Buck boost

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bzzzt

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This just aint adding up to me. I have a machine namplate is 230v single phase 24amps. Panel is 120/208v. I bought a Acme T-181052 buck boost 750va 12/24. It is rated 7.19kva/31.25a . I want to install a dedicated 30amp circuit to this. Am I ok or do I need to step it up to #8 with a 40a? If there is a dedicated circuit can you load a circuit more than 80% (not more than 100%))if it is non-continuous?

Thanks in advance
 
david luchini

david luchini

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For an autotransformer, the input needs to be protected with an OCPD not larger than 125% of the rated input current (allowing for the next standard size up.) For your transformer the input current would be 34.5A, so the largest OCPD could be 45A.

If your load current is 24A@ 230v, then the input current would be 26.4A @ 208V. As you have noted, if the load is non-continuous on this dedicated circuit then you could have a circuit breaker that is at least 100% of the load, or a 30A c/b in this case.

If the load was continuous, the c/b would need to be at least 125% of the load, or at least 35A.
 
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bzzzt

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Thank you for the reply.

I plan on tapping the 24v side of the secondary for secondary voltage 232v
 
david luchini

david luchini

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bzzzt said:
Thank you for the reply.

I plan on tapping the 24v side of the secondary for secondary voltage 232v
Click to expand...

I believe your output voltage will be 228.8V, not 232V. The transformer has a 10:1 ratio (240:24) so but applying 208V to the input, you'll get 20.8V on the second winding, and 208+20.8V at the output.
 
kbsparky

kbsparky

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Instead, get Acme T-1-81059. Its output is 16/32, and with that configuration, you will end up with a net gain of 28 Volts when connected to a 208 source.

236 is way closer to your target of 240 Volts.
 
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