Relay queston - Electric fan controller

[red.EDDIE.4x4]

ok, so i ordered a Derale electric fan controller from summit. its fairly straight forward, but i am confused on how many amps my fan is able to draw from the relay it has. i am going to run a chevy HHR fan.
here is what the top of the relay says: 12V 40/60A

then the sticker Derale put on it says this: Maximum Capacity 25 Continuous Amps

im confused, so can i run 40/60 amps based off the relay? OR can i only run 25 amps based on the sticker?

thank in advance guys.
-red.ED

 

[Fifty150]

DeRale has great tech support. Anyone with a question like this, deserves a real answer from the manufacturer.

The controller kit is designed to operate a fan rated for up to 25 amp. That sticker is for the entire kit......connectors, fuses, wires, et cetera.

The 40/60 amp relay is used because a 25 amp fan may experience a sudden surge in voltage as it kicks on.

DeRale kits like the one you selected are pretty well engineered. From my experience, they are good value. Spend a lot more, like twice as much, and you can buy a Painless Performance kit.

P/N - 30117

Dual Fan-Dual Activation Fan Relay Kit (185 degrees F On/175 degrees F Off)

• 

Click image to open expanded view

Painless
Painless 30116 Dual Activation Dual Fan Relay Kit
4 customer reviews





Price: $119.99 & FREE Shipping

 

[imp]

@shucker1

"surge in voltage"??

 

[Mbrooks420]

The relay is rated for 25 amps, all the time. The 40/60 rating is probably for inrush CURRENT that happens when most electric devices (surely a fan) pulls when starting out from a standstill. This only occurs for a very short time, and drops off rapidly as the fan picks up speed.

If your fan setup draws more than 25 amps when running, you’ll need a beefier relay.

 

[imp]

The relay is rated for 25 amps, all the time. The 40/60 rating is probably for inrush CURRENT that happens when most electric devices (surely a fan) pulls when starting out from a standstill. This only occurs for a very short time, and drops off rapidly as the fan picks up speed.

If your fan setup draws more than 25 amps when running, you’ll need a beefier relay.

@Mbrooks420
All true, about starting current, or inrush current.

Current ratings on relays refer to the amount of current the relay switch contacts can handle without giving out prematurely. When starting and stopping the fan motor, the contacts are most affected, especially on stopping, when a large inductive "kick" from the motor's magnetic field collapsing, can create a large arc as the contacts open. Thus, the more often the fan must turn on and off, the greater the wear and tear on relay contacts.

That may be why Ford set up my '94 5.0 HO (Mustang) electric fan to operate with a large "on-off" temperature differential. My cluster gauge would go nearly to max before the fan turned on, then dropped back down almost to thermostat closing temp. I hated that temperature swinging, and the electric fan is now history, replaced with a clutch fan. imp

 

[Fifty150]

Probably also explains the darn fuses blowing.

 

[imp]

Probably also explains the darn fuses blowing.

@Fifty150
Fuses are a whole 'nuther science in themselves, believe it or not. Consider this: A 50 amp fuse protects a circuit.........For whatever reason, if the current it's carrying gets up close to 50 amps., when will it "blow"? Should it carry 49 amps forever without blowing? If current hits 50 amps, should it blow "right away", or how long will it carry 50 before blowing?

These questions are what the designers and users of fuses are faced with. Generally, if the circuit being protected by a fuse carries a normal current of, say, 10 amps, the designers will provide a fuse rated at somewhat less than twice that value, depending on many other factors of course. So, a gizmo drawing 10 amps. gets circuit protection rated at 20 amps. 20 provides adequate safety against fire, or melting down of wire insulation.

All of this can involve "gotchas"!, of course. We are considering average conditions only, and no unusual ones. imp

 

[Mbrooks420]

Probably also explains the darn fuses blowing.

What size fuses are blowing? What’s the rated amperage or wattage draw of the motor(s)?

 

[Fifty150]

Apologies for late response. As I no longer have an Explorer, I am not keeping up with this forum.

With a fuse inline from the battery to the relay, the relays were getting hot, burning, and melting.

With the current generation of Derale fan controller, there is a 30 Amp fuse which is inline from the relay to the fan motor, not from the battery to the relay. There is also a diode inline for a secondary controller, which is typically hooked up to your A/C. As the fan motor surges and draws more electricity, the fuse blows to protect the relay and harness.

The controllers used to come with 25 Amp fuses. 25 Amp fuses would blow. I then went up to a 30 Amp fuse. As extra protection, I also installed a circuit breaker inline from the battery to the relay, which never tripped. The circuit breaker is extremely easy to bolt onto your battery tray area.