heat pump fan reversal

[Giles Harney]

Bryant 517E inside and 661CJ024-B outside unit.

i have observed that;

when fan is blowing air down, there is frost on the outside.

when fan is blowing air up the coils have less frost. this lasted about 15 minutes, so I suspect this is the defrost cycle?

is this correct for this unit?

Thanks!

-Giles

[SQLit]

Frost is usually a good sign that you need to call an a/c guy. Condensers will frost when over charged and under charged. Call some one soon.

[John Gilmer]

Actually, frost build up is normal on the outside unit of a heat pump. The defrost control will defrost if the coil temperature is below freezing for more than a predetermined time (1/2 to 1 hour). The outside fan should be OFF during defrost. The inside resistance heating should be ON and the inside fan should be on during the defrost cycle.

[CBhvac]

Down?

Frosting is normal, depending on humidity and temps. When a heat pump is running, many people assume wrongly that the frost indicates a low charge condition. Not so. Its the reversal of the fan thats getting me....somethings out of whack there...