Automatic Transfer Switch Problem

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Discussion Overview

The discussion revolves around the challenges faced by a user, Danilo, regarding the integration of a 3-phase automatic transfer switch with a 1-phase electrical supply. The focus is on the compatibility issues between the existing power supply and the generator, as well as potential solutions to prevent the transfer switch from misinterpreting the power phases.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Danilo describes a situation where a 3-phase automatic transfer switch is incorrectly interpreting a lack of phase due to the 1-phase power supply, leading to unwanted activation of the emergency generator.
  • Some participants express concern over the appropriateness of using a 3-phase generator with a 1-phase supply, suggesting it complicates the setup unnecessarily.
  • Danilo mentions a potential workaround involving a double delta or zigzag configuration to adapt the generator for 1-phase use, but highlights the main issue with the transfer switch's operation.
  • One participant questions the feasibility of connecting a 3-phase generator to a 1-phase system and suggests that a single-phase transfer switch might be a more suitable solution.

Areas of Agreement / Disagreement

Participants generally disagree on the suitability of a 3-phase generator for a 1-phase supply, with some advocating for a different approach while others focus on the existing equipment constraints. The discussion remains unresolved regarding the best method to address the transfer switch issue.

Contextual Notes

There are limitations regarding the assumptions made about the electrical configurations and the specific capabilities of the equipment involved. The discussion does not resolve the technical challenges presented by the integration of the generator and transfer switch.

danilorayob
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Hello,

I have an ONAN OTUDD100-4/1201C (Serial j810595543) automatic transfer swicth for a 30 KW 120/240 V 3PH Generator. The control panel is also 3PH. Nonetheless, the power company electric supply is 120/240V 1 PH 3 Wires. My issue is:

1. When we connect the above-mentioned current we will lack phase 3 and the transfer switch will interpret that there are only two phases and will, by default, start the emergency generator. Thus, I would like to know how to prevent this from happening.

Danilo
 
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Danilo,

Welcome to PF!

If you currently have a 240V 1 phase supply, why would you attempt to have a 3 phase back-up generator? This is a nightmare! "Supply is 120V/240V 1 PH 3 Wires" is standard single phase. There is NO good way to connect a 3 phase generator to your existing panel. Even if you did, you would need some way of balancing the load, and that is far more complicated than simply purchasing a 30kW single phase generator. I am not certain who decided you should purchase a 3 phase generator, but you should make them take it back, it is completely unsuited for your needs.

Fish
 
Dear Fish4fun,

I appreciate your concern and advice. Let me give you some background on the case. I am Nicaraguan and Nicaragua is a kind of wonderland where people buy equipment without knowing if they suit their needs. The problem is that the 30 KW 3PH Generator is already bought, is old and cannot be returned. Thus, I have to work with it imperatively. But this is the least of my problems because I can make the generator work as a 120/240 V 1 PH via a double delta or zigzag combination for 1 PH for the 12 lines coming out of the generator.

My real problem is the ONAN OTUDD100-4/1201C (Serial j810595543) automatic transfer switch which is 3PH and will interpret that 1 phase has failed and thus will not carry out its tranference function.

I appreciate your kind advice,

Danilo





Fish4Fun said:
Danilo,

Welcome to PF!

If you currently have a 240V 1 phase supply, why would you attempt to have a 3 phase back-up generator? This is a nightmare! "Supply is 120V/240V 1 PH 3 Wires" is standard single phase. There is NO good way to connect a 3 phase generator to your existing panel. Even if you did, you would need some way of balancing the load, and that is far more complicated than simply purchasing a 30kW single phase generator. I am not certain who decided you should purchase a 3 phase generator, but you should make them take it back, it is completely unsuited for your needs.

Fish
 
Can you purchase a 1 phase transfer switch? Other than that, I think you might not have any other options.
 

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