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Air up component need identification.

Posted: Tue Feb 05, 2008 7:22 pm
by sanger
Hey all im about to start installing an on board air system using 12 v air compressor and a tank to aid in airing up at the end of the day.

Can someone please varify if the component circled red is just and ordinary relay or does it have to be some special solenoid relay. The information id from the usa so this may be why i dont recognise the name.

Image

If anyone can shed some light on the situation that wouold be awsome.

Cheers sanger

Posted: Tue Feb 05, 2008 7:23 pm
by sanger
Sorry for the dark pic but its all i got.

Posted: Tue Feb 05, 2008 7:28 pm
by -Scott-
A solenoid is, technically speaking, not a relay - but mechanical relays work on the same principles as a solenoid, so I shouldn't drink and post.

Yes, the solenoid in the pic is essentially just a relay. In automotive circles, "relays" tend to be smaller with lower current ratings, and "solenoids" tend to be larger with higher current ratings.

The trick in that diagram is that the solenoid coil connects to earth through the body of the solenoid, to the chassis of the vehicle. There's no reason you can't run an earth wire from a different solenoid/relay.

The diagram shows a 35A fuse - I'd go for a relay/solenoid rated higher again, as switching an inductive load (i.e. a compressor motor) can create surge currents and/or arcing which can wear out the contacts.

I hope that made sense...

Scott

Posted: Tue Feb 05, 2008 7:52 pm
by sanger
Scott sweet as mate. So i can go to my local sparky and ask for a normal relay and i should be sweet, Correct?
Also what amperage fuse would you suggest to combat surge.

Cheers and appreciate the quick response

Posted: Tue Feb 05, 2008 7:59 pm
by -Scott-
A 35 amp fuse will be fine - it's more about finding a relay/solenoid rated higher, as that will reduce the chances of your relay/solenoid failing.

Take the diagram in with you, and show him/her what you're doing. A 20A relay will do the job, but I don't know how long it will survive. A 40A relay should be adequate. If you can get something rated higher for similar dollars, do it.

One word of warning - be wary of "horn" relays, as some of them aren't designed to be on for long periods. Make sure you buy something rated for "continuous duty."

Good luck,

Scott

Posted: Tue Feb 05, 2008 8:02 pm
by sanger
Legend mate thanks heaps for your input.