Plumbing and central Heating

[bja]

Air in a sealed pressurised gas heating system,
Can anyone help,

I have a four year old house with gas heating, running off a potterton Suprima 50L.
The system is installed useung speedfit plastic pipeing,with 10mm supplys to each radiator, including thermostaic radiator valves, hot water is via a Heatrae Megaflo unit,
This is not the best designed or installed system and leaves a lot to be desired,
All the downstairs radiators are connected by dropdown pipework from upstairs,

The problem I have, there is a small radiator in the downstairs cloakroom, which is not used and remains turned off, most of the time,

Due to the main radiator in the lounge being a bit slow on occasions, and only seems to produce any meaningfull heat when some of the other rads start to close down on the TRVs,
I have rebalanced the system, but to no avail,

What I have discovered is that if I turn the cloakroom rad on, this is also very slow, just barely getting warm, however after a few miniutes there is a very notcieable surge of air into the rad, and immediately gets very hot,
as does the lounge rad,
If I then turn the small rad off, and leave it a few days, I get the same problem, reacurring, and have to turn the small rad on again to release the air in the pipework,

The system seems to be holding up on pressure, with no noticable drop,

The system was last drained down about three years ago,

Any ideas how the air is getting into the system,?

 

[ChrisR]

It could be corrosion gas collecting slowly. Add a Superconcentrate corrosion inhibitor via the filling loop.
Sometimes microbore systems are a bit restrictive and a 6 metre head pump helps (check yours is on full speed)

 

[bja]

Hi chrisR
Thanks for your reply and advice,
I did consider it might be gas forming in the system, but due to the lack of any iron in the system to corroad , i thought it unlikely,
There is a 50/60 pump fitted, running on middle speed, any higher tends to be noisy,
I take your point about adding an inhibitor, It may be the builder never added any in the first place, surprise, surprise,
I will give it a go,
many thanks
bja

 

[stumpynut]

[I did consider it might be gas forming in the system, but due to the lack of any iron in the system to corroad , i thought it unlikely,]
Whats your radiators made of then [/quote]

 

[bja]

stumpynut
me not thinking
thats what getting old does for you?

 

[gavinda]

wrong sort of plastic.

ive got a park home site giving me a lot of gas/ sludge probs.. unfortunatley i only realised 2 days after warranty ran out that they had been built with NON-BARRIER pipe. these also are sealed system prems. have someone check your pipes for a barrier.