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ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
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ELECTRIC MOTOR DIAGNOSTIC GUIDE
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KNOB & TUBE WIRING
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LIGHTNING PROTECTION SYSTEMS
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LOW VOLTAGE TRANSFORMER TEST
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MOISTURE SOURCES in PANELS
MURRAY SIEMENS Recall
PHOTOVOLTAIC POWER SYSTEMS
PUSHMATIC - BULLDOG PANELS
REMOTE ELECTRIC POWER, PHOTOVOLTAIC
RUST in ELECTRICAL PANELS
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SE CABLE SIZES vs AMPS
SIEMENS MURRAY Recall
THERMAL EXPANSION of HOT WATER
THERMAL EXPANSION of MATERIALS
UNDERGROUND SERVICE LATERALS
VOLTS / AMPS MEASUREMENT EQUIP
VOLTAGE MEASUREMENT METHODS
WIND TURBINES & LIGHTNING
ZINSCO SYLVANIA ELECTRICAL PANELS
Electric motor test & repair guide:
This article 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.
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In this article we provide a diagnostic guide to determine and repair problems with electric motors. The page top photo was taken of of an oil burner electric motor not an air conditioning blower fan motor or pump motor, but you'll see that all of these electric motors look a lot alike. At left our photo illustrates the motor as typically found in a direct-drive HVAC blower or air handler assembly. (BLOWER FAN OPERATION & TESTING)
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.
What Are the 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 Table A 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:
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.
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.
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
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.
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.
Questions & answers or comments about how to troubleshoot electric motors such as air conditioning compressor motors, heating equipment burner or fan motors, swimming pool motors, water well pump motors
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