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Fin
01-18-2010, 04:42 AM
I'm putting in a washdown pump. 12 volt, 14 amp. What size of fuse should I put in? 15 amp or 20 amp or something else?

ReelJerks
01-18-2010, 05:16 AM
What is the wire size? This is typically how you size the fuse. The fuse is all about FIRE PROTECTION and not for protecting your pump. The wire size for your pump should be the SAME SIZE all the way to the power source, POS & NEG, and that size depends on the current draw and the length of run.

So in your case, 14 amp rated, you can run up to 15 feet using 12 ga marine wire. You should fuse this circuit with a maximum of a 20 amp ATC fuse. If you go longer, all this changes. Same for less than 10 feet.

Edd

Fin
01-18-2010, 11:10 AM
Oh no.

I could have slept nicely if I never would have asked.

The pump had, I'm guessing, 14 or 16 guage wire on it. In my ignorance, I ran 10 guage to the pump. (I was thinking bigger is better.) I connected the 10 AWG to my fuse holder, which I connected to the perko. There is a little 20 amp switch within a couple feet of the perko. Total wire length from the switch to the pump is about 7 feet, I'm guessing.

I put a 20 amp fuse in the holder.

Do I need to rip this out and redo?

ReelJerks
01-18-2010, 11:33 AM
Depends on how well you want to sleep in the future!
There are a few excellent books on Marine Wiring out there. A trip to Borders or some other store may be in order.

Edd

Fin
01-18-2010, 01:09 PM
A book now, huh? All these hidden costs are adding up. ;)

Or....maybe I just won't use my pump. ;D Wait! I do have a fire extinguisher and boat insurance. I should be fine... ;D ;D

I'll look into it a little more, Edd. Thanks for your help.

Fish_R_Us
01-19-2010, 02:58 AM
Your 10AWG wire is fine, as long as the circuit is protected by a 20A fuse. The wire size is a little excessive, however will still work.

ReelJerks
01-19-2010, 03:48 AM
Fish_R_Us is correct EXCEPT, your circuit should be protected by a MAXIMUM 30 amp fuse. 20 amp is fine but never more than 30 amp for this case.

Dennis
01-19-2010, 11:59 AM
The fuse is there to protect both the wire and the pump. If the pump is rated for 14 amps, I'd use a 15 amp fuse to start. However a bigger fuse might be needed for surge loads. The pump manufacture should be able to give you the correct fuse size.

Using larger gauge wire is not a problem. For marine applications a good marine tinned multi stranded wire is best.

just my .02

ReelJerks
01-20-2010, 01:33 AM
The fuse is there to protect both the wire and the pump.* If the pump is rated for 14 amps, I'd use a 15 amp fuse to start.* However a bigger fuse might be needed for surge loads. The pump manufacture should be able to give you the correct fuse size.

Using larger gauge wire is not a problem.* For marine applications a good marine tinned multi stranded wire is best.*

just my .02*

Comment about marine wire should have been 'ONLY WIRE' to use.
.....but everybody has 2 pennies.

Edd

ReelJerks
01-20-2010, 03:33 AM
Using larger gauge wire is not a problem.

This, from a BlueSea technical bulletin, will clear some of this up.

Choosing an Amperage Rating

Generally, circuit protection devices are installed to protect the wiring from overheating during overloads or faults. The simplest approach for selecting a circuit protection device rating is to choose an amperage rating that is equal to or less than the current rating, ampacity of the wire. If the wire ampacity is significantly greater than the load current, as might be with small loads or with wiring of increased size to reduce voltage drop, then a range of circuit protection values between the load requirement and the wire ampacity may be acceptable. Larger ampacity values reduce the probability of nuisance failures and reduce fuse heating; smaller ampacity values provide more conservative protection for the wiring.

In some cases, a product manufacturer may recommend that a specific fuse or circuit breaker size should be used with the product. If that is the case, the wire to the product should be selected so that the wire ampacity exceeds the recommended rating, which will protect both the product and the wiring.

Dennis
01-20-2010, 10:17 AM
Fire can occur either with the pump if the fuse isn't sized correctly or the wire if the gauge isn't of sufficient size for that fuse size or amperage. This should be treated as a unit.

ReelJerks
01-21-2010, 01:28 AM
The biggest problem is people not having 10 awg when required but they do have 12, so they use 12 awg. The problem is then compounded when they run this #12 the length of a 21 foot boat. FIRE!

Now in order to protect your gear, if you should wire your nice new sonar/graph with 7' of #8, then by all things that are holy, you should fuse that junction where the factory #16 wire joins the #8 with a fuse for the 16 awg.

One very good place to seek out wiring information is the Blue Sea site. Not only do they have excellent products, their help bulletins are written to USCG and ABYC standards. Oh yea.....it's FREE too!

Edd

Dennis
01-21-2010, 03:00 AM
Edd,

What size fuse came with your HDS 10?

Just curious.

ReelJerks
01-21-2010, 04:55 AM
Edd,

What size fuse came with your HDS 10?*

Just curious.





A 3 amp

BASS-O-MATIC
02-01-2010, 10:10 AM
Check the pump manufacture requirements for fuse size. If that cant be found then go 125% of load( 14 amp 125% + 17.5 amp fuse). 10 gauge wire is great up to 15' and if over sized it will let you upgrade to something bigger. But the fuse is your safty.

MJPFISHON
02-13-2010, 03:02 PM
That was great information boys, keep it up!! I'll get my boat in shape yet!! I read all these posts!! Thank you EDD. MJP