[TowerTalk] Wiring Sky Needle tower for 220 VAC

Jim Brown jim at audiosystemsgroup.com
Tue Nov 5 02:10:02 EST 2013

On 11/4/2013 10:48 PM, Ray Benny wrote:
> Has anyone done such a rewire of their control box to run the motor at 220
> VAC with the remainder of the box running 110 VAC? All relays and delay
> switches run on 110 VAC.

I don't know anything about the control box, but I know a lot about 
power wiring that might help you think through the schematic. Think of 
the power source as a center-tapped transformer with the neutral 
connected to the center tap -- 120-0-120 referenced to neutral. The 
controller must run between one side of 240V and neutral (not ground), 
and the motors must run between the two legs of 240

If the controller does nothing but sense position and drive relays that 
control the motors, it can run from 120V, while the motors run through 
the relays from 240V.  In other words, the control side (the logic and 
relay coils) are running from 120V (one side to the neutral) and the 
motor is running from 240v (120 - 120) through the relay contacts.

It may also be possible that the controller has dual primary windings so 
that you  can switch the controller so that its power transformer has a 
240V secondary, which could simplify things.  In that situation, you 
don't connect the neutral.  No matter what, we must connect the grounds 
(green wires) for safety, but we cannot use the ground (green wire) to 
carry current, even the small current for the controller. You're 
covered, because you've pulled a neutral for that purpose.

73, Jim K9YC

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