HEATING ELEMENTS
Power or electric heater capacity
Imperial
Metric
Power or electric heater capacity
Formulas
CFM x (T°2 - T°1) x 1.08
3413
CFM x (T°2 - T°1) x 1.08
kW = kW : Power in kW
3413
Imperial
Q x (T°2 - T°1) x 1,21
3600
Q x (T°2 - T°1) x 1,21
P = P : Power in kW
3600
Metric
3
Imperial
kW =
Metric
P=
CFM : Air volume in Cubic Feet per Minute
Q : Air volume in m /hour
kW : Temperature
Power in kW of air leaving heater in ∞F
P : Power
in kW of air leaving heater in ∞C
Temperature
T°2
Q xT∞2:
(T°2
-volume
T°1) xin 1,21
CFM CFM
x (T°2
- volume
T°1) xin1.08
3
:
Air
Cubic
Feet
per
Minute
Q
:
Air
kW =
P=
T∞1: Temperaturemof/hour
air entering heater in ∞C
T°1 : Temperature of air entering heater in ∞F
3413
3600
T°2 : Temperature of air leaving heater in ∞F
T∞2: Temperature of air leaving heater in ∞C
in kW
kW : Power in
T°1kW
: Temperature
of air entering heater in ∞F
T∞1:
Temperature of air entering heater in ∞C
Temperature
differential
∆T = T°2 - T°1 P : Power
Q : Air volume in m3/hr
CFM : Air volume in cubic feet per minute
Imperial
Metric
T°2 : Temperature differential
of air leaving heater in ∆
°FT = T°2 - T°1 T°2 : Temperature of air leaving heater in °C
Temperature
T°1 Imperial
: Temperature
entering heater in °F
T°1 : Temperature
of air entering heater in °C
kWofx air
3413
P x 3600
Metric
∆T =
∆T =
CFM x 1.08
kW x 3413
CFM x 1.08
∆T =
KW per square foot
∆T =
Imperial
KW per square
kW foot
2
kW
/ pi =
Imperial
kW / pi =
2
Duct area
S
kW
S
Imperial
Duct areaW x H
S=
Imperial
144
WxH
S=
144
Electric power
Metric
kW : Power in kW
S : Surface area in square feet
kW : Power in kW
S : Surface area in square feet
S : Surface area in square feet
W : Duct width in inches
S : Duct
Surface
areainininches
square feet
H
Height
W : Duct width in inches
H : Duct Height in inches
Single phase
Electric power
VxI
P =phase
Single
ou
LinePcurrent
= V x I ou
Single phase
Line current
P
Conversions
kW
/ m2 =
Metric
kW / m2 =
P
S
P
S
P : Power in kW
S : Surface area in m2
P : Power in kW
S : Surface area in m2
Metric
S : Surface area in m2
W :Duct width in meter
S : Duct
Surface
areaininmeter
m2
H
height
W :Duct width in meter
H : Duct height in meter
S= WxH
Metric
S= WxH
3 phase
V2
P=
R
V2
P=
R
I =phase
Single
V
I=
Q x 1,21
P x 3600
Q x 1,21
= V x I x 1.732
3Pphase
P = V x I x 1.732
3 phase
V2 X 1.732
R
V2 X 1.732
P=
R
P=
P
I=
3 phase
V x 1.732
P
V
I=
P : Power in Watts
V : Voltage in Volts
P :: Resistance
Power in Watts
R
in Ω (Ohm)
V
:
Voltage
in
Volts
I : Current in Amps
R : Resistance in Ω (Ohm)
I : Current in Amps
P
V x 1.732
∞F to ∞C
∞C to ∞F
BTU to kW
∞C to
= ∞C
∞F
1.8
(1.8
∞F=to
∞C
∞Fx ∞C) + 32
1 kW =
1 BTU/hre
= 0.29307 x 10-3 kW
BTU
to3413
kW BTU/hre kW
to BTU
∞F= (1.8 x ∞C) + 32
1 kW = 3413 BTU/hre 1 BTU/hre = 0.29307 x 10-3 kW
(∞F - 32)
∞C =
(∞F - 32)
1.8
mm to inches
Inches to mm
1 in =
mm
mm
to25.4
inches
1 mm =to
0.03937
Inches
mm in
1 in = 25.4 mm
1 mm = 0.03937 in
CFM to FPM
kW to BTU
FPM to CFM
1 CFM
1 FPM
1 FPM x S
1 CFM
CFM
to=FPMS
FPM
to=CFM
1 CFM
S :FPM
Surface
1
= area in square feet1 CFM = 1 FPM x S
S
S : Surface area in square feet
170712
06006_KS
Visit our web site at www.neptronic.com
1
HEATING ELEMENTS
Selection Guide
Element Types
Advantages
Open Coil
-
Excellent heat dissipation
Minimal pressure drop
Fast response time
More kilowatts per sq.ft.
Quick delivery
Standard Tubular
-
Less sensitive to humidity and dust
Suited for demanding environments
Excellent mechanical resistance
Heating element not in direct contact with air
Finned Tubular
-
Good heat dissipation
Less sensitive to humidity and dust
Suited for demanding environments
Excellent mechanical resistance
Heating element not in direct contact with air
Disadvantages
- Elements in direct contact with air
- Cannot be installed in humid environments
- Cannot be installed in dusty environments
-
Increase in pressure drop
Slower response time
Less heat dissipation
Less kilowatt per sq.ft.
Longer delivery
-
Increase in pressure drop
Slower response time
Less kilowatt per sq.ft.
Longer delivery
Static Pressure Loss
170712
06006_KS
Visit our web site at www.neptronic.com
2
HEATING ELEMENTS
Minimum Air Velocity
Open Coil Elements
Tubular Elements
170712
06006_KS
Visit our web site at www.neptronic.com
3