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Old 12-02-2014, 09:49   #1
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Fuse size for bilge pump

I'm in the middle of doing some rather major rewiring for my Sabre 34, cleaning up a lot of wires that do things like run straight to the battery (and including a new fuse panel to handle them). Right now, I'm installing a pair of bilge pumps complete with new wiring. The issue is fuse size.

The subject bilge pump is a Sureflo 700. It draws 3.5A, and the manual says to use a 5A fuse. I'll be running 12GA wire, and the pump itself has 16GA wire (that pisses me off, but that's another story!). The wires (including the 16GA on the pump) are rated for 20A or more. The auto switch is rated for 15A.

So here is my question. This circuit is the only circuit on the boat that will have a 5A fuse. I'd like to minimize the number of spares to carry (and yes, I know a fuse is a pretty small thing to carry!). Is there any reason why I shouldn't put in a 10A fuse?

Seems to me that the standard idea is a fuse protects the wire, and the wire is up to it.

Thoughts?

Harry
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Old 12-02-2014, 10:01   #2
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Re: Fuse size for bilge pump

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Originally Posted by sailingharry View Post
I'm in the middle of doing some rather major rewiring for my Sabre 34, cleaning up a lot of wires that do things like run straight to the battery (and including a new fuse panel to handle them). Right now, I'm installing a pair of bilge pumps complete with new wiring. The issue is fuse size.

The subject bilge pump is a Sureflo 700. It draws 3.5A, and the manual says to use a 5A fuse. I'll be running 12GA wire, and the pump itself has 16GA wire (that pisses me off, but that's another story!). The wires (including the 16GA on the pump) are rated for 20A or more. The auto switch is rated for 15A.

So here is my question. This circuit is the only circuit on the boat that will have a 5A fuse. I'd like to minimize the number of spares to carry (and yes, I know a fuse is a pretty small thing to carry!). Is there any reason why I shouldn't put in a 10A fuse?

Seems to me that the standard idea is a fuse protects the wire, and the wire is up to it.

Thoughts?

Harry
Harry,

This is the one place on a boat where you really wan to use the fuse to protect the device and use the 5A fuse the manufacturer recommends.

These fuses are sized so that if the pump becomes "stalled" with debris, or by ice, it won't overheat and catch on fire and the fuse will trip..... I have seen two pumps with the wrong fuses physically melt the pump when stalled. No fire, but darn close.

Ideally there would be a fuse in the bilge pump switch, and this can be 5A. the one at the battery, if home-running the pump, can be sized larger to minimize voltage drop across the fuse.
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Old 12-02-2014, 11:14   #3
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Re: Fuse size for bilge pump

Maine,

That is the very answer I had in the back of my mind, but didn't want to mention it (by doing so, people would say "yes, right, that's it).

Thanks for the answer (complete with real life examples!).

5A it is, and another 1oz of stuff in the spares drawer.

Harry
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Old 12-02-2014, 14:05   #4
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Re: Fuse size for bilge pump

you can always use a heavier gauge
For the "run" to the equipment,
And the "drop" is the wire that comes with the equipment usually short in length . Fuse always as the equipment load recommended.
. The "run" from the circuit panel where the heavier wire is used so as not to or minimize the voltage drop to the usage load point.
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Old 14-02-2014, 08:44   #5
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I agree with all the previous posts. Would just like to add that in my experience most installations have a separate -manual, off, automatic, switch- with its own fuse that is separate from the battery switch so you can turn off the battery switch and still have your bilge pumps operational. Also most switches come with a standard fuse which I have always replaced with a push button circuit breaker. its real easy to take out the fuse holder and put in the circuit breaker. It almost never happens but in an emergency if the breaker was thrown because of a jammed bilge pump it's simple matter unclogging the pump and resetting the breaker instead of searching for the proper fuse. Also you don't have to carry any spares. The breakers I'm talking about cost about 12 bucks. 1 more thing. Put a small bilge pump deep in your bilge and have a high-capacity pump higher up that only sees action in an emergency or failure of the small pump. I've had a lot of bilge pump and bilge pump switches fail so I highly recommend the backup
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Old 14-02-2014, 10:43   #6
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Buy switches failing I mean bilge pump float switches. And more often than the pumps.
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Old 16-02-2014, 09:11   #7
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Re: Fuse size for bilge pump

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I agree with all the previous posts. Would just like to add that in my experience most installations have a separate -manual, off, automatic, switch- with its own fuse that is separate from the battery switch so you can turn off the battery switch and still have your bilge pumps operational. Also most switches come with a standard fuse which I have always replaced with a push button circuit breaker. its real easy to take out the fuse holder and put in the circuit breaker. It almost never happens but in an emergency if the breaker was thrown because of a jammed bilge pump it's simple matter unclogging the pump and resetting the breaker instead of searching for the proper fuse. Also you don't have to carry any spares. The breakers I'm talking about cost about 12 bucks. 1 more thing. Put a small bilge pump deep in your bilge and have a high-capacity pump higher up that only sees action in an emergency or failure of the small pump. I've had a lot of bilge pump and bilge pump switches fail so I highly recommend the backup
Sparrow,

You have a lot of good points in there. Since you brought them up, let me expound on my installation.

* Coming off the battery fuse on each battery, I have a short run to a breaker, and then a small fuse panel. These two fuse panels are always hot (assuming nothing has blown), and are very close to the batteries.
* From the "main" battery (Trojan Golf Carts) fuse panel, I have the 5A fuse (my original question!) running to a 700 GPH pump deep in my bilge. It is on a #12 wire, part to minimize voltage drop and part to add "durability" in the bilge.
* From the "spare" battery (Group 26, I think) fuse panel, I have a 15A fuse running a 2000 GPH pump further up in the bilge. It is also on a #12, for the same reasons. It's only a 5' run, so voltage drop isn't really an issue.
* The small bilge pump is wired through the old "ON/Manual/Off" switch, but it is now only a "manual" switch. That is a MAJOR PEEVE for me! Who in their right mind thinks that a highly important safety feature like a bilge pump should have an "off" position? And when would you ever use it? And, if you use the "manual" it spring-returns to "off" and not "auto." The number of times I've pushed to manual, then released the switch (to the off position) and gone home is just scary! Now, you push to "manual" and the pump runs. The light shows when the pump runs. But the "off" and "auto" and fuse are all just leftovers. I may figure out a replacement switch at some point. And one last thing -- the "standard" way to wire those damn things is with a nice long wire, unfused, direct to the battery! You either have two fuses, or the first fuse is a the switch and the wire is a fire waiting to happen.
* I'm using the Attwood electronic switches. I only have a few months of use, and only in port, so I have no idea how long they will last, but I'm pretty impressed. I especially like the extended run time after "off" to try and get the last of the water out. I have about zero faith in any automatic switch, so I'm glad I have two pumps.

I think that I've now got a nearly idiot proof system. Two different pumps, two different batteries, nothing goes through the battery switch. No stupid "off" switch at the electric panel. The "primary" pump has a manual switch and indicator light right by the breaker panel. With the exception of the run up to the manual switch (which is only "live" when the switch is pressed), the round trip wiring length is 10 feet of #12 (actually, they share a #10 ground wire -- the only "shared" part of the system). The one thing I don't have is your suggestion of a breaker instead of a fuse.

Oh, as an aside -- those fuse panels do more than the bilge pump. They also provide power to other "vampire" loads that manufacturers all want to go direct to the battery post, like the battery monitor, the stereo "memory" power, the alternator sense, and the battery charger connections. They aren't "on the battery post" but they are 18" away with #4 or larger wiring, which is close enough for me!

Harry
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Old 16-02-2014, 09:33   #8
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Harry. It's a simple matter to replace that momentary on switch with one that stays on while manual or automatic. It's nice to be able to switch off when you're cleaning the impeller or replacing the pump or float switch. most boats have main battery switches so you can choose what battery your using or charging but also as a safety feature in case of a fire you can disconnect everything. and also when leaving the boat. My solar and wind generators also are separate from my main house breaker panel. One more thing I just thought of if you have a failure with your float switch it's nice to have ability to just turn the pump off or manual until the float is repaired.
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Old 16-02-2014, 14:44   #9
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Re: Fuse size for bilge pump

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Harry. It's a simple matter to replace that momentary on switch with one that stays on while manual or automatic. It's nice to be able to switch off when you're cleaning the impeller or replacing the pump or float switch. most boats have main battery switches so you can choose what battery your using or charging but also as a safety feature in case of a fire you can disconnect everything. and also when leaving the boat. My solar and wind generators also are separate from my main house breaker panel. One more thing I just thought of if you have a failure with your float switch it's nice to have ability to just turn the pump off or manual until the float is repaired.
Sparrow,

Yes, the switch is easy to replace, and I'll probably replace it with a push button. The real issue is getting rid of the "off" position, as it is far to easy to leave it there. Using the "off" for impeller clogs, or other such issues, seems sufficiently infrequent (hopefully never!) that I can simply reach into the fuse panel and pull the fuse (or open the breaker feeding that fuse panel).

I do have a battery switch, and it feeds almost everything. It also allows selecting the "main" or "reserve" battery for power, and in theory allows directing the charge (but I have an ACR to handle that). And of course, it provides that major safety feature of shutting everything down -- but I'm not sure that I want my bilge pumps to be part of "everything." Also, I like to leave my battery switch "off" when I'm not on the boat, but I still want my bilge pumps, battery monitor, etc to be live -- hence the 24/7 panels before the switch.

Harry
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Old 16-02-2014, 17:02   #10
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Harry. in my Original post I said that the bilge pump is usually separate. That way you can turn off your battery switch when you leave the boat and it will still be on. and I also have my solar panels and wind generator on a separate breaker panel. But like you said the light will come on when the pumps running whether its through manual or float switch being on. And I just reread your post and I don't understand why you don't have a bilge pump float switch on your small pump. add the float switch, keep your on off auto switch but make it so it stays on both ways and you will never leave it in the off position by mistake. And I have to edit one more time . it is not really that uncommon for your bilge pump to get clogged or your float switch to fail, in fact I've had it happen at least once a year, at least
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Old 16-02-2014, 17:24   #11
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Re: Fuse size for bilge pump

I'd go 10 amp. Let's face it, many application on boats the fuses dont match the device. If you are in dire need of the bilge pump, you dont want one piece of temporary debris blowing the fuse.
Think of it this way, the lighting breaker in your house probably is 20 amp. If you only have one light bulb on and it short circuits is the 20 amp overrated? The breaker is sized for many lights.
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Old 16-02-2014, 18:02   #12
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Re: Fuse size for bilge pump

debris doesn't short circuit the pump power wires. there is a huge difference. it'll just overwork the motor, draw say 7 amps, overheat, and catch on fire. if the wire or pump short circuits then yes it would blow a 10 as well. but they are different things.

there is many ways to wire a bilge pump. but somewhere along that line there should be a 5a fuse. and there should be atleast one fuse near the battery or source. I see lots those bilge pump switches with built in fuses. with 15' of unfused wire going to the battery.... in that case you'd need 2 fuses. but the battery one could be 10 or 15a. and that one should never blow. you'd never use both 5's. because if one blew you'd be hunting for the problem.

the best would be to have the auto and manual feed from different fuses
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Old 16-02-2014, 18:48   #13
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Re: Fuse size for bilge pump

Listen to mainsail. A second bilge pump with alarm is easy. My battery main does not turn off the feed to the bilge pumps. Proper sized fusing and wire protects the circuit. Simple.
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Old 17-02-2014, 15:32   #14
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Re: Fuse size for bilge pump

I've seen bilge panels set up in any number of ways. I personally like a push to reset breaker (sized correctly per the bilge-pump makers lit.) feed an on-on switch (non momentary) one side being manual the other side being auto. With the the push to reset there is little worry of shutting of the pump entirely by mistake but you do have to make sure you don't leave it running (an indicator light can help there)
The other setup is a fused lead from the battery bus before the batt switch (also containing radio mem etc) to the auto side and then having another lead from a convenient main panel switch tied to the normal DC bus. Which would than prevent leaving the pump running while leaving the boat.
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Old 17-02-2014, 16:01   #15
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Re: Fuse size for bilge pump

I try an avoid fuses wherever possible, nothing worse to have to go hunting for fuses, in extremis. I use appropriate sized circuit breakers almost everywhere. So for a bilge pump simply install an appropriate sized Cb.

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