Improving the Performance of Stove Hood Exhaust

That looks great... mine is still sealed up with an aluminum pie plate and duct tape since the time the birds got in and nested above the stove. As with the wasp nest, a good screen on the outside end is important too!

Yes the roof was redone not too long ago, and I believe they installed a new screen at that time, because there is one on there now....

If you survive the resulting fire let us know when the new motor fails. The original motor was constricting the 5" duct creating a higher speed air flow that keeps the motor cool. You have now put the motor into the wider part of the duct, the air flows past the motor more slowly so less heat is removed from the motor windings. For reasons of cost and profit these motors are sized with very little spare heat capacity so assuming you have replaced with a similar size of motor you can expect it to overheat and burn out relatively soon.

One of the problems of designing products that are pared down to the minimum is that they are "designed". Somebody did the calculations to see how little they could get away with. Did you redo the calculations before you reconfigured their pared down design?

That's hilarious....First of all, it is another exhaust fan, just a better design....secondly I'm an HVAC contractor with 40+ years of experience...thirdly, the motor is contained in a metal housing, just what do you expect to catch on fire? fourthly, the airflow has been increased...weren't you listening?

I am pleased you find it funny. If you can't laugh with me, you can always laugh at me. So you didn't do the calculations, you just relied on 40+ years of experience.

The total volume of air flow through the duct has increased. Has the rate of air flow past the motor increased?

The winding insulation on all motors is flammable and will char above it's rated working temperature. The charring usually creates a short circuit and the motor fails but if a short is not immediately created the carbon resulting from the charring reduces the winding resistance and increases the heat generated causing the insulation to ignite. You have had 40+ years as as HVAC contractor. I have had 40+ years as an electrical engineer, 25 of them as a consultant. I appeared as an expert witness in a court case relating to a fire caused in a powder coating oven when the defendant "improved the design" to "increase" the air flow without doing the maths.

I altered the design that was existing, by using a better designed system....I have not altered the design of the new install....The airflow is increased because the design is better...I have spent my life correcting problems, not creating them....I might add that a motor used in a stove hood is probably not that sensitive to varying air flow within a narrow range....

Still it wouldn't hurt to know how to calculate the air flow past the motor.....Maybe you would like to show and tell...? If so, please do....

Good job on the port and polish turbo installation!

Food will cook faster with the higher airflow.

(I just wonder if the pepper will make it to the food or be drawn up and shot on the roof)

Yes it's a 2-stage setup....I have 3-speed dual turbo fans feeding the intake...

The only problem with the "motor down" config is the accumulation of grease and such on the motor. When it is placed the other way the spinning of the fan provides some protection for gunk.

The accumulation of grease on all the components of the exhaust system is inevitable over time, that's why you replace them periodically...and clean the filter regularly....