• All-welded construction.
• RoHS compliant product avail-
able. Add “E” suffix to part num-
ber to specify.
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.
250 Series
Vitreous Enamel Power
®
‘Thin’ Stackohm
S P E ꢂ ꢃ F ꢃ ꢂ A T ꢃ O N S
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
0.125"
3.175 mm
0.625"
15.875 mm
0.031"
Diam.
0.794 mm
0.063"
1.588 mm
Diam.
0.125"
3.175 mm
0.110":
2.776 mm
10W & 20W
.952m
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.
9.25m
L
A
0.125" *
3.175 mm
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.
0.375"
9.525 mm
0.250"
6.350 mm
0.188"
4.763 mm
0.125"
3.175 mm
Diam.
F E A T ꢀ ꢁ E S
• 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.
0.109"
2.776 mm
Diam.
0.196"
4.979 mm
0.250"
6.350 mm
30W, 40W & 55W
.218m3
L
A
25.40m
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)
0.250" *
6.350 mm
0.125"
3.175 mm
o r d e r i n g i n f o
0.438"
11.113 mm
Series
RoHS Compliant
� ꢀ ꢁ ꢂ ꢃ ꢄ ꢁ ꢅ
*Reference dimension only; varies according to resistance value.
Coating
Wattage Tolerance Ohms
Blank = Vitreous
C = Centohm
S = Silicone
F = 1%
H = 3%
J = 5%
1R0 = 1 Ω
Note: When resistors are stacked, use washers or spacers as required to insure clearance
250 = 250 Ω
1K0 = 1,000 Ω
To calculate max. amps:
use the formula √P/R
and improve power dissipation.
K = 10% 25K = 25,000 Ω
25K5 = 25,500 Ω
Dimensions (in. /mm)
Max.
Series Wattage Ohms
Length L
Length A Voltage*
m a d e - t o - o r d e r p a r t S
F10
F20
F30
F40
F55
10
20
30
40
55
1.0-15K
1.0-50K
1.0-10K
1.0-25K
1.0-30K
0.750 / 19.050
2.000 / 50.800
1.250 / 31.750
2.000 / 50.800
3.500 / 88.900
1.000 / 25.400
2.313 / 58.750
2.000 / 50.800
2.750 / 69.850
4.250 / 107.950
187
815
281
655
1405
Terminal Type
See “Resistor Terminals for Tubular Cores”
Tolerance RoHS
J = 5% Compliant
See web-
site for
custom
core info
� ꢀ ꢁ ꢂ ꢃ ꢄ ꢀ ꢅ ꢆ ꢇ ꢈ ꢂ ꢂ ꢉ ꢄ
Series
Vitreous enamel:
25 = 250 Fixed
Wattage &
Core Code
See “Core and
Mounting Brackets
Ohms
(user supplies bracket for core TB) Example:
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
B = Stacking box
1R00 = 1 Ω
26 = 260 Adjustable Terminal Selection” S = Stacking stud, std. height
250R = 250 Ω
1K00 = 1,000 Ω
25K0 = 25,000 Ω
25K5 = 25,500 Ω
H = Stacking stud high
Silicone ceramic:
U = Unit type
45 = 450 Fixed
46 = 460 Adjustable
S ta n d a r d p a r t n u m b e r S f o r 2 5 0 S e r i e S
Wattage
Wattage
Wattage
Part No.
Prefix
Suffix
Part No.
Prefix
Suffix
Part No.
Prefix
Suffix
1
–––1R0E
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
1,500 –––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
1.5 –––1R5E
2
3
4
5
–––2R0E
–––3R0E
–––4R0E
–––5R0E
7.5 –––7R5E
10 –––10RE
15 –––15RE
20 –––20RE
25 –––25RE
30 –––30RE
40 –––40RE
1,250 –––1K25E
Ohmite Mfg. Co. 1600 Golf Rd., Rolling Meadows, IL 60008 • 1-866-9-OHMITE • Int’l 1-847-258-0300 • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com
33
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