Two electrical questions

[®smpr_fi_mac®]

First question: Can anybody tell me what I need to run this 90V, 1/4hp motor with 110V? The answer is probably really simple, but I'm confused. Note that it's *not* a permanent magnet motor.

Second question: Which two legs from my 10/3 (220V) line do I connect to this switch? It's a remote switch for my air scrubber. I *think* it's my two 110 legs and then the third leg runs directly to the motor. Please correct me if I'm wrong.

[TDKPE]

That's a DC motor.  Don't connect it to AC power.  If you want it to stay in working condition, that is.  

[TDKPE]

As to the switch, it looks like you could either run both hot lines to it and switch them both, or one hot and the neutral, and just switch the hot.  Though I don't know why you'd have a neutral for a 240V motor. 


You can switch just one hot line, and the motor will turn off, but if you do you'd want to have a disconnect on it or near it that disconnects both.  But that's normal and code required regardless.

[®smpr_fi_mac®]

TD--

I know I can't run AC *directly* to the motor. What I'm looking for is an adapter that will convert 110V AC to 90V DC.

On the 3 legs in the 10/3: Aren't two legs "hot" 110V and the third a common? I forget the nomenclature.

[TDKPE]

On the 3 legs in the 10/3:  Aren't two legs "hot" 110V and the third a common?  I forget the nomenclature.

Nomenclature - with cord, all conductors are counted.  10/3 cord has three insulated conductors, and is used for 120V (hot, neutral, ground), or for 240V (hot, hot, ground).

With cable, like NM or AC, the equipment ground is not counted, as it's always there.  For the same thing as 10/3 cord, you would specify 10/2.  The ground is already in there.

So for a normal 230V (nameplate voltage) motor, it's either 10/3 cord or 10/2 cable or building wire.  No neutral in either case, as it would have nothing to connect to because it would have no function.

[KLaz]

If it's 220V, then your black and white wires are both hot wires, use the other (green) for ground.  These wires are coming from your panel to this switch correct?  What is your amperage?  #10 wire seems a bit overkill for a fan motor.

[®smpr_fi_mac®]

KLaz, I ran 10/3 all around my shop for 220V so that 5hp motors won't be a problem. It's a small shop, and an expense that wasn't too great for the benefit. The 110V circuits are all 12/2.

TD, It's been a while since I've opened up the 10/3, and I'm not an electrician, so I may have forgotten. Aren't there actually *four* wires in 10/3? Three insulated and a bare copper? I think that's what's confusing me in your description. If there are four wires, and the bare one is ground, why is one of the three insulated conductors also ground?

Ugh. I need to open up my wiring book again.

[KLaz]

TD is right as 10/3 cord only has three wires, two hot and one ground (if using with 220V). 
 
Now there is is 10/3 wire with ground and you get 3 conductors along with a ground. You don't need that.  

You just need two wires and a ground for your application

[KLaz]

Here is a typical SO cord that I run from my 220V machines to a receptacle.  It is specified simply as 10/3

Black and white are my hot legs and the green is your ground.  That's it.

[attachment=23280]

[TDKPE]

What KLaz said.  The nomenclature depends on whether you're talking about cord or cable or building wire. 

Cord has many uses other than the common stuff we use, and can have many conductors inside, all of them insulated.  Power, control, signal, some mixture of the above (within certain restrictions), while the cable used in building wiring has but one use and comes in very limited configurations. 

So the flexible 'rubber' cord you're going to run from your receptacle to the air filter will need to be 14/3 or 12/3 SJO or SO cord or something like that, while the stuff in your wall is 10/3 NM (non-metallic, which includes a bare ground), or armored cable (unlikely if it's inside your wall), since you wired it to be 30A and 120 and/or 240V capable.

Remember that flexible cord counts all the conductors, and they're all insulated, while building wire only counts the insulated conductors but always has a bare ground, at least since they stopped making cable without the bare ground, back in the 70's I think.

Next time you're in a BORG, look at the cord on the big rack of cable reels and compare the number of conductors to the designation on the label.  Compare that to NM building wire, which has one more conductor than the designation (the bare ground).

Edit: Too slow - KLaz put up a good graphic of a 3-conductor cord.