HVAC fan inlet

1. A fan housing ( 184 ) for accommodating a fan ( 154 ) rotating about a central axis ( 500 ), the fan housing comprising:

an inlet ( 212 );

a diffuser ( 202 );

an inner diameter (ID) surface ( 200 , 210 ) facing the central axis; and

an outer diameter (OD) surface ( 240 ) facing away from the central axis, wherein:

a rim ( 220 ) at the inlet has a plurality of apexes ( 231 ) and a plurality of nadirs ( 233 );

the fan housing comprises a top cover mated to a lower member, the lower member being of molded plastic; and

the fan housing further comprises a separate grille secured to the top cover.

2. The fan housing of claim 1 wherein:

the housing has a mounting flange ( 250 ).

3. The fan housing of claim 2 wherein:

the mounting flange has a generally rectangular planform; and

the nadirs are aligned with sides of the rectangle and the apexes are aligned with corners of the rectangle.

4. The fan housing of claim 2 wherein:

the apexes are of protrusions along an underside of the mounting flange protruding downward and radially outward relative to the central axis.

5. The fan housing of claim 2 wherein:

in central longitudinal section, at a given axial position, the inner diameter surface and the outer diameter surface each have convex portions; and

at least at said given axial position, respective radial positions of the inner diameter surface and outer diameter surface convex portions vary in the circumferential direction around the central axis.

6. The fan housing of claim 5 wherein:

the convex portions extend from the rim ( 220 ) of the inlet.

7. The fan housing of claim 6 wherein at at least one circumferential position:

the outer diameter surface convex portion extends over a longitudinal span (H 2 ) of 5% to 40% of a throat diameter (D THROAT ) and a radial span (R S ) of 3% to 20% of D THROAT .

8. The fan housing of claim 7 wherein:

at the apexes, the radial span (R S ) is at least 200% of the radial span (R S ) at the nadirs.

9. The fan housing of claim 7 wherein:

at the apexes, the radial span (R S ) is 200% to 1000% of the radial span (R S ) at the nadirs.

10. The fan housing of claim 9 wherein:

the apexes are axially spaced from the nadirs by a height H 1 of at least 3% of a throat diameter (D THROAT ).

11. The fan housing of claim 1 wherein:

the apexes are axially spaced from the nadirs by a height H 1 of 4% to 12% of the throat diameter (D THROAT ).

12. The fan housing of claim 1 wherein:

the lower member includes a mounting flange.

13. A climate control outdoor unit ( 22 ) comprising the fan housing of claim 1 and further comprising:

a compressor ( 30 ) having an electric motor ( 32 );

a refrigerant-air heat exchanger ( 40 ) coupled to the compressor and extending around the central axis between a first header ( 120 ) and a second header ( 122 ); and

an electric fan ( 42 ) encircled by the fan housing and positioned to drive an air flow ( 520 ) along an air flowpath ( 521 ) across the refrigerant-air heat exchanger then through the inlet and out the diffuser.

14. The climate control outdoor unit of claim 13 wherein:

the refrigerant air heat exchanger has a footprint with four sides and four corners, an inter-header gap ( 123 ) at one of the four corners;

the apexes ( 231 ) are aligned with respective ones of the four corners; and

the nadirs ( 233 ) are aligned with respective ones of the four sides.

15. The climate control outdoor unit of claim 13 wherein:

the electric fan is atop the outdoor unit.

16. The climate control outdoor unit of claim 13 wherein:

the top cover is sheet metal.

17. The climate control outdoor unit of claim 16 wherein:

the apexes and nadirs are along the lower member.

18. A fan housing ( 184 ) for accommodating a fan ( 154 ) rotating about a central axis ( 500 ), the fan housing comprising:

an inlet ( 212 );

a diffuser ( 202 );

an inner diameter (ID) surface ( 200 , 210 ) facing the central axis; and

an outer diameter (OD) surface ( 240 ) facing away from the central axis, wherein:

in central longitudinal section, the outer diameter surface has a convex portion;

in said central longitudinal section, the inner diameter surface has a convex portion; and

at least at a given axial position, respective radial positions of the inner diameter surface and outer diameter surface convex portions vary in the circumferential direction around the central axis.

19. A climate control outdoor unit ( 22 ) comprising the fan housing of claim 18 and further comprising:

a compressor ( 30 ) having an electric motor ( 32 );

a refrigerant-air heat exchanger ( 40 ) coupled to the compressor and extending around a central axis between a first header ( 120 ) and a second header ( 122 );

an electric fan ( 42 ) encircled by the fan housing and positioned to drive an air flow ( 520 ) along an air flowpath ( 521 ) across the refrigerant-air heat exchanger then through the inlet and out the diffuser.

20. The climate control outdoor unit of claim 19 wherein:

the refrigerant air heat exchanger has a footprint with four sides and four corners, an inter-header gap at one of the four corners;

the inlet has first portions ( 230 ) aligned with the three remaining corners and second portions ( 232 ) aligned with the four sides; and

the first portions protrude axially beyond the second portions.

21. The fan housing of claim 18 wherein:

the inner diameter surface convex portion is partially along a sheet metal top cover of the fan housing and partially along a molded plastic lower member of the fan housing; and

the outer diameter surface convex portion is along the molded plastic lower member of the fan housing.

22. A fan housing ( 184 ) for accommodating a fan ( 154 ) rotating about a central axis ( 500 ), the fan housing comprising:

an inlet ( 212 );

a diffuser ( 202 );

an inner diameter (ID) surface ( 200 , 210 ) facing the central axis; and

an outer diameter (OD) surface ( 240 ) facing away from the central axis, wherein:

a rim ( 220 ) at the inlet has a plurality of apexes ( 231 ) and a plurality of nadirs ( 233 );

the fan housing comprises a sheet metal top cover mated to a molded plastic lower member; and

the apexes and nadirs are along the lower member.