Inlet and vents

[JackofAll]

May have a problem in that the inlet and exhaust will be quite close to the ASHP, moreso the exhaust.  The plan is to bring the vents out through the soffitt board but the ASHP will be under the exhaust vent. Any issues with this?

[Dreadnaught]

Best to put the intake upwind from the exhaust relative to the prevailing wind direction for your location (usually westerly in the UK).

 

And ensure the intake and exhaust are both on the same building elevation to ensure even wind pressure between them.

 

Separation: I would suggest 1.5 lateral metres minimum if you can.

[JackofAll]

3 hours ago, Dreadnaught said:

Best to put the intake upwind from the exhaust relative to the prevailing wind direction for your location (usually westerly in the UK).

 

And ensure the intake and exhaust are both on the same building elevation to ensure even wind pressure between them.

 

Separation: I would suggest 1.5 lateral metres minimum if you can.

Thanks @Dreadnaught, according to the drawing the exhaust will be upwind of the intake relative to prevailing wind. Am sure I could put in an extra couple of 90's to swap the configuration but would it be better to them running as straight to atmosphere as possible?

[Dreadnaught]

For peace of mind, personally I would want the intake up-wind unless the separation was say 3m or more.

 

I would not be too concerned about duct resistance assuming you're using big fat ducts. My MVHR uses external insulated Ubbink foam ducting that is 160mm internal diameter (190mm external diameter), which is comparably huge. The resistance is such ducts, which falls by the square of the diameter, is quite low.

 

I roughly calculated the internal flow rate within those ducts in my case to be 1.9 m/s (2.1 m/s on boost) which I considered acceptably low and should not cause problems of either pressure-drop or noise. You could do a similar calculation.