Edit: Delta DC blower has short 6" intake pipe, constricted to 4" at housing?

[Fitzhugh Freeman]

Edit: I titled this wrong earlier. It restricts down to just 4" not 5". Is there any reason this is a good idea?

I finally noticed that the 6" intake on the blower on my newly acquired delta 50-850 dc is attached to a plate with just a 4" hole, no transition, just a sudden restriction as the air goes through the plate that the intake is welded to and which bolts onto the blower frame.

The space between the impeller blades is 5" in diameter.

Should I replace the whole intake with a 6" intake pipe and mounting plate that does not have any such restrictions, just 6" clear through? Or should I leave it? What effect would having an intake with a diameter slightly larger than the center space between the impeller vanes?

I'm trying to maximize the setup however I reasonably can and making a new intake would be easy, just not sure if it is even worth it, or if it might backfire with the intake larger than the impeller ID.

Here's a photo:
Impeller and intake size.jpg

Any idea? I wonder if they did that to keep the motor from running too fast if it were unrestricted? Should I change it?

[Harold Weaver]

Fitzhugh,
I am no expert by any means, but the set up you have looks to be constricting. I have 3 drum top units, all Cincinnati Dustmasters, 1, 2, and 3 HP blowers, all with different sized fan blades, but all the blower housings have the same 7" diameter opening. I don't see why you cannot make another plate with a 6" round outlet/inlet there. You can even make it out of MDF 1/2". Oneida sells the appropriate sized angle rings with collar in many sizes for you to bolt on to connect your hose to.

[James Gunning]

That is wild, and is exhibit A showing how to do it wrong. The only way I could imagine a reason for that would be to choke the airflow enough to keep a small motor from overheating. If that's the case, very poor engineering decision from Delta. I would cut the portion inside the 6" collar out and bolt it back in place. Alternatively, what Harold suggested, making a new plate from plywood or MDF would work. I did that for my blower. Made of MDF to go from 5" to 6".

[Matt Morgano]

What size is the motor and the impeller.....It was most likely done to restrict airflow so as to not overload the motor.....that'd be my guess anyway.