Over time a vintage compressor can build up internal resistance and thus increase amperage. In doing so, the overload in the relay trips the circuit and shuts the system down preventing damage to the compressor. The resulting effect is that the compressor will come on for just a few seconds and then shut off. A 3-N-1 can be installed to increase initial power to the compressor and push it through the bind. Often this will extend the life of an older compressor. Like regular relays, 3-N-1s have to match up to their compressor's horsepower capacity. This information is typically provided on a tag on/near the compressor or relay. The SR8410 comes in two horsepower ranges:
1/12 - 1/5 HP
1/4 - 1/3 HP
Because most vintage refrigerators lack original wiring diagrams and because color coding was not standardized, the installer should have a basic understanding of electrical circuitry in order to install this part. The SR-8410 comes with a basic wiring diagram; however, original wires may need to be traced to their terminal points.