3-Phase Power Questions

Our electric brewery will be located in an industrial building that is fed with 3-phase AC power. Our electrician friend wired two of the hots, neutral, and ground to a Home Depot GFCI spa panel. The panel appears to be wired correctly and pressing the Test button works as intended.

When measuring voltage between each leg and neutral we get 120V, but sure enough, across the two "hots" we get 208V.

What is going to be the effect of only feeding 208V to the 5500W heating element - I'm guessing it will take longer to reach boil, but boil it will, correct?

Second, will the GFCI work as intended if it needs to - that is, will the fact that we're only using 2 of the 3 legs of the 3-phase power somehow cause problems such as GFCI not tripping when it needs to, or tripping when it's not supposed to? There are also 120V pumps powered off one of the hots and neutral.

Assuming that 5500 W rating is at 240 volts, you will only get about 75% of that at 208 volts, or 4131 watts. Whether or not that will boil depends on how much wort you are trying to boil and how well insulated your kettle is. The GFCI should work OK as it only measures the total current in the two hot wires and neutral which should always add up to zero (with current in one direction being positive and in the other direction negative) if there is no leakage path to ground.

DeafSmith said:

Assuming that 5500 W rating is at 240 volts, you will only get about 75% of that at 208 volts, or 4131 watts. Whether or not that will boil depends on how much wort you are trying to boil and how well insulated your kettle is. The GFCI should work OK as it only measures the total current in the two hot wires and neutral which should always add up to zero (with current in one direction being positive and in the other direction negative) if there is no leakage path to ground.

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Quoted for truth.

If you want 5500 watts, replace the element with one rated at 208V. Here's an example:

http://www.comfortgurus.com/product_info.php/products_id/7089

sdugre said:

If you want 5500 watts, replace the element with one rated at 208V. Here's an example:

http://www.comfortgurus.com/product_info.php/products_id/7089

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Great post!
That vendor has a lot of 'stuff' that fits our needs. They are one of the vendors on my Excel build source file.

Thanks a lot for your post.

P-J

Thanks for the great info, much appreciated. If we go with a 5500W element @208VAC, then it going to draw 26.44A, correct? Add a couple pumps and it's starting to get real close to 30A rating on the breaker installed in the panel. Seams like to do this "right", probably should go with 50A breaker and bring 50A into the control panel, along with heavier wire, etc. Or else live with longer heating times.

That's correct. With pumps, you're probably looking at about 28.5 amps.

As far as what's "right" with regards to upgrading, I'm sure you'll get opinions on both sides of the coin. I'm personally in the "a thirty amp feeder is rated for thirty amps" camp. Of course, upgrading to 50A opens up other possibilities for your brewery, so I see this as a personal decision based on your needs.