• Annnnnnd we're back! Got questions, suggestions, or comments, Guest? Post them here!

Stupid electrical question

Apr 1, 2019
18
Freedom 38 Sunset Spy Boston, MA
This stupid question occurred to me after I installed my new steaming/foredeck light yesterday, and I haven't been able to figure it out. The steaming light and the foredeck light are each wired to their own 5 amp breaker on my panel. The owner's manual says to "[p]rotect circuits with 1 amp fuses or circuit breakers to both red wires." My first thought was, "oh, I should swap those 5 amp breakers for 1 amp breakers like the instructions tell me to!" However, I soon realized that they don't make 1 amp breakers that fit my panel—the smallest Blue Sea makes is 2.5 amps.

So here's my question: are the 5 amp breakers I have just fine, or do I need to add 1 amp fuses somewhere in the mix?
 
Sep 28, 2008
1,056
Hunter 41DS Punta Gorda, FL
Wade the 5 amps will do you just fine! It will protect your circuit. You don't say but these new lamps must be LED to have a 1 amp protection. IMHO You should have no problem.
 
  • Like
Likes: Rich Stidger

Maine Sail

Moderator
Feb 6, 1998
11,014
Canadian Sailcraft 36T Casco Bay, ME
This stupid question occurred to me after I installed my new steaming/foredeck light yesterday, and I haven't been able to figure it out. The steaming light and the foredeck light are each wired to their own 5 amp breaker on my panel. The owner's manual says to "[p]rotect circuits with 1 amp fuses or circuit breakers to both red wires." My first thought was, "oh, I should swap those 5 amp breakers for 1 amp breakers like the instructions tell me to!" However, I soon realized that they don't make 1 amp breakers that fit my panel—the smallest Blue Sea makes is 2.5 amps.

So here's my question: are the 5 amp breakers I have just fine, or do I need to add 1 amp fuses somewhere in the mix?
The breaker is there to protect the wire. A 5A breaker is perfectly adequate for a properly sized, for voltage drop, deck or steaming light wire protection.
 
  • Like
Likes: uncledom
May 17, 2014
105
hunter 380 Plano, TX
Your 5a breaker will protect the existing wire from catching fire. What they are recommending is a 1a inline fuse on the hot wire headed to the light. I assume it is LED and might have a board that could flame out. The 1a prevents that. Cut the lead wire to the light after the breaker and any other branches. Attach the inline screw together fuse block and fuse. Done
 
Apr 1, 2019
18
Freedom 38 Sunset Spy Boston, MA
Your 5a breaker will protect the existing wire from catching fire. What they are recommending is a 1a inline fuse on the hot wire headed to the light. I assume it is LED and might have a board that could flame out. The 1a prevents that. Cut the lead wire to the light after the breaker and any other branches. Attach the inline screw together fuse block and fuse. Done
So you're saying that the manual is telling me to add fuses to protect the light?

By the way, this is the light: https://signalmate.com/navigation-light-models/combination-masthead-with-red-deck-navigation-light/
 
Jun 1, 2007
3,312
Macgregor 26S Hobie TI, Capri Coronado 15 Denver, Colorado
Did not look at the manual but its somewhat common for a manufacture to protect an electronic device from being wired up backwards (ie, you switch pos and neg) with an inline fuse. This is independent and not related to fusing to protect the wire from burning up in a short.

In this case, if you wired things up backwards, you just blow the fuse and not burn the device out. The manufacture knows what size fuse works for this safety mechanism. Replace the fuse, correct the polarity mistake and the device still works.

Your risk to ignore the manual. But my guess is that if you are careful about +/- polarity when wiring, the existing fuses that protect the wire would be all that is needed. But if you mess up and wire the polarity wrong and did not follow the manufactures recommendation for fusing.. burnt out device. Guessing here but if it were me, I would just be extra careful not to get the polarity backwards during wiring and likely no problem with the 5 amp fuse.
 
  • Like
Likes: heritage

Maine Sail

Moderator
Feb 6, 1998
11,014
Canadian Sailcraft 36T Casco Bay, ME
1- We have seen plenty of equipment destroyed by reverse polarity despite the correct size fuse being used. We have also seen plenty of equipment destroyed due to voltage transients, where the correct size fuse was used, and never blew but the equipment was destroyed. Why? Because fuses trip on over-current not on over-voltage. The situation where a fuse sized to the manufacturer recommendation matters most, is on a bilge pump, where a stalled rotor can actually start a fire if the fuse does not trip.. The fuses or breakers are there primarily to protect the wire from the massive amount of stored energy in the battery bank.

2- ABYC standards suggest that 16 AWG wire is the smallest allowable "conductor size" and 14 AWG was used.

"11.14.1.1.2 Conductors shall be at least 16 AWG.
EXCEPTIONS:

1. 18 AWG conductors may be used if included with other conductors in a sheath and do not extend more than 30 inches (762mm) outside the sheath.
2. 18 AWG conductors may be used as internal wiring on panelboards.
3. Conductors that are totally inside an equipment enclosure.
4. Conductors on circuits of less than 50 volts having a current flow of less than one amp in communication systems, electronic navigation equipment and electronic circuits.
5. Pigtails less than seven inches (178 mm) used as wiring on panelboards."



3- Pigtails on nav lights are likely using the gray area exception #4 above but the ABYC does not publish a max ampacity rating for 20AWG wire. The maximum allowable ampacity (max fuse/breaker size) for 18AWG under ABYC E-11 is 20A on 105C rated wire. Most non ABYC charts, for max ampacity, put 105C 20AWG at 11A to 13A. So again, the 5A breaker is still adequately protecting the 20AWG wire..

4- If it makes you feel better simply install a 14 GA in-line water-tight ATO/ATC fuse holder and 1A fuse on the back of the breakers load terminal. Just be aware that in-line AGC (glass fuse) fuse holders are one of the most problematic and most unreliable electrical components used on boats so try avoid them when ever you can..
 
Jul 13, 2004
51
-Manta Catamaran -Manta 40 Mystic, CT
I try to get rid of any glass fuses - even cutting them off supplied equipment and replacing with ATC - because I have so many problems with them over time.

Is it possible that the 1A fuse is recommended because of the 20g wire pigtail? The manufacturer doesn't know what is connecting that pigtail to the rest of the electrical system, so can only recommend for the known wire.

I would treat the 20g pigtail itself as the fuse in this case, and leave the 5A breaker to protect the wiring to it. Nothing to add, and if something goes wrong in the pigtail or LED board, then POOF - the pigtail opens. It is halfway up the mast in free air, so isn't a fire hazard.

Mark
 

Maine Sail

Moderator
Feb 6, 1998
11,014
Canadian Sailcraft 36T Casco Bay, ME
With a 5A breaker protecting the short 20 AWG pigtails the breaker will trip well before the wire even gets close to a fire let alone hot. Just for grins I tripped a length of 20 AWG in the shop with a 10A fuse while holding the wire in my bare fingers while touching it direct to a battery terminal. The wire never had a chance to get hot. Most maximum ampacity tables suggest 20 AWG can have a maximum ampacity, for over-current protection, of 10A to as much as 17A depending on wires insulation rating. 20 AWG 105C wire is well over double the 5A breaker and even cheapo 80C wire can handle double the 5A breaker....

 
Sep 24, 2018
473
O'Day 25 Waukegan
POOF - the pigtail opens. It is halfway up the mast in free air, so isn't a fire hazard.
When I was 16 I ran some 20 or 22 awg wire in my car straight from the battery with no fuse. I accidentally shorted it. The wire heated up so much that it left a burn mark in the carpet but it never went poof. I took pulled the wire off of the ground it had touched. I doubt my reaction time was less than three seconds.

I installed a heater and a 30 amp circuit in a detached garage once upon a time. I used 10awg solid wiring, two grounding rods, etc. It was late and I was tired. I came home and tried to hang something off of a bicycle hook next to the 1/2" conduit. Some stuff was in the way and I tried shoving it out of the way. Instead I hit the conduit hard enough to pull it from the box. Subsequently it pulled the 10awg wiring and sparks started flying. Within a couple of seconds one of the boxes caught fire. It was a very long 15 seconds of me going back and forth between blowing on the box and shielding my face all while waiting for the breaker to trip. This is what can happen when wires go poof, especially when grounding is less than ideal
 

Maine Sail

Moderator
Feb 6, 1998
11,014
Canadian Sailcraft 36T Casco Bay, ME
When I was 16 I ran some 20 or 22 awg wire in my car straight from the battery with no fuse. I accidentally shorted it. The wire heated up so much that it left a burn mark in the carpet but it never went poof. I took pulled the wire off of the ground it had touched. I doubt my reaction time was less than three seconds.

I installed a heater and a 30 amp circuit in a detached garage once upon a time. I used 10awg solid wiring, two grounding rods, etc. It was late and I was tired. I came home and tried to hang something off of a bicycle hook next to the 1/2" conduit. Some stuff was in the way and I tried shoving it out of the way. Instead I hit the conduit hard enough to pull it from the box. Subsequently it pulled the 10awg wiring and sparks started flying. Within a couple of seconds one of the boxes caught fire. It was a very long 15 seconds of me going back and forth between blowing on the box and shielding my face all while waiting for the breaker to trip. This is what can happen when wires go poof, especially when grounding is less than ideal
But the OP has a 5A breaker in the circuit and is not running bare wire, with no over-current protection, direct to a battery.....