On Thu, 18 Jul 2013 10:11:28 +1000, John G wrote:
Bob S laid this down on his screen :
On Fri, 12 Jul 2013 22:48:27 -0700, Gunner Asch wrote:
On Wed, 10 Jul 2013 14:14:03 -0400, Bob S
wrote:
I have a greenhouse with three fans from "American CoolAir".
The problem is that the motors keep failing. At the moment two are
running ridiculously slowly when powered on high speed. The other will
start and run on high speed, but bangs on startup at low speed; it is
as though the starter is kicking in and out.
The company keeps sending replacements, but I would rather have motors
that didn't need replacing. Is it possible to get drop-in replacement
motors that would actually work more-or-less forever?
The environment is not the greatest, with humid air blowing over them
in summer and the motors in cold air and being frozen in winter, but I
have had other appliances in similar conditions that never suffered a
motor failure.
The motor name labels say
Emerson
Model S63ZZJKW-7333
HP 1/2 RPM 1725/1140 SF 1.3
V 115 Hz 60 PH 1 Code L
A 7.2 SFA 9.5 AMB 40C
Made in Mexico
It looks just like the one in this pictu
http://www.federalindustrialsales.co...ph/m1-318.html
I have been through about 7 motors in the past couple years
That motor has Zero cooling. Notice..no internal or external fan on
it?
While it SHOULD provide its own cooling with the external fan...often
times they dont cool very well because of the design of the center hub
of the fan. The motor often times runs in a "dead air space"
Id consider getting a different style motor with an external fan. As
for the fan running slowly..that could be for several reasons.
1. Do you lubricate them properly and regularly?
2. Are the run caps going bad?
3. Is the start caps going bad?
http://www.coleparmer.com/buy/category/motor-1-3-hp
4. Are the motors actually the right hp for the load? Would a 1/2hp
motor be more appropriate?
Gunner
Thank you for the ideas.
The motor is positioned above the fan hub, connected by a belt, and is
actually in the air stream. Whether the cooling is adequate only the
designer knows, but it is not obstructed at least.
The motor name plate says that the motor bearings are permanently
lubricated. Is suspect that the fan hub also uses permanently
lubricated bearings, mostly because there were no lubrication
instructions provided and there are no oiling points. The bearing
housing for the fan hub is a good-sized chunk of hex stock open only
at one end.
The motor does not have an external "wart" for a capacitor. If there
are any capacitors present then they are concealed inside the
cylindrical housing somewhere.
The motors are 3/4HP, which seems to be the size that this company
suggests for a 36 inch fan.
Bob
Bob, I dont think you have ever really told us how these motors fail.
You seem to be saying that it might be bearing failure.
Then all the discussion about current, voltage etc is wasted.
Motor bearings last for decades if rated and cooled correctly.
Are yours cool?
Is there an undue side load? eg belts too tight.
Is the atmosphers corrosive?
There are two different failure modes.
One mode is that the motor is extremely rough-starting on low speed.
It is rough enough to shake the greenhouse structure. It seems as
though the torque is shifting rapidly from high to low and back again,
which I take to mean that the starter circuit is cutting in and out,
which in turn I take to mean that either the motor starter is
defective or the motor does not have enough power to accelerate the
fan.
The other failure mode is that the motor runs unreasonably slowly. The
motor may run at full speed when new, but before very long it gets
slower and never runs at full speed again.
The bearings do not seem to be seized up, they do not seem to have
excessive friction, they do not make noises.
Coolness is relative... The motors are not running hot enough to raise
immediate blisters if I touch the casing, but I would not want to
leave my hand pressed firmly against the casing for very long.
Belt tightness: If I push on them they move inward a short distance.
They are not loose enough to flap around and not tight enough to go
"twang". They seem of ordinary tightness to me. I have no
specification and no way of measuring it anyway.
Corrosive atmosphere? Well, it is a greenhouse, there is a lot of
moisture in the air, fertilizers and occasional insecticides are used.
The fans are sold specifically for greenhouse use and the company is
well-known and has been around for a long time, so I can only hope
that they have designed with the environment in mind.
Bob