Baxi Duotec 40 hot water issue

[white rabbit]

Was wondering if any of you chaps/girlies have come across this one?
Just installed a baxi duotec 40 on to an existing system. All new TRV's, magnaclean system installed, good strong mains pressure. Fired up boiler and central heating is working a charm, unfortunately when the hot water tap is on full/partially the boiler is making a horrendous deep bass sound sporadically.
Any thoughts??
Thanks for thoughts in advance.

 

[Toddyplumb]

Did you flush it ?

 

[white rabbit]

flushed out completely. existing system was regularly maintained, serviced and flushed out previously with inhibitor/cleaner installed. seems to come from the exchanger.

 

[Billy Bob Bob]

i also install /fix the duotec never had this problem,sure its not to high a pressure? what you getting on incoming mains?

 

[white rabbit]

installed service valve on cold mains and tried playing around with incoming pressure. still making noise

 

[Billy Bob Bob]

whats your incoming gas pressure must be 20mb or the pre mix burner will reverberate (this is very prone to this fault on a 40kw duotec)failing that you need to find out incoming water pressure over 2.5 bar you will get a noise

 

[white rabbit]

Thank you for the help folks. I will try these out tomorrow

 

[Toddyplumb]

Agree with Gas man on that the 40 needs 4 and a bit metres cubed on max.
Is there a flow restrictor on the cold inlet on the 40 as well ?

 

[Billy Bob Bob]

Agree with Gas man on that the 40 needs 4 and a bit metres cubed on max.
Is there a flow restrictor on the cold inlet on the 40 as well ?

no flow restricter,had this fault on a recent install got wales and west utilities out,could not get more than 18.5 incoming ,turns out they had to renew the incoming supply right up the drive with 20 at inlet end of noise and it sounded horrific

 

[white rabbit]

Cheers folks for the input, the problem was from utility company. Gas company exchanging pipes down the road from cast to plastic, which lead to iron filings being blown up to the meter and clogging up the governor. Thanx again.