Boiler noise, help needed

[stuwho]

Hi,

I have an Isofast condens boiler the problem I have is that when you turn the hot water on there is a hammering noise from the boiler. It lasts for a fair bit I usually turn the hot water off and it stops shortly after.

I'm not sure if this is related but the pressure is a bit low it was 1.3 bar now sitting at 1.4 and when I turned the blue knob below to top the pressure up it just poured out of an outlet next to it.
Not sure if that it is meant to have a cap on there as it does have a thread on it or if that it is a proper outlet.

Thanks in advance,
Stuart

 

[MIGEM]

Check that the pump is turning. Unscrew the plug from the front of the pump and check that it rotates when the boiler is heating your water. Not sure why you would have topped the boiler up if it was at 1.3 bar, but are you sure you didnt turn a blue cap on the pressure relief valve?

 

[stuwho]

Cheers MIGEM I'll check the pump when I get home

According to the instructions on the boiler the pressure should be 1.5 and the turning of the blue cap will top it up.

I know it wasn't much below but thought I might as well try it.

 

[MIGEM]

Topping the boiler up 0.2 bar, by only just cracking open the filling tap, more often than not, just fills it with aerated water and can sometimes add to a problem of trapped air.
Your filling loop is integral and shouldnt be discharging.

 

[joe-90]

Topping the boiler up 0.2 bar, by only just cracking open the filling tap, more often than not, just fills it with aerated water

If you don't mind me asking - where does the air come from to aerate the water?

 

[MIGEM]

Topping the boiler up 0.2 bar, by only just cracking open the filling tap, more often than not, just fills it with aerated water

If you don't mind me asking - where does the air come from to aerate the water?

Oxygen in the water.

 

[joe-90]

You mean like when you unscrew a bottle of lemonade?

 

[MIGEM]

That will be added carbon dioxide, would it not?

 

[joe-90]

It would but if the principle is not the same - then what is it?

 

[MIGEM]

Carbon dioxide is added and held at a higher pressure than the liquid. Take the top off....the gas escapes.
Water and oxygen being at the same pressure are equal until forced. Henrys Law.
No?

 

[joe-90]

Then why do they fill the system with air as you first stated?

 

[MIGEM]

They dont intentionally, but cracking the tap open 'Just' forces the water through at pressure and creates bubbles; the bubbles that fish would breathe. Not that there would be fish in his boiler. Ever filled a glass of cloudy water, only for it to settle clear? Bubbles.

 

[joe-90]

If I go to my kitchen tap and turn it on just a touch - I get water out of it - and nothing else. The amount of 'bubbles' would be negligible. Try it.

 

[MIGEM]

From your tap?

 

[joe-90]

Yes. My kitchen tap doesn't chuck out air bubbles - only water. How about yours?