From: Briant566
Sent: Friday, October 10, 2008 20:42 PM
Subject: Re: Fuses

Mel

 
If I remember Rogers batteries are at the from of the boat assuming bow thrusters are at the front there should be very little cable length and volt drop
 
I assume its controlled by a solenoid which is located near the motor and is only control cable size to a switch
 
As I said you never see large stater motors with fuses as current was always 600  to 800 amps  but you are taking seconds at at a time
 
So you can expect a fuse of that rating
 
One way would be to check the rating of the solenoid this would give you the max current
----- Original Message -----
Sent: Friday, October 10, 2008 12:27 PM
Subject: Fuses

 
Hi again all,
Brian's suggestions - compare with motor vehicle starter motors, (particularly for high compression diesel engines) is worth considering.
I believe that the motor in bow thrusters is often a starter motor and assume that, like the ignition key, the bow thruster 'port'  / 'starboard' lever is biased to a central 'off' position.  i.e. it cannot be left 'on' in either direction.  This bow thruster control switch presumably operates a solenoid on the unit - not sure quite how the change in motor direction is controlled - i.e. could reverse the motor polarity or could modify gearbox physical operation.
 
The vehicle starter motor itself, (rather than the solenoid),  is not fused.  Starter 'jamming' often occurred in my early days of motoring.  This could sometimes be cleared by rocking the vehicle, otherwise a spanner was required on the squared armature shaft at the back of the starter motor.  Obviously when 'jammed' the effect of turning the ignition key was 'nil' but, though we obviously didn't hold the key for more than a second, I don't recall any cables over-heating.
 
In view of this, do the manufacturers of bow thrusters recommend fusing and, if so, what do they recommend /
 
As I stated before, if the unit has been tested at 800A, (presumably while tightly moored and with a current shunt), then a fuse of at least 800A is essential as a smaller fuse will always blow !   If the 800A was 'peak', a lower rating 'anti-surge' or 'delay' fuse may suffice.
 
The last thing you want is, of course, a failure, (even a fuse), when manoeuvring near other boats - e.g. when mooring in a marina.
 
Further reading:
 
 
 
and more ....
 
Mel
 
----- Original Message -----
From: Briant566
Sent: Thursday, October 09, 2008 9:05 PM
Subject: Re: Fuses

 
 Hy Mell
 
on checking that 16mm cable would be tri-rated all cable we use is tri rated to reduce the physical size
 normal cable would be 20mm but bigger is better
----- Original Message -----
Sent: Thursday, October 09, 2008 4:38 PM
Subject: Fuses

 
Hi again Roger,
The most common fuses appear to be LEWMAR - typically 325, 400 & 500A but - presumably higher.
Not sure what the ANL stands for - possibly 'ant-surge' to withstand high PEAK current.
 
It occurred to me that Brian may have dealt with other equipment of similar power so ......
A copy of previous email and this email forwarded to him.
 
Regards,
Mel

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