Product Overview
Federal Pacific F3.15 Overload Heater Element - New Old Stock for Motor Overload Relays
Condition
This F3.15 heater element is unused, new old stock, clean and in excellent condition. The photographed unit shows five silver resistive wire loops formed over an orange-brown phenolic base, with two brass eyelet terminals and the part number "F3 15" stamped directly into the body. Light oxidation visible on the brass terminals is typical of decades-old unused stock and is not indicative of installation or service use. This unit is representative of our current stock of 8.
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Product Overview
The Federal Pacific F3.15 is a thermal overload heater element used inside overload relays to protect three-phase motors from sustained overcurrent. A low-resistance metal strip, formed here into five silver wire loops, generates heat proportional to the current the motor draws, simulating the motor's own thermal rise without breaking the circuit the way a fuse does. The element mounts on an orange-brown phenolic base and connects through two brass eyelet terminals, and the base is stamped "F3 15" for direct identification against a relay's heater table. Unlike fuses or circuit breakers, which protect the power conductors themselves, an overload heater like this one is sized to match a specific motor's full-load amperage and trips the relay through thermal action rather than interrupting current directly.
Key Features
- Brand: Federal Pacific, part number F3.15, stamped directly on the phenolic body
- Five silver resistive wire loops formed from a low-resistance metal strip
- Two brass eyelet terminals for mounting into the overload relay base
- Orange-brown phenolic insulating mounting base
- Condition: unused, new old stock
Applications
- Electricians replacing an obsolete Federal Pacific overload heater in a motor starter or control panel
- Maintenance techs stocking spares for FPE overload relays across multiple motor circuits
- Panel builders sizing overload protection to a specific motor's full-load amperage
- Buyers completing a matched set of heaters for a three-phase overload relay, typically installed three at a time, one per phase
Frequently Asked Questions
What does a thermal overload heater element do?
Inside an overload relay, this low-resistance metal strip heats up in proportion to the current a motor draws. If the motor pulls sustained overcurrent, the heat trips the relay's contacts and shuts the motor down before winding damage occurs. Unlike a fuse, the heater does not burn open the circuit - it works through the relay's mechanism and can be reset once the fault clears.
How do I know this is the right heater for my Federal Pacific relay?
Match the stamped designation, F3.15, against the heater table for your specific Federal Pacific overload relay and the full-load amperage of the motor you are protecting. The part number is stamped directly into the phenolic base of every piece we ship, so you can confirm the match before you install it.
Is this a new part or a used pull?
This is unused, new old stock, not a used pull from a relay. It has never been installed in service.
Why buy heater elements one at a time instead of a bulk lot?
Most three-phase overload relays use three matched heaters, one per phase, and a bulk surplus lot elsewhere forces you to buy far more than that. We sell this F3.15 heater each, so you can order exactly the count your relay needs, whether that is one spare or a full matched set. Shipping is $8 flat rate, free once your order passes $28, and orders leave our Idaho warehouse the same or next business day.
A five-loop resistive strip whose entire job is to get hot at exactly the right moment, so a motor never has to find out what happens without it. Match the stamped F3.15 to your relay's heater table, and this small phenolic block goes back to doing the job it was built for.
