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Oct 16, 2019
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Member Type
DIY or Homeowner
Hi there,

I have a condensing oil boiler running an open vented 3 zone CH system.
Z1 - Hot water tank.
Z2 - 7 radiators. (Grd Flr front).
Z3 - 4 radiators. (Grd Flr rear).
Some of my radiators are showing signs of trapped air on a regular basis.

I need to vent 2 rads (but sometimes all 4) in Z3 at least once a week since last autumn.
These 2 rads are closest to the boiler & always affected every time while the other 2 rarely.
I have a similar problem, but very rarely, in the 2 closest rads to the boiler in Z2 - maybe once a month.

Normal daily routine is as follows:-
Z1 switched on for 30mins by timer every morning.
Z3 is then switched on manually for up to 60mins when required - most days - weather dependent.
Z2 is then switched on manually for up to 60mins when required - most days - weather dependent.
Zones 2 & 3 are then run manually in the evenings as required.
I never run more than one zone at a time.

Anybody have any idea on where the air is coming from?
Do I have a leak in the system? - pipes are all under concrete floors with no visual signs of a leak.
Is the system drawing in air? - during the Z1 water heating session & then distributing it into Z3?

I have belatedly locked off the CH tank ballcock & set up a measuring device in the tank to check for water loss and will monitor this for a while.

Any suggestions?

c0c0nut
 

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