Working on heating side of system with an unvented cylinder, no G3?

[Fogster74]

Hi all,

I'm a competent DIYer with an engineering background and am active in Heritage Buildings. I never touch anything I'm not allowed to albeit I've worked on the wet side of my own heating on the central heating circuit before when I had a combi - balancing rads, add a Fernox TF1, washing through the system and running new rads from the manifold, and understand the nuances of s-type wiring etc.

I've recently moved into a large old property and the prior owners have massively underspecced radiators in a number of rooms (I've run heat loss calcs and they're about 20% of what's required in one room - a stupid bloody designer spring rad with an output of 1,200 BTU in an attic room with a heat loss of in excess of 6,000 BTU).

I would be delighted to drain down the system and put a "real" radiator in - but can I legally do so on an unvented system? And if so, is there anything specific I need to do or know?

I've tried finding a local G3 plumber but they seem to be impossible to source.

Thanks so much!

 

[Ben-gee]

Yes you can. G3 is only with regards to the unvented cylinder.
However if you have an unvented cylinder and don’t know exactly what you’re looking at, I strongly advise that you get this serviced and checked over - especially in light of the obvious mistake you have found, there may be potentially dangerous mistakes on the install that you are unaware of.
Regarding your radiator swap- just drain down to below the attic rad you are replacing (no need for a full drain down).
Alter pipework for new rad and top up system, don’t forget inhibitor, then vent as usual.