Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 13-06-2016, 18:42   #1
Registered User
 
Hoohaa's Avatar

Join Date: Jul 2011
Location: Sydney Aus
Boat: Swarbrick 40
Posts: 472
Images: 10
5 amp fuse keeps blowing?

I have recently installed a new AIS and splitter. We wired in a bus, which takes its power from the instrument switch on the pannel. If everything is running, the fuse will blow after a minute or so. I suspect we are overloading the 5 amp fuse but would like some input on what size I should be running. Note that the fuse does not blow if the AIS is switched off.
Here is a list of the equipment currently using that fuse and the manufacturers power consumption specs.

Class B Icom AIS MA-500TR, with its own gps antenna - Uses TX 1.5 amps & RX 0.7 amps (could someone explain what TX & RX mean?).

GME AIS Splitter (AISS120) - uses 1.15 amps.

Garmin GPS map 550S plotter with a Transducer - uses 1.25 amps.

If this data is correct then its a total of 4.6 amps..

Thanks for your help.
Jeff
__________________

__________________
Drinking hot tea on a hot day is like banging your head against a wall . It feels good when you stop.... "Terry" my dad.
Hoohaa is offline   Reply With Quote
Old 13-06-2016, 18:44   #2
Registered User

Join Date: Apr 2016
Location: Lake Belton, TX, USA, Earth: 3rd rock from the Sun
Boat: Vagabond 14
Posts: 422
Re: 5 amp fuse keeps blowing?

Shouldn't each of those have its own dedicated fuse?

TX = Transmit
RX = Receive
__________________

__________________
TurninTurtle is offline   Reply With Quote
Old 13-06-2016, 18:57   #3
Registered User
 
Hoohaa's Avatar

Join Date: Jul 2011
Location: Sydney Aus
Boat: Swarbrick 40
Posts: 472
Images: 10
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by TurninTurtle View Post
Shouldn't each of those have its own dedicated fuse?

TX = Transmit
RX = Receive
You might be right..?? Open to advise here..
__________________
Drinking hot tea on a hot day is like banging your head against a wall . It feels good when you stop.... "Terry" my dad.
Hoohaa is offline   Reply With Quote
Old 13-06-2016, 19:12   #4
Registered User

Join Date: Apr 2016
Location: Lake Belton, TX, USA, Earth: 3rd rock from the Sun
Boat: Vagabond 14
Posts: 422
Re: 5 amp fuse keeps blowing?

Each of those should have come with an in-line fuse holder and fuse of the correct size.

If you've got them all mixed up then check their manuals as they should indicate the correct fuse ratings.
__________________
TurninTurtle is offline   Reply With Quote
Old 13-06-2016, 19:13   #5
Registered User
 
pesarsten's Avatar

Join Date: Jan 2012
Location: St Pete
Boat: Sabre 34
Posts: 454
Re: 5 amp fuse keeps blowing?

In a perfect world, everything would be individually fused. Perhaps impractical in some cases. But, have you checked what the voltage is at the devices, a corroded connection in the supply line could cause a problem. It looks like you consume about 48 watts ( 12 volts x @ 4 amps). A poor connection that drops you supply to 10 volts would result in 4.8 amps draw. Too close for a 5 amp fuse. This would need to be adressed.

Perhaps put the AIS and Splitter on a separate 5 amp fuse for reliability.
__________________
All that is necessary for the triumph of evil is that good men do nothing. Edmund Burke
pesarsten is offline   Reply With Quote
Old 13-06-2016, 19:17   #6
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 12,224
Re: 5 amp fuse keeps blowing?

First question, is the fuse that's blowing connected to the switch on the panel or an inline fuse? If the later where is it located?

If the fuse is in the panel then if I understand you have a wire from the "Instrument" switch on the panel to a bus bar and then feed the instruments from the bus bar. I assume + and - wires to the bus, both from the panel?

If this is correct then what size wires are running from panel to bus bar and from bus bar to the instruments?

The reason for all this, the purpose of a fuse that feeds a bus bar is not to protect the instruments but to protect the wires, if you have a very small wire you need a very small fuse because a big fuse might allow enough current to heat the wire, melt the insulation and start a fire.

So if your wires are say 10-12 gauge you could easily and safely use a 15 amp fuse.

If you are trying to protect the equipment then an inline fuse on the hot wire to the device is where that should be. In that case use the size fuse recommended by the manufacturer.
__________________
The water is always bluer on the other side of the ocean.
skipmac is offline   Reply With Quote
Old 13-06-2016, 19:20   #7
Senior Cruiser
 
StuM's Avatar

Cruisers Forum Supporter

Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43
Posts: 6,507
Re: 5 amp fuse keeps blowing?

Fuse or circuit breaker? If CB, how old is it?

CB gets weaker with age and use.

As a rule of thumb, you shouldn't load circuit breakers consistently over 80% - doing so can cause them to trip after a while.
__________________
StuM is online now   Reply With Quote
Old 13-06-2016, 19:21   #8
Registered User
 
Hoohaa's Avatar

Join Date: Jul 2011
Location: Sydney Aus
Boat: Swarbrick 40
Posts: 472
Images: 10
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by TurninTurtle View Post
Each of those should have come with an in-line fuse holder and fuse of the correct size.

If you've got them all mixed up then check their manuals as they should indicate the correct fuse ratings.
Surprisingly they do not have an in-line. But if I install them it will still not solve my original problem. Yes the devices will be protected but they are still getting power from the original switch with the 5 amp fuse.
Am I thinking this through correctly. If I increase the fuse size without having the recommended in-line fuse for each of the items, then they could be damaged before, lets say 10 amp fuse blows?
__________________
Drinking hot tea on a hot day is like banging your head against a wall . It feels good when you stop.... "Terry" my dad.
Hoohaa is offline   Reply With Quote
Old 13-06-2016, 19:25   #9
Registered User

Join Date: Apr 2016
Location: Lake Belton, TX, USA, Earth: 3rd rock from the Sun
Boat: Vagabond 14
Posts: 422
Re: 5 amp fuse keeps blowing?

US Navy Electrical Safety Inspector (In a previous employment) says:

Each of these devices NEEDS to be individually fused because when you have a bunch on one fuse and it blows ITS DISABLING ALL OF YOUR NAV/SAFETY ELECTRONICS. (even though adding up the demands says it should work).

You don't know which one is drawing more than its supposed to... Just that the math says it should work.

Do it right.

For equipment reliability and fire prevention.

**************

Its OK to have a 10 amp rated line, with 10 amp fuse that then splits at a bussbar to the individual device fuses. Not ideal... but keeps you from running as many lines.
__________________
TurninTurtle is offline   Reply With Quote
Old 13-06-2016, 19:36   #10
Registered User
 
Hoohaa's Avatar

Join Date: Jul 2011
Location: Sydney Aus
Boat: Swarbrick 40
Posts: 472
Images: 10
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by skipmac View Post
First question, is the fuse that's blowing connected to the switch on the panel or an inline fuse? If the later where is it located?


If the fuse is in the panel then if I understand you have a wire from the "Instrument" switch on the panel to a bus bar and then feed the instruments from the bus bar. I assume + and - wires to the bus, both from the panel?


Correct. But the - is connected to a main earth which runs directly to the battery bank, not back to the panel.

If this is correct then what size wires are running from panel to bus bar and from bus bar to the instruments?

The reason for all this, the purpose of a fuse that feeds a bus bar is not to protect the instruments but to protect the wires, if you have a very small wire you need a very small fuse because a big fuse might allow enough current to heat the wire, melt the insulation and start a fire.

I can't tell you exactly what the wire gauge is, but they are substantial, so I am shore they will be able to cope. the equipment wiring is what came with the equipment. I am fairly shore that the Splitter and AIS do not have an in-line fuse supplied with it. but I did get the AIS second hand.

So if your wires are say 10-12 gauge you could easily and safely use a 15 amp fuse.

If you are trying to protect the equipment then an inline fuse on the hot wire to the device is where that should be. In that case use the size fuse recommended by the manufacturer.
The fuse is connected to the switch on the panel.



Jeff
__________________
Drinking hot tea on a hot day is like banging your head against a wall . It feels good when you stop.... "Terry" my dad.
Hoohaa is offline   Reply With Quote
Old 13-06-2016, 19:36   #11
Moderator
 
Adelie's Avatar

Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 4,362
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by Hoohaa View Post
You might be right..?? Open to advise here..
Turtle is right.
__________________
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
SailboatData
Adelie is offline   Reply With Quote
Old 13-06-2016, 19:37   #12
Registered User
 
Hoohaa's Avatar

Join Date: Jul 2011
Location: Sydney Aus
Boat: Swarbrick 40
Posts: 472
Images: 10
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by StuM View Post
Fuse or circuit breaker? If CB, how old is it?

CB gets weaker with age and use.

As a rule of thumb, you shouldn't load circuit breakers consistently over 80% - doing so can cause them to trip after a while.
Its a fuse..
__________________
Drinking hot tea on a hot day is like banging your head against a wall . It feels good when you stop.... "Terry" my dad.
Hoohaa is offline   Reply With Quote
Old 13-06-2016, 19:44   #13
Registered User
 
Hoohaa's Avatar

Join Date: Jul 2011
Location: Sydney Aus
Boat: Swarbrick 40
Posts: 472
Images: 10
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by pesarsten View Post
In a perfect world, everything would be individually fused. Perhaps impractical in some cases. But, have you checked what the voltage is at the devices, a corroded connection in the supply line could cause a problem. It looks like you consume about 48 watts ( 12 volts x @ 4 amps). A poor connection that drops you supply to 10 volts would result in 4.8 amps draw. Too close for a 5 amp fuse. This would need to be adressed.

Perhaps put the AIS and Splitter on a separate 5 amp fuse for reliability.
I have checked the voltage, as far as I can see it all looks good.
__________________
Drinking hot tea on a hot day is like banging your head against a wall . It feels good when you stop.... "Terry" my dad.
Hoohaa is offline   Reply With Quote
Old 13-06-2016, 19:45   #14
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Seattle
Boat: Cal 40
Posts: 2,398
Images: 7
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by Hoohaa View Post
Surprisingly they do not have an in-line. But if I install them it will still not solve my original problem. Yes the devices will be protected but they are still getting power from the original switch with the 5 amp fuse.
Am I thinking this through correctly. If I increase the fuse size without having the recommended in-line fuse for each of the items, then they could be damaged before, lets say 10 amp fuse blows?
From your manual -

One fuse is installed in the DC power cable. If the fuse blows,
track down the source of the problem, have it repaired, and
replace the damaged fuse with a new one of the proper rating.
(There's a picture following in the manual.)

Click on manual at this link
MA-500TR Class B AIS Transponder - Features - Icom America

You'll probably find all your electronics manuals will describe an inline fuse

Read #6 again about fuses protecting wires or devices.
__________________
cal40john is offline   Reply With Quote
Old 13-06-2016, 20:21   #15
Registered User

Join Date: Jun 2013
Location: canada
Posts: 1,617
Re: 5 amp fuse keeps blowing?

your instrument fuse should be large. say 15amp. I normally run 30a breakers for nav gear. then run cable to bus bar, then each unit has it's proper size fuse from bar based on the manual. or buy a blue sea fuse block to feed from the switch. https://www.bluesea.com/products/502..._Bus_and_Cover
__________________

__________________
smac999 is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
The mystery of the blowing fuse Orchidius Electrical: Batteries, Generators & Solar 11 02-07-2014 16:08
My 20 Amp Breaker Keeps Popping and Shutting Down Genset Turtlep Electrical: Batteries, Generators & Solar 4 26-07-2012 13:23
Cruisair Only Blowing Heat Captain Jay Plumbing Systems and Fixtures 9 12-04-2011 06:49
Perkins 4-107 Won't Stop Blowing Head Gaskets chihuahuas Engines and Propulsion Systems 34 30-10-2009 15:53
Blowing fuses in the bilge system ribbony Electrical: Batteries, Generators & Solar 19 10-05-2008 04:21



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 14:51.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.