next to the copper cylinder attached to two different water pipes in my airing cupboard are two boxes which have electric wires comming out of them. what are these boxes for and why do they make a load clicking/grinding noise when we turn up our therosat for the central heating.also is this why our central heating takes about 15 mins to come on. thanks sian & tom

sian & Tom, March 2007

they are motorised valves they open and shut. when you turn on your heating stat it sends a signal to your valve, pump, and boiler to come on so your valve will open to let the water through. one is for heating and one for hot water.if they are grinding they may be worn.
but unuseal. you can take the top of them and have a look, its only a motor and some mech inside. get someone to operate the stat and watch whats grinding inside.

hi-spec plumbing, March 2007