tap running until they stop. This may get the hot water working. You may then have to bleed your radiators in turn to get the CH going again.
Good luck. By the way, I'm not a plumber, just a DIY person.
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