Table of different connection methods of heating elements

Power formula OHM’S law
P = Power in watts U = Voltage
U = Voltage P = UI R = Resistance in ohms U = RI
I= Current in amperes I= Current in amperes
I= P/U  U= P/I I= U/R R= U/I P= U2 /R R= U2 /P

 

Heating elements connections

(Heating elements resistance “r” of unit power “p” with nominal voltage “U”)

 

Parallel wiring Serial wiring

 

Quantity of elements (n) Total resistance (R) Total power (P)
2 R = r/2 p = 2p
3 R = r/3 p = 3p
X R = r/x p =xp
NOTE: Watt density (W/cm2) for each element is unchanged
Quantity of elements (n) Total resistance (R) Total power (P) Heating element Watt density (w/cm2)
2 R = 2r p = p/2 Devided by 4
3 R = 3r p = p/3 Devided by 9
X R=Xr p = p/x Devided by x2

 

Delta and star element connections

Delta connection Star connection
Delta (triangle) connection:
The voltage supplied to the heating elements is the same than the power supply voltage measured between phases : U= Un
Supply voltage (U) 230V,
3 phases
230V,
3 phases
400V,
3 phases
400V,
3 phases
Heating elements nominal voltage (Un) 230V 400V 230V 400V
Watt density (W/cm2) No change  in watt density Watt density is divided by 3 Watt density is multiplied by 6 No change in
watt density
Total power (P) Total power is 3 time nominal power of one
heating element (P=3 p)
Total power is divided by 9.lt
is 1/3 of nominal power of one heating element (P= p/3)
Total power is 9 time nominal power of one
heating element (P=9 p)
Total power is 3 time nominal power of one
heating element
(P= 3p)
comments No problem solution This can be used a reduced power step by using a
Star/ Delta (triangle)
connection system
Never use Fire hazard! This is the most common configuration
Star connection :
The voltage supplied to the heating elements is the same than the power voltage divided byv3: U=1.737Un).
Example: power supply is 400V, the heating element is energized with 400/1.737= 230V
Supply voltage (U) 230V,
3 phases
230V,
3 phases
400V,
3 phases
400V,
3 phases
Heating element! nominal voltage (Un) 230V 400V 230V 400V
Watt density (W/cm2) Watt density is divided by 3 Watt density is divided by 9 No change in
watt density
Watt density is divided by 3
Total power (P) Total power is 1/3 of total possible power : it is the same than one heating element (P=p) Total power is 1/9 of total possible power.
1/3 nominal power of one heating element (P= 1/3 p)
Total power is 3 time nominal power of one
heating element
(P=3p)
Total power is 1/3 of total possible power. it is the same than one heating element (P=p)
comments Not recommended Not recommended This is the most standard connection, allows the same heaters to be used with 400V star connection or 230V delta connection without
power change
Not recommended