Relay Size

[chrwilkins30]

Got 4 55w on the roof and need to run relays. What amp size would you recommend. Plan on running two on each relay.

Also what size wire?

 

[Sasquatch_Ryda]

Just your plain old 30 amp Bosch relay will work just fine. 16g wire is more than enough.

 

[yyc_tbird_sc]

To figure out amperage, A=Amps, W=Wattage, V=Voltage

A=W/V

So...A=55/12=4.59A per light. Multiply this by 4 (for four lights) and you get a total of 18.36A.

A single standard 30A bosch relay will work for this without a problem. I would personally split the lights up into two different pairs, so that you don't have to have them all on at the same time. If you're going to go with them all on one circuit, then I'd be looking at a minimum of 14 gauge wire, with a preference towards 12. Be sure to keep your connections as weather-proof as possible, as any corrosion or bad connections will cause a loss of power, and possibly a hot spot in the wiring which could result in bad things.

*EDIT* I just re-read your post...you're already putting two on each relay. That's only 9.18A per circuit. *EDIT*

You can also invert this to be the following....
W=V*A
V=W/A

 

[Sasquatch_Ryda]

Yup, definitely solder and shrink tube all connections.

 

[chrwilkins30]

Yeah i already planned on heat shrinking all connection.