Vac Blower Size

[ronald pantelas]

How do you know what size blower you have? A stock Butler has a blower that is rated at 400 cfm. Is this a #4 Blower? My Butler has the bigger option blower rated at 500 cfm. Is this a #5 Blower. Thanks, Ron

 

[Shawn Forsythe]

Since manufacturers turn their blowers at differing percentages of capability, the only surefire means to determine blower type is either firsthand knowledge, or reading the blower identification/serial number plate on the blower itself. You can't tell by CFM output alone, but you could narrow the field.

 

[ronald pantelas]

Thanks Shawn

 

[Rex Tyus]

Shawn is actually being nice. Or at least tactful. This is one issue I have been bringing up for a while now. Call or right your manufacturer and request the exact model and blower speed of your unit. All this "rated" at and "rated" for is a bunch of bullshit. Blower rpm's at a given lift with unrestricted plumbing. Is that too much to ask :? The brochures of manufacturers mean nothing to me anymore. I want specifics. Good luck to you I will bet the first guy that gets your call will not even know what you are asking. But be persistent. The info you seek is worthy of an answer. A straight answer.

 

[Shawn Forsythe]

Rex is right, but even with the blower model designation and the RPM, it is still insufficient to determine blower output in which to compare units with same blower designations.

Here's why....

Once a manufacturer of a TM selects a blower size/model, he can opt for customization if the quantities are sufficient. An example would be the double shaft that many Hydramaster units use. Now that kind of customization has no impact on CFM. But another common customization does. It's called "high heat clearances". By utilizing a "shaved lobe" blower, the unit can withstand higher lift loads without overheating. Moreover, these same units are utilized to create greater exchange heat for blower HX packages, and the like. However, HHC blowers also do this at a detriment to CFM output the customer is never aware of. In fact, TM sales literature may declare the output of the standard blower, but the OEM underdrives and uses HHC to put those specs so far from the truth, it is ludicrous.

So in addition to Rex's recommendations to ask for:

Model
RPM

Also ask whether the blower uses High Heat Clearances or another modification from a standard unit, which might effect actual NET CFM.

Then do your own observation of entry and exhaust plumbing to determine if actual CFM characteristics are further diminished by poor plumbing design. Lastly, assess the vac relief valve to see how much CFM is lost through partial opening at normal cleaning vacuum lift levels.

 

[Rex Tyus]

In fact, TM sales literature may declare the output of the standard blower, but the OEM underdrives and uses HHC to put those specs so far from the truth, it is ludicrous.

See Shawn I knew you had it in you. I wish more people in the know would speak up about the deceitful claims that are made in the sales brochures by some.

 

[kmdineen]

Butler's stock blower is a 45, the larger blower is a 47.

 

[Greenie]

I like Shawn.

We'll probably both end up in the desert someday, but the ride will be worth it to make change in the world.

 

[RichardnTn]

In reality, all you can is a close guesstimate. Most of the blower manufacturers have the charts that give rpm/lift/cfm measurements but the only way to really tell is to put a flow meter on the vac outlet or where ever you want to measure from.... there are absolutely too many variables with each manufacturer.. as was mentioned, most give a cfm/hg number with no restrictions and maximum rpms....
What's ironical is my 45 turning at 3500 rpms is doing the same if not more than a 47 running at 2800 rpms. Some TM's run bigger blowers at lower rpms because at the same time they need to advertise low fuel usage and have decent air flow..... Best to all , Richard R