Circuit breaker in place of fuse

[John the kiwi]

On a different note:
Have you considered using an ammeter to see what current the pump is actually drawing?
Centrifugal pumps such as typical bilge pumps draw more current as the flow rate increases. They actually draw least current when the discharge valve is shut and no pumping is happening. (This seems counter intuitive to many and i expect howls of protest from some quarters, but i be a inguneer and do this for a living so trust me.)
Slow blow is good for the start up current draw which can be 4- 6 times higher than running current depending on motor design, but if your steady state current is too high, try throttling the discharge to reduce flow rate a little and thereby the current draw.
If on the other hand it is some sort of positive displacement pump like a diaphragm pump then the opposite applies. Restrict the outflow and the current draw will rise so if current is too high then maybe you are trying to push the water too far uphill?
I repeat , use an ammeter to see what current the pump is actually drawing. Until you do this you are firing shots in the dark..
Good luck

 

[fisherman]

Are yours Dorman Smith Loadmaster MCB's? The reason I ask is that this is what is fitted to my Rival 41C, also 24V. In keeping with this thread I believe that they are rated to quite high voltages and not just 24V. Where do you purchase yours from as I need some additional MCBs and would like to keep the panel looking the same.

I doubt it, just off the shelf at the factors.

 

[alahol2]

A question please...
If heavy duty wiring is used to a piece of equipment, a supplier quotes (say) a 6 amp fuse to protect their product, you put a 10 amp fuse in the line, how would you ever get more than (say) 6 amps into the product to damage it? Genuinely puzzled.

 

[sighmoon]

A question please...
If heavy duty wiring is used to a piece of equipment, a supplier quotes (say) a 6 amp fuse to protect their product, you put a 10 amp fuse in the line, how would you ever get more than (say) 6 amps into the product to damage it? Genuinely puzzled.

A short?

 

[alahol2]

A short?

Do you mean a short within the product?

 

[sighmoon]

Yes.

 

[alahol2]

Just seems odd that a supplier would expect (however remotely) a short within his own product.

 

[David2452]

Prepare for and protect against rather than expect, to do otherwise would be negligent, think about a domestic situation. Though the "house" cabling is protected in its own right, each appliance you connect to the 13a socket will have its own seperate fuse of the correct rating in its plug. It's not just conductor shorts that can cause overdraw situations, though in something as basic as a componet like a pump or motor consisting mainly of windings it is the most common, over temperature through using for long periods is another.

 

[pvb]

As far as I know, there is no other fuse protecting it.

The supply cable should be fused, as close to the battery as possible.

 

[David2452]

The supply cable should be fused, as close to the battery as possible.

Basically sound, but far too simplistic, take the following example as a standard install that may be done in either a new vessel fit out or as an ultra low voltage DC electrical refit: MRBF on battery of 150a to 25mm2 cable feeding distribution panel, or even 16mm2 cable with a 100a MRBF feeding a distribution panel dependant on the voltage drop calculation for the required loads. 2.5mm2 cable from the distribution panel to a point close to the load fused 25a at the panel, 6a fuse close to the load (within inches) to protect it, the final fuse of a rating to protect the load being nowhere near the battery but each level of conductor and the final load is correctly protected and the size of cable used is correct to obtain the level of voltage drop required not only for the 6a fused load but all the other loads that may (correctly) be applied to the distrubution panel.

 

[pvb]

Basically sound, but far too simplistic,

It wasn't my intention to present a treatise on boat wiring theory, just to point out the basic requirement that the supply cable ought to be fused, which it apparently isn't. You of all people should know that most installations fall far short of your ideal example.

 

[VicS]

Basically sound, but far too simplistic, .................... 2.5mm2 cable from the distribution panel to a point close to the load fused 25a at the panel, 6a fuse close to the load (within inches) to protect it, the final fuse of a rating to protect the load being nowhere near the battery but each level of conductor and the final load is correctly protected and the size of cable used is correct to obtain the level of voltage drop required not only for the 6a fused load but all the other loads that may (correctly) be applied to the distrubution panel.

But if this is a dedicated circuit for the 6 amp load ( pump in this case) sized at 2.5mm² to minimize volts drop the 6amp fuse can be the fuse in the panel. There is no need to fuse the circuit any higher unless there is other equipment on the same circuit.