Ohmite 850F250 50W 250 Ohm Wirewound Chassis Mount Resistor - Equivalent & Substitute Parts

Part Overview

The Ohmite 850F250 is a 250 Ohms ±1% 50W wirewound chassis mount resistor from the Metal-Mite®89 series, designed for high-power applications requiring precision resistance and thermal stability. This part is currently obsolete, making equivalent substitutes necessary for ongoing production and maintenance applications. The 850F250 features aluminum housing with flanged mounting, solder lug termination, and operates across a wide temperature range of -55°C to 275°C, making it suitable for demanding industrial and aerospace environments.

Substiute Parts

850F250

OhmiteIn Stock: 935850F250 Datasheet

Current PartRFQ

850F250E

OhmiteIn Stock: 824850F250E Datasheet

DirectRFQ

RH050250R0FC02

Vishay DaleIn Stock: 1198RH050250R0FC02 Datasheet

DirectRFQ

UAL50-250RF8

RiedonIn Stock: 1253UAL50-250RF8 Datasheet

DirectRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the 850F250 is determined by strict equivalence across all critical electrical and mechanical parameters. The following parameters must match or remain within acceptable tolerances for direct substitution:

• Resistance value: 250 Ohms (exact match required)
• Tolerance: ±1% (exact match required)
• Power rating: 50W (exact match required)
• Composition: Wirewound (exact match required)
• Temperature coefficient: ±20ppm/°C (exact match required)
• Housing type: Aluminum (exact match required)
• Mounting feature: Flanges (exact match required)
• Lead style: Solder Lugs (exact match required)
• Package type: Axial, Box (exact match required)

All three substitute parts meet these criteria and are therefore direct functional equivalents to the 850F250.

Parameter Comparison

Engineering Selection Recommendations

850F250E (Ohmite): This is the direct successor from the same manufacturer. It maintains identical electrical specifications and is currently in active production status. The 850F250E is RoHS compliant, making it suitable for applications requiring environmental compliance. Dimensional variations are minimal (1.933" L vs. 1.938" L; 0.583" H vs. 0.620" H), and it remains compatible with existing mounting configurations.

RH050250R0FC02 (Vishay Dale): This substitute provides equivalent electrical performance with moisture-resistant features. Operating temperature range extends to 250°C (versus 275°C for the main part), which may be a limiting factor in extreme high-temperature applications. The part is non-RoHS compliant and REACH affected. Dimensional compatibility is maintained within standard tolerances.

UAL50-250RF8 (Riedon): This option offers the widest operating temperature range (-55°C to 275°C), matching the original 850F250 specification. It is ROHS3 compliant and REACH unaffected, providing superior environmental compliance. Additional features include current sense capability, flame proof rating, pulse withstanding, and safety certifications, making it suitable for demanding industrial and safety-critical applications.

Frequently Asked Questions (FAQ)

Q: Can I use 850F250E as a direct replacement for 850F250? A: Yes. The 850F250E is electrically and mechanically equivalent to the 850F250. Both share identical resistance, tolerance, power rating, temperature coefficient, and mounting specifications. The 850F250E is the active production equivalent and is recommended for new designs and replacements.

Q: What is the primary difference between the three substitute options? A: All three substitutes meet the core electrical requirements (250 Ohms, ±1%, 50W, wirewound). The key differences are: manufacturer (Ohmite, Vishay Dale, or Riedon), product status (all active), RoHS compliance status, and additional features. The UAL50-250RF8 offers the broadest compliance certifications and additional safety features.

Q: Does the RH050250R0FC02 have any limitations compared to the 850F250? A: The RH050250R0FC02 has a maximum operating temperature of 250°C, compared to 275°C for the 850F250. For applications requiring operation above 250°C, the 850F250E or UAL50-250RF8 are more suitable.

Q: Are there dimensional differences between these parts? A: Minor dimensional variations exist within standard manufacturing tolerances. Length ranges from 1.933" to 1.969", width from 1.102" to 1.142", and height from 0.583" to 0.630". These variations are typical for wirewound chassis mount resistors and do not affect functional compatibility in standard mounting applications.

Q: Which substitute is best for RoHS-compliant applications? A: Both 850F250E and UAL50-250RF8 are RoHS compliant. The UAL50-250RF8 offers ROHS3 compliance, which is the most current standard. The RH050250R0FC02 is non-compliant.

Q: Can these parts be used interchangeably in existing PCB designs? A: Yes, all substitutes maintain the same electrical specifications, solder lug termination, and flanged mounting configuration. Existing circuit designs and PCB layouts remain compatible without modification.