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18Amp Relay
nickm - 29/8/16 at 05:28 PM

Hi
After some advice, i am fitting an immobiliser and one of the isolating circuits requires a 18amp relay i cant find a 18amp relay anywhere so do i fit one of the fused type (30 or 40amp) with a fuse rated to 18amp ?

Thanks

Nick M

David Jenkins - 29/8/16 at 05:57 PM

They probably mean "a relay that can handle 18A", so any relay that can handle more than that will be fine. Don't worry about the fuse, unless the circuit needs protection - if it's just cutting a circuit to prevent starting then this is probably not required.

gremlin1234 - 29/8/16 at 07:33 PM

a 30A relay should be fine, without any extra fuses

britishtrident - 30/8/16 at 09:35 AM

Fused relays are handy because they give you an easy quick method to test the relay operation without pulling the relay.

nickm - 30/8/16 at 06:40 PM

Many Thanks

May well go for the fused type for the sake of a couple of quid as the immobiliser cost £50

Nick M

daviep - 30/8/16 at 09:11 PM

quote:
Originally posted by nickm
Many Thanks

May well go for the fused type for the sake of a couple of quid as the immobiliser cost £50

Nick M


The fuse protects the switched contacts not the operating coil terminals.

nickm - 31/8/16 at 06:56 PM

Thanks
No point in fused then as relays are protectors anyway.

Nick M

02GF74 - 31/8/16 at 07:13 PM

quote:
Originally posted by nickm
Thanks
No point in fused then as relays are protectors anyway.

Nick M


That isnt quite correct. Relays are used to switch larger currents that may well exceed the capacity of the wiring or else the contacts thenmselves melt.

In other words either the wiring or relay contacts act as the fuse, i would not recomnend that. For the sake of £2 or less, fit an inline fuse of correct rating, 8A should be plenty for immobiliser.

daviep - 31/8/16 at 07:27 PM

quote:
Originally posted by 02GF74
quote:
Originally posted by nickm
Thanks
No point in fused then as relays are protectors anyway.

Nick M


That isnt quite correct. Relays are used to switch larger currents that may well exceed the capacity of the wiring or else the contacts thenmselves melt.

In other words either the wiring or relay contacts act as the fuse, i would not recomnend that. For the sake of £2 or less, fit an inline fuse of correct rating, 8A should be plenty for immobiliser.


Not sure I entirely understand / agree with this.

The relay / fuse has nothing to do with the immobiliser, the immobiliser is merely the switch operating the relay. Presumably the circuits that the relay will be switching are already fused.

Obviously the supply to the immobiliser should be fused with an appropriate fuse.

Cheers
Davie

britishtrident - 31/8/16 at 07:38 PM

quote:
Originally posted by nickm
Thanks
No point in fused then as relays are protectors anyway.

Nick M


Oh my ................

02GF74 - 31/8/16 at 07:41 PM

^^^^ what i was trying to say is that 18a relay wont limit current like an 18 a fuse, very likely it will supply quite a lot more amps.

nickm - 1/9/16 at 07:31 PM

Oh my

Yea poor use of english to call them protectors but i cant be that much of a muppet as im on my second build and all the fuel injection and ecu electrics work fine.

Nick M