Electric motor run direction and backwards-running motors:

Why would an electric motor suddenly start running backwards? Here we explain the causes and cures for a motor that is running backwards and we also discuss motors that are designed to reverse direction.

For those motors we give directions for a simple wire connection swap that can reverse the motor's run direction, and we include PDF downloads of detailed electric motor wiring guides that give direction reversal instructions for other electric motor brands and models.

Page top photo: a Dalton brand electric motor showing how we determine its run direction.

This article series describes A/C electrical motor troubleshooting: 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.

Run Direction of an Electric Motor: diagnose & fix

Here we describe the rotation or "run" direction of electric motors - clockwise or counterclockwise.

We explain why an electric motor might suddenly start running backwards, and we include instructions on how to reverse the direction of small electric motors by making simple wiring changes.

We also include a detailed example of how we reversed the direction of an antique Master Electric Co. brand motor and finally, we include free PDF downloads of detailed electric motor wiring and run direction reversal instructions.

Uni-directional electric motors run just one way: clockwise (CW) or counterclockwise (CCW) but not both.

Here our photo illustrates the motor as typically found in a direct-drive HVAC blower or air handler assembly.

While our page top photo shows the red reset button most clearly, the reset button on the motor at left may be harder to spot. Sometimes the reset button on an electric motor is hard to find, and sometimes there is no reset button!

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.

Article Contents

• BASIC ELECTRIC MOTOR COMPONENTS
• ELECTRIC MOTOR ROTATION DIRECTION - CAN AN ELECTRIC MOTOR RUN "BACKWARDS"?
• ACCIDENTAL REVERSAL OF ELECTRIC MOTOR RUN DIRECTION - causes
• HOW TO CHANGE ELECTRIC MOTOR RUN DIRECTION - reverse the rotation / spin
• EASY TEST FOR MOTOR WINDING DAMAGE
• MANUALS of INSTRUCTIONS for CHANGING MOTOR RUN DIRECTION - free PDF downloads

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Basic Components of an A/C Electric Motor

Such as used on heating and air conditioning equipment?

Before discussing how to diagnose air conditioner or heating system electric motors let's be sure we know what motor parts might be involved.

Or skip right to ELECTRIC MOTOR WON'T START / RUN if you prefer.

The electric motor has quite a few parts if examined in detail, switches, wires, possibly capacitors, oiling ports and more, but there are four basic parts to every HVAC electric motor:

1. Electric motor rotor:
   
   the rotor follows (turns in the direction impelled by) the rotating magnetic field and thus spins the motor shaft
2. Electric motor stator:
   
   the stator consists is a device or core containing start and run windings (of copper wire) wound around a central core to create a magnetic field.
3. Electric motor windings:
   
   the two windings are used to create an electrical field in the stator.
   1. Definition of Start winding:
      
      in an A/C (alternating current) electric motor electrical current flowing through the start winding is used just to get the motor spinning from a stopped condition.
      
      The start winding is disconnected, usually by a centrifugal switch, when the motor is up to speed.
      
   2. Definition of Run winding:
      
      in an A/C electric motor the run winding is what keeps the motor spinning once it has started.
      
      Current flowing through this winding produces a rotating magnetic field in the stator that keeps the motor shaft turning after the start winding has turned off.
4. Electric motor start switch:
   
   a centrifugal switch connects the A/C electrical power to the motor to the start winding on the stator until the motor has reached a speed typically of 75-80% of its full run speed (typically that's1725 rpm or 3450 rpm on newer high-speed oil burners).
   
   Also see ELECTRIC MOTOR CENTRIFUGAL SWITCH or PTC PRD

In addition to the basic electric motor components above there are two other features to know about when troubleshooting a motor.

...

Which way does an Electric Motor Run - Can Electric Motors run Backwards?

Information found on the electric motor's data tag.

Uni-directional electric motors run just one way: clockwise (CW) or counterclockwise (CCW) but not both.

In many applications the equipment driven by the electric motor will not work properly unless the motor drive shaft spins in a predetermined direction: clockwise or counter-clockwise.

Examples include HVAC unit blower squirrel cage fans whose blades won't move air if the fan runs backwards and oil burner or well pump motors whose oil pump or water pump won't move oil or water if the pump motor is driven in the "wrong" direction.

In a fixed-direction electric motor such as on an HVAC blower fan or an A/C or heat pump compressor, each time the motor starts its start capacitor and start winding give the motor a "kick" in the right direction.

Bi-directional & self-reversing electric motors run in either direction, CW or CCW

Bi-directional electric motors run in either direction and are used in applications in which the direction in which the motor spins doesn't matter to the equipment it's driving. "What the heck?" you're saying. Well here's a cute example - your home microwave.

Electric motors require a kick or to put it more like an engineer, a starting torque to overcome the resistance when the motor is to begin spinning from a stopped position. Compared to electric motors used in oil burners and air conditioning compressors, we don't need such a costly and heavy-duty electric motor to spin the rotating table in a microwave oven.

Instead, microwave (and some other self-reversing) electric motors use a clever design that allows for elimination of the start winding winding and also allows use of a lower-cost and less powerful electric motor.

When the motor has stopped the mechanism it drives remains pressed against the motor's drive shaft, providing a "driven load" ( the microwave turntable) against the direction the motor's shaft was last rotating.

When the motor is asked to start again it encounters this extra load due to the resistance provided by a mechanical mechanism in the turntable that was itself "wound" or loaded by the table's prior rotation.

The microwave motor, encountering this load, reverses itself to begin rotating in the opposite direction, one of less load, which gives a brief "no-load" interval that lets the microwave's turntable motor get up to speed.

In sum, the combination of a load or rotation resistance provided by the turntable mechanism and an automatic direction reversing feature in the electric motor gets the microwave motor spinning and the turntable rotating - which is why each time you start your microwave it is likely to rotate in the opposite direction from that of its previous cycle.

...

Can an Electric Motor Run Backwards by Accident or Because of Damage?

Watch out: yes it is indeed possible for some electric motors to run "backwards" following damage to the motor's start capacitor or windings.

We've had an occasional report of an HVAC motor running "the wrong way" or sometimes starting to run the the wrong way. For example the blower fan motor in an air handler can start and run backwards as can some air conditioner compressor unit cooling fan motors.

Typically an electric motor running in reverse direction is caused by (in order of probability)

• A failed electric motor starting capacitor
• A single speed single-phase motor leads are reversed on the motor's start winding connections
• A single-speed 3-phase electric motor has two of its supply leads reversed
• Belt driven air handler motors attached to a blower fan in a multiple-blower HVAC system can be turned backwards with the motor OFF and the squirrel cage fan rotating backwards because of air currents created by other fans that are on in the same system
• (For 2-speed electric motors you'll need to contact your motor supplier)

See POST a QUESTION or COMMENT for what appears to be an example of a backwards-running electric motor in an air handler.

Read the Information on an Electric Motor Data Tag to Determine the Motor Run Direction

In our photo at left you can see the notation on this electric motor data tag indicating the the motor is non-reversing and rotates counter-clockwise - designated by the words CCW ROTATION (red arrow).

If you enlarge the photo [Click any image to see an enlarged, detailed version] you will see text above the red arrow noting that this is a NON-REVERSING motor.

At ELECTRIC MOTOR DATA TAG we explain all of the information that can be found on the electric motor data tag.

Watch out: when buying replacement electric motors, fuel units, and blower fan assemblies to be sure they all are compatible. For example on oil fired heating equipment, the oil burner fuel units (the mechanical heating oil pump driven by the oil burner electric motor via a coupling) can be purchased as CW or CCW devices.

All three components have to be designed to rotate in a common direction:

1. the electric driving motor,
2. the oil burner combustion air blower fan assembly, and
3. the oil burner fuel unit or oil pump.

If the fuel unit is not rotated in the proper direction the heating appliance won't run - it won't receive fuel, and the driving motor and coupling parts may be damaged.

If a squirrel cage blower fan on an oil burner or inside of an air handler is spun backwards it will not move much air and equipment will not function properly.

...

How to Change Electric Motor Run Direction

Watch out: Determine proper rotation BEFORE coupling motor to load. Keep hands and clothing away from rotating parts.

Watch out: as we warn throughout all of these articles on electrical work, if you are not trained in proper, safe electrical work, stay out of your electric motor - you could be shocked or killed.

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. But depending on your electric motor type, phases (1 phase vs 3 phase), and voltage (120VAC or 240 VAC or other), other wires and wire color schemes will be used. We'll give several examples below showing which wires to swap to change electric motor run direction.

Typical 120V motor Wire Swap: Purple & Yellow

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

or

if your motor doesn't use purple, and if wiring differs (depending on whether the motor runs on 120V or 240V or other), here are some 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. 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.
  
  So if you can identify the start winding that'll be helpful.

How to Identify the Electric Motor Start Winding

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

Besides following the start capacitor wiring to the winding, another way to identify the start winding of your motor is to measure electrical resistance across the winding.

A start winding will have higher resistance than the run winding (for smaller 120VAC motors the start winding has about 3x the resistance of the run winding - perhaps around 4 ohms while a 240VAC motor will have more, perhaps 16 ohms on the start winding more than 2x the run winding)

Swap Leads to the Motor Start Winding

Besides following the start capacitor wiring to the winding, another way to identify the start winding of your motor is to measure electrical resistance across the winding.

A start winding will have higher resistance than the run winding (for smaller 120VAC motors the start winding has about 3x the resistance of the run winding - perhaps around 4 ohms while a 240VAC motor will have more, perhaps 16 ohms on the start winding more than 2x the run winding)

For motors that can be wired to run on either 120VAC or 240VAC the start winding will usually be just 120VAC - powered by one leg of your two 240VAC wires.

For common small induction motors it may be easiest to reverse the motor rotation direction by swapping the motor start capacitor leads in front of or behind the auxiliary (start) winding. (Qi 2019).

Small 3-Phase Electric Motor Run Direction Change

The above is for single phase electric motors; a 3-phase motor will be different.

On a 3-phase motor - provided it is fed with just 3 leads - you reverse its direction very easily by simply swapping any two power leads.

For a 3-phase motor with more than 3 leads you'll need the wiring diagram for the motor.

Below we provide IO manuals for ECM motors, single phase motors, and 3-phase electric motors.

Example of Re-Wiring a Motor to Change Run Direction

See HOW TO CHANGE RUN DIRECTION for a MASTER ELECTRIC 115V / 230V MOTOR - wiring an antique electric motor

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Simple Test for Motor Winding Damage

General advice: Electrical Tests to Check HVAC Blower Fan Motor or Outdoor Compressor Fan Motor Winding on Heating or Cooling Equipment or on Other Electrical Motors

Example: testing a blower fan motor winding: referring to the electrical diagram for your equipment, unplug electrical connectors at the fan motor.

Measure the resistance between each lead wire with a multimeter or VOM. The multimeter should be set in the X1 range.

For accuracy, don't measure when the fan motor is hot, allow it to cool off.

When the resistance between each lead wire are those listed in the specifications for your equipment the fan motor should be normal.

Zero resistance or infinite resistance are indicators of a problem.

See the electrical test tool & equipment articles listed at MORE READING

...

Electric Motor Manuals Include Changing Run Direction

The antique electric motor shown here is discussed in detail

at MASTER ELECTRIC COMPANY MOTORS

For an examples of electric motor wiring that includes wiring to select electric motor speed options as well as direction of rotation see the following guides.

Watch out: if you are not trained in proper, safe electrical work, stay out of your electric motor - you could be shocked or killed.

• COPELAND ELECTRICAL HANDBOOK [PDF] a helpful reference.

• MASTER XL RIGHT-ANGLE GEAR MOTORS & C-FACE REDUCERS SERVICE & REPAIR MANUAL [PDF] (2010) Master Power Transmission, 3300 Tenth St., Columbus IN 47201 USA, Web: www.master-pt.com - this manual is just gears - no motor.  - retrieved 2023/04/18, original source: d1odbfykel3oe2.cloudfront.net/wp-content/themes/reverie-master/images/pdf/manuals/E3614-XL-RA-12-28.pdf

• INSTALLATION, OPERATION AND MAINTENANCE OF RELIANCE® STANDARD INDUSTRIAL AC INDUCTION MOTORS - PDF is a book of wiring diagrams for the same series of motors when produced later under Baldor - as I'll explain in a historical note below.

• INSTALLATION, OPERATION AND MAINTENANCE OF RELIANCE® STANDARD INDUSTRIAL AC INDUCTION MOTORS - [PDF] book of wiring diagrams for the same series of motors produced later under Baldor
• 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
• IRONTON ELECTRIC MOTOR OWNER'S MANUAL [PDF] Northern Tool Northern Tool + Equipment Co., Inc. Burnsville, Minnesota 55306 USA NorthernTool.com Made in China - retrieved 2021/04/04 original source https://www.northerntool.com/images/downloads/manuals/29560.pdf
• Marathon, AC INDUCTION MOTORS [PDF] 56-5000 Frame, Manufactured for Allen-Bradley by Marathon Electric, Inc., retrieved 2021/04/04 original source: https://literature.rockwellautomation.com /idc/groups/literature/ documents/um/1329m-um001_-en-p.pdf
  Excerpts:
  
  These instructions must be followed to ensure safe and proper installation, operation and maintenance of the motor. They should be brought to the attention of all persons who install, operate or maintain this equipment.
  
  Changing Rotation
  
  1. Keep hands and clothing away from rotating parts.
  
  2. Determine proper rotation BEFORE coupling motor to load.
  
  3. Check rotation by jogging or bumping. Apply power to the motor leads for a short period of time, enough to just get motor shaft to rotate a slight amount to observe shaft rotating direction.
  
  4. Three phase - interchange any two (2) of the three (3) line leads.
  
  Single phase - reconnect per the connection diagram on the motor. Normally Open (N.O.) motor thermostats may be used in conjunction with controls installed by an OEM.
• MASTER ELECTRIC 115V / 230V MOTOR RUN DIRECTION CHANGE [Web page] Q&A on changing the wiring an antique electric motor
• MOTOVAIRO USE & MAINTENANCE INSTRUCTIONS for ELECTRIC MOTORS [PDF] (2019) Motovario, Teco Group, Motovario S.p.A. Via Quattro Passi 1/3 41043 Formigine (MO) Italy Tel. +39 059 579700 Paid-in Capital: Euro 18.010.000 i.v. Rea: R.E.A. di Milano n. 1863844 Website: www.motovario.com

• Qi, Fang, Daniel Scharfenstein, Claude Weiss, Clemens Müller, Ulrich Schwarzer ELECTRIC MOTOR HANDBOOK [PDF] (2019) Infineon, retrieved 2021/04/04 original source: https://www.infineon.com /dgdl/Infineon-motorcontrol_handbook-Additional TechnicalInformation-v01_00-EN.pdf?fileId= 5546d4626bb628d7016be6a9aa637e69
  
  Excerpt:
  
  The rotation direction can be set by the position of the capacitor in front or behind of the auxiliary winding as can be seen in Figure 18. [shown above]

• Sterling, SINGLE PHASE ELECTRIC MOTOR INSTALLATION & MAINTENANCE MANUAL [PDF] (2006) Sterling Electric Co., Irvine, California (800) 474-0520 Indianapolis, Indiana (800) 866-7973 Hamilton, Ontario (800) 809-0330 e-mail: sales@sterlingelectric.com www.sterlingelectric.com retrieved 2021/04/04 original source: sterlingelectric.com/manuals/Single Phase Motor O M Manual 032106.pdf
  
  Excerpt: Disconnect load and start motor. Check direction of rotation. Consult connection diagram on motor nameplate to change direction of rotation on bi-directional motors.
• Sterling, 3 Phase AC Induction Motors INSTALLATION AND OPERATION MANUAL [PDF] (2018)
• WEG, INSTALLATION AND MAINTENANCE MANUAL FOR NEMA LOW VOLTAGE ELECTRIC MOTORS [PDF] WEG Electric Motors Corp. 2100 Brighton-Henrietta Townline Road Rochester NY 14623 USA Tel: 716-240-1000 , retrieved 2021/04/04 original source: https://www.stevenbrownassociates.com/ pdf/drivers/electric/weg/motor.pdf
  
  Excerpt: This manual covers all the three-phase and single-phase asynchronous squirrelcage induction motors, from 140T to 580T frame sizes. The motors described in this manual are subject to continuous improvement and all information is subject to change without notice. For further details, please consult WEG.
• WWE, AC INDUCTION MOTOR IO MANUAL [PDF] Installation And Maintenance For Fractional Single-Phase and Polyphase AC Induction Motors This Manual Covers WorldWide Electric’s NT, NAT, NATE, NTJ, NATJ, NATEJ, WSSNV, WSS, NAWSS, NAWSSE, SSPE, FM, and FD Models - WorldWide Electric Corporation 3540 Winton Place, Rochester, NY 14623 Sales Support: (800) 808-2131 Technical Support: (844) 993-7378 www.worldwideelectric.net
  Excerpts:
  
  This manual includes procedures for the safe and proper transportation, storage, installation, connection, operation and maintenance of WorldWide Electric motors. For your protection, please read these instructions carefully before attempting to install, operate or service the motor.
  
  If rotation must be changed allow the motor to stop completely. Interchange any two incoming power leads of a three-phase motor to change the direction of the rotation. See wiring diagram.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

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

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.

...

Continue reading  at CAPACITORS for HARD STARTING MOTORS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see ELECTRIC MOTOR RUN DIRECTION FAQs - questions & answers posted originally at this article

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Suggested citation for this web page

ELECTRIC MOTOR RUN DIRECTION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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