Ohmite 250 Series Thin Stackohm Vitreous Enamel Power Resistors Instructions

: June 13, 2024
: Ohmite

Table of Contents

FEATURES
SPECIFICATIONS
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

Ohmite 250 Series Thin Stackohm Vitreous Enamel Power Resistors Instructions

When limited space is a consideration, choose Ohmite’s “thin” stack able 250 Type resistors. These oval-shaped ceramic-core resistors feature a low profile to permit installation in spaces with minimal height. They are also equipped with integral mounting brackets so they can be fastened to a chassis and stacked in locations with limited surface area.
When properly fastened, the mounting brackets add a heat sinking benefit resulting 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 conducts heat to mounting surface.
Low profile for use in equipment where space is limited.
All-welded construction.
RoHS compliant product available Jan. 2006 Add “E” suffix to part number to specify

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 mounting 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 surface.
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

Note: When resistors are stacked, use washers or spacers as required to insure clearance and improve power dissipation.

*Reference dimension only; varies according to resistance value
Dimensions

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

Adjustable versions available. Consult factory.
Other sizes available. Consult factory.
Also available in low cost Centohm coating. Consult Factory

STOCK PART NUMBERS FOR STANDARD RESISTANCE VALUES
Instructions