30 Ohmite Mfg. Co. 1600 Golf Rd., Suite 850, Rolling Meadows, IL 60008 • Tel. 1-866-9-OHMITE • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com
Ohmite Mfg. Co. 1600 Golf Rd., Suite 850, Rolling Meadows, IL 60008 • Tel. 1-866-9-OHMITE • Fax 1-847-574-7522 • www.ohmite.com • info@ohmite.com 31
STOCK PART NUMBERS FOR STANDARD RESISTANCE VALUES
250 Series
‘Thin’ Stackohm®
Vitreous Enamel Power Resistors
1 –––1R0
1.5 –––1R5
2 –––2R0
3 –––3R0
4 –––4R0
5 –––5R0
7.5 –––7R5
10 –––10R
15 –––15R
20 –––20R
25 –––25R
30 –––30R
40 –––40R
50 –––50R
75 –––75R
100 –––100
Dimensions (in. /mm)
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
125 –––125
150 –––150
200 –––200
250 –––250
300 –––300
400 –––400
500 –––500
600 –––600
750 –––750
800 –––800
1,000 –––1K0
1,250 –––1K25
1,500 –––1K5
1,750 –––1K75
2,000 –––2K0
2,500 –––2K5
3,000 –––3K0
3,500 –––3K5
4,000 –––4K0
5,000 –––5K0
6,000 –––6K0
7,500 –––7K5
10,000 –––10K
12,500 –––12K5
15,000 –––15K
20,000 –––20K
25,000 –––25K
30,000 –––30K
35,000 –––35K
40,000 –––40K
50,000 –––50K
Shaded values involve very fine resis-
tance wire and should not be used in
critical applications without burn-in
and/or thermal cycling.
= Most popular stock values
= Stock values
= Non-stock values subject to mini-
mum handling charge per item
Adjustable versions available. Consult factory.
Other sizes available. Consult factory.
Also available in low cost Centohm coating. Consult Factory.
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
*Reference dimension only; varies according to resistance value
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 minimal
height. They are also equipped
with integral mounting brack-
ets so they can be fastened to
a chassis and stacked in loca-
tions with limited 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 Jan. 2006 Add “E” suffix to
part number to specify.
Note: When resistors are stacked, use
washers or spacers as required to insure
clearance and improve power dissipation.
SPECIFICATIONS
Material
Coating: Lead free vitreous
enamel.
Core: Ceramic.
Terminals: Tinned lug with hole.
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 .04” (1.016mm) thick.
Reduce rating by 15% when
mounting on non-metallic sur-
face.
Overload: 5 times rated wattage
for 5 seconds.
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
rating (measured from lug to
mounting bracket)
To calculate max. amps: use the
formula √P/R
