Fuse sizes?

[rodneym]

Friends,

Making 2 mods to beat the heat...

First, I added a dual pusher rig from Acton (I know, more for looks...) BUT, I'm using the original Kirkham circuit which had a Spal puller, rated at 20A, with a 30A fuse. The pusher motors are rated at 4A each. So, how should I fuse them? 15A, 20A? (I used the original circuit for the pushers because the new bigger puller requires a more robust, discreet circuit).

Then, I replaced the original Spal puller with a H.O. Spal 30102113, rated at 26A. I ran a separate circuit with a 70A relay and heavy gauge wire. So, the fan runs at 26A but Spal recommends a 30A fuse, believe it or not!!!??? Shouldn't it be 40A? I know I can test it but isn't there a safety factor built in to the size fuse used?

Aside from hearing me ramble about my evil doings, how would you protect 8A and 26A (running) respectively?

Thanks!

[ERA Chas]

Originally Posted by rodneym

Aside from hearing me ramble about my evil doings, how would you protect 8A and 26A (running) respectively?

Thanks!

Just the way you did. I'd run the 30 as a test (for the protection) and go up if it trips constantly. You'll seldom need the pushers except standing still. thy will just maintain temp if they're even slightly good. They freewheel at like 20 MPH+ anyway.
General question R-why the heat issue now? Did you change pulleys for + boost?
Or just drivin' like a maniac (like I would)??

[rodneym]

The heat 'issue' isn't new, or excessive. At the first show I attended with the new motor, I overheated waiting in line. I cn't remember exactly how long the wait was, probably over 20 mins, just creeping one car length every couple mins. When I got in and turned off, I popped a hose. Bottom line, even on a moderate temp day, she will overheat sitting still, no question. Ergo the bigger fan. NO room for a shroud.
It's just a lingering issue that I finally addressed.

Chas, I understand trying out a 30A fuse on the puller and see if it blows, but I'm not clear on your suggestion for the pushers?

[patrickt]

1) See my thread on pushers and pullers: Cool Modification - For Pusher Fans Only, Though

2) Fans pull a variable amount of current depending on their conditions -- remember, they're electric motors not light bulbs. The long and the short of it (get it, short) is that so long as the fuse is less than the burn up current of your wiring then you will be protected. So long as it is not a fast-blow fuse, going above the max current is all you need. So, you have a wide choice of fuses without worrying about being wrong.

3) If you want to know the true current numbers, you have to put a gauge on your wiring (as per my thread) -- you can not rely on specs alone.

4) If you are grounding your fans to the frame, make sure that the path of the frame to the negative terminal of the battery is nice, clean, and of a fat gauge. If the negative battery cable runs to your block or head, you must be able to trace with your hands a fat gauge ground path from the engine or head to the frame, ie a fat ground strap, a fat ground wire, etc. In other words, pretend that the motor mounts, trans mounts, brake cables, and the like are all made of rubber and glass and provide no path for the return current. You must do this even in an aluminum car. Your fans will still run even with a half-ass grounded return path, but they will perform much better with a clean, high-gauge path. The ground path from the frame to the battery terminal is an often-overlooked problem -- correcting it makes everything on your car work better, your food tastes better, your dog smells better, and so on....

[patrickt]

Hmmm, thought I talked about my inductive ammeter in that thread, but it was on this link right here: 300 amp X 12 volt Circuit breaker

[rodneym]

Originally Posted by patrickt

1) See my thread on pushers and pullers: Cool Modification - For Pusher Fans Only, Though

2) Fans pull a variable amount of current depending on their conditions -- remember, they're electric motors not light bulbs. The long and the short of it (get it, short) is that so long as the fuse is less than the burn up current of your wiring then you will be protected. So long as it is not a fast-blow fuse, going above the max current is all you need. So, you have a wide choice of fuses without worrying about being wrong.

3) If you want to know the true current numbers, you have to put a gauge on your wiring (as per my thread) -- you can not rely on specs alone.

4) If you are grounding your fans to the frame, make sure that the path of the frame to the negative terminal of the battery is nice, clean, and of a fat gauge. If the negative battery cable runs to your block or head, you must be able to trace with your hands a fat gauge ground path from the engine or head to the frame, ie a fat ground strap, a fat ground wire, etc. In other words, pretend that the motor mounts, trans mounts, brake cables, and the like are all made of rubber and glass and provide no path for the return current. You must do this even in an aluminum car. Your fans will still run even with a half-ass grounded return path, but they will perform much better with a clean, high-gauge path. The ground path from the frame to the battery terminal is an often-overlooked problem -- correcting it makes everything on your car work better, your food tastes better, your dog smells better, and so on....

1) I agree with Chas on the 8 track.
2) Check. What I'm generally observing is that fuses are about 1.5x's the 'rated' current, and if there's no fuse of that size, it's bumped up. The Spal suggested fuse for the puller surprised me but according to your explanation, it seems ok. For now...
3) Check.
4) I'm good here.

Thanks.

[patrickt]

If the fuse doesn't blow, then it's the right size. Unlike a circuit breaker, which will blow at a lower current spec as it gets hotter. A 40 amp circuit breaker that is mounted to your firewall under the hood can easily blow at, say, 30 amps. The circuit breaker manufacturer has a chart that shows you about where it clicks off depending on how hot it is, but most car guys on here don't know that and just assume that 40 amps means 40 amps....

[ERA Chas]

Rodney-Dude,
AVOID 'car show' idling traffic jams-for lots of reasons. You make junk out of the plugs is one. Your spectacular car is for YOU to enjoy, not the sheep at shows that gawk, show and tell (lies).
If you are stuck in parade-type conditions in a street traffic jam, pop out, and prop the hood back edge (like 3" or more) with a cushion or something to get heat out. Puking a hose is pretty serious and ruins your day. But warp a head............
I won't go there.
Most sincerely,

[rodneym]

I hear you there.
Believe me, my KMP is no show car. It's a driver, no question. I was new to the area and the engine new to me so I did a couple shows last year.
There's an informal show in my 'neighborhood' once a month and that's enough.
I'd much rather have a couple Cobra buddies come over for a BBQ and a drive around the hill, than fart around a show and look. I'll take my daily driver for that.
On to the cooling, I've been caught in traffic many times even though I plan carefully. It's just a $#!tty feeling when traffic stops on the freeway for no reason and the temp clock starts ticking

[Rick Parker]

Rodneym:
When the Spal fan (or any fan for that matter) first clicks on it will momentarily (for a split second) pull more amprege than after it is moving. 30A should be good. And its always a good idea to carry some spare for any fuses used throughout the car. If you have an amp gauge you will see the needle "flick" negative for a split second as the circuit for the fan closes.

[Rick Parker]

Rodneym:

A good way to do it is to hard wire the fan through a High quality 40 Amp 4 prong normally open relay and control the closure of the relay with a thermo fan switch in the cooling system that is on a fused circuit and carries a manual overide. I have a Fluidyne radiator with the fan switch in the lower section of the RH tank, with the key off if the fan circuit is closed (over 193 degrees) the fan will run for about 3-4 minutes as it cools it down, at which time the fan switch opens and the fan quits running (unless in manual overide).



PS...The Rug did NOT go in the car!!!

[vector1]

it might take a few more amps than what the appliance is rated at to get it moving.

[rodneym]

Anectdotal conclusion:
The new wiring, 70A relay and 30A fuse are all working well on the new H.O. Spal...
It was in the 80's on Saturday and after a drive I let the Cobra idle for quite some time in the driveway (to Chas' chagrin) seeing if the temp would hold. It hovered at 99-100 C with the fan on, and it normally would have crept up to 115+, even in cooler temps. So it worked! I know you all were on the edge of your seats
And one more anectdote, the twin pushers did NOTHING. Some knew that, others said they get a little help but nothing for me in my 'controlled' environment.
They do look cool, though

[patrickt]

More importantly, do you have a sprinkles bottle attached to the side of the oil pan to catch the coolant overflow?

[rodneym]

Don't be rediculous.
I use one of those mini airline bottles of Jack Daniels.
I'd use a mini bottle of Laphroaig but these are Cobras, not Bentleys.