Blower wiring - Is split 220 kosher?

[turbodig]

I've got 4 110v motors. Is it advisable (and code-kosher) to run a 220 line to it, and split the phases? Ie, tie the neutrals on the motors together, and run 2 off one phase, and 2 off the other?
Or would this cause an imbalanced load issue?

My alternative is to run 2 30a 110v circuits, which I can do, but I don't really like the idea of having multiple power cords.

Thanks,

Dig

[86rocco1]

I think it depends on how your 220 line is wired up. If you've got 3 conductor wire (the 2 power wires plus a ground wire), welders, air compressors and other 220v only equipment are often wired this way, then I would say it's probably not advisable. But if you've got 4 wires (2 power, 1 neutral and a ground), clothes dryers and cooking stoves are wired like this then, it would be acceptable

[turbodig]

[49-1183904562]

[color=#000000]A Primer in Flow bench wiring. Any and all please add and correct as you see fit.

My take on flow bench wiring, About 30 years ago I spent a couple days in the hospital with RF burns on some fingers and a slower heart rate. My dad (an EE) told the doctor

[Tony]

Excellent writeup Rick.

I agree 220/240 v is the only way to go with any sort of reasonably sized flow bench.

While wiring two motors in series is entirely practical, and certainly works, it has one slight disadvantage. If one motor blows up, it will usually destroy it's mate. It is probably preferable to use the white fourth wire, and power each motor individually from 110 as suggested by Rick. That way, if one motor spits the dummy, only that motor dies. It is only a minor point, but if the white fourth wire is available, it is best to make use of it.

The only thing I can add to Ricks excellent Primer, is to always use plastic handled switches and knobs if possible. Any metal handled toggle switches carrying 110/240v must have the exposed metal part grounded to the green/yellow wire. This usually happens automatically in something built into a metal cabinet, but a wooden structure with metal switches or knobs can be very dangerous if the exposed metal is not grounded.

Something similar can happen with motor speed controls. The temptation might be to remove the "guts" from it's plastic box, and mount it behind a metal front panel. This can be very dangerous. Safest to leave it enclosed in it's plastic box, and extend the control shaft using plastic parts. A very simple (flexible) shaft coupler could be made from rubber fuel hose and hose clamps.

[bruce]

I went to Lowes today and picked up a Square D QO 100amp panel for roughly $22, I already have 6 - 15 amp QO breakers so I figured I spend a tad more and go QO instead of Homeline.

6/3 wire is $2.17 a foot and that will handle how many amps? And how far from the main box can I run to an outlet?



Edited By bruce on 1200874596

[martyester]

6/3 is good for 55 amps per US National Electrical Code. How far do you intend to run the wire Bruce? Is this going to be the feed wire for the new circuit breaker panel? Short runs of 6/3 will carry much more.

[bruce]

I'm going to setup my bench as discussed here and as Larry C. has discussed with me for sometime now in emails. I never took the time to see how much a 100amp box cost and after reading this post I realized it was the cheapest and safest way to go!

My shop is maybe 30 feet from my main panel, this would feed my new bench subpanel through a 4 wire dryer outlet. I have a 200amp service just could not run any other major appliances while the bench is running!! LOL

[thomasvaught-1]

Super Flow benches are wired up with the 3 wire deal and do use 110 motors in series (whites tied together) with each black wire for a motor set going to one leg of the 220 wiring. I promise you if one motor dies, it WILL kill the second motor.

I wire my benchs using the 4 wire method. 2 black wires, a white wire, and a green wire. Breakers in a panel on the bench then going to a main
on the bench and finally to a 4 prong 4 wire electrical source.

Just like house wiring and works very well.

A shop tried to run one of my benches on three phase 208 volt power and destroyed several motors from overspeed until we identified the wiring error.

There should only be 110 volts across any given vacuum motor with my
wiring and typically rarely over 10 amps draw on any given motor.

Tom V.

[49-1183904562]

Just a quick update and clarification.

3 conductor US 220/240 service, there will be two different configuration you may come across depending on where you live and how old your shop or home is. First is in older homes it was not uncommon to find the main panel Neutral lug bar BONDED to the ground lug bar with a Green Bonding screw or made as one bar, this ties the Neutral to Ground (remember the old two prong duplex outlets with no ground). But with the advent of GFCI this went away. So a 3 conductor 220/240 Say stove or Dryer outlet may have one of two types of wire going to it, the first is two black or black & red insulated conductors and one white insulated conductor, the other will be two insulated conductors (black, black or black, white or black, red) and a bare ground.

If you have an outlet that is wired with the two insulated conductors and a bare ground DO NOT TRY TO WIRE YOUR BENCH TO SPLIT OUT 110/120 CIRCUITS AS YOU WILL BE CREATING A POTENTIAL GROUND FAULT. What I am saying is never under any circumstance use a bare wire as NEUTRAL.

If the third conductor is insulated you can use it to wire as neutral but the main panel must have been BONDED or you will have to make sure this wire is connect to the Neutral Lug Bar and also Ground your bench with a fourth separate wire.

If you are not sure ask a professional in your area even if it is just to come evaluate your current wiring configuration.

Rick

[thomasvaught-1]

Thanks for the additional info Rick.

You think you could post up a schematic like I did in the forums with a wiring schematic?





Tom V.

[49-1183904562]

[color=#000000]I have been thinking about Tony and Tom both emphatic that the second motor will blow if the first goes. So I thought I would pose a couple cinereous of what is going on and maybe a safety precaution that might save a motor. When one of these universal motors goes bad it can be one of several failures, frozen bearing, armature short/open, a brush failure etc. The two wires of the motor connect to the Brushes and the field winding in parallel. If the armature is not getting voltage the motor does not create the necessary circuit load. Now if I am thinking about this correctly if we take the armature out of the picture the field winding just becomes a conductor and the second 110/120 motor now sees 200 + volts and self destructs. So my thoughts are since the circuits perceived load is almost cut in half, current is going to almost double.

Lets say these motors on the average draw 7 amps running full load, Ohms law says current = voltage divided by resistance so in this case the motor is acting like 17+/- ohms. ( yes i know this is AC and it is not exact) So if we use two motors in series and connect them to a 220/240VAC circuit it is 7 = 240/34, resistance doubled and voltage double current stayed the same. Now one motor goes bad and the field becomes a pseudo conductor, lets say not 100% but close say the voltage across motor 2 goes to 200VAC 200/17=11 the circuit now draw 11 amps and motor 2 spins out of control until it self destructs. Since your 15amp 220 breaker the motors are connected to doesn

[49-1183904562]

Tom i will Draw one up and post it I will also try to take some pics of some of the basic components.

Rick

[martyester]

To add the fuse between the two units is a good idea. However, 10 amp fuse is not a good idea. Motors at time zero (the instant the motor turn on) has theoretically infinite current draw. Motor has at turn on (theoretically) infinite torque and therefore infinite current draw. The time period the current is very high is very short (milliseconds). This is what is called surge current. A motor at turn on will see more than three times the operating current. Fuses blow very quickly and will more than likely blow. A circuit breaker would be a better choice and are rated by time and temperature. As an example, a 20 amp circuit breaker will be rated at 20 amp for 100% of the time at normal temperatures. As the temperature rises around the breaker, the breaker will trip at a lower current and if the temperature is lower it can handle more than it is rated at. As for time the shorter the duration of the current spike, the more a circuit breaker will handle. So, if the motor is rated for 10 amps continuous draw, it would be necessary to put a 15 amp breaker between them. Not to be too windy, the down side to the breaker is it may not react quick enough to the failure to protect the second motor. In my line of business (aircraft), breakers are only to protect the wiring and not the product.

[thomasvaught-1]

Quote:

"Now if I am thinking about this correctly if we take the armature out of the picture the field winding just becomes a conductor and the second 110/120 motor now sees 200 + volts and self destructs. So my thoughts are since the circuits perceived load is almost cut in half, current is going to almost double."

When the electrician had the bench wired at 208 on each leg the amps across a motor was about 20 amps and the motor was screaming in rpm. All of the failures were from overspeed (fan distruction) or armature + brush contact failure (severe arcing). A similar motor on 110 would pull 7-9 amps and about 13 amps on start-up.

We have circuit breakers for each motor now with the 110 V type 4-wire wiring.

If the motor sees the 220 volt power across the motor the noise will be apparent and then you will hear the massive "boom" when the fan comes apart. If you have a clear port hole where you can look at the brushes sparking on the armatures, the normal arcing will be minimal. With the increased voltage, the arcing will be a large fireball. I would worry about a potential fire on a wooden bench. An enclosure box with formica on the inside of the enclosure probably would be fine.

Tom V.