DIY Doctor UK DIY Forums

I have a glowworm 30 Ci combi boiler which has been great since it was installed.
but yesterday the hot water stopped running hot and is permanently cold.
The boiler pressure has stayed at 1.3 bar and the radiators heat up if i turn the heating on, its just when any hot tap is turned on the boiler does not fire up.
My girlfriend said that she had a shower this morning and it was hot all the time (about 15 mins) but when i tried (about three hours later) the basin taps or the bath or the shower i could get no hot water at all.


any help greatly appreciated.

thanks.

To the best of my knowledge, combi boilers need a minimum rising-main pressure, so that, when a tap is opened, pressure drops, and trips a pressure-switch in the combi, which then fires-up the boiler. If at peak water-use periods in your district, mains-pressure is deficient, this switch will be unable to sense the opening of a tap. Check your boiler pressure requirements, then ask your water board if they are providing its req. pressure at all times of day. Mornings are high demand, with bathing/breakfast/washing-machines/dishwashers taxing the water supply.

Thanks for the reply.

There has been no hot water at all no matter what we do, at any time of day or night

The pressure is still ok and the heating comes on fine, just no hot water.

anybody had similar, or know what prob might be???

thanks in advance.

The rising- main pressure may still have dropped, enough to cause the problem;-- check with the Water Board, and quote the date your hot supply stopped heating.

If the pressure is remaining OK, the chances are it's the boiler's flow switch not picking up hot water flow, a blocked domestic hot water heat exhanger or jammed/blocked diverter valve. Easy to check these - first run a hot tap and see if the boiler lights up. If it does, check the flow going to the radiators (far left pipe out of the bottom) to see if it's getting hot. If it does, the fault is either the diverter valve or diverter motor. If it doesn't, but the boiler is on, then it's likely to be a blocked heat exchanger. If the boiler doesn't fire at all, then the flow switch is the most likely culprit!

Hope this helps! Paul

Thank you for the reply.

The boiler and heating are working fine.
The diverter valve is also clicking into place.(so i took this to be working).
Ive taken out the flow sensor and had a look.

There was a bit of muck inside the chamber and the magnet was covered in debris.
I cleaned it all up including the magnet and the paddle now rotates quite freely. This was replaced and the hot water came on again for about 30 mins. (just enough time for a bath). Then it stopped again, On further examination i noticed that water was travelling up inside the flow switch and into the electrical connection at the top. (I noticed a slight crack insde the plastic chamber when i took it apart for the second time).
I think that a new flow sensor will be ordered anyone recommend any parts sites or should i go for a copy part seeing as though it is only a plastic tube witha plastic paddle inside.

thanks again......

Manufacturer's no for flow switch is 2000801910. They're not cheap mind, so be sure it's that bit that's faulty! Would love to give you a few part sites/no's to try, but would get wiped by the doc so can't!
:cry: Hope it's working soon!

Paul

Thank you for the reply,

I was 99.99% happy that it was the flow sensor as the terminals were wet and it had a slight crack internally. i did get a new part for about £50.00 + delivery, it came the next day and it was clear that it has been slightly modified (redesigned) as the vertical size is different, and it has been reinforced with extra fins where the old one cracked. It slotted in no problem and 'hey presto' HOT water whenever i need it....

It was worth the £50.00 for peace at home.

Thanks again for your help.

where is the flow switch located please?