>"Frank Ayers" <w2fca@qsl.net> asks
>
>>A blower related question - I have a Dayton 4C006 blower. The
>>published ratings for it start at a static pressure of 1/2 in
>>and go up to 1.2 in. there is a note in the 0 inch static pressure
>>column which says - "overloaded, do not operate under .5 in SP"
>>I've asked my friendly neighborhood Granger dealer why that is
>>and they have no idea. Anybody know?
>
>Once you stall the blower, there's no airflow to cool the motor, and it
>will overheat relatively quickly.
>
? Maximum load on a blower is with free flow delivery. During a
cavitation condition, the airflow stalls and, since the motor is not
working as hard, it speeds up slightly. Also, the typical motor has a
radial-wheel impeller on the armature to cool itself.
>If you plot the product of air flow and backpressure you should get a graph
>that's roughly parabolic, and ideally you'd want to operate near the peak
>of the curve and above your minimum required backpressure.
>
>From an airflow standpoint, Rich is right -- the blower's not too big until
>it blows the tube out of the socket. From an equipment reliability
>standpoint, you want an appropriately sized blower.
>
>Added benefits to having the right size blower? It's quieter, more energy
>efficient,
? If energy efficiency is a concern, Dayton motors run so hot you can't
hold your hand on one that has been on for an hour. However, in KL7-land
Dayton motors are useful for warming hands in winter.
>and lasts longer.
>
>But with the junk most of us use, "big enough" is all you need.
>
? ... measuring pressure with a manometer is better than guessing. I
know a K5 who claimed he tell how good a vacuum capacitor was just by
"eyeballing" it -- until the day we measured the leakage on a vacuum cap
with my high-pot tester.
cheers, Jim
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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