Electric motor run direction questions and answers:

Frequently-asked questions about the cause of & repair for electric motors that run backwards.

This article series describes A/C electrical motor troubleshooting: here we provide an electric motor diagnostic table, a troubleshooting guide that helps diagnose and repair most electric motor problems for motors found on HVAC equipment in buildings such as air conditioners, furnace or air handler blower fans, oil burner motors, well pumps, and condensate return pumps.

A/C Electric Motor Run Direction FAQs

Questions & answers about the run direction of electric motors & why a motor might run backwards, posted originally

at ELECTRIC MOTOR RUN DIRECTION

Also see ELECTRIC MOTOR DIAGNOSTIC GUIDE

Fatal Shock Hazard Warning: Inspecting electrical components and systems risks death by electrocution as well as serious burns or other injuries to the inspector or to others. Do not attempt these tasks unless you are properly trained and equipped.

Photo: a vintage electric motor from the Master Electric Company, ca 1963.

Which way do I look at the motor to determine its rotation direction?

When a motor is designated as counter clockwise, what is the frame of reference – looking straight at the front side of the motor with the shaft pointing straight out at you or looking at the back side of the motor when it is mounted in the condenser with the fan blades attached?

For example, a counter clockwise motor by the first definition would be spinning the fan blades in a clockwise direction when you look down on the condenser. - On 2023-07-19 by Fred E -

Reply by InspectApedia Publisher (mod) - from which end do we view a motor when determining its direction of rotation?

@Fred E,

Thank you for a helpful question: the definition of "clockwise" and "counterclockwise" for an electric motor, by IEC standard, is that you view the motor from the load end or driven end.

Example: If you are looking at a motor that has a single output shaft that drives a pulley or gear, you would view the motor from the shaft end onto which the pulley is mounted.

Then if the shaft (and pulley) spin to the right (like the hands of a clock) that's a "clockwise" motor rotation, and if the motor shaft rotates to the left, again viewed by looking at the end of the motor's driven shaft, that would be a "counter-clockwise" motor rotation direction.

In our illustration below our large fat red arrow shows that when determining the direction of rotation of an electric motor we view the motor from the load-end or driven-end or output end of the motor shaft.

Our oval arrows show that this motor is rotating in a "clockwise" or "left to right" direction.

 

My electric motor only runs backwards

My motor is running only in reverse direction - On 2023-03-20 08 by Sanketh sindhe b s -

Reply by InspectApedia Editor (mod) - electric motor only runs backwards

@Sanketh sindhe b s,

A motor may reverse direction after a power surge or re-wiring error - please step through the diagnstic and corrective steps given above on this page, and don't hesitate to ask follow-up questions.

Table Saw Motor smoked and now sometimes won't start

I have an old table saw I replaced the bearings on the motor and reassembled & it started ok but after a while it smoked. I quickly shut it off & it only smokes when run for a time. I now find the motor occasionally will not start.

I disconnect the power and turn the motor & it starts but I still have the problem of not starting.
Can anything be done or is it not worth it. On 2022-11-2 by Roydon

Reply by InspectApedia (Editor) (mod) - burned up table saw motor winding

@Roydon,

Sounds like you have a burning up motor winding. For a valuable commercial motor there are professionals who will rebuild them. For a small electric motor it's probably not worthwhile.

Why is Toro leaf vacuum motor running backwards?

I have a Toro leaf vacuum and mulch that was working really well. After emptying the bag I turn it back on and it runs backwards now. I put it away for the season and next time I used it worked fine until I turned it off and restarted backwards again, WTH. Thanks On 2022-03-29 y John Kidd

Reply by Inspectapedia Com Moderator (mod) -

@John Kidd,

Probably the cause of that motor running backwards is one of those listed in the article above. Please do take a look.

Motor keeps reversing its direction

My indoor blower, at first seemed like it was short cycling. But in actuality it was pulsating forward and then reverse. What's up with that. Couldn't find start cap, going to check windings next. HELP MEE... LOL - On 2022-03-1 by Jim

Reply by Inspectapedia Com Moderator (mod) -

@Jim,

That sounds like just the sort of problem we describe above on this page. Let's start by looking through that discussion and trying those diagnosis and repair steps.

I suspect that your motor wiring has an intermittent short circuit.

Switching yellow and orange wires changed furnace blower motor direction

had a single phase 110 v motor for a furnace going CCW. Found the ORANGE / YELLOW & switched TADA CW Correct rotation On 2021-12-14 by dave

Reply by Inspectapedia Com Moderator (mod) -

@dave,

Nice going, and thank you for taking the time to post that detail here, as it will help other readers who face the same problem with correcting the run direction of their electric motor.

2Hp 3450 RPM electric motor that is wired for CCW rotation. Need to reverse the rotation to CW.

I have an old 2Hp 3450 RPM electric motor that is wired for CCW rotation. Need to reverse the rotation to CW.

Unfortunately the name plate is pretty messed up so cant read complete or even if I can reverse the rotation on this motor. It is a single phase 115V with two external capacitors.

I have added the image of the motor with labels as to how it is currently wired. Any help would be greatly appreciated, - On 2021-04-03 by Kenneth

[We added color clues and larger labeling to Kenneth's photo - Ed. ]

Reply by (mod) - how to reverse the run direction of a "Power Tools Co." 2hp electric motor

@Kenneth, I'm too scared of burning you up to pretend I know the right answer, but we do have both a clue in the wiring notes on the motor label (enlarged below) and in our article on this topic found above on this page

ELECTRIC MOTOR RUN DIRECTION - topic home, https://inspectapedia.com/electric/Electric_Motor_Direction.php

where you'll find

Manually-reversible Electric Motor Run Direction

By swapping wire connections on some electric motors it is possible to change or reverse the motor direction. For example on some motors,

Typically purple and yellow wires or wire pairs permit this change.

Purple to purple = rotate clockwise

Purple to yellow = rotate counter-clockwise

For an example of electric motor wiring that includes wiring to select electric motor speed options as well as direction of rotation see [live link on the topic page I cited]

Dayton Electric Motor Wiring Diagram [PDF], Dayton Electric Mfg. Co., 5959 W. Howard St., Niles IL 60714 USA, retrieved 2017/07/09, original source: Grainger.com

Your motor doesn't use purple, and wiring differs depending on voltage you're supplying but it's a start.

Other wire change examples to switch electric motor run direction:

Switch Yellow and Blue wires (ending with RED->Yellow & BLUE->Black

Concept: we're reversing polarity at the motor start winding. So if you can identify the start winding that'll be helpful.

If your motor uses a starting capacitor, see which motor winding is wired to the start capacitor - that's the start winding.
When you find the start winding, just swap the two wires that connect to the two ends of the start winding - that should change its direction and thus the rotation direction of the motor at start-up.

More examples of easy wiring changes to reverse motor direction are given above on this page.

Watch out: It was nearly impossible to find a motor manual and wiring diagrams for your electric motor because of its unfortunate name "Power Tools" - searches with that phrase drown us in results that were not helpful.

But you might have better luck if you can decode more of the motor's manufacturer or model number and then use those to search for IO manuals and wiring diagrams, or you might contact the OEM of the company that made the device on which your motor is used.

Which Way is my Pool Spa Heater supposed to run?

Hi I have recently replaced the capacitor on my pool/spa heater since then I haven’t use it ,nowt that I went to use it I find out that the heater isn’t heating the pool/spa i turn on the spa to heat the water and i run it for 3 hours and the temperature of the water stay the same at 76

so my question is does the fan of the heater weds to blow air in or out of it ir which way is it supposed to Spin , by replacing the capacitor courier installed it wrong si that the fan it’s spinning the wrong way as of now if I put my hands on top of the fan of the heater it’s blowing air but my concern is if is supero be the opposite please help - On 2020-12-07 by Dario Ruiz -

Reply by (mod) -

In order to have a clear understanding of your question can you confirm that what we are discussing is a pump that moves water not a blower that moves air?

No tell us, dios the motor start or is it failing to run at all?

Bellsaw Electrdic Planer Runs Backwards

Just got a very old planner/saw "Bellsaw". hooked it up an it runs backwards. I have wiring diagram off of motor tag an changed wires around incase that was the problem. No luck. all 4 wires coming out of motor are black so color coated diagram does me no good at this point.

IT is a Wagner alternating current motor, type-RA, frame-225, model-B1211 M 295, 3 Hp, 1750 RPM, 1 phase, 60 cycles. is the information on the tag. any info would be helpful. - On 2020-11-27 by Cindy

Can I reverse the motor giving hydraulic power to a car lift?

Just purchased a replacement hydraulic power unit for a 2 post car lift, but the motor has a sticker that has the rotation in opposite direction. Can I remedy this by swapping wires or do I need to order another one? On 2020-10-18 by Abel

Reply by (mod) -

Abel

Some motors are wired such that you can reverse the rotation direction. To know about your specific motor you'll need to identify the brand and model and check the instruction manual

Air Conditioner COndenser Fan motor runs backwards

AC Condenser fan 1/6 hp 208v
The motor would not run.
I replaced the capacitor
Now a call for cool: motor runs slow
Thermostat satisfied: runs backwards. On 2020-06-06 by Dennis -

Reply by (mod) -

Dennis

A you may suspect, a bad (or mis-wired) starting capacitor can let a motor run backwards as can other causes listed in the article above.

However, if we are sure that the voltage to your motor is correct, then I suspect the motor was and is now failing.

Thermo King Double-Shafted Blower Fan Motor Run Direction Repair

I picked up a double shafted blower from a guy I know, and it has no nameplate, no specs, no info at all, however it did have a piece of sticky paper slapped on it and read 115v 3 phase (don't know who wrote it) Is there such a thing as 115v 3 phase?

The motor has 3 terminals labeled T1, T3, T4, the Ohm reading for all windings is 4.3 Ohm's, If it was a capacitor run motor the windings would have different values.

Using a variac I did experiment with wiring it up different ways using a run cap on the extra terminal and with a high enough MFD the motor will run in the right direction but it struggles unless the MFD is over 100 and with the cap connected the amp draw comes up to 10 amps before I bring the variac up to 120v ac,

however if I disconnect the cap after the motor is up to about 70% speed (max rpm is either 3000 or 3450) the amps goes down but the motor can't keep it's speed up while loaded blowing so much air and it stalls out. So what I'm trying to figure out is what is this motor?

is it 120vac? 240vac? single phase? 3 phase? - On 2020-01-23 by hl4ehalflife -

Reply by (mod) - Thermo King double shafted blower motor rating and wiring determination

Thanks for the interesting photo and questions, HL.

I did a reverse image search combined with your phrase double-shafted blower motor to find some similar products like the

THERMO KING DOUBLE SHAFT MOTOR 104-651 1.5 HP 1600 RPM 27 VDC 52 AMPS - see the pair of images I'll post below.

Perhaps this is a HVACR air handler motor ? The country of original/use would also of course give a clue about voltage and phase specifications.

Followup by hl4ehalflife

Hey Dan, I have no idea where it came from, I've never seen a blower like this in HVACR, When I had the blower off just one side the motor was able to reach full speed after disconnecting the cap and man does it ever blow some air.. If I had to guess each side is moving between 600 to 700CFM.

Reply by (mod) - How to figure out an electric motor rating if there is no data tag,

For figuring out a motor rating if there is no data tag, from various sources I've reviewed, the general approach:

Determine motor's rated voltage: feed the mystery motor using an automatic transformer that allows you to vary the output voltage - input voltage to the motor.

Increase the voltage until the motor speed reaches steady state; that's probably the motor's rated voltage level. Ideally measure the motor's rotating speed and record it as it speeds up. Note that for typical HVAC motors in the U.S. the two standard speeds are 1725 or 3450 rpm but you already knew that.

Determine the mystery motor's amperage rating: with the motor rotating at its rated speed increase the load on the motor and record the current drawn, taking care not to overload the motor (watch the speed).

This engineering website has useful tips
https://www.eng-tips.com/viewthread.cfm?qid=314985
Excerpts:

You have to know:
what kind of motor[dc,induction,synchronous] and at least no. of poles,frequency,stator length and bore diameter.

For induction motor the electromagnetic force E=.95*Voltage [approx.] Within 20% precision:

E=4.44*frq*w*kform*Fi [frq=frequency 50 or 60 Hz]

Fi=2/pi()*tau*li*B

B=7000-9000 gauss [0.7-0.9 Wb/m^2] Magnetic flux density in air gap

kform=0.8-0.9 depends on ratio Y/tau

Y=coil[loop] width

w=no.of turns in series per stator phase.

tau=Dstator*pi()/no.of poles

and

I will supouse is a low voltage motor (< = 600 v)

1. take a look of the connection block and you can have an idea, (6 wires connected in star= high voltage, connected in delta= low voltage)ej: 380/690, 380(d), 690(y) or maybe 230/400, 220(d)-400 (y), if the motor is with out block terminal then take a look of the end wire quantity (12, 9 or 6)and how are wired.

2. then estimate the power output (by taking all sizes of shaft gross, frame bolt distances and shaft center height, then you can estimate the frame.

3. uncouple the motor (if it is), perform a megger, if is ok , connect the motor in low voltage connection (d) and run then read the no load current and speed.

4. the full load current will be 3* that current(aproach)

with frame, no load and rated current and speed go to catalog and find the match motor.

and the electronics stack exchange offers these
tips to find the rated voltage of the induction motor without nameplate data
https://electronics.stackexchange.com/questions/194353/tips-to-find-the-rated-voltage-of-the-induction-motor-without-nameplate-data

finally
Snell group appears to have expertise on this; you may want to ask them for help.

https://www.thesnellgroup.com/blog/can-i-test-motor-without-nameplate-information

of all of these, without special equipment such as a variable voltage output transformer and a type of dnyamometer or an rpm measuring device (some optical ones are inexpensive), looking at the number of terminals for possible wire connections is the simplest and most informative starting point. i attach an example motor wiring diagram from leeson. [Click to enlarge any image]

Of course the blower could have had some other industrial application.

Followup by hl4ehalflife

I do own a non-contact tachometer for RPM measuring as well as several variac's, Can any of those methods be used if the motor is 3 phase and only have access to single phase?

Reply by (mod) -

It's possible to run a 3 phase motor on single phase current with some ancillary equipment but you'll need a variable frequency drive and some wiring tips. Precision Electric, a vendor of VFDs has advice at https://www.precision-elec.com/how-to-run-a-3-phase-motor-on-single-phase-power/

Followup by hl4ehalflife

Actually I just remembered that I have a 3 phase washing machine motor (belt drive front load washer) Would that work to create 3 phase?

Yea I don't have a VFD or a spare 3 phase motor to rig up a rotary phase inverter.

Reply by (mod) -

Hl

I'm afraid this conversation has soared into the stratosphere well above my level of competence. I think there's a three phase motor is one that's designed to run on 3-phase current but it doesn't produce three phase current

Followup by hl4ehalflife

So it the motor is 3 phase, it draws about 5 amps @ 3350Rpms at 110vac. I find it odd that its only a 120v motor yet it's 3 phase.

Frigid 3-Speed Motor Floor Fan VEL20TS spins backwards after I repaired it - what's happening

Curtis said:

I have a vintage Frigid 3-speed floor fan model VEL 20TS (looks kind of like this but much older and blue) [shown below] that was in bad condition,

the plug was broken, the 3-speed switch was broken, a wire inside the motor was broken off (wouldn't run at all),

so long story short I have replaced/fixed all the issues but a new problem has cropped up...

the motor is spinning in the wrong direction,

The motor has 4 wires, a common (yellow) low speed (red), med speed (blue) high speed (black), each speed works but is just rotating in the wrong direction and that baffles me..

I know a lot about motors and such and know that I COULD reverse the motors rotation by taking it apart and flipping the rotor 180 degrees but than the wires wouldn't be long enough to reach the switch.

I just don't understand why this is happening. - On 2020-01-01 by - Curtis

Reply by (mod) -

Curtis:

1. are the fan blades a backwards (just flip the fan blades over) ?

If not

2. the fan motor has been damaged internally or you made a wiring error

3. on SOME electric motors (but probably not your fan) there are start & run capacitors (or a combined start/run cap) that can be damaged and thus the motor could start backwards.

Details of the causes of reversed motor direction are in the article above. Let's start by stepping through those diagnostics.

Followup by Curtis

It wouldn't matter if the fan blade was on backwards, it would still blow in the wrong direction just less efficiently. This motor does not have any cap's, this motor is just a very basic 3-speed synchronous motor. - On 2020-01-09

Reply by (mod) -

it sounds as if you've ruled out all of the options except for motor that's damaged internally such as perhaps by a power surge or mechanical failure that shorts wires

Followup by Curtis

The winding look good, the amperage it draws when running isn't over spec (5amp) however it does have kind of a burny smell to it, how would a short in the winding make it go to other way? wouldn't it just draw higher current?

Reply by ( (mod) -

Curtis

Is there a data tag on the motor and if so does it indicate that the motor can be wired to run in either direction? (I suspect not on a simple fan motor)

This is a single-phase AC motor, right? Otherwise for DC or 3 phase motors there are other possibilities. (DC just switch the power leads).

And we're sure there's no start/run capacitor, right? (Sorry)

Is there a start winding whose leads are reversed?

About the winding, I've not encountered it myself but some techs tell me that a burned motor winding can cause the motor's run direction to reverse. That would be consistent with a burnt odor that you mentioned

Followup by Curtis

Unfortunately there is no tag on the motor, it's just a simple 120AC single-phase 3-speed fan motor, no run cap just a switch for each fan speed, I've had to motor apart to repair a corroded wire and to clean the dust out of it too.

Reply by (mod) -

It's going to trouble but perhaps you can find contact for the fan manufacturer, armed with model no. and maybe serial no. (as they may change whose motor they use) then ask the mfg what motor it is and who makes it.

Also have you actually tested the windings? m

find our articles on

ELECTRIC MOTOR DIAGNOSTIC GUIDE - home

I'll see if I can find other things to look-at or try;

Followup by Curtis

I have Ohm'ed the winding and got the following (Low) 5.9 Ohms, (Med) 5.4 Ohms, (High) 3.7 Ohms, no shorts to ground.

Reply by (mod) -

Those ohms readings look reasonable.

You may have seen ELECTRIC MOTOR TESTS - Electrical Tests to Check HVAC Blower Fan Motor or Outdoor Compressor Fan Motor Winding on Heating or Cooling Equipment or on Other Electrical Motors - at https://inspectapedia.com/electric/Electric_Motor_Diagnosis.php#GenAdv
for which I'd welcome any suggestions

Followup by Curtis

I'm filmier with HVAC as I've worked on them for 19 years, Short of rewinding the motor I figure it's toast...

Reply by (mod) - floor fan motor runs backwards, debugging trials

Yeah and the cost of further fooling around trying to fix it is probably more than a new motor.

That's exactly when I tell myself I I can tear the whole thing down to bits as I've got nothing to lose, and I might see something interesting inside.

On 2020-01-23 by hl4ehalflife

I'm trying it out right now and it is working, the 3 phase motor creates back EMF and that's where I'm getting the 3rd phase from.

Reply by (mod) - phase current is usually applied to power large, heavy-use electric motors.

Hl

Agreed; 3 phase current is usually applied to power large, heavy-use electric motors.

This must have been a heavy-usage blower (or motor converted to power that blower) in a location where only 120VAC was available.

This illustration of the electrical wave forms of 3 phase current is from Wikipedia's entry on the subject - https://en.wikipedia.org/wiki/Three-phase_electric_power

See DEFINITION of ELECTRICAL POWER PHASES - Single Phase vs Two vs Three Phase Electrical Power

Wood Cutting Machine Started Rotating Anti-Clockwise: how do I fix it?

MY WOOD CUTTING M/C( GL110 YURI GREEN LINE)MOTR STARTED ROTATAING ANTY CLOCKWISE? HOW TO RECTIFY? On 2018-06-2 by VINOD KUMAR

What causes phase love in a non capacitor induction motor¿ the strart windings that is - On 2018-06-16 by Anonymous

Reply by (mod) -

My best explanation is given in the article above. Indeed it's possible that from damage an electric motor can switch direction and begin to run backward.

Well pump won't spin - what do I try first?

I pulled up my well pump because it was abandoned by previous owner. ( They put in a whole new well). It is 300 ft deep, I pulled it up and found that it is oil filled, but when power is applied, it tries to start one direction, and can't, then tries the other direction, and can't.

I tried helping it by spinning g the shaft by hand but nothing helped. It is a 2 wire 240v sta-rite motor. What can be wrong? On 2018-05-07 by Scrawny Conan -

Reply by (mod) -

Possibly a bad start - run capacitor.

What makes a shop fan run in opposite direction

What makes a shop fan run in opposite direction in 1st&2nd gear and start smoking, but run in right direction in 3rd gear fine On 2017-06-09 by loveel

Reply by (mod) -

Loveel

I agree that's a curious question.

I but can guess that we've got one of the "motor runs backwards" causes listed in the article above like a bad start capacitor AND perhaps a shorted motor winding that are taken out of the circuit once the motor gets up to speed in the higher gear.

 

On 2023-02-25 by Mikee - No matter how I wire it this motor runs backwards

I have an old 3-phase AC HVAC motor with 160V DC battery back-up capability. The motor has DC four inputs which I assume are brushes and the Field windings. The problem is no matter how the DC side is wired, it turns backwards. (the AC turns correctly) I have tried all wiring combinations on the DC inputs and no luck.

Anyone even hear of an issue like this? I'm mind blown, any help would be appreciated.

A little more info. There are 4 brushes which drop when the AC side fails and then the DC side takes over.

On 2023-02-26 by InspectApedia Editor - DC motor runs backwards

@Mikee

DC motor runs backwards?

I'm unsure of the cause of this DC run direction problem. Almost always when the DC motor runs backwards it's because you've reversed polarity in two of its connections.

Check to see if the brushes have been removed and replaced in the wrong (swapped) position. In particular, when re-assembling the motor, if you mis-align the end plate that determines the exact position of the brushes, that could cause the DC motor to run backwards.

Check to see if motor rotor orienting magnets have been moved from their proper position.

Also, we read that when dis-assembling and re-assembling a DC motor it's possible for the motor to lose its electrical field orientation. A repair procedure described in SOME DC motor guides involves "flashing" the motor's coils by directly applying 12V DC to the motor's field coils (with proper connections of + and -) during re-assembly.

Post a photo of the motor's data tag showing it's brand and model model number and let's both look for the specific IO manual for that motor to get its run direction problem fixed properly.

 

On 2022-06-22 by Trevor - I switched wires to reverse motor direction and now it hums and burns but doesn't run

I have a very old one and a half horsepower motor that I bought at a yard sale it is 115 volts or 230 volts and has a ring on the back to change direction I have been running this motor many directions for about a week and one day I tried to switch directions and the motor would not run

so I tried to go back the other direction still would not run so I moved the ring in between directions and got the motor to start but it ran very weak and slow and started burning I am not sure what else to do whether I should put brushes in it or not but I can't figure it out

On 2022-06-22 by InspectApedia-911 (mod) - Changing run direction is basically done by moving one wire connection between two points on the motor windings

@Trevor,

Watch out: TURN IT OFF immediately if you haven't already - to avoid a burn-up

I'm not expert on this but I think the control you were swapping is probably corroded, loose, or defective.

Changing run direction is basically done by moving one wire connection between two points on the motor windings.

IF that switch was loose or corroded it might simply fail to make good electrical contact.

I hope - but don't know - that it couldn't possibly be establishing a connection, albeit a weak one, between both terminals at once - which might certainly fry a motor.

"Connect line leads to terminals 1 and 4. To change rotation, interchange blue leads on terminals 1 and 4"

I have a perfectly good, healthy 1952 English Electric 240v (uk) 1/4HP Single phase, which has been used for many years, with my small modelling lathe. it is wired for CW when viewed from the pulley end. I have never had a reverse on my lathe, but really could do with it.

As part of a complete lathe overhaul/rebuild, I have now got to the stage of working on the Motor. I am now about to renew the perished old mains cable, and have today removed the cover plate. (See photo of terminal housing)

The Note inside the terminal cover states the following:

Quote: "Connect line leads to terminals 1 and 4. To change rotation, interchange blue leads on terminals 1 and 4"

I now plan to fit a new 240v lead, but also to include an additional 1.5mm 4 core lead, and a new 240v DPDT switch, (cross - wired for polarity switching).

The intention is to disconnect the 2 Blue wires from the terminals 1 & 4, and to instead connect them directly to one pair, from the 4 core cable, and up to the switch. The other pair would then return back directly onto terminals 1 and 4.

This should then provide forward and reverse switching. (As long as the motor is fully stopped, prior to switching over !)

My issue is that the so called blue wires are actually jet-black. (See photo) But the only other two are Red. Before I start doing anything, can I assume I am correct that these 2 Black wires are in fact the Blue ones stated in the cover plate (ie - starter coil wires) ? Thanks in advance
On 2021-08-31 by Gary Armitage -

On 2021-08-31 by inspectapedia.com.moderator - in single phase motor, when you reverse two leads to change its run direction, you're reversing the polarity of its start winding

@Gary Armitage,

I am not much more certain than you and together it's betting your lathe motor not mine, but as there are no other wires in the photo that could be providing the role of those "BLUE LEADS" I'd assume the two dark leads to terminals 1 and 4 are just what you and the instructions indicated.

As yours is is a single-phase motor, (by your description and because there are only two hot leads to the motor) when you reverse two leads to change its run direction, you're reversing the polarity of its start winding.

So if inspection of wiring or wiring diagram confirm that those two dark leads go to the start winding, (and this is a single phase motor), then you'd be more-certain.


For other readers:

A 3 phase motor would have three hot leads, and by convention if we were going to reverse a 3 phase motor start and run direction we'd probably swap leads 1 & 3.

 

Need to reverse the motor rotation from CCW to CW

I have an old 2Hp 3450 RPM electric motor that is wired for CCW rotation. Need to reverse the rotation to CW. Unfortunately the name plate is pretty messed up so cant read complete or even if I can reverse the rotation on this motor. It is a single phase 115V with two external capacitors.

I have added the image of the motor with labels as to how it is currently wired. Any help would be greatly appreciated On 2021-04-03 by Kenneth

Reply by danjoefriedman (mod) - Here is how to reverse the motor rotation from CCW to CW

@Kenneth, I'm too scared of burning you up to pretend I know the right answer, but we do have both a clue in the wiring notes on the motor label (enlarged below) and in our article on this topic found at

ELECTRIC MOTOR RUN DIRECTION - topic home

where you'll find details of various methods of reversing a motor's run direction

Manually-reversible Electric Motor Run Direction

By swapping wire connections on some electric motors it is possible to change or reverse the motor direction.

Typically purple and yellow wires or wire pairs permit this change. Purple to purple = rotate clockwise

Purple to purple = rotate clockwise
Purple to yellow = rotate counter-clockwise

For an example of electric motor wiring that includes wiring to select electric motor speed options as well as direction of rotation see [live link on the topic page I cited)

Dayton Electric Motor Wiring Diagram [PDF], Dayton Electric Mfg. Co., 5959 W. Howard St., Niles IL 60714 USA, retrieved 2017/07/09, original source: Grainger.com

Your motor doesn't use purple, and wiring differs depending on voltage you're supplying but it's a start.

Other wire change examples to switch electric motor run direction:

Switch Yellow and Blue wires (ending with RED->Yellow & BLUE->Black

Concept: we're reversing polarity at the motor start winding. So if you can identify the start winding that'll be helpful.

If your motor uses a starting capacitor, see which motor winding is wired to the start capacitor - that's the start winding.

When you find the start winding, just swap the two wires that connect to the two ends of the start winding - that should change its direction and thus the rotation direction of the motor at start-up.

On 2021-04-04 by Ken

@danjoefriedman, Thank you, This motor has two external capacitors will start in trying to identify the start winding and work from there. I greatly appreciate your help and will get back with you once this is going.

Ken

On 2021-04-04 by danjoefriedman (mod)

@Ken,

Thank you for the follow-up I'm of course very interested as we will both learn something from this. Take a look at the article to which I referred you for more details and options.

On 2021-04-10 by Ken

@danjoefriedman,

This motor has both a start capacitor (Red wire on #4 lug), it also has a run capacitor (blue wire on #5 lug). I conducted a continuity test on all of the wires. I have continuity on all of the wires. So if I am testing wires on any fo the lugs they all have continuity with each other.

On lug one I have the Line1 (Power - black wire) and a black w/ yellow strip wire (BY). BY goes directly to the reset switch. Lug 4 - red wire from start capacitor. Lug 5 - Blue wire from run capacitor, Tan wire to reset switch, and an orange wire that goes to winding. Lug 6 - Yellow wire (to motor), white wire (to motor) Line2 (Power - neutral).

I did a test on all wires by moving them from one lug to the next etc. The motor will revers direction and operate normally if I switch red wire (lug 4) with yellow wire (lug 6) but will only run for 10 secs and then the reset switch is tripped.

Any other configuration results in trip reset switch, blown breaker, motor rotation of about 100 rpms, or no operation. Any other ideas would be much appreciated. Thanks

On 2021-04-10 by danjoefriedman (mod)

@Ken,

We figure that the start capacitor is wired to the start winding - Terminal 4. So you've got that figured out;

DId you take a look at any of the motor manuals at our home page on this topic ELECTRIC MOTOR RUN DIRECTION ?

We'd like to find the wire from the other end of the start winding.

 

Why would a shop fan motor run backwards in higher gear

What makes a shop fan run in opposite direction in 1st&2nd gear and start smoking, but run in right direction in 3rd gear fine On 2017-06-09 by loveel

Reply by (mod)

Loveel

I agree that's a curious question. I but can guess that we've got one of the "motor runs backwards" causes listed in the article above like a bad start capacitor AND perhaps a shorted motor winding that are taken out of the circuit once the motor gets up to speed in the higher gear.

 

On 2016-12-08 by Dan mcallister - Oil burner motor vs pump vs blower rotation direction

On a Beckett burner if the fuel pump on the left side turns counter-clockwise and the blower on the right side with the squirrel cage turns doesn't that mean that that blower motor has two turn clockwise to make the oil pump turn counter-clockwise this was a big discussion and I was told I would have to turn counter-clockwise

I don't believe that is correct and the risk of sounding dumb can somebody tell me if I'm right or wrong I believe that if the oil pump is turning counterclockwise the blower motor has to turn clockwise

On 2016-12-09 by (mod) re: 3 oil burner components & motor run direction must all agree

Dan

On most oil burners the 3 components are hooked up in this order, often from right to left:
Motor

Squirrel Cage fan
Fuel unit

The motor couples to the fan that couples to the drive shaft of the fuel unit (fuel pump in your note)

They all spin in the same direction.

If a motor runs backwards (because of damage or mis-wiring) some components might also rotate but the system won't work at all.

In sum I agree with you. Besides anybody can simply LOOK into the oil burner assembly to see how things have to run.

On 2017-03-19 by Colette

@Dan mcallister, yes, you are correct.

On my Beckett, it has an arrow indicating a CCW direction.

On the covers of both the blower motor and the Beckett, it has a picture of the cage with an arrow going CW from the furnace opening. Hope that helps. And, thank you! Your inquiry helped me! Thank you for your understanding of the units!

On 2017-03-19 by (mod) re: motor run direction stamped on a Beckett oil burner motor

Colette

Thanks for the comment, that will help other readers.

Indeed while from the factory we'd expect all of the oil burner components to be correct, at BLOWER FAN ASSEMBLY CLEANING https://inspectapedia.com/aircond/Air-Handler-Blower-Cleaning.php we include an example of how easy it might be for a technician to install a squirrel cage fan backwards with respect to its drive motor shaft - it'll spin fine but it wont' deliver air in that position.

 

 

On 2016-12-05 by Grant

I had problems in the summer and replaced a small circuit board in the outside compressor and the unit seem to run fine in the cool mode. After I flipped it to heat mode although I had a little heat I noticed a lot of ice build up on the outside compressor coils.

Then we had a power outage yesterday and I noticed the fan running in reverse when the power came back on? The one thing I cant be sure of was it running in reverse when I changed the circuit board in the summer. suggestions please!

On 2016-12-05 by (mod) re: why does my motor run backwards after a power outage

Grant,

You might want to review the article above for explanations of common causes of an electric motor running backwards. That's a good place to find things to check and repairs to try.

I suspect you'll find a bad start capacitor

 

Determine run direction for a Bauknecht single phase motor

I have a Bauknecht single phase motor, start and run windings are not fastened to the switch, how can I tell the polarity of the start and run windings before fastening the wires to the switch. On 2016-11-09 by Bob W.

Reply by (mod) re: how to identify electric motor terminals to wire it correctly

Bob,

To identify the specific terminals on your motor and thus the right wiring connections you need just the motor brand (Blaunecht) and model - see your motor's data tag. Then if you don't already have a wiring diagram for the motor I'd contact the company's tech-support:
Whirlpool UK Appliances Ltd
209 Purley Way
Croydon
CR0 4RY
United Kingdom
Tel: 0344 815 8989
Web: http://www.bauknecht.co.uk/

 

How to turn a motor from left to right with button system

How to turn a motor from left to right with button system - On 2016-10-14 by Aditya mukati -

On 2016-11-09 by (mod) re: how can I tell polarity of run and start windings on an electric motor

Aditya:

If your electric motor uses a starting capacitor to operate, you can reverse the starting direction of the motor by reversing the start winding polarity. It should be a simple circuit design to provide either a pair of start buttons or a cycling button that reverses the polarity on the start windings.

To reverse motor direction the motor will, of course, have to stop fully before re-starting in the opposite direction. Matthias Wandel, over at Woodgears.ca has written a nice, clear article on reversing electric motors of various phase and size designs. See https://woodgears.ca/motors/reversing.html

 

Hydraulic fork lift motor runs backwards after I replaced the brushes

I have an old Clark 24v forklift. Before I got it some one put new brushes in the hydraulic pump motor. NOW THE MOTOR RUNS IN THE REVERSE DIRECTION. I tried swapping the power leads but it still rotates the wrong way. Can you help me? Thank you. - On 2016-08-12 by Ron W. -

Reply by (mod)

Ron:

There are several reasons a motor runs the wrong direction, including the explanations I give in ELECTRIC MOTOR RUN DIRECTION

Let me know if that helps you out. You can find that article also (though I've given the link) by searching InspectApedia for "electric motor runs backwards"

 

Question: heat pump ran fine, then started blowing heated air out through the return registers

Turned on our heat pump and system was working fine for about 3 hours. Without warning, the system started blowing heated air through the return. System had been off for about 2 weeks as we transitioned from summer to fall/winter. The filter on the system had just been changed. System is off now. What we thought was smoke was dust from the system. The air handler/return had been replaced about 5 years ago. Again, system seemed to be working fine. Any ideas? - A.S. 11/13/2013

Reply: check for an air handler blower motor running backwards

A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone. You will find additional depth and detail in articles at our website. That said I offer these comments:

I'm guessing that in shifting from cooling to heating mode, your system correctly reversed refrigerant flow and began using the heat pump to heat building air, OR is running off of back up heat, perhaps electric, depending on outside temperatures. So the delivery of heat does not sound like it's part of the problem about which you ask.

Key in your statement is the rather unusual observation that air started blowing out of the return registers.

I suspect that you have a problem with the blower fan motor, wiring, or controls. It is possible for some electric motors to actually begin to run backwards.

While a typical air handler blower fan uses a squirrel cage fan that does not move much air when it spins in the wrong direction, it will move some. And blowing air backwards through the return ducts might indeed be expected to dislodge dust, blowing it back into the occupied space.

Ask for service from your HVAC company, and see if the technician finds a bad electric motor winding, start capacitor, or electronic control, or possibly a control damaged by a power surge or outage.

Reader follow-Up:

We finally got resolution for our system. We had a bad capacitor replaced with the correct size. A few years ago, a capacitor went bad in the air handler and the technician replaced it; the issue (speculation) was that since he did not have the correct size on his truck, he used a smaller size that was minimal at best. It finally wore out. - A.S. 12/4/2013

Reply: Thanks so much ..., I'm glad it's resolved - I had not considered a too-small start capacitor installation as a source of later starting capacitor failure but it makes perfect sense.

 

Thank you to our readers for their generous comments

On 2017-05-0 by Qahtan Al-zaidi

Thank you for the explanation. It is really helpful in diagnosing such a.c motor faults

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Continue reading  at ELECTRIC MOTOR RUN DIRECTION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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• CAPACITORS for HARD STARTING MOTORS
• DEFINITION of ELECTRICAL POWER PHASES - Single Phase vs Two vs Three Phase Electrical Power
• ELECTRIC MOTOR DIAGNOSTIC GUIDE - home
• ELECTRIC MOTOR RUN DIRECTION - topic home
• MASTER ELECTRIC COMPANY MOTORS

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