Likely cause for leaking ventilation fan

Question

My roof has two DX11VSR ventilation fans that were installed about a year ago.

I have had repeated issues where rainwater gets into the ventilation ducts attached to these fans and then leaks through the ceiling. I have been able to confirm that it is the fans that are leaking by running a hose pipe with sprinkler attachment over the top of the fan covers at a vertical angle. This reproduces the leak in the exact spot that I see the leak during heavy rain, but despite all my efforts I can’t work out how the water is actually getting into the vents. The subcontractor who installed them made several ineffective attempts to fix leaks and has now stopped operating.

I checked the manual for this fan and in the troubleshooting section it says that if the fan is leaking then the drain spout could be clogged. However there is no indication where the drain spout should be!

Can anyone provide any guidance on further troubleshooting this leak and things I can try to resolve it?

Edit: I have added side views of the fan. It does have a curb. The curb is metal, but the screws on the fan base visible in the south and north views are going into wood - I think there is some wood piece on top of the curb. One of the "fixes" the contractor attempted was to cover the join between the base of the fan and the curb with mastic. There is no pooling of water around the join between the curb and the roof.

Also here is a video showing the leak from inside the house and then showing how the water was falling on the fan.

Answer 1

Note: Based on additional photos, there is a curb. I am leaving the answer in place for now as it contains useful diagrams.

According to the manufacturer's installation instructions, the fan base is supposed to be attached to a curb raised above the roof surface, with that curb sealed to the roof all the way around. The curb is supposed to be made of 18 gauge or thicker galvanized steel.

I see no raised curb in your photo, but rather what seems to be the top of the fan base flush(!) with the roof surface. I would expect that water could puddle there and enter either through a gap at the square edge of the base, or between the base and the circular part of the vent.

I'm no fan expert, but this seems like a botched installation to me.

I would try to use a black roof sealant like Loctite PL "Roof and Flashing" to seal the square edge of the fan base to the roof and also where the circular part meets the square fan base.

Cutaway view of sample fan:

Installation diagram for wood framed roof showing curb supporting fan base:

Image showing a prefab curb and optional hinge (for easy inspection/access)

Answer 2

I was eventually able to resolve the problem. I took the fan off and found that the contractor who had installed it had put a rough wooden frame on top of the steel curb. I was able to see that water was getting into the vent at the corners where the pieces of wood joined - before I took the fan off I had run the hose on it, so I could see that it was still damp at one corner and there was water pooling in the vent below.

I tore out the wood and used self-tapping #14 tek screws with integrated gaskets to attach the fan assembly directly to the curb (as the installation manual Armand provided specified). After assembling it this way, running the hose on the fan did not reproduce the leak and a month later there has been no further leak (despite a lot of rain).

The subcontractor who did the installation is no longer in business, but I think he might have installed the wooden frame to try to reduce the noise from the fan that was audible in the room downstairs. I didn't notice any increase in noise after removing it.