Pressure problem in condensing combi

[robbo32]

I hope someone can give me a hand! I've got a Baxi 130 HE Combi Condensing boiler. A local plumber fitted the filling loop and repressurised it last week (it had dropped below 1 bar) to about 1.5 bar.

A day later the pressure was up to over 3 bar. The pressure release valve was open and merrily trickling water outside. I bled some radiators to take the pressure back down to 1.5 but the next day the same problem, the pressure was back over 3 bar and the prv was open. Plumber that repressurised the boiler doesn't want to know - said it was OK when he left it.

The filling loop is definitely in a closed position. Any ideas what could be causing the pressure build-up? Could the filling loop be leaking or is there something more sinister?

Help appreciated!

 

[tonyn]

remove the filling loop see if it hapens again

 

[NickH]

It sounds like the valve may be letting by. Once the system has been pressurised the loop should be disconnected. If the valve is letting by you will see it leaking.

BTW sounds like a s**t of a plumber, sorry mate were not all like that.

 

[Mike Jackson]

There's a couple of possible problems.

1. Filling loop letting by - disconnect it and see if the pressure still goes up.

2. Expansion vessel lost it's charge pressure - keep an eye on the pressure gauge when the heating comes on. It should rise by a maximum of around .5 bar. If it keeps going up try recharging the pressure vessel.

3. Worst case scenario, water to water heat exchanger has failed and is topping the CH up continually - after checking previous 2 shut off main cold feed into boiler and see what happens.

Mike

 

[robbo32]

Thanks for your help guys. I'll try disconnecting the filling loop for starters and see how that goes.

Cheers

 

[Bobdisk]

Hi, I know this is an old thread, but its nearest my problems. I have a Baxi HE130 that has done the same thing, lost almost all pressure in the CH, although it kept working ok. Dont know how long it took to loose pressure, but CH has worked hard over the last couple of cold weeks after a holiday was Heathrowed. I left it off for 8 hours, could not find any leaks anywhere at all. I first measured the pressure (with a tyre pressure guage!!) in the pressure vessel, it was 0.5 bar. I then recharged using the loop to 1.5 bar, (centre of the guages green area). The vessel now reads 1.65 bar. It ran ok for 15 mins, the pressure shot up to 3 bar! So I let it down, its now running ok at 2 bar. Any ideas why pressure should drop, with no leaks? Are the results from the vessel normal? If it has to be repressurised, how is this done?

 

[mikegas]

you need to measure the pressure in the vessel with the system empty and vessel disconnected or leave boiler drain off open. You repressurise it the same way

 

[Toddyplumb]

When you checked the pressure on the expansion vessel did any water come out ?

 

[Bobdisk]

Dont think there was any water, I pushed the tyre pressure guage on quickly, waited a couple of seconds (its an electronic guage) and took it off quickly so there was no time for any to escape if there was any. After re-pressurising the water, the system varies between 1.2bar cold and 2.8 hot. I will re-charge the vessel at the weekend. I take it that I only have to let enough water out to allow the pressure to go down to zero, its not neccessary to drain completely ? and it ok to use a car tyre pump ?

 

[stevetheplumber]

yes ok to use car pump leave the prv open when you pump of youll be pumping into a sealed system

 

[Bobdisk]

Thanks. I will look for water in the vessel, before doing it, and post results, Saturday or Sunday.

 

[Bobdisk]

Tested the vessel, no water coming out of the valve, so I let enough water out to reduce the system pressure to zero, then pumped the vessel up to 1 bar. Then re-pressurised the system to 1.5 bar (centre of the green area on the boilers guage). After a couple of days use, the system pressure has settled to 1.2 bar cold and 2.6 bar hot, how does that sound? (There is a second, more accurate pressure guage where I can see it, as the boiler is in the attic) I suppose I should put in more rust inhibitor, as letting out 5 or so litres will have significantly diluted what is there??