Advice - No hot water flow

[steve12345]

About me: non-professional, average DIY guy. new to this forum.
My boiler: Glowworm Flexicom24cx combi


Long story short, yesterday I set about removing a sink and radiator from a bathroom that's soon to be renovated. I turned off the mains water at the stop-cock, as well as ensuring the heating wouldn't kick in.
Completed the job, turned stop-cock tap back on and checked for leaks – all good!
I noticed the boiler was reporting it had very low pressure so I topped it up to 1 bar with the filling loop hose.


End result:
Central heating – fires up and radiators work fine
Cold taps – good pressure works fine
Hot taps – very low pressure, flow quickly falls to a dribble then stop. Boiler doesn’t fire up on demand as it should.


I then noticed that the boiler pressure was increasing ever so slowly, 1.1 bar, 1.5, 2.0, and now settled on 3.5 bar after a few hours.




I suspect what's happened is I had the sink taps (hot & cold) open when I turned off the mains water suppy and stupidly didn’t turn the boiler off at the mains. So it might have been trying to supply hot water when there was no cold coming in and this has broken something.
No error messages or funny smells though.
The increasing pressure in the CH system might be down to either me opening up the stop-cock more than it was originally, or possibly not turning off the filling loop hose fully.




Can anyone offer any advice or opinions as to what might be the cause or things to check for?


So far I'm guessing...
a) burnt out pump for the on-demand hot water system
b) accidentally fiddled with a valve setting on a pipe into the boiler when using the filling hose
c) incorrectly drained and refilled the system resulting in trapped air or broken sensors




Many thanks, and yes I shouldn't be allowed near any plumbing again!
Steve

 

[jtsplumbing]

Have you turned of both the filling loop valves under the boiler if not hot water will not work

 

[Alex Knight]

Bet the filling valves havent shut off properly, boiler shouldn't be getting to 3.5 bar though...

 

[Stoney Ground]

It will equalise with the mains pressure, PRV should be cleaning the patio nicely

 

[jonnyswamp]

Filling valves not shut off properly causing over pressure and maybe the cold isolation valve under the boiler is only slightly open, as in when no hot tap opened for a while the pressure would build up enough to give you a short burst when the hot is opened again, but not enough to give any real flow, until just a dribble comes out

 

[steve12345]

Thanks for all your replies and tips, it's now better but not perfect.

* I reduced the high boiler pressure back down to 1.5 bar by bleeding a radiator

* Checked the filling loop taps, one was very stiff to turn which made me think it was closed when it was not. This is now shut off properly resulting in a stable boiler pressure and less water being stolen from the hot water supply. Not sure why both need to be off though, surely just one closed tap is enough?

* The inline tap on the cold supply for the DHW was not fully open, doing this has now increased the flow enough for the boiler to recognise a demand and to start heating

* The hot flow is still poor compared to cold, but sort of working ok for now. I've only just moved in to the house so can't remember what the flow was like before, it might have been the same. Plan is to redesign the kitchen soon anyway so will need to reposition the boiler and get a professional to recheck all this.

One final thing. I'm wondering if the cold supply into the boiler is still restricted in some way, resulting in a lower than expected hot water flow. Below is a photo of the pipes, there are two devices and a tap attached to cold supply, each of which looks old and worn. Is it worth me trying to replace them or can I just swap this whole length out for a straight piece of copper?
Should the tap be fully open or half way?
What does the 'dial' at the bottom do and should I be checking it?

Thanks again!

 

[jtsplumbing]

Just looking at the poor condition of fittings , bottom one with is a pressure reducing valve, to boiler, next is a stopcock that could be faulty , next is a blue anti scale cartridge that could be blocked, and as your in a hard water area Proberly find that the plate heat exchanger is also scaled any one of these will restrict flow through boiler

 

[Riley]

Whilst it's been covered flexicoms turn off the water to the taps when you're filling the heating side. I'd suggest your valve is stuck minutely open and the grey plastic tap head is slipping