Unvented System Pressure

[Syd98]

Seems and odd question but thought i'd ask.
Local heating engineer tells me no problems, but here's my question.
System is unvented, Megalfo (10yrs old), 4yr old WorsBosch boiler. Had a problem with pressure creeping up. eventually put to bed by changing the filling loop.
When fitted system pressure was relieved and expansion valve pressure checked and found to be good t 0.5 bar as recommended. System refilled pressurized to 1 bar and air bleed off with AAV etc.
Heating and hot water works fine no problems.
Now the question.
The system pressure gauge only shows 1 bar and when system on and hot only shows 1.2bar? The system when good before always went from 1 cold to 2 bar hot?
Any ideas why the system works and only a pressure increase of 0.2bar?
No passing of water into tundish on system either.
Am I worrying about nowt or could there be another problem.

 

[Dan Robinson]

Life's too short. Move on.

 

[Agile]

You may be confusing the boiler pressure with the pressure in the Megaflo!

It all seems normal and correct!

Tony

 

[Syd98]

I mean system pressure, which as always run from 1,bar cold to 2 bar hot.. But now it's 1 bar cold 1.2 bar hot.. Only asked for a logical answer as to what this pressure differential as changed. I am a engineer so understand how these systems are supposed to work

 

[dcawkwell]

I mean system pressure, which as always run from 1,bar cold to 2 bar hot.. But now it's 1 bar cold 1.2 bar hot.. Only asked for a logical answer as to what this pressure differential as changed. I am a engineer so understand how these systems are supposed to work

This is correct operation what you had before was caused by insufficient air charge in the expansion vessel. The expansion vessel should absorb most of the expansion with very little pressure increase.