Megaflo System - Pressure.

[Syd98]

Hi there, I have a megaflo unvented system, which is 15years old. over the years it as been fine, with a few issues, I.e new boiler 5 years ago, new filling loop, and a replaced expansion vessel, which at the same time 2 years ago the 3 bar pressure relief (RWC) cartridge was changed.
However..
New pressure problem. The system as worked fine all summer on hot water, but the missus decided she was cold the other night (?) and switched the heating on, I didn't think much of this, but when outside I noticed that the discharge pipe was wet.
Went up stairs and felt the tundish, also wet?
Pressure when cold was just below 1 bar, so topped back up to one bar, checked the vessel and pressure on the air side at the Schrader valve.
I'm thinking could be a faulty seat / seal on the 3bar pressure relief (RWC) cartridge?
Any one answer why it only happens when H/W and C/H on?
Thanks in advance
Syd

 

[hertsboilers]

The discharge might be from the cylinder, not from your heating system.

Megaflo is famous on their internal air gap failure. Google "megaflo internal air gap" you will know the answer.

 

[Syd98]

Ok. I will give this a go at the weekend (only time I have the chance), if I remember this may have been done once before, I have a couple of questions, What causes the air gap to go?
How long with the lowest hot tap open and me holding the tpr valve for the air gap to replenish, if I remember it takes a while to empty?
Thanks for the reply. appreciated.