strange noises

[boilerbunny]

I had to replace a radiator so I took the opportunity to change my pump (grundfoss 15/60) like for like, 2 zone valves (tower to honeywell 22mm), and chemically flushed the 11 year old pipework, and removed and cleaned the radiators.
Anyway got all that done and got things up and running again, all the air purged (I think), but after about an hour the system started to make noises. The best way I can describe it is a cross between a low groaning and the deeper sounds a whale makes.
Has anyone any idea what this may be?
I have tried the pump on different setting but it still occasionally comes back. I've also opened my bypass fully, it seems to have some effect but there is still some noise intermittently.
The boiler is an ideal turbo 2/24 condenser supplying 13 radiators over three floors with the pump and valves at top level and the boiler at the mid level. At a guess I would say the noise is from around the boiler but I'm not certain.
Can anyone offer any thoughts on this or had any experience of this kind of thing? I'd be grateful of any help

 

[Slugbabydotcom]

Cant hear the noises from here but from what you have told me there could still be some air in the system. By-pass should be slightly open when the system is running normally

Try this to clear airlocks

With the system warm close the bypass
Close all the rads [at one end] barring one. Run it for a while then open the next rad valve. Close the first rad off and continue through the system so that there is one rad open at all times

The best way I can describe it is a cross between a low groaning and the deeper sounds a whale makes.

You sure the neighbours werent having sex at the time?

 

[boilerbunny]

Hi Slug, I've tried that with no success.
I now have the bypass open about half way and it's slightly noisier when the noise happens, and slightly higher in pitch.
As it is not cold yet it may be there is not enough of a circulation path through the heating system, as it's ok when heating up in the morning for about the first hour.
Not sure whats going on really.

 

[Slugbabydotcom]

may be there is not enough of a circulation path through the heating system

I'm inclined to agree but if its not air then the possible causes are many and it could be time to call someone out to it. However you do seem to be a capable guy so Ill just throw some of my ideas at you as you request incase something clicks

Noise could be kettling. I know you said the system was flushed but are you sure the heat exchanger was flushed properly? Kettling is usually caused by a slow flow of water through the boiler.

Pump could have debris in it or a manufacturing fault making it ineffective and it is possible you have fitted it the wrong way!

Not au fait with this boiler but the temperature difference between flow and return could be and probably is a part of the 'setting up'. In short, the by pass setting could be crucial.

Please leave the following to a qualified person

I'm unable to get any info on the boiler but I know that some ideal boilers are prone to having weird and wonderful burner set ups, some of which can be noisy. A lot of them need a flue gas analyser for correct setting up. Noise from a worn fan is possible