Can a Zig-Zag Transformer Provide a Neutral for 3-Phase HVAC Control Circuits?

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SUMMARY

The discussion centers on the use of a zig-zag isolating transformer to provide a neutral point for a 3-phase HVAC control circuit that lacks a neutral supply. The project requires a transformer capable of handling approximately 15A for a control circuit operating at 1-phase 230V, powered by a 3-phase 400V supply with a 400A breaker. Participants emphasize the importance of consulting a licensed electrician for installation and sizing guidance, as well as identifying manufacturers that supply zig-zag transformers.

PREREQUISITES
  • Understanding of 3-phase electrical systems
  • Knowledge of HVAC control circuitry
  • Familiarity with transformer sizing and specifications
  • Experience with electrical safety regulations and standards
NEXT STEPS
  • Research zig-zag transformer specifications and sizing methods
  • Explore manufacturers of zig-zag isolating transformers
  • Learn about electrical code requirements for HVAC installations
  • Investigate the role of licensed electricians in commercial electrical projects
USEFUL FOR

Electrical engineers, HVAC technicians, project managers overseeing HVAC installations, and anyone involved in designing or implementing control circuits for 3-phase systems.

halam
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Hi

We have a project where we have to install an HVAC system but only a 3-phase supply is available. While that is fine for the motors inside the unit, it means that there is no neutral available for the control circuitry.

I am aware that a "zig-zag" isolating transformer can provide a neutral point in a 3 wire system but I have not used it before.

The control circuit will require approx 15A, what is the correct method of sizing the transformer, also is there any manufacturers out there that can provide this product?

Attached is a possible solution, as it mentions the zig-zag option. Would this fulfill the requirement?

Some details for our project:
Available supply: 3ph 400V (400A Breaker)
Control Circuit: 1ph 230V (24no 230V Contactors & 4no Siemens PLCs - Approx 15A)
 

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halam said:
Hi

We have a project where we have to install an HVAC system but only a 3-phase supply is available. While that is fine for the motors inside the unit, it means that there is no neutral available for the control circuitry.

I am aware that a "zig-zag" isolating transformer can provide a neutral point in a 3 wire system but I have not used it before.

The control circuit will require approx 15A, what is the correct method of sizing the transformer, also is there any manufacturers out there that can provide this product?

Attached is a possible solution, as it mentions the zig-zag option. Would this fulfill the requirement?

Some details for our project:
Available supply: 3ph 400V (400A Breaker)
Control Circuit: 1ph 230V (24no 230V Contactors & 4no Siemens PLCs - Approx 15A)

Welcome to the PF.

You need to use a licensed electrician to help you with this project. We cannot help you here.
 

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