Manifold system air lock likelihood?

[Oz07]

We've set up all the pipework for the manifold on the heating. Spoke to speed fit they say fitting manifold upside down is fine you just swap the air valve and bleed off valve to upper and lower bars, then turn them the right way round.

 

My pipework is going all up into ceiling void then back down to rad's. Property is a bungalow with direct runs to each rad.

What is the likelihood of air becoming trapped in the system? I'm fine bleeding air off from radiators and from the manifold but am I risking any air getting trapped up top or does the pressure in the system push it round? Do i need to take any precautions?

 

Air doesn't get trapped in a garden hose when you turn it on and it goes up and down so I think i'm over worrying but I don't understand the physics or whatever is involved.

[JFDIY]

The hose doesn't get air locked because the flow rate is sufficient enough to drive the air out.

 

On a radiator circuit the flow will be a fair bit lower and could be insufficient to displace the air, it will take the easiest route and might mean that one of your rads will not be easy to bleed the air from. 

 

That said you can probably force the bleeding of it by closing off all other circuits and running each one at a time until the air is out.

 

Personally I think I'd look at fitting the manifold at the highest point, even if in the roof space, then have an automatic vents on the manifolds and remote mount the pump if needs be for space constraints?

[Oz07]

The pump is with the combi. As had been said I can force the air through by closing off all but one circuit. Pressure would be mains pressure so same as a garden hose would be. Does this mean I'd be able to push any lock through?

 

Unfortunately can't mount the manifold higher than pipework I'd be going up through airtight layer onto unheated loft. Pita. 

[Nickfromwales]

You can purge each run, one at a time, with cold mains to get rid of all the air, but even with inhibitor air ( gas given off by the rads slowly corroding ) will collect at the high point and eventually cause another airlock. 
Putting AAV’s at the high point is an option, or T’s with drop pipes and manual vent caps will also work ( if you cannot go any higher than the high point ). 
The CH pump on / prior to the manifold will not push the air through if it’s a full floor height of head up and back down again. ?

[Triassic]

1 hour ago, Nickfromwales said:

The CH pump on / prior to the manifold will not push the air through if it’s a full floor height of head up and back down again. ?

Could you position the pump on the highest manifold so the head would reduced to a minimum, say 100mm, thus reducing the likelihood of an air lock. An AVV positioned on this manifold would also help.

[Dreadnaught]

I'm following this discussion with interest as I am planning a bungalow too and had intended to run much of my plumbing through the open-web joists in the ceiling/roof, like @Oz07.

 

(In my case I have a flat roof.)

In my case, I am not intending to have any radiators, just UFH. Would this mean I aim unlikely to have a problem I wonder?

 

Edited January 22, 2020 by Dreadnaught

[Nickfromwales]

2 minutes ago, Triassic said:

Could you position the pump on the highest manifold so the head would reduced to a minimum, say 100mm, thus reducing the likelihood of an air lock. An AVV positioned on this manifold would also help.

 

5 hours ago, Oz07 said:

 

My pipework is going all up into ceiling void then back down to rad's.

If the manifold has to go low then no, but if it can go much higher up the wall then yes. 
 

Honest answer is.... why not just drill holes through the wall? Or do the pipes run through attic / ceiling  space and then down? 
This will work with a purge at the commissioning stage, but recurring air locks will be an issue over time.  

[Nickfromwales]

5 minutes ago, Dreadnaught said:

I'm following this discussion with interest as I am planning a bungalow too and had intended to run much of my plumbing through the open-web joists in the ceiling/roof, like @Oz07.

 

(In my case I have a flat roof.)

In my case, I am not intending to have any radiators, just UFH. Would this mean I aim unlikely to have a problem I wonder?

 

No. You’ll just have AAV’s up high to deal with that. 
Do you still have to do a flat roof? Or will you have an attic / other accessible void above?

[Dreadnaught]

Thanks @Nickfromwales.

 

1 minute ago, Nickfromwales said:

Do you still have to do a flat roof? Or will you have an attic / other accessible void above?

 

Sadly the gods of planning have decreed a fully-flat roof (with greenery on top). No choice. I will however have lots of 300mm open-web joists just begging for pipe runs.

[Nickfromwales]

Dependant upon where your airtight layer is of course  
Pipe work shouldn’t be outside that really, even more so for heating primary’s. 

[Dreadnaught]

3 minutes ago, Nickfromwales said:

Dependant upon where your airtight layer is of course  

 

Good point. Airtightness lawyer at ceiling level (Pro Clima Intello Plus under WarmCel, just like MBC usually do).

Was intending to seal the pipes as the passed through the membrane. Warmcel is pretty airtight too on its own.

But you raise a good challenge to my thoughts.

[Nickfromwales]

My pleasure lol. 

[Dreadnaught]

It will only be cold and hot water, no heating pipes, and only to supply one en-suite.

I guess I will need a handful of Pro Clima seal grommets for pipe feed-throughs.

 

(I am also wondering whether to run a gas pipe through the joists too, but that's another story).

[Oz07]

9 hours ago, Nickfromwales said:

You can purge each run, one at a time, with cold mains to get rid of all the air, but even with inhibitor air ( gas given off by the rads slowly corroding ) will collect at the high point and eventually cause another airlock. 
Putting AAV’s at the high point is an option, or T’s with drop pipes and manual vent caps will also work ( if you cannot go any higher than the high point ). 
The CH pump on / prior to the manifold will not push the air through if it’s a full floor height of head up and back down again. ?

Cheers Nick. I can't have manifold higher as will then be through my air tightness layer. Would it be possible to periodically purge air locks in each circuit if it became an issue? Ie turn all circuits off then push it through? How often is air likely to accumulate in the pipework rather than rad and cause this issue?

I was trying to eliminate most of the joins in the building by having it done this way. 

[Nickfromwales]

If it’s sealed and pressurised then it would be periodic rather than frequent, but the risk of it being more problematic would be real.

If you purge each loop one at a time it may push through, but that would be down to trial and error. If you’re putting an automatic bypass in ( so all rads can have TRV’s ) then fortify that with a gate valve so you can close that off 100% for future purging. You’ll need 100% of the pump flow to do the purge effectively, so you deffo don’t want the bypass operating whilst doing so. Closing the bypass / using it as isolation should be avoided. 

[Oz07]

Cheers Nick thanks again. Will have towel rad without trvs so will act as bypass. Plumber seems to think we will be able to push the air round like you say. Got pipes connected up to manifold today think I will swap the clips for screw on ones. Get the pipes off the board then bin the airfelt.