Advice - No hot water flow on-demand

[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.

So in short, low pressure in hot water, high pressure in CH.

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

 

[Andy™]

pressure increasing slowing will be the fill loop valve not closing properly

your hot water problem might be cold water feed into boiler not fully open

 

[Sharpend]

As Andy has said, the filling loop hasn't been closed properly, this would in its self sort hot water problem, the pressure is too high so do not operate heating until you remove the over pressure, use jug under bleed nipple and release water whilst heating is off. 

 

[Andy™]

most boilers dont have a high pressure switch, only low pressure. the blow off should stop the pressure going too high (usually set at 3 bar)

 

[Sharpend]

Yes quite correct. However some boilers need the blow off replacing after it blows, so just trying to save expense. 

 

[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.  Here 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!

 

[Steve12345]

Reposting this reply as the images didn't work first time....

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.  Here 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?  Photo of dial

Thanks again!

 

[roys]

To me it looks the bottom dial is a pressure gauge on the out side of a pressure reducing valve.

 

[Rob_the_rich]

it does look like a pressure reducing valve. I wouldn't remove it without having your plumber look at it and test the system prior to moving the boiler.

Remember that pressure and flow rates are two different things. You seem to have high pressure but low flow. If you remove the valve, a pressure spike could damage the boiler.

The liff device is a scale inhibitor, which might be full of scale. Or there could be a partially blocked inlet filter on the boiler.

If it is working ok for now, then leave it alone.

 

[Andy™]

the hot water flow is always less than the cold, the boiler simply cannot heat the water quick enough to have a flow rate same as the cold feed

 

[Sidewinder]

The bottom valve is a PRV, however, I am guessing that this picture is taken with no flow, i.e. no taps open.

Thus you have going on for 6 bar of static pressure on the PRV output as this is where the gauge is connected on these PRV's I use lots of them.

That is unless the gauge is goosed.

These valves come preset to 3 bar.

There is a straight slot for a screwdriver in the top of the cone to the left of the pressure switch in the picture posted.

Find out which line this is in and draw water down it, turn the pressure down all the way when there is water flowing, then stop the flow and see what the pressure rises to.

IF, it returns to 6 bar the PRV is goosed, change it.

If it doesn't, then turn the pressure up slowly until you hit 3 bar and try the system again.

IF, there is an intact plastic film over the adjuster, then the PRV is goosed, change it.

I don't like the Caleffi PRV's I've had too many issues, noisy, leaks, failures etc.

So, I now exclusively use Honeywell.

 

[leesparkykent]

The bottom valve is a PRV, however, I am guessing that this picture is taken with no flow, i.e. no taps open.

Thus you have going on for 6 bar of static pressure on the PRV output as this is where the gauge is connected on these PRV's I use lots of them.

That is unless the gauge is goosed.

These valves come preset to 3 bar.

There is a straight slot for a screwdriver in the top of the cone to the left of the pressure switch in the picture posted.

Find out which line this is in and draw water down it, turn the pressure down all the way when there is water flowing, then stop the flow and see what the pressure rises to.

IF, it returns to 6 bar the PRV is goosed, change it.

If it doesn't, then turn the pressure up slowly until you hit 3 bar and try the system again.

IF, there is an intact plastic film over the adjuster, then the PRV is goosed, change it.

I don't like the Caleffi PRV's I've had too many issues, noisy, leaks, failures etc.

So, I now exclusively use Honeywell.

Isn't a PRV a pressure relief valve not a pressure reducing valve which is what the one in the pic is? 

 

[Sidewinder]

Isn't a PRV a pressure relief valve not a pressure reducing valve which is what the one in the pic is? 

Well I use the term PRV to mean Pressure Reducing Valve with regard to these devices.

This is one of the issues with this medium of communication.

Unfortunately there is not a defined standard abbreviation for either device.

 

[Steve12345]

Thanks again.  That picture was taken with all taps open and water flowing.  The reading on the gauge never seems to change regardless of what I do so I suspect it may well be bust.

Time for a professional to give everything the once over me thinks

Cheers