Megaflow over-full - need to reduce pressure

[RobAnybody]

First EVER post - so please play nicely. Professionally installed Megaflo 250l unvented system 12 months ago in conjunction with loft conversion. Gauge (on red expansion tank) used to read around 1 bar. Suddenly, and with no alterations to the system (no changes whatsoever) it's circa 2.8 bar COLD and reads OVER 3 bar when hot. More than coincidentally, the TPR is letting water in / through the tundish, causing an intermittent drip from the overflow - I guess that's its job! Just in case it was anything to do with the dreaded bubble, I followed the instructions and re-bubbled (air-volume re-charge) but made no difference.
Can't reach the installer - and HeatRae Sadia say it's nothing to do with them insofar as they consider it to be a heating system/boiler problem and not the Megaflo per se, despite the drip drip drip in to the tundish.
Local engineer ('phone conversation only) suggests that I should relieve the pressure from 3 bar 'back' to 1 bar by simply letting water out of one of the furthest away downstairs rads. Can it REALLY be this simple? Question is (also) if the gauge has been reading 1 bar for 12 months and it's JUST changed to 3 bar, if we've not done anything to the system, what has caused the change? Surely the same problem will simply repeat itself. Is it SAFE to just 'let' some water from a downstairs rad to solve the problem? Any and all CONSTRUCTIVE comments gratefully received.

 

[powell30]

Perfectly safe to reduce the pressure via a rad bleed valve. As to why it has shot up it's possible the iso valve is letting by raising the water pressure or the expanssion vessel may have lost it's charge or may need replacing.

Get a G3 competant engineer to check it over

 

[RobAnybody]

Perfectly safe to reduce the pressure via a rad bleed valve. As to why it has shot up it's possible the iso valve is letting by raising the water pressure or the expanssion vessel may have lost it's charge or may need replacing.

Get a G3 competant engineer to check it over

Dear powell30,
Thank you very much indeed for the swift response. Now to prove my ignorance yet further.... the expansion vessel charge - that's the so-called 'bubble' - right? When I follow the instructions for "air volume re-charge" writ large on the Megaflo itself, this is nothing to do with the charge within the expansion bottle? Sorry to appear / confirm thick!

 

[powell30]

The bubble inside the megaflo is to allow pottable hot water to expand. The external expansion vessell is for system water that is pumped around the boiler/rads/tank.

It's this that needs a recharge.......use a foot pump and recharge it (drain system water first) if it holds job done, if not replace vessel

 

[RobAnybody]

The bubble inside the megaflo is to allow pottable hot water to expand. The external expansion vessell is for system water that is pumped around the boiler/rads/tank.

It's this that needs a recharge.......use a foot pump and recharge it (drain system water first) if it holds job done, if not replace vessel

Again, thank you - could not possibly have asked for a speedier or indeed more helpful response - v grateful indeed