Myson Apollo banging noise

[Stuphd]

Hi,

I have a myson apollo system, every time it starts up in the morning or night it will start up and after about 2-3 minutes it shuts down and goes out with big bangs for about 10-15 seconds and it sound like the water is going back up into the exspansion tank? it only does it once after that its fine. it been on for three days and only did it once? Someone has been in and drained it down then put some sort of chemical in cut in to a pipe to check to see if it was blocked but was not.
I can bleed my heaters twice a week and theres always air in them aswell!!
(Comes on runs for 2-3 minutes, clicks off then bangs away then comes back on and then it fine?) I
ts doing my head in!!!
Thanks for any help.

 

[Soggy_weetabix]

Circulation problem, or gas vlv may be sticking. You obviously have a problem with air ingression, which would be the primary cause.

David

 

[namsag]

Your problem is a faulty pump over run stat . It is not returning to its normal position after use which would give power to pump straight away on demand for heat or hot water. It is staying in it`s pump over run position which senses heat within the boiler compartment after use to allow pump to stay on to disapate heat... which is why you get thumping and banging on initial start up ( pump not coming on till stat senses heat in the compartment) . straight forward repair part approx £20 and a twenty min job. Your air problem could be caused by water boiling up initially before pump kicks in.. Always bleed rads with pump off.

 

[Slugbabydotcom]

Has someone closed off the by-pass valve by any chance ?
Whaetver, try opening it a turn or 2 before spending money

 

[namsag]

And why would a closed bypass cause banging on start up ?

 

[Slugbabydotcom]

These boilers are designed to work with a temperature difference of 11°c. If the bypass is closed then none of the hot flow water coming out of the boiler is re-circulated to keep this temp difference. The sudden increase in temperature is too much for the water in the heat exchanger resulting in kettling. The boiler will then shunt until some warmer water comes back through the return.

I dont disagree with what you said namsag not in the least . My point was that I have seen banging on startup caused by someone turning off the bypass valve thinking it was an isolation valve when working on a system or after a leak.

It costs nothing more than a few minutes of time just to check.

 

[Stuphd]

Your problem is a faulty pump over run stat . It is not returning to its normal position after use which would give power to pump straight away on demand for heat or hot water. It is staying in it`s pump over run position which senses heat within the boiler compartment after use to allow pump to stay on to disapate heat... which is why you get thumping and banging on initial start up ( pump not coming on till stat senses heat in the compartment) . straight forward repair part approx £20 and a twenty min job. Your air problem could be caused by water boiling up initially before pump kicks in.. Always bleed rads with pump off.

Namsag
Well it looks like your were right
I got the pump over run stat ckanged and its not made any noise at all It only took the plumber about 15-20 mins to fit,
Thank you very much, its made my wifes xmas!!!
Cheers