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.
• All-welded construction.
• RoHS compliant product avail-
able. Add “E” suffix to part num-
ber to specify.
SPEciFicATiONS
‘Thin’ Stackohm
®
Vitreous Enamel Power
0.031"
0.794 mm
Diam.
0.125"
3.175 mm
0.110":
2.776 mm
0.250"
6.350 mm
0.125"
3.175 mm
Diam.
0.196"
4.979 mm
0.250"
6.350 mm
0.125"
3.175 mm
Diam.
0.109"
2.776 mm
0.188"
4.763 mm
Diam.
0.063"
1.588 mm
0.125"
3.175 mm
0.375"
9.525 mm
250 Series
0.625"
15.875 mm
0.375"
9.525 mm
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)
FEATurES
thick. Reduce rating by 15%
when mounting on non-metallic
• Small size-to-power ratio.
surface.
• Stackable
Overload:
10x rated wattage for
• Integral mounting bracket con-
5 seconds if max. voltage is not
ducts heat to mounting surface.
exceeded.
• Low profile for use in equipment
Temperature coefficient:
where space is limited.
1 to 20Ω: ±400 ppm/°C.
Over 20Ω: ±260 ppm/°C
ordering info
Dielectric withstanding
Series
RoHS Compliant
voltage:
500 VAC: 10 and
20 watt rating. 1000 VAC:
30, 40 and 55 watt rat-
ing (measured from lug to
Coating
Wattage Tolerance Ohms
Blank = Vitreous
F = 1%
1R0 = 1
Ω
mounting bracket)
C = Centohm
H = 3%
250 = 250
Ω
To calculate max. amps:
S = Silicone
J = 5%
1K0 = 1,000
Ω
K = 10% 25K = 25,000
Ω
use the formula
√P/R
10W & 20W
L
A
0.125" *
3.175 mm
0.375"
9.525 mm
0.938"
23.813 mm
30W, 40W & 55W
L
A
0.250" *
6.350 mm
0.438"
11.113 mm
�½�½�½�½�½�½�½�½
*Reference dimension only; varies according to resistance value.
Note:
When resistors are stacked, use washers or spacers as required to insure clearance
and improve power dissipation.
25K5 = 25,500
Ω
made-to-order partS
Terminal Type
See web-
site for
See “Resistor Terminals for Tubular Cores”
custom
core info
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”
Tolerance RoHS
Compliant
J = 5%
�½�½�½�½�½�½�½�½�½�½�½�½�½�½�½
Mounting Brackets
(user supplies bracket for core TB)
B = Stacking box
S = Stacking stud, std. height
H = Stacking stud high
U = Unit type
Ohms
Example:
1R00 = 1
Ω
250R = 250
Ω
1K00 = 1,000
Ω
25K0 = 25,000
Ω
25K5 = 25,500
Ω
Series Wattage Ohms
F10
10
1.0-15K
F20
20
1.0-50K
F30
30
1.0-10K
F40
40
1.0-25K
F55
55
1.0-30K
Dimensions (in. /mm)
Max.
Length L
Length A Voltage*
0.750 /
19.050
1.000 /
25.400
187
2.000 /
50.800
2.313 /
58.750
815
1.250 /
31.750
2.000 /
50.800
281
2.000 /
50.800
2.750 /
69.850
655
3.500 /
88.900
4.250 /
107.950
1405
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
S ta n d a r d pa rt n u m b e r S f o r 2 5 0 S e r i e S
Wattage
Ohmic value
Ohmic value
F55J–––
55
F10J–––
10
F20J–––
20
F30J–––
30
F40J–––
40
F10J–––
10
Part No.
Prefix
Suffix
–––1R0E
–––1R5E
–––2R0E
–––3R0E
–––4R0E
–––5R0E
–––7R5E
–––10RE
–––15RE
–––20RE
–––25RE
–––30RE
–––40RE
Part No.
Prefix
Suffix
–––50RE
–––75RE
–––100E
–––150E
–––200E
–––250E
–––300E
–––400E
–––500E
–––750E
–––800E
–––1K0E
–––1K25E
Wattage
Ohmic value
F55J–––
55
F20J–––
20
F30J–––
30
F40J–––
40
F10J–––
10
Part No.
Prefix
Suffix
–––1K5E
–––2K0E
–––2K5E
–––3K0E
–––4K0E
–––5K0E
–––6K0E
–––7K5E
–––10KE
–––15KE
–––20KE
–––25KE
–––40KE
Wattage
F20J–––
20
F30J–––
30
F40J–––
40
F55J–––
55
1
1.5
2
3
4
5
7.5
10
15
20
25
30
40
50
75
100
150
200
250
300
400
500
750
800
1,000
1,250
1,500
2,000
2,500
3,000
4,000
5,000
6,000
7,500
10,000
15,000
20,000
25,000
40,000
= Standard values; check availability
using the worldwide inventory
search at www.ohmite.com
1.000"
25.400 mm
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
OHMITE [ OHMITE MFG. CO. ]
