Automatic Air Vent Locations

Hi,
I have a new Grant Combi heating system in my bungalow. The 28mm flow and return pipework enter the loft region and splits into two 22mm heating circuits one for each half of the bungalow.

The 22mm pipework is insulated and sits directionly onto the joists and where a radiator is needed I drop down a pair of 10mm pipes insulated and buried in the wall. There will eventually be about 20 radiators.

I occurs to me that it could be difficult to get air out of the pipework when new raditors are fitted etc.

What would be the best way to get the air out of the system? I am able to fit shutoff valves and automatic air vents as required etc.

Also there is no inhibitor in the system yet since there is only one raditor at present. How long can I leave it like like before I need to add the inhibitor?

Regards
FarmerJo.

Think what will happen to t he air in the pipe and where it will accumulate. Radiators have vent points. F&E cistern auto vents. Auto air vents are ok but they tend to leak and also entrain air if ill located.

If this is installation will be using single panel type rads 11(K1) then 10mm feeds will be fine, if using larger doubles 21/22 (P+/K2) then I would recommend 15mm feeds.

Vents need to be at the highest point(s) of the system, if the backbone is in the attic with feeds dropping down then I would install 200>300mm verticals with manual vents on the flow and return at those highest point or where the pipe rises/drops to the boiler. Vents should only be needed when the system is filled and then rarely after that as long as the system isn't leaking (pressure test) and properly inhibited.

Add enough inhibitor as soon as the system is being used, in relation to the amount of water until system full completed, it's not expensive. Then I would drain, flush and re inhibit once the system is finished. Don't forget a filter.

As @Madrab says two verticals with manual air vents on them, automatic air vents sound, good but they are all cheap crap and leak for fun, they will give you nothing but bother, also if you use compression fittings on the manual air vents you have the perfect place for topping up or adding inhibitor

Also, if possible put the vent stems near to the trap hatch - makes it easier to bleed as you only need to get up and reach.

Many thanks for all the help, it is greatly appreciated.

Regarding the feeds into larger radiators. Is the 15mm pipe better because a 10mm would take too long or not be able to heat up a larger radiator?

Is it critical as to how close the vents are from the boiler or can they be anywhere which is a high point in the system? My current pipework uses 28mm flow and return pipes from the boiler which go up the wall and then across the utility room where they enter the main room and are each split (22/28/22 tees) into two separate circuits for each half of the bungalow. Would I be able to use a pair of 200/300mm uprights in each of the two 22mm circuits and fit manual air vents to each? Is a manual air vent a bit like the air vents on radiators that require a key to open and close?

Just one last thought on this if I may, you comments would be appreciated. Is there any benefit in adding a number of manual air vents. For example, One of the two flow/return heating circuits (which I will be working on first) will go around a large room with about 4 or 5 large radiators (need to work this about a bit better I know) in like a ring formation all around the outter edge of the room. At one corner a pair of pipes will also be fed off in to a bedroom and then finally into the bathroon. Was wondering if it made sense to add a pair or vents for the main room, the bedroom and then the bathroom etc. What do you think?

Is there any recommendation as to what a reasonable inhibitor is to use? There seem to be lots of types about?

I have a mag-one filter already fitted which I think can be used as a filling point for the inhibitor, would that sound feasable?

Sorry so many questions!

Regards
Farmer Jo

Yes I like the idea of the air vents being near the loft hatch. Is it OK to run a 15mm elbow from the top of a vent and length of 15mm pipe to get it near the hatch?

Regards
FarmerJo

FarmerJohn said:

Regarding the feeds into larger radiators. Is the 15mm pipe better because a 10mm would take too long or not be able to heat up a larger radiator?

Click to expand...

10mm is restrictive and the further away from the boiler, the lower the pump head, therefore the feeds nearer the pump will always get more flow so it would be a really lengthy balancing process. 15mm is less restrictive and therefore less effected and it will always heat up faster and 10mm is much more noticeable the larger the radiators get. To maximise the efficiency of any CH system, the target is to get it all to heat up at the same time to optimum temp as quickly as possible. You mention large radiators, if so really try to avoid 10mm, I know it is easy to work with but the system won't thank you for it.

The closer the vents are to the boiler then the easier it will be to bleed the air from the system, how many to use depends on the system size. Yes you could vent each zone separately. Don't elbow the uprights, keep them vertical. Yes the manual vents are pretty much like the vents on rads, they fit into compression fittings with a female end.

Inhibitor is a personal choice, I use Instinct (Scalemaster) but others use the other main brands of Sentinel/Fernox. I wouldn't recommend you use the non branded or cheap and cheerful.

Great advise and I will change to 15mm radiator pipework and have ordered some Fernox inhibitor and manual air vents.

I have one last question. Would it be OK to run 15mm pipe from the 22mm flow and return pipes so that I can get them close to the loft hatch. They could either be on a slight incline upwards or horizontal and then I could fit an elbow and raise them to a height of 200-300mm with manual air vents at the top etc? This would then be about 6M from the boiler. Alternatively part of the pipework already passes right by the loft hatch but this goes right around the room making the distance from the boiler 20-30M.

Regards
Farmer Jo

Minimise any dead legs off of the flow and returns, small verticals created as bleed points are fine but no long section of pipes. Verticals off of the pipes at the hatch should be ok, just means the system has further to push the air to get to the bleed points.

Putting the verticals at the point where the pipes rise into the attic just makes it much easier to capture the air and bleed, that's all.

Hi Madrab,

Now I am clear on exactly what needs to be done (just gotta do it now).

Many thanks for your help and patience.
Best Regards
Farmer Jo

No bother @FarmerJohn, happy to help. Any other issue then fire back on, plenty of experienced bods on here who are happy to help.

Just try to avoid the key board google warriors that think they can but then cause havoc.