No hot water but pump and are pipes hot

[u664541]

Hi, 1st post so any (good) advise welcome!
2 weeks ago I drained my central heating down (glo-worm wall mounted boiler by the way), all OK but today found there to be no, or very little, hot water. The boiler fires up and the pump and pipes going in and out of the hot water cylinder are hot but there's hardly any hot water. The boiler has been on for 5 hours now!! Have resorted to the emersion heater for the short time....
I have checked for any taps that might have been left on accidentally!
Any ideas? Thanks in advance.

 

[Ed Sirett]

I presume that you refilled the heating after you drained it down ?!?

You have probably got an airlock preventing the primary water from going through the coil to heat the HW cylinder.

Have a look to see if there are any bleed points, especially in the airing cupboard.

Switch the pump to a higher setting (temporarily) if it is not on the maximum setting already and the controls to HW only.

Sometimes the air can be got out via the screw cap at the back of the pump.

 

[u664541]

....that in the last week (drained system down 2 weeks ago) the pump has been making a dull humming noise. I plan to drain system down again tomorrow as it was filled with Fernox de-scaler and sludge breaker-downer. Previously I had thought the pump, which is at least 8 years old, might be a problem as the rads at the bottom of the house never got too hot, whereby the upstairs ones were piping.

Will also test the impeller on the pump.

Thanks for the info so far!