I've never heard of it before - you seem to work in a different climate. Entrainment of rainwater is common and is controlled by sizing the louver to a published face velocity. Possible suggestions: alter the location with respect to the prevailing wind, keep louver face velocity low, build an awning over the louver, provide a sudden change of direction before entering the ductwork so that centrifugal force will force the snow to collect elsewhere.

I usually size intake louvres at 350 fpm across the face area. I have not had any problems using this method.

Yes, I've had this problem before in the North Central States. We,ve gone so far as build a plenum behind the louver with a drain in the bottom that goes to a floor drain in a mechanical room. Wind driven snow is going to drift in and you have to make provisions for it!

PhilW

There is a proprietary product available for this application.
I will be happy to give contact info via e-mail if you want.
You can let me know at <pi-cats.usa.net> if required.

When it comes to light or powdery snow, I do not think there is any louver that can stop all snow entry. The only solution I have been able to work out is to assume it will enter, then pitch the bottom of the duct or plenum to louver or to a drain.

Re the Light / Powdery snow problem, just an idea - Has anyone tried the sand louvre? In the middle east we used them for inlet and exhaust (they were necessary for sand storms). If I remember ?ork and ?arrier offered them as an option. Although they were used all year in the middle east it could be a solution, noted they do have a high pressure drop and were relatively expensive.