How do you know it isn't moving air? Hold a piece of paper really close to the baffles and sees if it pulls it up. Many people assume the hood will really suck things up from a great distance but that's not the case.

In addition to weissman's suggestion, the symptoms could be consistent with not moving air.

Assuming that there is a damper in the path, the damper would block air trying to go the wrong way, so the fan would not be moving air except within itself.

Usually these fan motors are designed so that they start and run in only one direction, thereby making it unlikely that the fan can run backwards. But not all motors are of this type.

It would probably be worthwhile, after trying weissman's suggestion, to remove the fan and plug it in and see what output it has.

I would add that between the time I tested the dual-register venting above my wall ovens and later that year when I found one filter was staying clean, that one of the two dampers had become bound closed due to some additional screws added to the ducting. So check the damper for free movement while the fan is out.

kas

Thank you for the responses... Let me answer some of the follow-up...

The hood is only moving a small amount of air (measured at approx 200CFM above the stove halfway to the roof in the new 10" ducting. So, it is moving a small amount of air, but nowhere near the 1200CFM that it is rated at.

There damper above the stove is not blocked or sticking, so that isn't the issue either.

I'm not an expert in centrifugal fans, but everything I can find is that is should spin in one direction for it to operate correctly. However, if it spins/operates in the wrong direction, it will still move a small amount of air, which is what mine seems to be doing.

In regards to the fan itself, it just plugs into the actual hood, so I'm not sure it is wired improperly. I'm guessing it could have been manufactured incorrectly? Has anyone ever seen one of these fans operating in the wrong direction?

Thank you again for the comments.

Here is a link to a video of my fan spinning in the wrong direction. I just turned it on then off again so you can see the direction of operation. This obviously is opposite of the pictures in my previous post, so that is why I've come to the conclusion that it is probably my issue.

https://www.dropbox.com/s/0fsysw5itbzzomn/IMG_0976%20%281%29.MOV

Link doesn't work for me.

Sorry about that. Try this link.

https://www.dropbox.com/s/0fsysw5itbzzomn/IMG_0976%20%281%29.MOV

Well, I had a Viking tech out to the house, and he confirmed my suspicions. The fan motor is in backwards, causing it to rotate in the incorrect direction. Since the unit comes as one piece, it looks like Viking assembled the product wrong at the factory. Nice job Viking!

Works in Austraila :)

What did they do to handle the issue?