Ideal Isar HE35 whistling

Hello, I have inherited an Isar HE35 that has been working well but is now starting to whistle when working hard.

The whistle sound is generally only heard when filling the bath with the bath tap fully open. Opening the cold tap can reduce the noise. The sound gets louder as the system works harder. The sound is not there when the CH only is running.

Sometimes, there will also be another noise (at the same time) that has a different pitch to the whistle and is a lower drone tone.

The whistle is louder at the top outlet but can also be heard towards the lower parts of the unit.

No issues with error codes etc.

Any suggestions appreciated, Thanks

Collapsing flexible tap connectors?

What type of bath taps have you?

Does it do it when running the basin or sink?

has the boiler been serviced recently?

Can you hear the noise outside?

Thanks Dan,

Bath taps 1/4 turn style.

Have just fiddled with the temp when running the tap in the sink. It normally doesn't make the noise even when turned full on. If i turn the thermostat temp up then the noise will start for the sink as well even with the tap only half on.

Can hear the noise outside.

Not sure when last serviced as I have only been here 6 months but was intending to get it serviced in the spring.

Thanks.

Would love to hear the noise. It is possible... this kind of thing is soooo subjective.

have you got a high water pressure

The CH pressure is at 0.8Bar or 12 psi and drops about 1psi when the DHW is being used.

Haven't seen it higher than 1 bar when not in use and at 1.2 Bar when running.

The noise I think is from air or gas and varies according to the amount of heat it is generating even with a constant flow of water.

The lower tone noise is possibly water / valve etc but hard to really determine as the whistle sound is quite loud. There doesn't appear to be any hammer from the DHW outlet pipe.

Thanks.