208/120 wye 3 Phase

[nathan909]

I don't do much if any commercial, so a have a couple of load question on a building I don't have access to yet.

Info:
The panel is a G1836ML3150 150amp 208Y/120
After outside meter at main there is a boltswitch 200amp 3 pole fuse block
The cable run is less than 100ft to main 4/0 AWG

First I'll be adding another panel so I don't overload panel ~150amp 208Y/120

Question is can I run this:

L1-L2 80 amps
L2-L3 60 amps
L3-L1 50 amps

L1-N 30 amps
L2-N 25 amps
L3-N 50 amps

About 52kVA?

 

[Smart $]

Assuming all loads have the same power factor, the line current, all loads combined, would be:

Line A - 131.6A
Line B - 123.5A
Line C - 130.4A

46.1kVA

 

[Smart $]

Welcome to the forum. :thumbsup:

 

[Saturn_Europa]

Assuming all loads have the same power factor, the line current, all loads combined, would be:

Line A - 131.6A
Line B - 123.5A
Line C - 130.4A

46.1kVA

What equation did you use to calculate this, sir?

 

[nathan909]

Another question, not sure if I should have started a new thread??

On the 208v 50a & 60a L-L legs, I need to run single phase 240v +/-10% appliances.

I was going to try to cover up to, 10,000watts @ 240v on the 208v 50amp
and 12,000watts @ 240v on the 208v 60amp

So I need a Buck Boost Transformer Correct?
Will 2 of these work, one after each breaker?

A Buck Boost Transformer 3kVA In 240/480VAC, out 24/48VAC
like:
http://www.alliedelec.com/hammond-power-solutions-q003dtcf/70191829/

I was hoping this would get me 250v before any line loss

Please point out any holes in my thinking.:? That's why I'm here.

 

[nathan909]

What equation did you use to calculate this, sir?

I could have figured it wrong, but I though it was
L1 142.5a
L2 146.25a
L3 145.25a
N 23a

 

[Smart $]

What equation did you use to calculate this, sir?

I used an Excel calculator I put together to do both conventional and vector math. The current amounts I provided earlier are results of the vector math... but the conventional math is really close.

Line A - 131.2A
Line B - 122.6A
Line C - 130.3A

Make three columns: A, B, C. Take each load kVA load and divide it by the number of lines it is connected to. Put the "per line kVA" result in the respective columns. When all loads are listed, total columns and divide each total by the line-to-neutral voltage.

 

[Smart $]

Another question, not sure if I should have started a new thread??

On the 208v 50a & 60a L-L legs, I need to run single phase 240v +/-10% appliances.

I was going to try to cover up to, 10,000watts @ 240v on the 208v 50amp
and 12,000watts @ 240v on the 208v 60amp

So I need a Buck Boost Transformer Correct?
Will 2 of these work, one after each breaker?

A Buck Boost Transformer 3kVA In 240/480VAC, out 24/48VAC
like:
http://www.alliedelec.com/hammond-power-solutions-q003dtcf/70191829/

I was hoping this would get me 250v before any line loss

Please point out any holes in my thinking.:? That's why I'm here.

Looks like you already understand the nuances. Can't see any holes... just perhaps different choices from what I may (with emphasis) have made.

 

[Smart $]

I could have figured it wrong, but I though it was
L1 142.5a
L2 146.25a
L3 145.25a
N 23a

I have to apologize. My numbers above are in error and yours are correct. :ashamed1:

Here's my "corrected" numbers:

Conventional
Line A - 142.6A
Line B - 146.2A
Line C - 145.3A


Vector
Line A - 143.4A
Line B - 146.6A
Line C - 145.3A
N - 22.9A

 

[nathan909]

I have to apologize. My numbers above are in error and yours are correct. :ashamed1:

Here's my "corrected" numbers:

Conventional
Line A - 142.6A
Line B - 146.2A
Line C - 145.3A


Vector
Line A - 143.4A
Line B - 146.6A
Line C - 145.3A
N - 22.9A

No problem, I really appreciate you helping me check my work!


As far as the 2 "Buck Boost Transformer 3kVA In 240/480VAC, out 24/48VAC" I wanted to double check this:
208v 60a breaker will be adequate for that xformer and a 240v 50amp load (about 12000 watts)?
208v 50a breaker will be adequate for that xformer and a 240v 42amp load (about 10000 watts)?

You said that you may have gone a different route, with cost being a factor, what could/should I do different?

Thanks again for your time!

 

[Smart $]

No problem, I really appreciate you helping me check my work!


As far as the 2 "Buck Boost Transformer 3kVA In 240/480VAC, out 24/48VAC" I wanted to double check this:
208v 60a breaker will be adequate for that xformer and a 240v 50amp load (about 12000 watts)?
208v 50a breaker will be adequate for that xformer and a 240v 42amp load (about 10000 watts)?

You said that you may have gone a different route, with cost being a factor, what could/should I do different?

Thanks again for your time!

Th kVA on a 208V-boosted-to-240V circuit is essentially the same for both pre- and post boost.

A 50A, 240V load is 57.7A at 208V.

A 42A, 240V load is 48.5A at 208V.

Both 60A and 50A breakers respectively are good as long as the loads are noncontinuous.


As to which hardware, I'm not going to get into personal preferences, or as I can say in this case lack thereof.

 

[nathan909]

Th kVA on a 208V-boosted-to-240V circuit is essentially the same for both pre- and post boost.

A 50A, 240V load is 57.7A at 208V.

A 42A, 240V load is 48.5A at 208V.

Both 60A and 50A breakers respectively are good as long as the loads are noncontinuous.


As to which hardware, I'm not going to get into personal preferences, or as I can say in this case lack thereof.

Thanks, but you brought up an issue I want to cover.

As you referenced "noncontinuous" loads. Would this still be functional(hardware) and/or acceptable as continuous multiple receptacle circuit?

Edit:
Or Would it be better/acceptable to step up the breaker 120% (ie 50a to 60a) and the exceed the rating of the panelboard as long as the total true load will be under panel rating?

 

[Smart $]

Thanks, but you brought up an issue I want to cover.

As you referenced "noncontinuous" loads. Would this still be functional(hardware) and/or acceptable as continuous multiple receptacle circuit?

Edit:
Or Would it be better/acceptable to step up the breaker 120% (ie 50a to 60a) and the exceed the rating of the panelboard as long as the total true load will be under panel rating?

The calculated load per Article 220, with the continuous load portion factored 125%, must not be greater than the rating of the OCPD protecting the panelboard... and the OCPD rating cannot exceed the panelboard rating.

The sum of the branch circuit breaker rating can and often do exceed the panelboard rating... except for a certain situation regarding interconnected power sources under 705.12(D).