"Gas" in Radiators

[GraRob]

Some advice please;

I've a Potterton Promax Fsb boiler and an open vented system which is suffering from excessive gas in 2 towel radiators.

I've established that the system needs drained, flushed & refilled with inhibitor, as the Magnaclean filter was quite heavily contaminated with black gunge, and the water in the system is pretty black. It was drained and treated 2 years ago.

The 2 radiators in question need frequent bleeding, however all over radiators seem fine. Presumably as their neer the top of the system etc.

I've fitted auto-bleed valves, however, they dont seem to be working and the radiators still have gas trapped at the top. I'm assuming this is because the small hole in the auto bleed valves have possibly clogged up.

I've assumed the gas is from the corrosion products in the system and should get better when the system is flushed & re-treated.

So (and sorry for the long post) the CH pump makes a bit of a "whooshing" noise when it first starts up, which I assume is the gas in the system.

However, I'm wondering if the pump may be actually failing, and is drawing in air when it starts up. Theres no leaks visible.

I've also checked the pump isn't over pumping into the header tank, and I've also run it at different speeds.

Also the pump is noisier (I think) but may be imagining it.

Lastly (honest), the boiler very occasionally goes into overheat trip (red light flashing) and I usually need to waiting for 15 minutes or so until it will reset.

So, I'm wondering if all of these symptoms point to a knackered CH pump?

I'd welcome any advise of suggestions.

Thank you

 

[ianmcd]

How do you know that it is gas and not just air ?

 

[GraRob]

How do you know that it is gas and not just air ?

I dont, and I've purposely used the term gas, as air is also a "gas".

 

[Madrab]

I dont, and I've purposely used the term gas, as air is also a "gas

Why??

If it is air then there is probably a leak in the system, if it is gas then in central heating terms then it's a completely different issue that your system has. So we purposely use each term to mean a different thing

 

[ScottishGasMan]

Air is gas. Were just used to using the term gas as the explosive invisible hydrocarbon thingie.

1st thing, really easy test. Find out if its Air or Hydrogen in the radiator. Get something smallish the shape of a test tube, or in worst case an old 300ml bottle (just be a little carefull if using something like a bottle) and next time you bleed the radiator, hold the tube upside down over the air release hole on the bleed point as you bleed it, then quickly take a lighter to the open end of the tube after turning it up the way, hydrogen will burn very quicky with a distinct pop noise, air will do nothing.

 

[GraRob]

Air is gas. Were just used to using the term gas as the explosive invisible hydrocarbon thingie.

1st thing, really easy test. Find out if its Air or Hydrogen in the radiator. Get something smallish the shape of a test tube, or in worst case an old 300ml bottle (just be a little carefull if using something like a bottle) and next time you bleed the radiator, hold the tube upside down over the air release hole on the bleed point as you bleed it, then quickly take a lighter to the open end of the tube after turning it up the way, hydrogen will burn very quicky with a distinct pop noise, air will do nothing.

At last a helpful reply. Much appreciated, I'll do that tomorrow.

Thank you.

 

[Gorners]

Air is gas. Were just used to using the term gas as the explosive invisible hydrocarbon thingie.

Not quite. ‘Gas’ in the form of stuff that provides fuel for your boiler is short for ‘gasoline’. ‘Gas’ in the chemical sense is an element that is not liquid or solid, like air. It’s also used to describe someone that won’t shut the hell up.

Yes we’re getting pedantic but in a plumbing forum, even a DIY one, you’re going to have to expect confused replies if you’re going to mix up these terms.

 

[ScottishGasMan]

Not quite. ‘Gas’ in the form of stuff that provides fuel for your boiler is short for ‘gasoline’. ‘Gas’ in the chemical sense is an element that is not liquid or solid, like air. It’s also used to describe someone that won’t shut the hell up.

Not to be too pedantic. But gasoline is liquid petrol, nothing to do with the term "Gas" in UK pluming and heating. In the UK Industry gas literaly means Gas (as opposed to solid or liquid) So its quite correct to state that there is gas in a radiator until its tested and proven as to what gas or mixture there of is in the radiator

 

[Gorners]

Not correct I’m afraid, gas as in gasoline is flammable, in fact it’s only the vapour off gasoline which is flammable, the liquid itself is not, hence why our gas needs to be treated with such care.

 

[ScottishGasMan]

Not correct I’m afraid, gas as in gasoline is flammable, in fact it’s only the vapour off gasoline which is flammable, the liquid itself is not, hence why our gas needs to be treated with such care.

That may be, but gas as in gasoline has got F*ck all to do with the gas that (is obviously not gasoline) that is fuel for your boiler.

 

[Gorners]

 

[GraRob]

Deary me, I've no idea why posts in this section gets so animated & people getting uptight & angry. It's supposed to be a help forum.

I only popped on to get some advice, not to start another flame war on here.

I'm quite comfortable using the term gas, and as a charted engineer, (in case you think I'm a dope) I use the collective term "gas" to describe Nitrogen, Hydrogen, Oxygen, etc, every day.

https://en.m.wikipedia.org/wiki/Gas

Anyway, back to my issue, I'll discover today whether its Hydrogen gas in the system or Air.

Scottish Gas Man - Thanks, much appreciated, & for the record, my boiler is "gas" fired, and most certainly isn't "gasoline" or petrol as it's called in the UK....

 

[Gorners]

It was just a joke mate. I’m with you. Hope you get it sorted.

 

[Madrab]

Well just to add another pedantic layer to it, if the term 'gas' is used to describe something then in boiler terms it could multiple meanings, therefore it is non specific and can lead to confusion, which it has. Of course it is grammatically correct but that isn't the point, the word 'gas' isn't normally used to describe air in the context of radiators we would always use the word 'gas' to describe the presence of hydrogen and not air.

If the word 'air' is used then that is specific & everyone knows what is being discussed, therefore no confusion.

 

[Lower]

Have you tried bleeding the pump to see if you can get any air out and cure the 'whoosh' noise? There's a big screw in the centre of the pump which is the bleed screw for the pump.

Sounds like you have a leak somewhere in the system that is drawing in air. With no pumping over, inhibitor in the system and all radiators bled, you shouldn't be getting enough corrosion going on to fill the tops of your radiators.