beneteau_305_553
Well-Known Member
I'm looking for a 50 amp circuit breaker for the anchor windlass. Can I use an industrial MCB on 12 v Dc
50 Amp MCB for 12 v DC
- Thread starter beneteau_305_553
- Start date
colinmi
Well-Known Member
Yes you can.
Either a single or double pole unit will be OK. Its the current that operates it, not voltage.
Cheers
Colin
Either a single or double pole unit will be OK. Its the current that operates it, not voltage.
Cheers
Colin
VicS
Well-Known Member
[ QUOTE ]
Its the current that operates it, not voltage.
[/ QUOTE ] But aren't switches for DC applications designed to take account of the greater arcing that can occur at the contacts.
I thought switches often had a much lower current rating when used on (low voltage) DC than on AC mains for that reason.
Its the current that operates it, not voltage.
[/ QUOTE ] But aren't switches for DC applications designed to take account of the greater arcing that can occur at the contacts.
I thought switches often had a much lower current rating when used on (low voltage) DC than on AC mains for that reason.
nedmin
Well-Known Member
Why not use a high rupturing capacity fuse?
Gothik29
Active Member
I agree with VicS - any device should be checked for DC as well as AC rating. For an anchor windlass where you want the circuit breaker to trip if the load on the chain is too great (rather than damaging the motor) the likelihood of the circuit breaker operating is higher than most other circuits, so you want to be especially careful to make sure the circuit breaker will isolate the circuit when you need it.
bedouin
Well-Known Member
For the same reason you should really check with the Windlass manufacturer as to the type of breaker to fit. There are at least four different tripping characteristics available (type B,C,D,K ) - you want one that is tolerant to the high start up current but trips quickly if the motor is stalled.
Getting the wrong one, even if the current is correct may either result in it tripping every time you operate the windlass, or with it failing to protect the motor if it gets overloaded.
Getting the wrong one, even if the current is correct may either result in it tripping every time you operate the windlass, or with it failing to protect the motor if it gets overloaded.
ean_p
Well-Known Member
google 'heinemann' and you can order a unit to suit you needs (from a menu selection of all kinds of features)and if you don't know what you want they will tell you. Like carlingswitch but better.
rogerthebodger
Well-Known Member
Yes Vic you are correct but it is the breaking (switch off) of inductive DC loads that causes the big spark that damages the contact.
In this case the MCB would not normally be used to start and stop the windlass but the relay controlling the windlass which would normally be designed to break the DC load.
The only time the MCB would open is if the current exceeds the rating which if selected correctly would not be very often.
In this case the MCB would not normally be used to start and stop the windlass but the relay controlling the windlass which would normally be designed to break the DC load.
The only time the MCB would open is if the current exceeds the rating which if selected correctly would not be very often.
misterg
Well-Known Member
[ QUOTE ]
Yes Vic you are correct but it is the breaking (switch off) of inductive DC loads that causes the big spark that damages the contact.
In this case the MCB would not normally be used to start and stop the windlass but the relay controlling the windlass which would normally be designed to break the DC load.
The only time the MCB would open is if the current exceeds the rating which if selected correctly would not be very often.
[/ QUOTE ]
There's more to it than that - DC contactors / circuit breakers need to be designed to extinguish the arc that occurs as the contacts open - the arc extingushes itself ~100 times a second for AC. There's a real risk that the first time the trip opens in anger, a DC arc will continue long enough (a few 1/10ths of a second??) to melt the contact material which forms into a drip and shorts the circuit breaker permanently. Commonly described as the contacts "welding together". You then have no protection, and even trying to open the breaker manually will fail.
So IMHO, get something with an appropriate DC rating.
Andy
Yes Vic you are correct but it is the breaking (switch off) of inductive DC loads that causes the big spark that damages the contact.
In this case the MCB would not normally be used to start and stop the windlass but the relay controlling the windlass which would normally be designed to break the DC load.
The only time the MCB would open is if the current exceeds the rating which if selected correctly would not be very often.
[/ QUOTE ]
There's more to it than that - DC contactors / circuit breakers need to be designed to extinguish the arc that occurs as the contacts open - the arc extingushes itself ~100 times a second for AC. There's a real risk that the first time the trip opens in anger, a DC arc will continue long enough (a few 1/10ths of a second??) to melt the contact material which forms into a drip and shorts the circuit breaker permanently. Commonly described as the contacts "welding together". You then have no protection, and even trying to open the breaker manually will fail.
So IMHO, get something with an appropriate DC rating.
Andy
rogerdog
Well-Known Member
buy the proper DC rated component with the correct trip characteristics - at high currents if a fault developed its not just going to be the motor that is at risk -if the trip doesn't open (and is the only protection) the wiring itself will (extremely) rapidly overheat with potential for a fire etc.
