Hella Marine Mini ISO SPDT Relay, 24V, 20A, Resistor Coil Suppression
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Overview
The Hella Marine 933332161 is a 24V Mini ISO SPDT (Form C) relay with a mounting bracket for switching higher-current DC loads from a low-current control switch.
It is rated for 20A continuous on the normally open contact and 10A on the normally closed contact at 85°C, with up to 120A inrush capacity. The housing carries an IP54 rating and the relay is rated for -40°C to +85°C ambient temperature.
Resistor coil suppression is built in, which helps reduce voltage spikes and electrical noise when the relay switches on and off.
Key features
- 24V coil, SPDT (1 Form C) switching with five terminals (30, 87, 87a, 85, 86)
- Continuous load rating: 20A (N/O) and 10A (N/C) at 85°C; maximum inrush load up to 120A
- IP54 enclosure rating for protected installs behind panels or inside lockers
- Built-in resistor suppression on the coil; coil resistance 271 ohm ± 10%
- Compact Mini ISO format with a body roughly 26.2 mm square and about 23.7 mm high, plus an integrated mounting bracket
- 6.3 x 0.8 mm tin-plated blade terminals (ISO 8092) for use with common Mini ISO relay sockets
Installation and setup
Mount the relay on a bulkhead or bracket in a protected space such as behind the helm, inside an electrical locker, or within an electronics cabinet. IP54 is fine for incidental moisture and dust, but it should not live where it can be soaked or submerged.
Use a proper 5-terminal Mini ISO socket and crimped connections sized for the circuit current. Fuse the load circuit close to the power source, keep high-current runs short, and route the coil trigger through your switch panel or control output. For saltwater installs, protect the terminals with boots or heat-shrink and a small amount of dielectric grease.
Compatibility and fit
This is a 5-terminal SPDT relay, so it can be wired for normally open or normally closed operation depending on how your circuit is laid out. When replacing an existing relay, confirm the terminal layout (30/87/87a/85/86) matches your socket and that your load current stays within the continuous ratings.
It is intended for 24V DC systems. If your boat runs 12V, use a relay with a 12V coil so the control side pulls in correctly.
Use cases on board
On a 24V boat, this relay is commonly used to switch spreader lights, deck floods, cockpit accessories, or other loads where you want the high-current run kept near the distribution point while the helm control only carries coil current.
It suits refits where you are cleaning up wiring behind a switch panel, adding a dedicated relay for auxiliary lighting, or separating control wiring from heavier load wiring to help reduce voltage drop.
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