Bin fan breaker

A question for you sparkies out there. I have a 10 HP grain bin fan that has been burning out the breaker every year or two. The picture is the tag on the fan. I don't know if it gives you enough information or not. The fan runs constant for two weeks or maybe a little more after harvest. After that it's run once a month for a few hours for a few months or until the grain is removed from the bin. This fan was new 8 years ago so it has not seen all that much use but it has been doing this since it was new. There is another fan on this bin that does not wreck the breaker. The breaker for the problem fan runs warm, the breaker for the fan that is not the problem runs cool.

The fans are fed by six gauge copper lines, the line to the problem fan runs 60 feet, the line to the non problem fan runs 30 feet from the breaker box. Both fans were on 50 amp breakers but last time when I replaced a breaker for the problem fan I replaced it with a 60 amp. That 60 amp breaker lasted two seasons before it quit instead of one season like the 50 amp breaker did and one side of the bad 60 amp breaker is now darker than the other side. The electrician who did the wiring suggested I need 4 gauge wire running to the problem fan but he did not offer to replace the 6 gauge with 4 gauge even though he is the one who under wired it as he claims. He passed away not long after he told me this so now I am on my own.

So now the question; is a 60 foot run of #6 copper inadequate for this fan or is there something else wrong.

Are the fans and motors identical? If so, swap the two, and see what happens. You would only be out your time, and no $ spent.

Yes they are identical. I have not checked voltage to the fans.

You need to get voltage & amp reading, otherwise it is all guess work. If you wire is too small you will see voltage drop difference from the supply panel to the fan panel.

That data plate is not real clear to me, I see 230 single phase but not a clear HP or amp rating?

Any other info for the motors????

Kevin is right... you need a voltage and amperage numbers. That will help you determine if you have a bad motor, a bad wire, or too small of wire.

Good luck

38 amps, 230 volts, 1 phase.

(quoted from post at 20:30:43 11/12/17) 38 amps, 230 volts, 1 phase.

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OK, the amps seem light for that HP.

Now if he has 208 or something less than 240 he will drive the amps up and the breaker will not hold.

Testing is in order.

Motor name plate is not real clear. But for a single phase motor at 230 Volts AC, 7.5 HP would be 40 Amps full load. 10 HP would be 50 Amps full load.
Googling the part number "AX24-1012-WC" gives the following:
24" Brock Axial Fan with Control - 10 HP 1 PH 230V
Someone else can look up the wire size needed, but I seem to recall that it may need a special breaker to withstand the motor starting current.
When we were using three phase motors, there was a motor starter, an overload device and a special breaker all sized for the motor HP.

According to the motor amp chart, a single phase, 10 HP, 230v motor, under full load, pulls about 50 amps.

I don't know if yours are running at full load, but if so, they are right at the limit. A motor needs a breaker 120% of it's rated amperage, so 50x1.20=60.

Really need to put an amprobe on the circuit, see what is happening. There could be a mechanical issue causing the motor to over amp, or low voltage will bring the amps up.

The #6 wire "should" be good no further than it is run, but #4 would be better.

Another possibility, the buss bars in the panel could be burned from repeated breaker failure. If there is an empty slot, try moving the breaker. Small panels are cheap, may just need to replace it.

Steve I just googled a voltage drop calculator and came up with a 2.2volt drop over 60 feet at 120 volts for a single 6 gauge wire. That’s not enough to get excited about is it? The bus bar does have a small amount of black buildup where the breaker clips on.

Look for poor connections that can cause heating. If the overheating goes on for too long, metals get soft and do not grip as well. The breaker clamps, wire lugs, etc. are good places to check.

I hate to say it but . I think all fan manufacturers, under size
and over rate there fans. Fan motors don't last as long as they
used to. If this is a centrifugal fan , then this is a fairly
common problem. We haven't come up with a good answer yet.
Probably replaced at least a half dozen motors so far this
season.

(quoted from post at 17:39:54 11/12/17) Motor name plate is not real clear. But for a single phase motor at 230 Volts AC, 7.5 HP would be 40 Amps full load. 10 HP would be 50 Amps full load.
Googling the part number "AX24-1012-WC" gives the following:
24" Brock Axial Fan with Control - 10 HP 1 PH 230V
Someone else can look up the wire size needed, but I seem to recall that it may need a special breaker to withstand the motor starting current.
When we were using three phase motors, there was a motor starter, an overload device and a special breaker all sized for the motor HP.

Click to expand...

your information is right. It is a Brock 24' that I have been told is 10 HP

(quoted from post at 20:09:36 11/12/17) I hate to say it but . I think all fan manufacturers, under size
and over rate there fans. Fan motors don't last as long as they
used to. If this is a centrifugal fan , then this is a fairly
common problem. We haven't come up with a good answer yet.
Probably replaced at least a half dozen motors so far this
season.

Click to expand...

IMHO, those direct fan motors have VERY small bearings, compared to a similar HP standard motor.

Combine that with the fans getting out of balance due to debris and even mangled bugs stuck to them (some airfoil blades are even hollow and get dust inside), and you have bearing failures causing the rotor to contact the stator and ruin the motor, and as well as winding failures from the constant vibration.

Mostly I am going to restate what others
have said. The fan draws 38 amps by the
tag, so the #6 are technically big enough.
You could step up to a 70 amp breaker but I
don't think it will fix the problem. What
I would do it move that breaker to that
there is a breaker space above and below it
to allow it to cool. They make plastic
breaker blanks so you can safely cover any
old unused holes.

I have had a bin do the same, while a
bigger breaker fixed it, while I was
working on it one very cold morning my
hands kept getting cold because when the
fan was on there was air being forced into
the panel through an old screw hole that
didn't have a screw anymore. I considered
drilling an 1/8" kyle through the back of
the panel and into the bin right behind the
breaker. It's amazing how much air was
being moved with a small hole this size.

I could certainly move the breaker to another location. lots of spaces left in the panel. By the looks of this last breaker only one side got hot or one side was hotter. I'm still going to check connections at the motor.

I'm with Steve about a mechanical issue, wondering about a bearing that drags just a little or a slightly bend armature. Pulling a few extra
amps to burn out the breaker. need to check amperage before getting carried away.

The possibility of a 208 volt service and not 230 was mentioned and the fact you saw black marks on the bus means move breaker or clean bus. Calculations I did show the wire size to be good.

All the upstream breaker does is provide short circuit protection. Thermal protection is provided by the motor starter . Sad to say few are the people who know the difference .
38 FLA motor uses a 70 Amp breaker .

I just put two new fans on this year. They are 10 hp
centrifugal type and nameplate says 38 amps as
well. Lookin in the manual it says to size it with a
125 amp breaker and 6awg wire for up to 60 foot
and 4awg thereafter. I assume the large breaker
size is for the significant current draw at startup. It
takes 4-5 seconds to start those fans. I can get a
picture of the page later if you wish.

My uncalibrated meter and current clamp show 200
amps momentarily at startup and 45 when running.

I did mention 208 back on page 1. Until volt and amp readings are taken we are all kind of guessing.

The 50 amp breaker seems to small for that motor & B&D says 70 which seems closer to proper. I forgot to look at my tables at work.

(quoted from post at 16:51:12 11/13/17)
All the upstream breaker does is provide short circuit protection. Thermal protection is provided by the motor starter . Sad to say few are the people who know the difference .
38 FLA motor uses a 70 Amp breaker .

Click to expand...

Found my glasses and reconsulted the code book. 38 amp is possible at 10HP with the two pole high efficiency motor if it has power factor correction caps at the motor.
38 FLA calls for a minimum of 47.5 amp wire which would be #8 copper with R75 insulation. Maximum breaker size is 90amp.
As previously stated the breaker buss bars maybe dirty and free space on each side of the breaker while not required, it is a good idea where possible .
Is the breaker subjected to vibration ?