Re: OT--Electrical Question


"PrecisionMechanical" <precisionmachinist@xxxxxxxxxxx> wrote in message
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"jeff" <jalowe44INVALID@xxxxxxxxxxxxxxxxxxx> wrote in message
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Mark wrote:

Motor is 3-phase. As far as the air flow reversal; I think that there
would
have to be a very high positive air pressure in the building for that
to
happen. But, at this point, anything is possible.


check for an open/missing phase.


Yup.

Good possibility the fan contactor is going bad else there's a loose
terminal someplace nearby.



Ill elaborate some here, since I have a few minutes to spare....

Where you have fresh make up air requirements, and a multi staged system in
operation....what can happen is that one unit ends up drawing in outside air
through the damper belonging to the other unit, or similar.....maybe natural
draft because a main bay door is opened...thus "kick starting" the second
stage fan (that has the dropped leg)....in essence, it becomes its own "mini
rotary converter"...

Other similar scenarios exist....for instance, where it concerns the
condensor instead of an evap fan, then high winds can often provide enough
momentum where a phase is dropped....

Handy tool to use here might be a 'laser pointer thermometer'....beings that
a bad termination or contact usually runs decidedly warmer...

I once had a rpc connected that was simply too small...what happened was
that I HAD to let the Bridgeport motor come to a complete stop...else upon
reversal, the idler motor would reverse instead....

==

And to the OP, do appreciate let us know what you find out.

--

SVL


.

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