current question

[will-max dairy]

Assumption 1: This heating element is in fact three phase, and is intended to be used with a phase-to-phase voltage of 208 volts.

Assumption 2: We'll assume that the heating element is delta, although what it looks like internally doesn't matter. It could actually be wye with a disconnected neutral.

Assumption 3: You wish to power it with three phase power with a phase-to-phase voltage of 240 volts.

When performing three-phase calculations, we always convert a delta configuration to its wye equivalent. That way we can just work with a single phase. The wye equivalent of 208V phase-to-phase delta is 120V phase-to-neutral wye. (208 divided by the square root of three)

Checking our work against the published specs for your heater, at 66.6 amps the power per phase is 8040 watts. (120V times 66.6 amps) The total power is 24,120 watts, which agrees with your 24 kW spec.

The wye-equivalent phase resistance is 1.8 ohms. (120 divided by 66.6)

The wye-equivalent phase-to-neutral voltage for 240 volts phase-to-phase is 139 volts. (240 divided by the square root of 3).

The current per phase is 77 amps. (139 divided by 1.8)

The power per phase is 10,700 watts. (139 times 77). Total power will be 32 kilowatts. (10,700 times 3)

And this would agree with my "smell tests"
For power, power is proportional to the square of the voltage.
240 squared over 208 squared is about 1.33... multiply that by 24KW and you get 32KW.
For current, current is proportional to the voltage.
240 over 208 is about 1.15... multiply that by 66.6A and you get 77A

And yes...

The current should go "UP"... and yes... it SHOULD be as simple as what you just calculated.

With some big IFs...

IF the internal wiring of the equipment can safely accommodate the different configuration.
IF the OP can correctly identify the equivalent phases to connect to.
IF there is no other chance for botching a connection

Math is simple, but not everything in life is reduced to math alone.

We haven't seen a picture of the pot... or even a picture of the wiring box on it... you know, like when you wire up a motor... you open up the junction box on the side; and there are detailed instructions for how to wire it for 120, 240... whatever. We can make assumptions about how it's connected to make the math work. But we need to say that they are assumptions and they need to be verified.

I've said my peace. It's time to let others roll their dice and move their mice.

PS... no baiting was ever intended...and I've done plenty of wiring as a non-electrician... so, I get that we all do a little cowboy engineering...but when people start throwing actual numbers at a non-electrician...then all assumptions should be stated clearly. This is a serious amount of power, the consequences of a miswiring are much more catastrophic than wiring the ammeter on the dash of your 2N Ford backwards...

 

[John T]

I’m an EE plus an attorney and dont know which of me could generate more words or get deeper in the weeds regarding a fairly simple answer. I enjoy and appreciate all my fellow sparkies when it comes to electrical questions and the abundance of responses. While I could do the math I’m still not feeling that energetic so my simple answer to a simple question without going deep in the weeds is to agree with jmor the answer is UP

Y’all have a god day now and as I’ve always noted any electrical or legal question really draws em out. A good bunch of folks here. Best wishes everyone

John T

 

[will-max dairy]

I’m an EE plus an attorney and dont know which of me could generate more words or get deeper in the weeds regarding a fairly simple answer. I enjoy and appreciate all my fellow sparkies when it comes to electrical questions and the abundance of responses. While I could do the math I’m still not feeling that energetic so my simple answer to a simple question without going deep in the weeds is to agree with jmor the answer is UP

Y’all have a god day now and as I’ve always noted any electrical or legal question really draws em out. A good bunch of folks here. Best wishes everyone

John T

No umbrage taken John.

As an EE and an Attorney... at places that I've worked... you would be an "officer of the company"... and you would sign Declarations of Compliance that would say something like... "The current would go up."...and then your signature would be at the bottom.

In my world as a line-worker EE that did the EMC, safety and reliability compliance verification... I would often provide people like you with documentation about a foot deep that actually validates that it goes up. How much it goes up. What the conditions are to make it go up that much. What assumptions were made. What the tolerances are around those ratings. etc, etc.

Much of that documentation would be backed by standards documents, from NFPA, IEC, UL, CSA, etc... and that documentation would stack taller than either of us.

And I would also provide the technical writers with all of the "do not eat the dessicant" -type warnings... to keep you and other officers of the company out of jail.

There are often many, many words behind simple statements.

It's trained into me, and hard to shut down.

Rest up and cheers.

 

[John T]

No umbrage taken John.

As an EE and an Attorney... at places that I've worked... you would be an "officer of the company"... and you would sign Declarations of Compliance that would say something like... "The current would go up."...and then your signature would be at the bottom.

In my world as a line-worker EE that did the EMC, safety and reliability compliance verification... I would often provide people like you with documentation about a foot deep that actually validates that it goes up. How much it goes up. What the conditions are to make it go up that much. What assumptions were made. What the tolerances are around those ratings. etc, etc.

Much of that documentation would be backed by standards documents, from NFPA, IEC, UL, CSA, etc... and that documentation would stack taller than either of us.

And I would also provide the technical writers with all of the "do not eat the dessicant" -type warnings... to keep you and other officers of the company out of jail.

There are often many, many words behind simple statements.

It's trained into me, and hard to shut down.

Rest up and cheers.

Thanks Will no umbrage taken none intended lol. I enjoy sparky chat there are a fine bunch of engineers and electricians on here. Most of my work was on the secondary side of things. I was only having fun with my post but since I’m not yet up to par and didn’t feel like getting deep in the weeds as I usually do !!!!! So just answered the basic question to which we all agree the answer is UP. Thanks for your detailed analysis !!!

John T. Semi retired but never too old to learn or try and help

 

[olddavid]

Too many assumptions to give the OP a safe answer.

 

[JMOR]

No umbrage taken John.

As an EE and an Attorney... at places that I've worked... you would be an "officer of the company"... and you would sign Declarations of Compliance that would say something like... "The current would go up."...and then your signature would be at the bottom.

In my world as a line-worker EE that did the EMC, safety and reliability compliance verification... I would often provide people like you with documentation about a foot deep that actually validates that it goes up. How much it goes up. What the conditions are to make it go up that much. What assumptions were made. What the tolerances are around those ratings. etc, etc.

Much of that documentation would be backed by standards documents, from NFPA, IEC, UL, CSA, etc... and that documentation would stack taller than either of us.

And I would also provide the technical writers with all of the "do not eat the dessicant" -type warnings... to keep you and other officers of the company out of jail.

There are often many, many words behind simple statements.

It's trained into me, and hard to shut down.

Rest up and cheers.

No proof was necessary, as I'm sure all readers have seen by now that you re a man of many words!

 

[will-max dairy]

I'm sorry that I was baited into being so derailed into all the BS discussion of circuit configuration/wiring of elements/etc. , as the man's only questions was "does current go up or down if he applied 240 vs 208 volts?". My first response is all that should have ever been said, "up". Almost all the rest is a derailment. Sorry.

"UP" was the best answer

No proof was necessary, as I'm sure all readers have seen by now that you re a man of many words!

Heavy sigh... and a laugh.... guilty as charged.

"UP" was the best answer. And all that was asked for.

The rest, is actually none of my business, and I should have left it at that.

 

[will-max dairy]

Pictures are worth a thousand words.

Both diagrams are 208 3Phase, 66.6 Amps (RMS) per phase.

Both are possible configurations of the existing elements. Delta with 5.4 Ohms per element. Y with 1.8 Ohms per element.

Both should result in higher current per phase, and total power produced if connected to 240V 3 Phase. (there were never any lies detected in that statement)

Notice that no neutrals are drawn. 3 Phase is usually implemented so they aren't needed, due to balanced loads. But sometimes they are there for various reasons. By "usually"... usually a delta, because of the statement below.

The behavior of these two possible configurations is different, in the situation where one element burns out (opens), especially if there is a neutral that may now have to carry the unbalanced current.

Further interpretation is left to the motivated reader. Especially if there are neutrals involved, because they get messy.

No warrantees given or implied.

LTSPICE is a free program, if anybody wants to fiddle for themselves.

 

[John T]

The OP didn’t mention he intended to rewire be it Y or Delta or how he was currently configured, so there being no changes and since impedance, Y or Delta or other wiring wasn’t changed and I = E/R I again agree with JMOR if voltage goes up current goes up DUH.. However I enjoyed all the deep techy 3 phase Y and Delta chat even if it bored non engineers and electricians and other sparkies and didn’t change the basic UP answer. Hey we sparkies gotta have our fun and days on here lol Thanks for the deep sparky chat everyone,

PS fun story for sparkies. I was just starting power engineering when my boss took me on an electrical problem at a building. We pulled into the parking lot and my boss asked if they had y or delta service. I had no idea and asked if he had the buildings blueprints etc. He looked at me and said. Look up there are the 3 transformers on the pole just look and see DUH. Years later I was in charge and took a fresh out of school young lady EE on a job and pulled the same thing on her. She thought I was a genius lol lol

John T. In RV in Texas and have to stay the winter here instead of Florida as the past 16 years. Wow I sadly will miss it and all my southern friends, tractor shows, warm weather and bluegrass grrrr.

 

[47fivewindow]

Too many assumptions to give the OP a safe answer.

That's ok. I think he bailed after the 2nd post.