125mm duct

[JackofAll]

Plan is to run intake/exhaust out through eaves. 150mm duct supplied but when insulation is added it will be very tight. So I thought reduce to 125mm out through eaves, contacted BPC to check if any in stock(which they do) but will void warranty if using 125mm on vent axia plus B. Anyone have to do similar and has if affected performance in any way?

[JohnMo]

Rather than guess, work out pressure drops and compare to fan curves. Smaller duct equals fan having to do more work, more noise, and no warranty from the sounds of it. 125mm sounds small for anything bigger than a small flat.

 

Anywhere else to route to?

[Conor]

I'd sooner keep the larger diameter and forgo the insulation on any tight sections rather than drop the diameter down.

[JackofAll]

3 hours ago, JohnMo said:

Rather than guess, work out pressure drops and compare to fan curves. Smaller duct equals fan having to do more work, more noise, and no warranty from the sounds of it. 125mm sounds small for anything bigger than a small flat.

 

Anywhere else to route 

No where else to route.