Help Wiring Furnas style drum switch to 9" SB w/ Westinghouse motor

My 1934 vintage 9" came with a 3 position toggle switch that I'm trying to replace with a 6 pole, Furnas style drum switch (from McMaster-Carr). It looks like it should be pretty easy but one problem is that I can't find any marking on the 4 wires coming out of the motor. The P.O. had them numbered 1-4 with tape labels where he spliced them so I'm not going to trust these numbers. The toggle switch is wired per the 1st sketch. All I know for sure is the toggle did work as a forward/reverse/off switch and that terminals A or B are connected to the center terminal when in Fwd/Rev position.

The plate on the WH 1/4 Hp type FH motor (single phase, 110V) has a plate where the wires come out that looks like 2nd sketch. The motor looks like it could be original to lathe. Can anyone help me hook this motor properly to the drum switch (3rd sketch)?

I found the last sketch on an old post and if I knew which motor terminal was which it would probably do the trick.

No one can help me with which wires are which on the motor?

Hi,

I haven't wired up the motor for my lathe yet. Hell, I haven't even run it once. But I don't think it should be too hard to figure it out.

Do you have any pictures of your motor? Are then any stickers/labels on it that might identify the wires? With the motor I got, there is a small cover on the side, under which the cables from the wire where connected to a small board with terminals on it. Maybe that will help you identify it?

Can you see colors on the wires coming from the motor you got? The motor I have had 5 wires coming out of it: white, black, red, orange, green. The green is just earth ground, so that leaves only 4 wires.

Ok, been doing a little reading. I think you will need to post pictures if anyone will help you in wiring this up. There really is no standard to follow, and each motor, each switch could be set up differently differently.

Start with the drum switch you got. With nothing connected to it, open it up, and take pictures of the contacts for all 3 positions: neutral, forward, reverse.

Then take pictures of your motor. There probably is a plate on the side, and two screws holding it. Remove the plate. See if there is a label on the backside of that plate. Take a picture of it. Also take a picture of how the motor is wired behind the plate to the cable coming out of it. You should see some terminals labeled L1, L2, 1, 2, 3, 4, 5. Make note of the color of the wires coming out of it, and which terminals they are connected to.

First, we need to be sure which kind of switch you have. Most furnas switches have the connections in an 'L' shape like this:

But some are more like cutler-hammer:


Assuming you have the first type, you want something like this:


To identify which wire is which, use a voltmeter to test for continuity between the various motor terminals. The readings will drift because of the capacitors, but it is not required to know which is the start, and which is the run, just which pair go together. The two coils can be switched on the diagram above. If it rotates backwards from what you want, switch the wires on one of the coils.

allan

Thanks for the responses guys. I was able to use a DVM to figure out the starting loop and running loop (I read somewhere that on a split phase motor, the starting loop has fewer windings, lower resistance). The switch connections are exactly as in the Furnas diagram from my previous post. The motor and wires coming out are as shown. Someone must have replaced the wires at some point since they are all one color.

Hello,

You got an older motor than I thought. Hehe. Since it is single phase, and there is no capacitor piggy backed on it, I think it is safe to assume it is a split phase motor. In this case, there will be two windings in it: starting and running. The windings are in parallel, but the starting winding is disconnected by a centrifugal switch after the motor reaches 75% of its speed, at which point only the running winding has current going through it. So first thing is first, you have to identify which wire pairs are for which winding. From wikipedia:

https://en.wikipedia.org/wiki/Ac_motor#Split-phase_induction_motor

"A split-phase motor has a startup winding separate from the main winding. When the motor is starting, the startup winding is connected to the power source via a centrifugal switch which is closed at low speed. The starting winding is wound with fewer turns of smaller wire than the main winding, so it has a lower inductance (L) and higher resistance (R)"

Since there are 4 wires coming out of it, and there are 2 coils inside, there are only 2 possible pairs of wires that will have a resistance between them when checking with an Ohm meter. One resistance will be higher than the other. The pair of wires that has a higher resistance will be the starting winding. The pairs of wires that has a lower resistance will be the running winding. Separate the two pairs, and mark the wires so you know which are the ends of which coil.

Next, you really have to verify that the switch you have, matches the one in the diagram you provided. There are 6 contacts on the switch, and the diagram shows you which contacts are shorted together in the forward and reverse positions. If you are 100% sure this is accurate, then proceed forward.

This is the combination of internal connections in the switch that seems to be common. Make sure this is what you have, or the wiring will not work right.


I have a Furnas drum switch as well, and the internal connections are different. Note the difference. This might be what you have too. I don't know.



So, assuming the first style is what you have, you would wire the motor up as shown in the diagram below:



The running winding (lower resistance) is marked with blue letter R, and its wires coming from the motor are connected to the switch terminals colored green.

The starting winding (higher resistance) is marked with red letter S, and its wires coming from the motor are connected to the switch terminals colored purple and yellow.

The 110V power line is coming in from the right. The hot (black wire) is connected to the switch terminal colored black. The neutral (white wire) is connected to the terminal colored white. These could be easily reversed, and functionally it makes no difference which one goes to which terminal, since we are dealing with AC current. So the neutral could go to the black dot, and the hot could go to the white dot. The difference between neutral and hot is that the neutral is the center tap of the transformer on the pole outside your house, and it's tied to ground. Normally, when you are wiring a switch for a lamp in the house, you are "supposed" to switch the hot wire, while the neutral wire is always connected to one end of the light bulb. Ideally, both the neutral and hot could be switched at the same time, but it's cheaper to just use a single switch for wiring a lamp. Since you are dealing with a motor and a drum switch, this consideration could be irrelevant. You might want to look at what the internal connections are inside the drum switch when it is in the off position. If there are no connections at all in the drum switch when it is set to off, then which way the hot and neutral are wired makes no difference.

Now examine how the Neutral and Hot wires are connected through the switch to each of the motor coils.

The running coil is connected to Neutral and Hot in the same exact way for both the forward and reverse positions of the switch.

Now the starting coil is a different story. In the forward position, the purple end of the starting coil goes to Hot, and yellow end goes to Neutral. In the reverse position, the purple end goes to Neutral, and the yellow end goes to Hot.

So..............

When you connect the wires from the running coil to the switch, which end goes where doesn't matter, Pick one orientation and stick with it.

When you connect the wires from the starting coil, pick one orientation, and try it. If you set the switch to forward, and your lathe is running as it should, then you are done. If however, your lathe is running backward with the switch set to forward, then simply reverse the wires from the starting coil inside the switch, and that should fix it.

In theory.

Hopefully this helps, but I make no guarantees. Proceed at your own risk. If anyone out there wants to add or correct anything, please do.

Best of luck.

One more thing. You should probably use a 3 prong AC cord, that has a Hot(Black), Neutral(White), and Ground(Green) wires inside it. Connect that green ground wire to the metal enclosure of the drum switch. That way, should something inside the switch comes loose few years down the road, you won't get electrocuted, since it will simply short to the grounded drum switch enclosure and pop a circuit breaker.

Thank you very much for the detailed help Iron Man. I had the starting and running coils mixed up (based on assuming running coil had more windings/more resistance). And I'll for sure be using a ground wire!

I got it all hooked up and it works great! Thanks again for the help.