Glow Worm 23C Boiler - Repeated Low Pressure

[Sibs]

The short version...
Glow Worm 23C boiler is repeatedly losing pressure (red warning light flashes, and pressure reading on the LED flashes). Opening the filling tap re-pressurises the system, but I have to do this repeatedly (pretty much every time I leave the heating / hot water unused for more than a couple of hours!)


The long version...
I've had problems with the boiler for a while. It's the same boiler that was here when I moved in, and it's always had occasional problems with low pressure, which tended to be resolved by opening the filling tap as instructed in the manual. However, the pressure reading never went very high even when the system was hot, and opening the filling tap pretty much always resulted in water leaking out from under the boiler (even when the boiler was indicating low pressure!)

Around Xmas time I had some more critical problems, the boiler wouldn't fire at all, the error light was constantly flashing. Luckily I have emergency boiler cover, and someone came, found it was the overheat sensor tripped, and reset. This happened again a few weeks later, and was reset again. The engineer set the central heating temperature on the boiler slightly lower (3/5 rather than 5/5) in the hope of stopping it happening again, and recommended a powerflush (because radiators were slightly cooler at the bottom than the top - but didn't seem to give any reasoning why this might help the overheating problem). I haven't had a powerflush, and it hasn't overheated again since...

The blue filling valve then broke off entirely (it's only clipped on by a few flimsy plastic bits), so the filling valve got replaced - while the engineer was doing this, he found the pressure sensor in the boiler wasn't working correctly, so this was also replaced. Engineer also explained this was probably why I was getting low pressure faults, but then water would leak out of the boiler when the filling tap was open. I thought, great, hopefully this will fix all my problems!

Unfortunately not. Now the system seems to work fine when the heating or hot water are on, but when nothing is on (ie. middle of the night or when I'm at work) the system loses pressure and I have to re-pressurise. This means I'm effectively having to re-pressurise by opening the filling tap twice a day! Every morning so I can have a hot shower, and every evening when I get in from work so I can have some central heating!

The pressure sensor appears to be working now. I've seen it go up to about 1.5, which I'd pretty much never seen before, and when it reports low pressure and I open the filling valve I don't immediately get water leaking out implying it's already correctly pressurised. Instead I hear water filling for a short period, and then the error clears, but it's very frustrating having to do this twice a day, and I'm concerned this implies a wider problem. I can't see any evidence of leaking radiators, or that the boiler is leaking...

Any advice on how to get to the root of the problem? Does anyone think the powerflush might be useful?

Thanks[/b]

 

[TCCHeating]

If you are losing pressure the water must be going somewhere. You either have a leak on the system or boiler. Or the water is being released by the prv. Have a look outside for a short bit of 15mm copper pipe and see if it us dripping

 

[Piers1989]

Firstly you need to identify where the problem is, is it the boiler or the system?

unless you can see clear signs of leaks from the boiler or the PRV pipe outside its not likely to be the boiler.

A simple test you could do to identify which is the issue:
1 - top the boiler and system up to a higher than normal pressure, 2.5 should be about right for the test.
2 - isolate the flow and return valves underneath the boiler, thus creating 2 separate circuits. the boiler being one and the system being the other.
3 - leave it for as long as it would usually take to lose pressure, so for example if its overnight leave it overnight. Don't use the boiler for this period of time so turn all heating controls off and don't use the hot water.
4 - check the pressure reading on the front of the boiler after stage 3. If the pressure on the boiler still reads 2.5 then you have confirmed that the boiler is holding its pressure. if this is the case slowly open the flow and return isolation valves and see if the pressure reading then drops. If it does the water in the boiler is replacing what has been lost on the system and it proves the leak and pressure loss is the system rather than the boiler.

I hope this helps

Piers

 

[Sibs]

Thanks for the replies, after a fair bit of searching found a slow leak around one of the radiator valves. The water was getting absorbed by a wooden rim around the base of the pipe, so only realised when I noticed the wood was slightly discoloured.

Tightened the nuts very slightly, and it appears to have stopped, and this evening when I got home from work the pressure was still OK, so am hopeful it's sorted!

Thanks again.