Need to replace HVAC motor

[Max]

Yup, I replaced my filters a couple of weeks ago with the 90-day ones.

I contacted Heil and they were no help. They said that they don't do retail. I don't want them to sell me a damn motor, I want them to help me locate a supplier or give me a model number of a suitable replacement. I will be going into a supplier next week with the old motor in tow and see what mileage I get with that.

[LazyPup]

Based on the information on the data tag you posted that is a very common motor. Take the old motor in hand and go to any reputable HVAC supplier, and any counter man worth a second cup of coffee will have your replacement motor in hand before you can walk from the door to counter and say good morning.

[Max]

I'll be doing that tomorrow LazyPup. There is a Johnstone dealer just about 10miles from my work and I plan on stopping off there at lunchtime tomorrow.

[Max]

I got the motor off and the funny thing is that after I huffed and puffed to get it off it seems to spin around just fine now. I guess that's something to do with me beating on the fan to try and get it off the motor. I'm still going to get a new one as there's obviously something wrong with it.

Cheers, Max

Edit: I never did get the fan off so I'll probably just get a new one of those as well.

[lonestarheir]

"I never did get the fan off so I'll probably just get a new one of those as well."

That is why us HVAC Companies get paid so much money - proper tools for proper job, at least that is the way it is supposed to be. I spend alot of money on my companies tools and am glad to pay the heafty price to make my job easy. I guess that a lot of co's would have not taken the time to remove the fan as well and would have just sold you a new one. Oh well, that is how the cookie crumbles.

Good luck and hope everything goes well with your fan motor.

Have you changed your filter this month?

[Max]

I know what you are saying. When I used to do my own mechanics I built up a collection of tools that made routine jobs much easier. One tool that springs to mind is a flywheel puller, perhaps that is similar to what is required to remove the fan? Is there more to removing the fan than just brute force? It seems that the bolt is what is used to hold the fan in place and once it's removed the fan should just "fall off". I know I am exagerating. Gave it a burst with good ole WD40 but no luck.

[lonestarheir]

A blade puller is what you need - there are various types, but short of buying one(aprox $ 40-80)
your best bet is to do as you planned and buy a new one. Johnstone should have one. Just for grins you can try sanding the shaft between the motor and blade, once this part is sanded down good, knock the blade back towards the motor and sand the long part of the shaft. This will sometimes work, if done right, otherwise just buy a new one.

Have you changed your filter this month?

[Max]

Thanks again lonestarheir. I think for grins I'll just take a sledgehammer to it.

[Max]

Got my new motor and fan today. The guy in the shop tried get the old fan off with the fan puller but it didn't budge. Perhaps if I had known that a fan would cost $50 (with the attachment assembly) I would have asked him to be a little more motivated.

Looks like this going to be a little more complicated than I first thought but should still be doable. My old motor / fan assembly came off with just three wires attached, the new motor has 8 wires. OK, 4 of them are to control the direction of the motor so it's not that ominous. What is slightly confusing to me is that I got a new capacitor which connects between the brown and brown/white wire coming from the motor. My original motor did not have this configuration. It should become clearer when I get it all home and have the opportunity to look inside the condensor unit. Everything is clearly printed on the side of the motor (which is FASCO by the way, hopefully not a FIASCO) so I think I should be all set.

Thanks for the help guys.

EDIT: oh yeah, one more thing. Any suggestions for cutting the motor spindle? Will a hacksaw work just fine?

[LazyPup]

You new motor wiring is not nearly as ominous as you may think.

That is a single speed motor therefore the BLACK wire goes to LINE 1 on the contactor, WHITE goes to LINE 2. (common)

A brown wire is always a capacitor wire.

If the motor has a BROWN with White Stripe wire it goes to the capacitor Identified terminal (Capacitor common) Look for a painted red dot or a depressed dimple in the top of the capacitor. If the capacitor is not indexed you may use either terminal as common and connect the brown wire to the opposite terminal.

The color scheme fo the rotation wires may vary, but if you desire clockwise rotation connect the matching wires together, it you desire counter clockwise rotation connect the opposites together.

The excess motor shaft can easily be cut with a hacksaw, however if you have sufficient vertical clearance there is no need to cut off the excess.

I have attached a general illustration, Carefully check it against the wiring diagram on your motor before hooking up.

[Max]

Thanks, LazyPup. What you have said above matches nearly* exactly what it says on the motor body (minus your helpful additional detail) so I have more confidence. I don't have any clearance above the fan so I need to chop the spindle down. The previous motor spindle is about 2" long, the new one is nearer like 8" so I need to chop off about 6".

* Just to backup for a second, there is a slight difference between what you have said and the motor label. I have a green / yellow wire that needs to be attached to ground but other than that it's the same. That's my fault, I told you that I only had 8 wires when I really have 9.


EDIT: what is the capacitor for by the way? I have electronics experience from about 15 years ago (I was an apprentice in my late teens before I changed to computing) so I know what capacitors do in general.

[Max]

Got it.......

"The purpose of the starter capacitor is to provide a delay in a (typically) single-phase motor so that the motor has a chance to start turning without being hit with a deterring current before it gets up to speed"

[Max]

Got home, the motor doesn't fit. It looks the same size and it's the correct spec but the screws don't line up with the holes in the unit top. Do you think I can just screw more holes and fit the new motor or take the motor back? I was also wrong before when I said there was no clearance for the spindle. I was thinking of the fan assembly with the unit top UPSIDE DOWN. There is plenty of room for the spindle but I still think I will need to cut off a couple of inches, not 6 like I first thought.

Cheers, Max

[LazyPup]

You should be able to drill new holes without any big problem, just be sure you keep the motor exactly centered.

Now for your wiring question:

Per the National Electrical Code in all cases a bare, green or green with yellow strip wire is ground.

In most instances a motor will not have the green ground wire because it effects the electrical ground through the motor mount, however, because condenser fan motors are often supported on rubber vibration dampers they also include the green bonding wire attached to the motor house, and which is to be attached to any metal portion of the condenser housing.

NOW TO TRY TO EXPLAIN CAPACITOR FUNCTION:

First we have to understand basic AC voltage:



If a magnet is placed inside a coil winding and then rotated the magnetic lines of flux from the magnet will induce a voltage into the winding. In the case of the single pole generator as illustrated it would produce DC voltage.

If we then divide the winding into two parts and ground it at the center, as the magnet turns one side is charged positive while the opposite side is charged negative, and the polarity then changes every time the magnet goes past the center tap. This will produce ALTERNATING CURRENT. The speed of the rotating magnet is kept constant to insure the change takes place 60 times per second (60 hertz current) thus we must illustrate alternating current as a sine wave,constantly changing from zero to peak positive, to zero, to peak negative, back to zero and repeat the next cycle.



As you can see from the AC sine wave, residential AC has two poles, line 1 and line 2. The voltage then alternates 60 times per second (60hz) from zero to 120+ back to zero down to 120- and back to zero.

Voltage is technically a measurement of the difference in potential, therefore if we measure from line 1 to common we will find 120v and if we measure from line 2 to common we will also find 120v, but if we measure from line 1 to line 2 we will find a potential difference of 240v (+ 120 plus -120v = a differance of 240v).

All 120 volt devices connect from line to common.

240 volt devices use a double pole breaker to connect the device from line 1 to line 2. (Technically a common is not required.)

To understand a motor we must also understand inertia. Inertia is a physical force of nature that tries to keep a resting body at rest, or a moving body in motion unless acted upon by an outside force.

Thus if we just apply power to a motor winding while it is stopped, both the windings and the armature are energized but inertia tries to keep the armature at rest.(This is what is called "Locked Rotor". Many motors will have a LRA amperage rating, that is the locked rotor amps or the amount of energy required to start the motor.

We then need some physical force to begin the rotation.

A second set of windings is then installed in the motor and arranged so they are about 10 or 15 degrees out of alignment with the run winding. As the motor winding is energized, the start winding is also energized. The start winding being slightly out of alignment then tries to pull the armature in its direction which overcomes inertia and starts the rotation. Simple 120v motors such as you would find in a bench grinder have a mechanical Centrifical switch on the end of the armature shaft. As the speed of rotation increases a set of govenor weights swing outward and trip the switch to disconnect the start winding.

A 240 volt motor such as your fan motor also has two sets of windings, the run winding and the start windings. The run winding is wired directly to the power source, but the put a capacitor in the circuit between the source and the start winding. The capacitor causes a momentary delay in the power arriving at the motor winding, thus as the sine voltage on the run winding is changing from peak down to zero, the capacitor delay causes the start winding to be peak while the run winding is zero and vice versa. In this manner it has the effect of having one motor inside of the other, one at peak power while the other winding is at minimum and constantly changing.

This not only doubles the effective power of the motor,it also maintains a smoother balance of power against the load and a more evenly balanced load on the electrical service.

[Max]

Thanks again LazyPup. I have ANOTHER question after taking the side panel off the unit. The existing capacitor has THREE terminals. One of the terminals has a light blue wire that goes to the condensor (at least that is what I call it, it's the only other thing inside the unit and says, "charged with oil" on the top). The other two terminals connect to the red supply wire and the motor brown wire respectively.

To summarise the existing wiring:

MOTOR (3 wires)
BLACK - black supply
RED - red supply
BROWN - capacitor

CAPACITOR (3 wired)
RED - red supply
BROWN - motor
BLUE - condensor

I hope that makes sense. If not I can take a picture. I can't do that just now as we are about to run out to dinner.

Oh yeah, the capacitor I have right now has TWO terminals (as does every other capacitor that I've seen).

Thanks, Max