Glowworm betacom 30: Pressure and exp vessel probs..still

[bster]

I need some help! I've got a betacom with a split exp vessel, due to the limit space and time I have to work on the boiler I fitted an external expansion vessel. The vessel is located on the the second floor of a three storey house and the boiler is on the first/ground floor.

Im still having problems with the boiler hitting 4bar (on the boilers gauge).

Ever since fitting the boiler the pressure was always on the high side when hot (2.5-2.8bar) so I guess the original exp vessel (8lt/0.5bar)was under pressurised or sized for the system. The new vessel is a 12 lt and I've tried it a 1bar and .8 bar. But the tenant keeps phoning to say its back over 3bar!

The filling loop is disconnected also so no let by.

Last time I was at the house (sat gone)I had the heating running on max for 2 hrs (9 rad 3 storey system) and the pressure remained stable at just over 2bar, and thought it was sorted.

Btw- the original split expansion vessel is still connected, should I cap it off?

So can someone give me guidance on the correct method of setting the pressure in the vessel to suit the system?

Thanks

 

[picasso]

you might have a passing plate heat exchanger, cant see it being any thing else if you have isolated the filling loop.

 

[bster]

Not 100% sure but I think the pressure is only rising when system is hot. So I don't think it's a split plate hex. But I'll check for sure on weekend. Thanks

 

[picasso]

As the house is 3 storeys high the static pressure will be about 1 bar,so to get some pressure in the top rads the pressure should be about 1.5 bar cold at the boiler, as the ex vessel is on the second floor you should set the precharge at about 1.2 bar, it shouldent go above 2 bar with a 12 ltr vessel.

 

[bster]

Right I'll try 1.2bar on weekend, I need to set this when the vessel is drained of system water yes?

Thanks and I'll repost on the results of my 5th visit to the property in 5 weeks!

 

[picasso]

Right I'll try 1.2bar on weekend, I need to set this when the vessel is drained of system water yes?

indeed