New laser and EXHAUST

[Jamie Bourland]

Hi. My first post.
Our school bought a Universal VLS 3.50 Laser Engraver.
We connected it to a 1 HP Penn State Industries dust collector (DC660 I think) hanging above, mounted upside down to get the ducts aimed the right ways.

The laser specs call for 350 cfm and the fan specs are 660 cfm, max static pressure 8.5 inches.

Can someone please explain more fully the static pressure spec? The fan very quickly developed a disturbing noise that comes and goes rapidly and I think we are overworking it.

Air must go up about 4 feet through 4" hose, through the fan, then air is pushed sideways about 7 feet through 4' metal duct to get outside.

Thanks for any help

[Scott Shepherd]

You're not overworking it, that's for sure. I can't explain all the static pressure stuff properly, but you've got the right size blower and you aren't overworking it. If it's making a noise, it's something else.

I've used that same blower for years with no issues at all, running about 20'-30' of pipe.

[Jamie Bourland]

Thanks Steve! This is the only forum I belong to where you cant' choose a "handle".

I just found some charts and info that makes sense (almost) and of course I believe you.
The motor housing also gets hot, at some spots very hot.

Having it upside down doesn't matter, right? I've never taken apart any electric motor that was position-dependent like that.

Here's the charts I found.
http://www.airhand.com/designing_charts.aspx#chart2
http://www.airhand.com/designing.aspx#resistance

[Scott Shepherd]

The housing will get hot, that's normal. It's an electric motor spinning a very heavy piece of metal inside the housing. I can't imagine why the motor orientation would matter, but someone else might have some insight into that being good/bad/indifferent.

[Rich Harman]

I doubt you can overwork the fan. Ever notice when you put your hand over the end of your shop-vac hose that the motor speeds up? The load on the motor is greatest when the most air is flowing through it. Restrict the air going in and the fan/impeller will stall (aerodynamically stall, not like when you overload an engine and it stalls) and it will speed up. It takes less energy to spin a stalled fan than one that is efficiently moving air.