CH noise, again

[Someuser08]

Is there anything that could be used in general to quiet down simple whoosh sound that CH emits (not cracking sound of pipework expansion or air bubbles with running water). It's kind of the same sound which could be heard in other parts of the house when a tap is opened.

Special inhibitor (I have fernox f1 dosed already)? Boiler pump speed reduction? Lockshield valves closure?

 

[mogget]

Pump speed reduction but it's important to maintain minimum flow to the boiler, and set any auto bypass valves correctly.

 

[Someuser08]

OK, so I read up on that. My boiler (vaillant 831) doesn't allow speed adjustment, but it has a two speed pump, which automatically adjusts based on heat output (d.0 which is set at 18 atm). Supposedly if that value is 14 or below - only slower speed will be used.

The reason all this noise started I think is because I have switched to smart heating system with most TRVs controlled by it as well, so now at any given time there are fewer radiators on leading to less resistance in the flow and therefore faster running water. I have 12 rads, 4 of them without TRVs at all (albeit small ones in the bathrooms, toilet and kitchen). The rest are on smart TRVs but during the night there are only between 1 and 3 additional rads opened. That probably means that 18kw d.0 setting is too much anyway, so can I reduce that to 14 to try and limit the pump?

Also as I only need to resolve this for the bedrooms - shall I also reduce the flow using lock shield valves and maybe opening another rad downstairs via a regular TRV?

 

[mogget]

I'm a DIYer not a professional, but my understanding is that pumps on combis have to remain as set at the factory to maintain hot water performance.

 

[Someuser08]

Yes, that's why I'm not touching the pump settings. I only wonder if reducing heat output will help in this situation.

 

[mogget]

If your heat loss is below the 14kw value you could try adjusting d.0 and see if that makes any noticeable difference.

 

[Someuser08]

So a bit of a result - with d.0 setting of 14 the pump indeed doesn't rump up and is noticeably more quiet. I also moved one of the rads to regular TRV to help flow as well as dosed Fernox F2 just in case.

P.S. heating now only reaches about 60 degrees from what I can see (out of 70 set), so could be an issue with subzero temperatures, but it is quite rare in SE where I am.

 

[mogget]

As it's a condensing boiler, there shouldn't be any problem with 60degC flow, as long as it's adequate to keep the house warm.

You can always bump it up when it's really cold.