Automatic Transfer Switch Problem

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The discussion revolves around the challenges faced by a user with an ONAN OTUDD100-4/1201C automatic transfer switch connected to a 30 KW 3-phase generator, while the power supply is 120/240V single-phase. The main issue is that the transfer switch misinterprets the single-phase supply as a failure of one phase, causing it to activate the generator unnecessarily. Participants highlight that using a 3-phase generator with a single-phase supply is inappropriate and suggest considering a single-phase generator or transfer switch instead. The user is constrained by the fact that the generator is already purchased and cannot be returned. The conversation emphasizes the need for a compatible solution to prevent operational issues with the 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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