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outback
07-06-2013, 11:19 AM
I have a blower motor on my central AC. It is a dual shaft motor. How do I determine if the motor rotates clock wise or counter clock wise?

The motor has a label perpendicular to the motor shaft. If I needed to guess, the motor end, below the label, would be the front of the motor.
Then facing the front of the motor and the shaft would be the point to determine shat rotation. Is this correct???

I hope this is not a CCW motor.

Jim

lakeside53
07-06-2013, 11:26 AM
Dual shaft? then one side is CCW and the other CW! Connect the power to it and you'll know...

MaxHeadRoom
07-06-2013, 11:29 AM
When you say label, do you mean arrow label? If so this is usually situated near one end?
Also the 'driving' or 'load' end is usually the farthest from the termination end.
And CW/CCW would be viewed looking into the end of the shaft.
Is this a new motor or existing, in-situ?
Max.

outback
07-06-2013, 12:00 PM
This is the central AC unit at our summer home on the Mississippi. It is a mobile home type AC. Even though the unit is 40 years old it cools great.
Not cheap to run though but for a weekend place it has done the job. Last few weekends the AC has been tripping the circuit breaker. We reset the breaker and the AC may run a couple of days then trip the breaker again.

I thought replacing the fan motor could be something I could do myself. I have no experience tinkering with AC beyond basic electricity.

I need to place an ammeter on the wires to see what is pulling all the current, the fan or the compressor. Not sure if I have one here at the river.

I guess if the motor is dual shaft it would be both CW and CCW depending on orientation.

I found a clamp on ammeter. The blower pulls 17 amps at startup then drops to about 4.4 amps. Fan is rated for 5.2.
Next I checked the compressor. At start up the compressor pulled 10 amps and I thought no problem. Then the compressor kicked in and the current jumped to 20 amps and remained there. The circuit breaker is 25 amps so it is about maxed out. I'm not sure if the wire I checked was for the compressor or the entire system. Wow,,,,that's 4400 watts per hour. It never was cheap to run.

Should I replace the circuit breaker?
Jim

sch
07-06-2013, 12:17 PM
Fan motor likely 1/3 to 1/2 HP, or 3 to 5 amps at 110V. Compressor will be 3-5x this at least, maybe more even if 220v. For manufactured home, will be under 4T rating. Compressor
is more likely to be the problem, but fan is cheap to replace. Dual shaft implies
squirrel cage type blower.

lakeside53
07-06-2013, 12:22 PM
20 amps on a 25 amp breaker is right on the limit. unless it's a special breaker rated for continuous use (and the wiring is upsized accordingly) , it's only designed for 80% continuous of max rating. I'm betting you have a compressor or other problem.

outback
07-06-2013, 12:51 PM
Fan motor is 3/4hp 230 V. It could be the start up current if the fan trips the breaker. Current could increase after several cycles during the day.
The entire unit is running on borrowed time. I'll bet a replacement unit won't last 40 years.

I think I can buy a new blower motor for about $85. Is it possible to replace the compressor?

The AC always starts up in the late morning. About 4:00PM the breaker trips.

Jim

andywander
07-06-2013, 01:22 PM
If the circuit breaker is old, as they age they do get easier to trip, in my experience.

Also, it it may be a thermal type, and since you use the AC when it is hot out, that would just exacerbate the problem.

I'd pop in a new breaker before spending money n anything else.

MaxHeadRoom
07-06-2013, 02:20 PM
Is it possible to replace the compressor?

Jim

Not without a recharge and recovery set.
You have to recover the old refrigerant now due to environmental laws.
Max.

Black_Moons
07-06-2013, 02:55 PM
Im no AC expect, but I wonder what happens to there power consumption when you get low on gas?
Might increase and start tripping the breaker.

But yea, if the breaker has triped a few times, they have been known to get 'easier' to trip.

PS: those squirrel cage fans have confusing blades, they actualy face 'forward' into the wind (looks like it should be 'sucking' the air into the center), and the fan will blow air out (towards the exhaust on the radial) reguardless what way the motor spins, but much more air if it spins the correct way.

The centrafugal action overpowers the blade angle and the forward curve of the blades actualy helps move *more* air (at low pressures). Just watch the fan as it spins down after its been powered.

MaxHeadRoom
07-06-2013, 03:39 PM
Im no AC expect, but I wonder what happens to there power consumption when you get low on gas?
.

Normally current goes down.
In most provinces here, you need a licence to work on A.C.
The latest systems run around 400lb/sq-in now.
Max

darryl
07-06-2013, 06:09 PM
If there's a squirrel cage fan on the motor, it should run in a direction which the arc on the blades face. If they don't have an arc, then assume that the arc is the side of the blade facing more towards the outside than the inside.

Or you can blow shop air outwards from inside the cage and note which way the cage wants to turn. This is the way it should be spun by the motor.

Black_Moons
07-06-2013, 06:28 PM
If there's a squirrel cage fan on the motor, it should run in a direction which the arc on the blades face. If they don't have an arc, then assume that the arc is the side of the blade facing more towards the outside than the inside.

Or you can blow shop air outwards from inside the cage and note which way the cage wants to turn. This is the way it should be spun by the motor.

http://cr4.globalspec.com/PostImages/200811/Fan_Impeller_Veloc_60203503-CD60-7938-CED9EE2C7F52366B.bmp
HVAC fans have 'forward curved' blades for high velocity at low pressure.

J. Randall
07-06-2013, 10:11 PM
Jim, I have to ask, have you gave the condenser coils a through cleaning? If not it could just be excessive head pressure in the heat of the day.
James

armedandsafe
07-07-2013, 01:06 AM
A very common problem with older model cage fans is bearings loading up and getting stiff. The seals are no longer tight (if there were ever any seals,) the lubricant gets hard, they load up with dust and just generally get tired.

Pops

becksmachine
07-07-2013, 09:54 AM
20 amps on a 25 amp breaker is right on the limit. unless it's a special breaker rated for continuous use (and the wiring is upsized accordingly) , it's only designed for 80% continuous of max rating. I'm betting you have a compressor or other problem.

I would assume (dangerous!!) that both the fan and the compressor were powered by the same breaker, making the total 24.4 amps?

Dave



I found a clamp on ammeter. The blower pulls 17 amps at startup then drops to about 4.4 amps. Fan is rated for 5.2.
Next I checked the compressor. At start up the compressor pulled 10 amps and I thought no problem. Then the compressor kicked in and the current jumped to 20 amps and remained there. The circuit breaker is 25 amps so it is about maxed out. I'm not sure if the wire I checked was for the compressor or the entire system. Wow,,,,that's 4400 watts per hour. It never was cheap to run.

Should I replace the circuit breaker?
Jim

winchman
07-07-2013, 02:04 PM
The compressor starts with very little load, so the initially low current draw is normal. The current increases as the system pressure builds up. In the late afternoon, the system pressure (and current draw) after startup would be highest.

If the coils are reasonably clean, I'd go with the suggestion to replace the circuit breaker. It's the least expensive and easiest thing to do, and it's likely to be the culprit.

Rosco-P
07-07-2013, 03:18 PM
Start cap for compressor is getting old, that could account for the high starting amps. Hard start kits are available that you piggy back into the compressor circuit, gives the compressor a bigger kickstart. Check for a bulge in the bottom of the can, one sign that it has absorbed a lighting hit in the past. Replace it if so.

Black_Moons
07-07-2013, 03:51 PM
Rosco-P makes another good point, a damaged start (and/or run) cap could greatly increase current requirements.
They should also be pretty cheap, $20~40 I would think. (Same with the breaker. Maybe up to $60 for the breaker depending on style/current requirements)

big job
07-07-2013, 03:53 PM
I still confused "as said above" wrap a thin rope around it and spin it when it blows thats the direction=spun with a rope its
either going to suck or blow squirrel cage or blades dont matter.

Rosco-P
07-07-2013, 06:21 PM
Rosco-P makes another good point, a damaged start (and/or run) cap could greatly increase current requirements.
They should also be pretty cheap, $20~40 I would think. (Same with the breaker. Maybe up to $60 for the breaker depending on style/current requirements)

Agreed, a 2 pole 25A should be cheap, unless it's some thing weird like a Bulldog push-a-matic or Federal Pacific breaker.

Don Young
07-07-2013, 09:04 PM
Be sure the coils are clean. Sometimes the fins can be clogged pretty bad and it is not easy to see that they are. A dirty condenser coil can raise compressor current quite a bit.

Paul Alciatore
07-07-2013, 09:59 PM
I wouldn't start by replacing the fan motor. Observe it in operation and if it seems to be moving a good volume of air, then it is probably OK. Some of the other suggestions above are better starting points, like cleaning the coils. A 40 year old unit has had a lot of time to accumulate dirt. Buy a spray can of coil cleaner and have at it. It may work wonders.

I have had to do the same thing. If you are going to replace the motor, it needs to match the unit in more ways than just the direction of rotation. Physical mount, RPM, HP, Voltage, etc. Get a part number from the nameplate along with all the other information there and go to the AC's manufacturer. At 40 years old, they may not still have replacement parts, but get as much information from them as possible. Then go to someone who sells motors, like Grainger or a local motor repair shop and talk to them about a replacement. They should be able to either find the OEM part or suggest a proper replacement. Or a repair shop can rebuild the original motor.

This will ensure a good replacement in all respects, not just the direction of rotation.

mickeyf
07-07-2013, 11:29 PM
Should I replace the circuit breaker?

If what you means is "just put in a larger one" then NO, Please!

winchman
07-08-2013, 03:35 AM
It sounds like this is a "package unit" with all the components in one enclosure. I remember working on them a couple times, and they had a squirrel cage on one end to circulate air through the house and a regular fan blade on the other to blow air through the outside coil. The regular blade should give you a clue about the direction of rotation.

A squirrel cage blower will blow the same way regardless of the direction of rotation, but the amount of air it delivers will vary dramatically.

Guido
07-08-2013, 12:28 PM
As Winchman says: Squirrel cage blowers will move air while spinning in either direction. Measuring amp load on motor will vary quite differently; correct rotation is easily demonstrated/checked. Learned while working one summer, wiring/installing new AC systems.

--G

outback
07-11-2013, 04:33 AM
I checked the breaker and realized it is 30 amp and not 25 amp. The AC units pulls 20 amps. I'm going to replace the breaker with a new 30 amp breaker and see what happens.

The AC unit is a "self contained unit" like someone said. Kinda like a giant window AC unit. Installing a new one should y be a mater of a few wiring connections, something I could probably do myself.

Thanks for the help.
Jim