Roof Exhausters Belt-Driven or Direct Drive?

[krtpworks]

Which is preferred, Belt-Driven or Direct Drive? Why?

Thanks so much for your input!

[twcpipes]

IF you can hit the static pressure fairly close and get the required air you are looking to attain, direct drive is much better. Really quite simple reasons:
No belt to replace, No bearings to grease and eventually replace, since the blower longevity increases due to lower service requirements the blower will remain in service longer, and the blower operation sound levels are much lower since there is no drive noises or vibration. This could become critical depending on the application the exhauster is used for.

If though, you need to adjust blower speed to attain a desired air flow then a pulley must be adjusted hence a belt drive is required.
Hope this helps.
tom

[ceng]

we normally try to specify belt drive,just for balance purpose. And for long run, if you have to add some air on this fan, you have better chance to keep the existing fan, just use a longer motor.

[twcpipes]

Sorry, I thought you asked why a direct drive might be better than a belt drive. Sounds like you already had your answer before you asked the question. In your case it would appear you need belt drive and the maintainence schedule that goes with it since you have another post here about laboratories.
tom

[boat racer]

Belt maintenace ..... one of my pet peeves.

If the manufacturers would get off of a few more pennies ... maintenace can be lowered drasticly. If there is space, going to 2 belts or going up one size (A to B, B to C) dramaticaly reduces maintenance and increases the life of the belts and pulleys.

If you have full service contracts that include free belt maintenace .... do this upgrade as each pulley wears out and never worry about them again between annual inspections

In my opinion, most belts and pulleys are marginally sized ... making mucho moola for us

[ceng]

twc pipe, what I post here is not related with my first post.

[krtpworks]

To the three people who answered me (twcpipes, ceng, and boat racer): All excellent answers! Thank you so much for your input on my belt-drive vs. direct drive fan question. Your input is very much appreciated and will certainly contribute to wiser fan selections in my future.