relay or not?

[takotruckin]

im planning a rewire of my baja in the near future, and have a question, (yeah, just one, for now)

should i use relays? i have 4 100 watt lights, which will be on two circuits, this little deal here http://www.opamplabs.com/eirp.htm came up with about 17 amps per circuit. im also planning on converting my housings to HID, which should draw even less current. i was thinking of using these switches http://www.delcity.net/delcity/servlet/ ... 340&page=1 without relays, to make it simple. they are rated for 30A @12VDC, so is there any reason why i should run relays?

[Ol'fogasaurus]

I personally like to use relays. That way, the power to the lights do not run through the switch which can be a problem with high draw lights. The power source for the relays do not run throught the switch either but wired directly to the relay which is designed to handle the load. The switch only activates the relay which means the switch is required to deal with a lot less load.

My two-bits on this.

[DesertGuy]

As long as the switch can handle the max load, and everything else is equal... I think using relays is a matter of personal preference and the primary purpose of the wiring in the car. In my application I could have done it either way. All components could handle the draw. I opted for relays because I did not want upwards of 20 amps sitting behind the dash resting on a switch. However, many desert race cars forego relays as one more thing that can go wrong. Keep in mind a "race car" is ran hard for a limited time, then prepped after each race. I just wanted a little piece of mind... but I think you could argue either way.

[Ol'fogasaurus]

Good post.

Up until lately I didn't uses them as much for lights and some other electrical components. I was trying to simplify the electrical system but sometimes that is not good either.

I had some electrical compontents not work as well as they were capabile of because the switches were pretty much maxed out on the load they were expected to carry. Some of the switches were rated at higher loads than they actually functioned at.

Not only is it a personal thing, it is also an experience thing also.[/code]

[2088 bob]

A little known fact about switches is not so much their current handling ability but their ability to handle the make and break current of the circuit.
When one opens a switch under load, especially some of the loads generated by really hi powered lighting,a substantial arc is produced at the switch contacts at the moment they open,which has a tendency to erode the switch contacts rather quickly, leading to eventual and fairly rapid failure of the switch

the design of a good quality set of relay contacts, is better suited to deal with this arcing Thus keeping the circuit more reliable for longer periods of time
So if you are considering using just switches for some of your higher current loads consider them for circuits that you turn on and leave on and circuits that are being asked to be switched alot consider using relays for those

[takotruckin]

ok. the lights will be relayed then. thanks for the help guys. beware, i will have more questions as i do this thing

[2088 bob]

Tako the questions are why we are here