boiler losing pressure - ch pipes not leaking.

[Chuck]

Still it was surprising to see water literally spurting out of the condensate pipe,

By 'spurting' I asssume you mean the condensate siphon emptying and releasing a cupfull of condensate every few minutes?

My interpretation of the evidence presented so far is that as the system heats up, the pressure rises to the point (P_hot) that something acts as a pressure relief valve. (This could be the 'official' PRV or if could be a cracked joint somewhere, with the HEX as a likely suspect.) The system will then operate happily like this (at P_hot) until it is allowed to cool at which point it will be apparent that water has been lost (pressure drops to P_low).

This would be confirmed if the next time the system heats up the pressure starts at P_low, rises to P_hot again and then drops back down to P_low when cold.

As others have already suggested, an empty/faulty expansion vessel and the PRV are the most common cause of such symptoms.

 

[bright spark]

If you're gonna pressure test boiler only do it t 4 bar. That's d max it'll take according t Quinta Pro brochure. Especially if it's still under warranty.
These exchangers are known t pop their clogs from time to time.
Listen t Shaun, he knows his stuff

 

[dan_the_plumber]

press shraeder valve pin on expensive vessel. Water coming out? Replace Eco vessel.
Test air pressure in expansion vessel...Repressurise as needed.
Has PRV been blowing off? Leave a party balloon over discharge pipe over few days to find out. Replace as needed PRV.
Repressurise boiler...does pressure gauge shoot straight up? No expansion space in vessel.
Is customer Repressurising boiler? What are that setting it to? Fiddlers
Large amount of corrosion in system? Nitrogen produced, leaves system via auto air vent. Pressure drops. Flush and add inhibitor

Dan

 

[king of pipes]

As above the first thing to check is the expansion vessel, on a system like this it will need to be drained to check the internal pressure i would think the charge pressure would measure between 1-2 bar ? depending on meters of head , on a system that size the vessel size would need to be around 36 litres it maybe the one fitted is to small it should not be fitted laying on its side eithier and i would expect it to be red or grey in colour not blue as these ade normally used for potable water ? , all the heating pipework should be insulated and its not a good idea to have a calor gas bottle stored internally in there , check for a gas saftey certificate on the property , check the benchmark in the boiler manual ? something does not look right here. Regards kop.

 

[darriusdax]

As above the first thing to check is the expansion vessel, on a system like this it will need to be drained to check the internal pressure i would think the charge pressure would measure between 1-2 bar ? depending on meters of head , on a system that size the vessel size would need to be around 36 litres it maybe the one fitted is to small it should not be fitted laying on its side eithier and i would expect it to be red or grey in colour not blue as these ade normally used for potable water ? , all the heating pipework should be insulated and its not a good idea to have a calor gas bottle stored internally in there , check for a gas saftey certificate on the property , check the benchmark in the boiler manual ? something does not look right here. Regards kop.

View attachment 30007

aye. the blue expansion is indeed on the cold mains for some reason, the red expansion vessel (50 litre) is out of shot to the right of the picture. we will deffo check this when we go back.
it is one of these awkward ones where the guy has spent a fortune with his boiler repair company and they say that there is no fault in the boiler set up, but from what he has said.. they did not check the expansion vessel, nor the internal coil, nor the hex... they isolated the boiler and tested its pressure cold.. ie not running. that is useless.
we were only brought in to gas test the flow and return within the house - look for a pipe leak...
thanks kop

 

[dan_the_plumber]

Priority checks:
Leaking rad valves
Expansion vessel
Leak on boiler
PRV
Leaking pipe work (usually compression joints)
Nitrogen leaving system
Air ingress

That's it I think

 

[Stoney Ground]

The 2 FI-C elbows on that cylinder look like they have had leaks around them.

If they leak at 70c, your gas test won't detect it if tested cold.

 

[king of pipes]

Leak on the primary coil in the hot water cylinder is another thing worth checking cheers kop

 

[dan_the_plumber]

Leak on the primary coil in the hot water cylinder is another thing worth checking cheers kop

Good call...any tips as to how to do that please?

 

[king of pipes]

Pump some food colouring in the heating system via the filling loop if its shows up in the hotwater then bingo flush out do repairs . cheers kop