Bilge pump questions

[jhance]

1. At what age should they be replaced if they continue to work fine?
2. Current pump is a 500 gph 2003. Pump has "2.5A fuse" written on top by manufacturer. Actual fuse at panel is 10A. I assume a higher fuse is installed soas not to have any concern over blowing the fuse unless there is a real problem (thermal runaway)?
3. Looking at installing an 800 gph which draws 3A. Recommended fuse is 5A. I'm thinking I should just stick with the existing 10A fuse as installed at the panel?

 

[Comodave]

The fuse is there to protect the wiring. So fuse size also depends on the wire size. Wire size will depend on current draw and circuit round trip lenght.

 

[jhance]

14 gauge wire

 

[Nordlund Xpress]

I'd suggest considering adding a 2nd bilge, a 2,000 GPH or 4,000 GPH. A small pump keeps things dry, a larger pump deals with real water flow. Depending on the size of you boat, more could be a great idea.

 

[Comodave]

I'd suggest considering adding a 2nd bilge, a 2,000 GPH or 4,000 GPH. A small pump keeps things dry, a larger pump deals with real water flow. Depending on the size of you boat, more could be a great idea.

Absolutely.

What is the round trip length of the wire?

 

[psneeld]

Some fuses are to protect the smallish wiring inside the device. Some bilge pumps have been known to burn (melt cases) but not sure I 've ever heard of one actually starting a boat fire.

While the fuse also protects the wire run to the device... I would not go too far above the recommended fuse size.

Total pumping capacity is important and redundancy in the system is just as important as well as the float switch array.

As far as age of pumps...hard to say but some live in a mess of nasty bilge water and others hardly ever get their feet wet. That's strictly a judgement (comfort) call.

 

[jhance]

Absolutely.

What is the round trip length of the wire?

Round trip maybe 30'

 

[jhance]

Some fuses are to protect the smallish wiring inside the device. Some bilge pumps have been known to burn (melt cases) but not sure I 've ever heard of one actually starting a boat fire.

While the fuse also protects the wire run to the device... I would not go too far above the recommended fuse size.

Total pumping capacity is important and redundancy in the system is just as important as well as the float switch array.

As far as age of pumps...hard to say but some live in a mess of nasty bilge water and others hardly ever get their feet wet. That's strictly a judgement (comfort) call.

Mine never see water other than when I occasionally test them.

 

[O C Diver]

1. At what age should they be replaced if they continue to work fine?
2. Current pump is a 500 gph 2003. Pump has "2.5A fuse" written on top by manufacturer. Actual fuse at panel is 10A. I assume a higher fuse is installed soas not to have any concern over blowing the fuse unless there is a real problem (thermal runaway)?
3. Looking at installing an 800 gph which draws 3A. Recommended fuse is 5A. I'm thinking I should just stick with the existing 10A fuse as installed at the panel?

Read the directions on the bilge pump package for fuse size! I had a small fire in my charter boat from a too large fuse and automated bilge pump. While the rule is to protect the wiring with proper size fuses, it is important to protect unfused equipment with a manufacturer specified size fuse.

Regarding frequency of pump replacement, it depends. If you have a dry bilge where the pump never runs, that might be the best case scenario. If you have one or more stuffing boxes that intentionally drip, that may be the middle ground. Boats that leak either water they sit in or when it rains, might be a worse case scenario. My rule of thumb was to replace all pumps when buying a boat unless they were less than one year old. Pumps that only run when being tested, every 10, 15, or 20 years depending on how many days from land you will be. The pump that runs every day and maybe multiple times per day while underway, 1 to 5 years depending on how far from land you are.

My rule was atleast 2 pumps in every compartment that's water tight from other compartments.

Test your pumps and float switches with water. Once a year I tested all pumps with a freshwater dock hose. This allowed me to turn the water off if there was a problem and prove the pumps and float switches operated properly. In the relative scheme of things, testing the pumps with water is free (only your time).

Ted

 

[jhance]

Read the directions on the bilge pump package for fuse size! I had a small fire in my charter boat from a too large fuse and automated bilge pump. While the rule is to protect the wiring with proper size fuses, it is important to protect unfused equipment with a manufacturer specified size fuse.

Regarding frequency of pump replacement, it depends. If you have a dry bilge where the pump never runs, that might be the best case scenario. If you have one or more stuffing boxes that intentionally drip, that may be the middle ground. Boats that leak either water they sit in or when it rains, might be a worse case scenario. My rule of thumb was to replace all pumps when buying a boat unless they were less than one year old. Pumps that only run when being tested, every 10, 15, or 20 years depending on how many days from land you will be. The pump that runs every day and maybe multiple times per day while underway, 1 to 5 years depending on how far from land you are.

My rule was atleast 2 pumps in every compartment that's water tight from other compartments.

Test your pumps and float switches with water. Once a year I tested all pumps with a freshwater dock hose. This allowed me to turn the water off if there was a problem and prove the pumps and float switches operated properly. In the relative scheme of things, testing the pumps with water is free (only your time).

Ted

Thank you. I don't see another fuse on my pump circuit other than the 10A at the panel. Manufacturer says "2.5A" fuse. So are you saying there should be a 2.5A fuse (most likely close to the bilge pump) that is just for the pump (so two fuses in the circuit)? My pumps are never in water and have been advised not to mess with them if they are working fine. It's just that they are now 22 years old and that makes me nervous as I know materials deteriorate on their own and I'm not sure how confident I am that, if there were an issue, these pumps could last pumping water continuously for many hours...

 

[Discoverer]

1. At what age should they be replaced if they continue to work fine?
2. Current pump is a 500 gph 2003. Pump has "2.5A fuse" written on top by manufacturer. Actual fuse at panel is 10A. I assume a higher fuse is installed soas not to have any concern over blowing the fuse unless there is a real problem (thermal runaway)?
3. Looking at installing an 800 gph which draws 3A. Recommended fuse is 5A. I'm thinking I should just stick with the existing 10A fuse as installed at the panel?

1. Replace after about 10 years as a preventive measure, even if it’s still working, some plastic parts may degrade.
2. 10A fuse is too high for a 2.5A pump. Fuses are meant to protect the wiring from overheating and fire, not just the pump. Check the wire gauge, if it’s 16 AWG, 3A fuse is the right one.
3. Install a 5A fuse as recommended. to protects both the pump and wiring. A 10A fuse in this setup exceeds safe limits, that could allow excessive current and overheating the wires.

 

[O C Diver]

Thank you. I don't see another fuse on my pump circuit other than the 10A at the panel. Manufacturer says "2.5A" fuse. So are you saying there should be a 2.5A fuse (most likely close to the bilge pump) that is just for the pump (so two fuses in the circuit)? My pumps are never in water and have been advised not to mess with them if they are working fine. It's just that they are now 22 years old and that makes me nervous as I know materials deteriorate on their own and I'm not sure how confident I am that, if there were an issue, these pumps could last pumping water continuously for many hours...

No.

Put the 2.5 (no more than 3 if you can't find 2.5) amp fuse in the panel. It makes no difference where the fuse is in the circuit as far as amp draw. The entire circuit sees the same amperage. Using a smaller fuse than the wire is capable of amperage drawing, isn't a problem.

Bilge pumps work till they don't. Replace the pump and thank it for its service. Replace the hose and float switch while you're at it.

Ted

 

[Bmarler]

I would consider adding another pump to the ten amp circuit. A nice big one. Let the little one do most of the work, the big one comes online if necessary.
Individually fuse the pumps at their connection point.

 

[O C Diver]

I would consider adding another pump to the ten amp circuit. A nice big one. Let the little one do most of the work, the big one comes online if necessary.
Individually fuse the pumps at their connection point.

While that seems like a good suggestion, it's better to have two pumps on two separate circuits. Circuit breakers can go bad and fuses can fail. If you're looking for redundancy, separating failure points as much as possible offers the most reliability.

Ted

 

[Bmarler]

While that seems like a good suggestion, it's better to have two pumps on two separate circuits. Circuit breakers can go bad and fuses can fail. If you're looking for redundancy, separating failure points as much as possible offers the most reliability.

Ted

Agreed, but this gives a level of redundancy without stringing new wire. Not sure of the OPs level of DIY-ness.

 

[CharlieO.]

What is the consensus on wiring bilge pumps directly to the battery with the appropriate sized inline fuse?

 

[Bmarler]

What is the consensus on wiring bilge pumps directly to the battery with the appropriate sized inline fuse?

That’s essentially how mine are. I have a power post before the buss bars for the bilge pumps and alarm.

 

[rslifkin]

What is the consensus on wiring bilge pumps directly to the battery with the appropriate sized inline fuse?

I'm not a fan of it. It leads to messy wiring, and I don't like having anything powered that can't be quickly shut off with a battery switch in case of a failure or emergency. A separate "emergency loads" panel is fine, but it should have its own separate switch bypassing the main house battery switch. It shouldn't just be "always hot" with no way to cut the power other than disconnecting a cable.

 

[Fleming]

Always use the fuse size recommended by the manufacture for motors!!

Everyone is right in that we 'normally' fuse for the wire size, but motors are different. Motors are fused to not exceed the 'Locked Rotor Current'. If a piece of debris gets caught in the pump impeller and stops the motor the current will rise to a certain point, the locked rotor current value, and then it will very slowly start dropping while at the same time heating up (ohms law). If you put a fuse in that is larger than the locked rotor current (larger than the manufacturer recommends, because that recommended value is set below the locked rotor current) then the fuse will never blow and the motor will eventually catch on fire.

Always use the fuse size recommended by the manufacture for motors!!

 

[jhance]

No.

Put the 2.5 (no more than 3 if you can't find 2.5) amp fuse in the panel. It makes no difference where the fuse is in the circuit as far as amp draw. The entire circuit sees the same amperage. Using a smaller fuse than the wire is capable of amperage drawing, isn't a problem.

Bilge pumps work till they don't. Replace the pump and thank it for its service. Replace the hose and float switch while you're at it.

Ted

Why would the manufacturer install a 10A fuse for a single bilge pump? I think there is some risk if you install a small fuse? A 3A fuse is more likely to unknowingly blow, then you don't have a bilge pump when you need it?

 

[Fleming]

No.

Put the 2.5 (no more than 3 if you can't find 2.5) amp fuse in the panel. It makes no difference where the fuse is in the circuit as far as amp draw. The entire circuit sees the same amperage. Using a smaller fuse than the wire is capable of amperage drawing, isn't a problem.

Bilge pumps work till they don't. Replace the pump and thank it for its service. Replace the hose and float switch while you're at it.

Ted

No, bad advice. It DOES matter where the fuse is in the circuit. ABYC standards are quite clear that overcurrent protection should be within 7 inches of the source of power. Up to 72 inches if the source of power is the battery AND the conductor is in a sheath (other than the wire insulation). Up to 40 inches if the power source is other than a battery AND in a sheath.

If there is a short to ground in the circuit before the overcurrent protection the fuse blowing/breaker tripping does not stop the fault, the short circuit is still completed.

And see my other post above about always using the manufacturer recommended fuse size. If the pump says 2.5 amps, use a 2.5 amp fuse not a 3 amp.

 

[O C Diver]

What is the consensus on wiring bilge pumps directly to the battery with the appropriate sized inline fuse?

There's an "always on" fuse panel on my boat that comes off the battery bank. From there, the four bilge pump circuits go to a control panel in the pilothouse. My reasoning was that I wanted them separate from the main panel (not fused by the breaker on the main panel), but still able to control the pumps (turn off, and bypass the float switch if it failed) without going into the engine room.

Ted

 

[O C Diver]

No, bad advice. It DOES matter where the fuse is in the circuit.

Reread my post. The part about where the fuse is located is based on the whole circuit seeing the same amperage (this was in reference to the original poster suggesting it should be closer to the pump). I was making a case for putting it in the control panel, not near the pump.

Ted

 

[Fleming]

Reread my post. The part about where the fuse is located is based on the whole circuit seeing the same amperage (this was in reference to the original poster suggesting it should be closer to the pump). I was making a case for putting it in the control panel, not near the pump.

Ted

I read your post. I quoted your post. You said it doesn't matter where in the circuit the fuse is located. It very much does matter. It needs to be right at the source of power.

 

[O C Diver]

Why would the manufacturer install a 10A fuse for a single bilge pump? I think there is some risk if you install a small fuse? A 3A fuse is more likely to unknowingly blow, then you don't have a bilge pump when you need it?

Some pumps take a 10 amp fuse. Some take much more; some take much less. If the panel comes with a 10 amp fuse and your bilge pump draws 12 amps, wouldn't you change the fuse to 12 amps?

Why would a 3 amp fuse be more likely to blow if the pump hadn't failed? The manufacturer specified the fuse based on it consuming less in the worst case scenario.

Ted

 

[O C Diver]

I read your post. I quoted your post. You said it doesn't matter where in the circuit the fuse is located. It very much does matter. It needs to be right at the source of power.

From my original post:

"It makes no difference where the fuse is in the circuit as far as amp draw."

The point you keep missing is that the reason not to put it near the pump was based on the whole circuit seeing the same amperage draw.

In the preceeding sentence I told him to specifically put the fuse in the control panel.

Ted

 

[rslifkin]

Some pumps take a 10 amp fuse. Some take much more; some take much less. If the panel comes with a 10 amp fuse and your bilge pump draws 12 amps, wouldn't you change the fuse to 12 amps?

Why would a 3 amp fuse be more likely to blow if the pump hadn't failed? The manufacturer specified the fuse based on it consuming less in the worst case scenario.

Ted

Exactly. Wire size determines the maximum safe fuse size. In some cases, it may be desirable to use a smaller fuse so that it can also protect from certain types of equipment faults. If the wiring is sized larger for voltage drop and could handle 20A, but the device connected only draws 3.5A in normal use, I'd probably use a 5A fuse on the circuit. The wire will be protected either way, the difference in voltage drop across the fuse will be minimal, and there will be less risk of a fault in the device causing an overheat and fire without blowing the fuse.

 

[Fleming]

Exactly. Wire size determines the maximum safe fuse size. In some cases, it may be desirable to use a smaller fuse so that it can also protect from certain types of equipment faults. If the wiring is sized larger for voltage drop and could handle 20A, but the device connected only draws 3.5A in normal use, I'd probably use a 5A fuse on the circuit. The wire will be protected either way, the difference in voltage drop across the fuse will be minimal, and there will be less risk of a fault in the device causing an overheat and fire without blowing the fuse.

This is just plain wrong when we're talking about a bilge pump. Read my post about locked rotor current above. For everything other than motors we fuse for the conductor size, but not motors.

When a boat catches fire and you make an insurance claim and they narrow it down to the bilge pump the overcurrent protection is going to be the first thing the investigator checks. When they see you put a 5 amp fuse in a place where the manufacturer recommended a 2.5 amp fuse they're going to deny your claim.

For other than a pump, what you wrote is correct. But not for a bilge pump. The OP can test it. Go stick a screwdriver in the impeller of your bilge pump with the 10 amp fuse. It won't blow. Then put your hand on the pump casing and feel how hot it gets.

 

[rslifkin]

This is just plain wrong when we're talking about a bilge pump. Read my post about locked rotor current above. For everything other than motors we fuse for the conductor size, but not motors.

When a boat catches fire and you make an insurance claim and they narrow it down to the bilge pump the overcurrent protection is going to be the first thing the investigator checks. When they see you put a 5 amp fuse in a place where the manufacturer recommended a 2.5 amp fuse they're going to deny your claim.

You're actually agreeing with what I'm saying. With some loads (like motors) it's a good idea to downsize the fuse to protect against a fault in the equipment (such as a locked up bilge pump) rather than sizing to the largest fuse the wire can handle.

 

[jhance]

This is just plain wrong when we're talking about a bilge pump. Read my post about locked rotor current above. For everything other than motors we fuse for the conductor size, but not motors.

When a boat catches fire and you make an insurance claim and they narrow it down to the bilge pump the overcurrent protection is going to be the first thing the investigator checks. When they see you put a 5 amp fuse in a place where the manufacturer recommended a 2.5 amp fuse they're going to deny your claim.

For other than a pump, what you wrote is correct. But not for a bilge pump. The OP can test it. Go stick a screwdriver in the impeller of your bilge pump with the 10 amp fuse. It won't blow. Then put your hand on the pump casing and feel how hot it gets.

I would think, with a bilge pump, you wouldn't want the fuse to be "touchy" and blow unless there were a REAL problem. Otherwise you have a blown fuse that you don't know about and your boat sinks when the pump fails to come on. So it seems risky to me to put in a fuse that is only a little above the rated current of the bilge pump. Maybe I'm wrong, but if the pump motor seizes, it's going to generate a lot more amps and should trip the 10A fuse. The manufacturer of my boat put 10A fuses at the main panel on all three separate bilge pump circuits with 14 awg, each with a 500 gph pump.