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240vac to 24vac control transformer used for 120vac low current.

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
Got a 240v to 24v control transformer. Do people use the primary side for 120v?

The primary is two windings connected in series. For 120v use one side and the center. Thinking about doing this for low interval & low current (.200A) service.
 
If there is a center tap on the primary input that uses half the windings, applying 120V should result in 24V output. YOu could get yourself a voltmeter and just test it and see what you get on the output.
 
To explain more:

I have a 240vac to 24vac control transformer. The primary side is two windings in series with a center tap.
If I use one of the primary windings for 120vac, would cause a imbalance on the primary side?

I am thinking about this in terms or eliminating a control transformer (240 to 120). The 120vac would be intermittent use but would be switching in
Asco relays for releasing water in a air compressor system.
 
As long as you don't exceed the amperage rating of transfomer there will be no imbalance. Keep in mind that going from 240v to 120V will result in twice the amperage going through the primary, so you'll need to take your rated amperage for the transformer and divide by 2 when using 120V.
 
I'm not sure that the answers are getting at what the OP wants to do. I think he's trying to use a center tapped 240/24 volt transformer as an auto-transformer to provide a small 120V source. I apologize for the lousy circuit diagram, but I don't have any decent tools for this sort of work.

circuit.jpg
 
That's it. Primary is 240vac and secondary is 24vac.

Since the two valves (inductive load) could turn on and off at random I was thinking about transients propagating through the 24vac.
 
I'm not sure that the answers are getting at what the OP wants to do. I think he's trying to use a center tapped 240/24 volt transformer as an auto-transformer to provide a small 120V source. I apologize for the lousy circuit diagram, but I don't have any decent tools for this sort of work.

View attachment 257842

This idea is very suspect in my mind. A control transformer is intended to provide isolation between the voltage source (primary side) to the devices (secondary side) on the other side, basically preventing damage to the 24V devices in the case of power surges, etc...

If you want to get 120V from a 240V source, you need a simple transformer that has primary of 240V with 120V output.
 








 
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