# Three phase heater wiring and load calculations

MaheshChhatbarDecember 23, 2012

I have a heater unit of 18 KW
It is a Three Phase unit in which I have connected 4 x 1.5 KW heater across each Phase to Neutral.
thus having 3 x 4 x 1.5 KW = 18 KW Total.
It draws appx 24 amps per phase and appx 1 amp in neutral due to little imbalance in heater.
The above are connected as Star or WYE. We have appx 240 V across Phase to neutral.

Not I intend to increase my heating to appx 27 KW.
I am to place an order for 1.5 heaters rated at 415 VAC
I will be connected the heaters as Delta.
That is 6 heaters is connected across two phases.
Thus I will be connecting 3 x 6 x 1.5 KW Heaters = Total 27 KW.
What I wish to know is what will be the ampears drawn from each phase of the supply.
I am confused.

Thanks & Best Regards

Mahesh

Thank you for reporting this comment. Undo
kalining

Very confusing. there is no neutrol in 3 phase. Ohms law.
do the math. Total amps or amps per element ?

December 24, 2012 at 4:24PM
Thank you for reporting this comment. Undo
mike_home

I was curious as to how to solve this problem so I did a little research. I think my answer is correct.

Changing the configuration from wye to delta increases the voltage across each heater by a factor of 1.73 (square root of 3). The heater voltage becomes:

240V * 1.73 = 416V

If you want to dissipate 27KW of total power then divide by the voltage to get the current through the heaters:

27000W/416V = 64.9amps

To get the line current through each heater divide the total by 3:

64.9amps/3 = 21.6

The currents from the supply is the summation of the currents in the heaters. The line currents are out of phase by 120 degrees so you need to multiple by 1.73:

21.6amps * 1.73 = 37.5amps

Below is a link for a wye and delta calculator. You can plug in any two numbers and calculate the others.

Merry Christmas

December 25, 2012 at 10:56AM
Thank you for reporting this comment. Undo
weedmeister

Y-connected 3-phase does have a neutral. Delta connected does not.

December 26, 2012 at 7:05PM
More Discussions
Need help with selecting Eff Heat Pump replacement.
20 yr old American Std Heat Pump stopped working. ...
2015hvac
Moving floor vent to toekick area
Hello. We are renovating our kitchen as well as baths...
cathy725
Blown in insulation vs spray foam
I am looking for advice. I have a home built in 2000...
mkrafczyk
gas wont come on. forced air gas fired furnance
the Furnace was starting then running a couple minutes...
waterguytexas
New HVAC install in So Cal
Hi Everyone, I just got a quote from Home Depot contractor....
revlimit
Foremost Bathroom Naples 31 in. W x 22 in. D Vanity in Warm Cinnamon with Left
Home Depot
Kidwise Kaleida Disco Inflatable Jumper - FJC-201-01-B
\$429.00 | Hayneedle
Set of Four Blue Fish Placemats
\$42.00 | FRONTGATE
Fabbian | Stick Pendant Light - Cylinder
\$998.10 | YLighting
Aston Court Three-Light Bath Fixture
\$205.00 | Bellacor
Three-Piece Plum & Lilac Reversible Comforter Set
\$24.99 | zulily