air in central heating

[bobby_la_mesma]

Dear All

I have a worcester bosh 30CDI conventional boiler fitted into an open vented system. I have a "S" plan design which has the correct dose of Sentinel X100 in it.

I have found that if I set the boiler temperature control to above setting 5, that the system is noisy and constantly requires bleeding at the radiators. It is particulary noisy after the system has been off for over 24hrs. A glugging noise will come up through the motorised valve which controls the feed to the central heating pipes.

I have fitted manual air vents to the system at the highest points and have bled the system from these valves and radiators daily for the past 6 weeks. The system runs smoothly and quietly for a couple of days and then needs to be re-bled

The pipes are all free from blockages and I have a combined feed and expansion pipe. I have done the test at the cistern, with a glass of water and found that the system is not drawing air in through the expansion pipe. Due to the layout in my building the cistern is only about 50cm above the boiler, which does conform to the min height as published in the manual.

I know the simple answer is to not set the boiler temperature control above 5, however I just like to ask the experts who visit this site if they have any ideas which I could i try.


Many Thanks

Bob

 

[bobbo85]

Turn pump down sounds like its pumping over,is your pump on 3,if so just turn down to 2

 

[bobbo85]

the header tank is at the min but the expansion is going into the cold feed so its low and with a powerful p[ump it will be pushing up is the water warm in the tank,why not think about making it a sealed system,with a expansion vessel ,will stop any of this trouble if ,pump lowered doesnt

 

[bobby_la_mesma]

Thanks for the info

The pump is a Grundfos 15-60 and is already set to (1). I'll have a look at making it into a sealed system unless any other ideas come up from this post.

Bob

 

[bobbo85]

Bobby,it seems like its losing water somewere if your venting the rads ,so unless youve a leak under the floor and its ok when the heats on and doesnt start until the system is stone cold and the tank cant reblenish it quick enough it must be a expansion proplem

 

[bengasman]

Just convert to sealed. Why it is on an open vent is a complete mystery to me, as a sealed system has several major advantages. Unless you live in a massive detached house, I would rate it down to the minimum as well. 30 kW is enough to power almost 40 metres of radiator at the same time, do you have 20 rooms that all have a 6’ radiator?