Ohmite Mfg. Co. 1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com 33
Standard part numberS for 250 SerieS
250 Series
‘Thin’ Stackohm®
Vitreous Enamel Power
1 –––1R0E
1.5 –––1R5E
2 –––2R0E
3 –––3R0E
4 –––4R0E
5 –––5R0E
7.5 –––7R5E
10 –––10RE
15 –––15RE
20 –––20RE
25 –––25RE
30 –––30RE
40 –––40RE
Dimensions (in. /mm) Max.
Series Wattage Ohms Length L Length A Voltage*
F10 10 1.0-15K 0.750 / 19.050 1.000 / 25.400 187
F20 20 1.0-50K 2.000 / 50.800 2.313 / 58.750 815
F30 30 1.0-10K 1.250 / 31.750 2.000 / 50.800 281
F40 40 1.0-25K 2.000 / 50.800 2.750 / 69.850 655
F55 55 1.0-30K 3.500 / 88.900 4.250 / 107.950 1405
50 –––50RE
75 –––75RE
100 –––100E
150 –––150E
200 –––200E
250 –––250E
300 –––300E
400 –––400E
500 –––500E
750 –––750E
800 –––800E
1,000 –––1K0E
1,250 –––1K25E
1,500 –––1K5E
2,000 –––2K0E
2,500 –––2K5E
3,000 –––3K0E
4,000 –––4K0E
5,000 –––5K0E
6,000 –––6K0E
7,500 –––7K5E
10,000 –––10KE
15,000 –––15KE
20,000 –––20KE
25,000 –––25KE
40,000 –––40KE
= Standard values; check availability
using the worldwide inventory
search at www.ohmite.com
Ohmic value
F10J––– 10
F20J––– 20
F30J––– 30
F40J––– 40
Wattage
Part No.
Prefix
Suffix
F55J––– 55
Ohmic value
F10J––– 10
F20J––– 20
F30J––– 30
F40J––– 40
Wattage
Part No.
Prefix
Suffix
F55J––– 55
Wattage
Ohmic value
F10J––– 10
F20J––– 20
F30J––– 30
F40J––– 40
Part No.
Prefix
Suffix
F55J––– 55
0.625"
15.875 mm
0.031"
0.794 mm
0.125"
3.175 mm
Diam.
0.063"
1.588 mm
Diam.
0.125"
3.175 mm
L
A
0.110":
2.776 mm
0.250"
6.350 mm
0.375"
9.525 mm
10W & 20W
0.125"
3.175 mm
0.188"
4.763 mm
Diam.
0.109"
2.776 mm
Diam.
0.196"
4.979 mm
L
A
0.250"
6.350 mm
0.125"
3.175 mm
0.438"
11.113 mm
30W, 40W & 55W
0.375"
9.525 mm
0.125" *
3.175 mm
1.000"
25.400 mm
0.250" *
6.350 mm
0.938"
23.813 mm
0.375"
9.525 mm
When limited space is a con-
sideration, choose Ohmite’s
“thin” stackable 250 Type
resistors. These oval-shaped
ceramic-core resistors feature
a low profile to permit instal-
lation in spaces with height
restrictions. They are also
equipped with integral mount-
ing brackets so they can be
fastened to a chassis and
stacked in locations with lim-
ited surface area.
When properly fastened,
the mounting brackets add
a heat sinking benefit result-
ing in a smaller size per watt.
Durable 250 Type resistors are
fully welded and coated with
lead free vitreous enamel.
FEATURES
• Small size-to-power ratio.
• Stackable
• Integral mounting bracket con-
ducts heat to mounting surface.
• Low profile for use in equipment
where space is limited.
• All-welded construction.
• RoHS compliant product avail-
able. Add “E” suffix to part num-
ber to specify.
SPECIFICATIONS
Material
Coating: Lead free vitreous
enamel.
Core: Ceramic.
Terminals: Tinned lug with hole.
RoHS solder composition is 96%
Sn, 3.5% Ag, 0.5% Cu
Derating: Linearly from 100% @
+25°C to 0% @ +350°C.
Electrical
Tolerance: ±5% (J)
Power rating: Based on mount-
ing a single resistor on a metal
surface measuring 10” (254mm)
square by 0.04” (1.016mm)
thick. Reduce rating by 15%
when mounting on non-metallic
surface.
Overload: 10x rated wattage for
5 seconds if max. voltage is not
exceeded.
Temperature coefficient:
1 to 20Ω: ±400 ppm/°C.
Over 20Ω: ±260 ppm/°C
Dielectric withstanding
voltage: 500 VAC: 10 and
20 watt rating. 1000 VAC:
30, 40 and 55 watt rat-
ing (measured from lug to
mounting bracket)
To calculate max. amps:
use the formula √P/R
ordering info
made-to-order partS
See web-
site for
custom
core info
Tolerance
F= 1%
H= 3%
J= 5%
K= 10%
Ohms
1R0 = 1 Ω
250 = 250 Ω
1K0 = 1,000 Ω
25K = 25,000 Ω
25K5 = 25,500 Ω
RoHS CompliantSeries
WattageCoating
Blank =Vitreous
C=Centohm
S=Silicone
Ohms
Example:
1R00 = 1 Ω
250R = 250 Ω
1K00 = 1,000 Ω
25K0 = 25,000 Ω
25K5 = 25,500 Ω
Series
Vitreous enamel:
25 = 250 Fixed
26 = 260 Adjustable
Silicone ceramic:
45 = 450 Fixed
46 = 460 Adjustable
Wattage &
Core Code
See “Core and
Terminal Selection”
Terminal Type
See “Resistor Terminals for Tubular Cores”
Mounting Brackets
(user supplies bracket for core TB)
B= Stacking box
S= Stacking stud, std. height
H= Stacking stud high
U= Unit type
RoHS
Compliant
Tolerance
J= 5%
*Reference dimension only; varies according to resistance value.
Adjustable versions available. Consult Ohmite.
Other sizes available. Consult Ohmite.
Also available in low cost Centohm or Silicone coating. Consult Ohmite.
* Maximum Voltage is based on Ohm’s Law [V=√P*R] as limited by the resistance
value of specified product
Note: When resistors are stacked, use washers or spacers as required to insure clearance
and improve power dissipation.
