ELECTRIC FANS PER RELAY

[Guest]

Hello.

 

Would you run an 80W electric fan PER 30amp relay or can the relay handle 2x 80W fans. The maths of it suggests the latter, so part of me thinks 1x relay for these two fans.

 

However the bonus of running 1x relay PER fan gives you the back-up of having a "spare" relay & fan should one fail to work.

 

The wiring for 1x relay PER fan is not a lot greater than running 2x fans via 1x relay.

 

Both fans would "ignite" when the sensor reaches its "on" position.

 

Thoughts ??

 

Many thanks.

 

Richard.

[dougbgt6]

Watts = Volts  x Amps suggests a running current of 6.6 amps per fan however, the start up current will be many times higher. Depends how sophisticated your fans are at dealing with back EMF but I would go for two relays.

[Guest]

Hello Doug.

 

Many thanks for your reply and have been thinking about the set-up since my initial post.

 

The start-up draw is about 10amp; however even though well within the relay capacity I am minded to use a relay per fan.

 

One relay can then be wired to live "ignition-off" and the other to live "ignition-on".

 

This will ensure that when required both fans switch-on with the engine running and then when the engine is switched off, 1x fan will still be able to run if the rad temp / sensor so demands it. 

 

Many thanks.

 

Richard

[rogerguzzi]

Hello Richard

                     I fitted a dual thermostat switch to my Spitfire one fan cuts in at 83degs and out at 78degs and the other 88degs and out at 83degs.(I think/ will check)

 

I have arranged the wiring to have an overide switch with centre off and on left and right and they are wired 1st fan or both.(2 relays and led's to show when on and individual fuses)

 

I found in Spain last year the second fan never came on on its own only when I got twichy!

 

I run a full width radiator with the sensor in the bottom of the radiator and 2 x 9" fans.

 

Roger

 

 

[Guest]

Hello Roger.

 

Many thanks for your email and a very neat installation + dash display.

 

Very useful and all noted.

 

Regards.

 

Richard.

[TomL]

I'd do two relays; it future proofs the installation for more switching options in the future, should you wish to introduce for example another temperature-sensor (as Roger has done) or your own suggestion of one with ignition-suppy and the other with a permanent-supply.

 

Tom