New Radiators Not Working

[John.g]

May be worth checking the pump settings as well, if settable, as it may be set to some very low variable setting as suggested above.

 

[hometech]

The new rads get hot when all, the other rads are closed off. Could there still be air in the main circuit in this instance?

it is a certain bet..unlike the idea of balancing a variable pump system as the answer...

 

[hometech]

May be worth checking the pump settings as well, if settable, as it may be set to some very low variable setting as suggested above.

its a new boiler,,,,ErP...what is wrong with people....he cannot alter the pump speed

 

[hometech]

The new rads get hot when all, the other rads are closed off. Could there still be air in the main circuit in this instance?

Now I'm not a qualified heating engineer with an NVQ but I do hold an MEng in electronics and I'm certified engineer through the engineering council so understand that what I say cannot possibly compete with an NVQ plumber but this is based on my personal experience in my home.
Large pipe run, air trapped. Cannot remove the air despite placing air vents in the pipework. My symptoms were radiators would work then they would not and they would alternate back and forth.
I had increased the pressure but the losses meant it could never reach the offending section of air. As I operate with low temperature heating, I decided to add an air vent in the offending section in the form of a large radiator. These videos of the commissioning of the large radiator might SOUND familiar to you. Video1 is radiator getting its first fill from the main 22mm primary pipe where I suspected the air lock was. Video 2 is opening the lockshield. Long story short, air gone, noise gone, system fine. 4 separate heating engineers had no idea what was happening because "they had never seen that before" LOL
In conversation with a retired plumber (some would say heating engineer) who specialised on schools and churches heating systems told me that it often took twice as long as the install job to remove the trapped air.

 

[Scott_D]

its a new boiler,,,,ErP...what is wrong with people....he cannot alter the pump speed

There has been no mention of the make/model of boiler or if the pump is even inside it.

 

[John.g]

There has been no mention of the make/model of boiler or if the pump is even inside it.

Both were/are system boilers so presume pump is internal?.

 

[Chuck]

Any air in the system is always going to be at atmospheric pressure i.e. 1 bar.

You are mistaken. It'll be at the same pressure as the water that surrounds it. In an unvented system, which is what I believe we are discussing, it'll be somewhere in the range 2–3bar (absolute). For for a vented system, the pressure is only 'atmospheric pressure i.e. 1 bar' at the top, i.e. the location of the free liquid surface in the expansion tank.

 

[Scott_D]

Both were/are system boilers so presume pump is internal?.

Lots of people confuse the boiler types. Some boilers allow you to adjust the pump settings in the installer menus.

 

[hometech]

There has been no mention of the make/model of boiler or if the pump is even inside it.

If the boiler is less than 5 years old

You are mistaken. It'll be at the same pressure as the water that surrounds it. In an unvented system, which is what I believe we are discussing, it'll be somewhere in the range 2–3bar (absolute). For for a vented system, the pressure is only 'atmospheric pressure i.e. 1 bar' at the top, i.e. the location of the free liquid surface in the expansion tank.

so as you increase the water pressure you increase the air pressure making air impossible to remove from any system ever. Thanks for that. Just out of interest, how does that work with boyle's law? I've added a BBC bitezie for reference Volume and pressure in gases – the gas laws - Temperature and gas calculations - GCSE Physics (Single Science) Revision - BBC Bitesize - https://www.bbc.co.uk/bitesize/guides/zc4xsbk/revision/3

 

[Chuck]

If the boiler is less than 5 years old

so as you increase the water pressure you increase the air pressure making air impossible to remove from any system ever. Thanks for that. Just out of interest, how does that work with boyle's law? I've added a BBC bitezie for reference

You don't seem to understand the difference between 'pressure', which does not affect the motion of bubbles, and 'pressure gradients', which do. In this context, Boyle's law tells you that as the pressure in the system water is increased the bubbles of trapped air shrink in volume.

 

[hometech]

You don't seem to understand the difference between 'pressure', which does not affect the motion of bubbles, and 'pressure gradients', which do. In this context, Boyle's law tells you that as the pressure in the system water is increased the bubbles of trapped air shrink in volume.

solubility of air in water...increase pressure..increase temperature...both increase solubility. So upping the pressure and temperature removes air locks as it dissolves the air in water. It's also known as Henry's law of solubility. You over think things bro

 

[Chuck]

I really shouldn't rise to the bait of a straw man argument but anyway. . .

solubility of air in water...increase pressure..increase temperature...both increase solubility.

Wrong again. In the temperature range relevant to heating systems, the solubility of air in water decreases with increasing temperature.

So upping the pressure and temperature removes air locks as it dissolves the air in water.

If a system is air-locked at its normal operating temperature and pressure then the scope for increasing the pressure or reducing the temperature is too limited for this to be a viable way to fix the problem.

 

[SimonG]

solubility of air in water...increase pressure..increase temperature...both increase solubility. So upping the pressure and temperature removes air locks as it dissolves the air in water. It's also known as Henry's law of solubility. You over think things bro

That must be the biggest load of crap I've heard on here.