| We will be discussing changing a direct drive | | | | Once the blower assembly is on the floor, we |
| blower motor and capacitor on a traditional up | | | | turn it on it's side and remove the screws or |
| flow gas furnace as would be found in a | | | | bolts that hold the mounting bracket to the |
| basement of a home as these types of furnaces | | | | assembly. We then turn the blower over again |
| are by far the most common. Changing motors in | | | | and remove the set screw or bolt that holds the |
| horizontal units in an attic or a crawl space are | | | | motor shaft onto the wheel at the hub. With this |
| very similar but will vary with the equipment. If | | | | done, we should be able to turn the assembly on |
| you are not comfortable with working on 120 volt | | | | it's side and the motor should drop out of the |
| equipment please consult a professional Heating | | | | assembly. We say "should" because 7 out of 10 |
| and Air Conditioning company to do this work. | | | | times it will, the other 3 times we will have to |
| Before we begin, we go shut off the main 120 | | | | gently tap on the end of the shaft with a brass |
| volt power to the furnace. This may be able to | | | | drift and hammer to drive it out of the wheel. |
| be accomplished by turning off the switch at the | | | | Often we will have to use WD40 on the shaft |
| furnace where the main power comes into the | | | | first and sometimes may need to use sand cloth |
| furnace. Sometimes this switch is mounted on the | | | | on the shaft if there is any rust present. Beating |
| floor joists above the furnace, or on the side of | | | | on the shaft with a hammer will ruin the shaft and |
| the furnace itself. In the interest of safety, we | | | | it will not come out of the wheel! A new wheel will |
| also shut the breaker off at the main house panel. | | | | be needed if this happens. |
| We use of a volt meter to be sure the power is | | | | With the motor out we can now remove the |
| really off. | | | | mounting bracket and attach it to the new motor. |
| The next step is to remove the screws or bolts | | | | Some motors have the bracket welded to the |
| that hold the blower assembly up inside the | | | | motor from the manufacturer so they will not |
| furnace. Some blowers are on a sliding track while | | | | require this step. Now everything is reversed for |
| others are simply held in by these bolts or screws | | | | the re installation of the motor. We must be sure |
| so it is a good idea to use a small 2"x4" piece of | | | | the wheel spins freely in the assembly without |
| lumber to lower the blower out of the furnace as | | | | hitting anywhere before we raise it back with the |
| the holding screws are removed. If there is a | | | | 2"x4" lumber into the furnace. Once it is bolted |
| control board attached to the blower assembly all | | | | back in place we reach in to the wheel area and |
| wires should be labeled so that if any wire is | | | | spin it once again to be sure it is running free. |
| knocked off it can be re installed on the correct | | | | All that is left is to re install the wires (including the |
| terminals that it came from. Hopefully the blower | | | | green ground wire that goes to a metal unpainted |
| assembly will come down with all the wires in | | | | part of the blower), on the control board or fan |
| place. If there is a control board mounted on the | | | | center and mount the new capacitor or re use |
| blower we will have to remove it with the wires | | | | the old capacitor if it is the correct one for the |
| all attached and tie it up out of harms way. The | | | | new motor. We now go turn on any power |
| same is true of any other component mounted | | | | source switches and or breakers that we |
| on the assembly. | | | | previously had shut off. Turn the thermostat up |
| Once all this is done we should be able to remove | | | | to call for heating and our furnace should be |
| the wires from the motor and capacitor, but first | | | | running at this point. Be sure the rotation of the |
| the capacitor wires must be shorted out with an | | | | motor is actually blowing air through the registers, |
| insulated screwdriver by touching the screwdriver | | | | if not we may have to reverse the rotation wires |
| to both terminals of the capacitor at the same | | | | on the motor. We will now check the amp draw |
| time. Not doing this will result in us getting a nasty | | | | of the motor with an amp meter and compare it |
| shock if we touch those terminals with bare | | | | to the amp rating that is on the motor or |
| hands! Now we remove all the motor wires from | | | | documentation that came with the motor to be |
| where they are attached to the furnace control | | | | sure the motor is operating as it should be. This |
| board or fan center (we have labeled all these | | | | amp draw check must be done with the blower |
| wires before this). | | | | door on however. |