What size circuit breaker for windlass?

[Montanan]

Please note that for the windass the maximum load is rated at 4 times the working load. The analysis in the reply posts have been based on working load amperes and not the higher maximum or peaking amperes.

For the 1200 watt rated windlass the working load of 284kg, 624 lbs and the maximum load is 1136kg, 2500 lbs.

The Working ampere is stated to be 120 amps at 12 volts and 75 amps at 24 volts.

If the windlass is operating under a high load the ampere will be far greater than the 120 / 75 ampere of a Working load which much higher amperes [say up to 4 times higher draw under maximum load] could readily trip a fast acting circuit breaker of 150 amp.

One needs to assess the load the windlass is operating under when the breaker trips as part of the circuit analysis, i.e., the job being done.

[home_maarten]

Think that the primary function of the breaker should indeed (as mentioned before by others) be to protect the wire. You do not want an over heating wire to cause fire - much better to trigger the switch more than you would like, than to have to find that you forgot your fire extinghuisher (or it doesn't work because like most of us, you never bothered to check the expiry date).


Once you have established that your wire (and your batteries) can withstand (supply) the kind of amps as per some of the above calculations without breaking, burning or melting, you can think of increasing breaker setting amps...

[rvich]

If there is any place on board the boat that I don't want voltage drop, it is my windlass and my starter. They both draw a lot current and both motors overheat if the voltage drops.

Measure the resting voltage at the windlass and compare it to the batteries. Then find an accomplice and measure the voltage with the windlass running. We won't worry about a load on it yet.

Calculating the current using 12 volts is fine if that is what you really have. Any large voltage drop should be addressed. The motor will last a lot longer.

[noelex 77]

Originally Posted by Nicholson58

Circuit protection is sized to protect wire.

This has been stated several times in this thread, but with a windlass the circuit breaker value and characteristics have a role to play in protecting the windlass from overheating.

Wotname’s post is correct:

Originally Posted by Wotname

By the way, other posters have stated the purpose of the circuit breaker is protect the cable but in the case of a windlass I disagree, one circuit breaker can protect the windlass and the cable - providing the circuit breaker is less than the current carrying capacity of the cable used. In fact, Muir requires a circuit breaker for warranty purposes.

So if you installed extra large cables to supply your windlass you cannot increase the size of the circuit breaker over the manufacturer’s recomended size, even if the wire is capable of safely carrying a much higher current.

The circuit breaker has to be the correct size for the windlass. The supplying wire needs to be able to safely carry this current, but wire size does not dictate the circuit breaker size (other than defining the minimum) in this case.

[sdj]

If you want the correct fix, you really should have a dedicated battery for the windlass, with little to no length of cable at all. Therein begins the the problem of charging it correctly - the recommended way would be from a higher-voltage system with the proper charger, be it from 24 or 48VDC, or from 110/230V mains from your inverter - which on the face of it, is perfectly simple.

[noelex 77]

An explanation why the circuit breaker rating is primarily dictated by the windlass not the wire may be helpful, but it is complicated.

The graph below shows a typical relationship between current and power for an anchor winch. This graph is actually for the Maxwell 4000 model, which is the anchor winch I have fitted to my new boat. This is a 24v windlass and larger than most yachts fit, but the concepts are the same. Note it is a 24v windlass.

However, the graph should give you some concept of how the current varies with load.

Note in particular that the current increases significantly after the working load is reached. So Maxwell recommend fitting a circuit breaker of 150A (@24v) which corresponds roughly to the working load. However, the current rises significantly and the windlass will draw around 450A (@20v) at its full rated output.

A 150A circuit breaker will pass 450A for a very short time and then will trip. The idea is if the circuit breaker size and trip characteristics are appropriate, the 150A circuit breaker will allow the windlass to develop its full rated power for a short time, but then will trip preventing the windlass overheating. The rated power listed on the brochure cannot be maintained for long and the appropriate circuit breaker protects the motor.

The graph shows the value and trip characteristics of the circuit breaker are important if you want the anchor winch to develop its full rated power, but be protected from overheating that would occur if the windlass delivered this power for too long.

[smac999]

He does not need a windlass battery for a 4M run, that is Ridiculous.

Get a volt meter and clamp meter at the windlass to see what’s going on for real.

And yes. Breakers / fuses are always for both the wire and equipment . And must be suitable for both. Or you can put 2 in. At at wire beginning. And 1 at load. But that is silly.

[Mauruuru]

The locked rotor amps are probably 10 x the full load amps. If you are just pulling in chain or rode and its tripping something is wrong. It may not be possible to break the anchor free of the bottom using the winch-use the boat to do that then try lifting with the windlass.

[skenn_ie]

A motor won't draw it's max power, all the time. It will draw what is required to lift whatever the load it, up to (probably) a bit more, unless it is Chinesium. If it frequently trips, a bigger motor might be in order. Otherwise, a different time-constant on the breaker should work.

[Wotname]

Originally Posted by home_maarten

(Very) few comments:


- the HR2500 is 1200W, whereas the one under discussion is 1000W. ................

The OP says he has a Muir Cheetah.
Muir documents the Cheetah as a HR2500 which has a 1200W motor.

Where is the evidence that the OP has a 1000W motor?

[Wotname]

Originally Posted by noelex 77

This has been stated several times in this thread, but with a windlass the circuit breaker value and characteristics have a role to play in protecting the windlass from overheating.......


.........
The circuit breaker has to be the correct size for the windlass. The supplying wire needs to be able to safely carry this current, but wire size does not dictate the circuit breaker size (other than defining the minimum) in this case.

Exactly!

It is really simple, the manufacturer (Muir) supplies a 150A breaker for the OP's winch. A proper installation needs a wire size suitable to carry 150A.

[model 10]

Originally Posted by Wotname

Exactly!

It is really simple, the manufacturer (Muir) supplies a 150A breaker for the OP's winch. A proper installation needs a wire size suitable to carry 150A.

Carry a 150A how far? Does little good if you only have 6v at the motor.

[jamhass]

Originally Posted by Ecos

Carry a 150A how far? Does little good if you only have 6v at the motor.

Wotname is correct as written. The "how far" should be in every boater's DNA. Yeah, unfortunately it is not, much to Calder's chagrin.

[nofacey]

Just a note.....several posts suggest upgrading the wiring to match the circuit breaker (which I support)......That doesn’t necessarily mean replacing the original run with heavier cable; doubling the run would work too. Definitely cheaper, likely easier to boot.

[Wotname]

Originally Posted by Ecos

Carry a 150A how far? Does little good if you only have 6v at the motor.

I really thought it was self evident; as jamhass points out!

Originally Posted by jamhass

Wotname is correct as written. The "how far" should be in every boater's DNA. Yeah, unfortunately it is not, much to Calder's chagrin.

But perhaps it isn't self evident if you don't read the posts. Rather than you going back over all the posts, let me do the hard work for you.

Here's your answer, in the opening post...

Originally Posted by Cliffhanger

........ I have about 4m of 4AWG (25mm) cable.


...........

So let me repeat,

Originally Posted by Wotname

......It is really simple, the manufacturer (Muir) supplies a 150A breaker for the OP's winch. A proper installation needs a wire size suitable to carry 150A.

The voltage drop will be fine in the OP's situation.

But if in doubt, work it out it!