3 Phase or Single Phase

[Haldir]

I have 4 systems used to perform a process – a press, extruder, and two ovens. In the past three of the four units were 240-230V single phase systems with one of the ovens being a 3 phase 208V system (Delta).

Someone told the ME I’m working with that the three phase saves on your electrical bill because it keeps the line balanced; however, it would take 8 of these ovens to significantly imbalance the line according to the manufacturer of the heater elements (How can I prove this?). Now the ME is pushing to have all four units 3 phase and the bosses are buying in. But I do not see the use because all we will do with the 3 phase within the other three units is pull off one phase for one single phase 3 horse motor (or smaller heater) and another phase for the logic PS.

I personally would like to use 240V single phase on all because three of the systems would not need to be changed and I know you can use the standard three prong 240V plug – which most facilities and possible customers would have.

Are there any industry standard plugs/receptacles for 3 phase 208V power or do you need to use J-Box connections?

What are the advantages/disadvantages of 3 phase over single phase here or viscera?

 

[wareagle]

You pay for energy in the form of kwh. It doesn't matter if you use single phase equipment or three phase equipment. If the ovens are the same wattage you will use the same amount of energy.

 

[Haldir]

Thanks for the feedback wareagle. In reality yes, the wattage is the same whether it’s 3 phase or single phase; however, the power company will “compute the demand used for billing purposes on the assumption that the load on each phase is equal to that of the phase with the greatest load.”

 

[twosockets]

Haklir,

That is a very odd way of calculating a demand charge! Is this a U.S. utility? If so, I would ask to see a copy of their rate structure.

Greg May
Two Sockets - Two Meters, Inc.
WEB:

http://www.socket-two-me.com

 

[wareagle]

I agree with Haldir. Utilities usually have a kw or kva demand meter to establish the demand for your service. The rates then are applied to your demand and kwh. The meter will caculated the correct demand. There should not be any assumptions. You need to check this out.