Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 13-06-2016, 20:55   #16
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 smac999 View Post
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
Sounds like a plan, Thanks..
I will figure out the gouge of the wire I have used and will probably use a 10 amp and make shore the in-line fuses are installed.
Thanks.
__________________

__________________
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, 21:05   #17
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?

Quote:
Originally Posted by smac999 View Post
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

Even better than the 10 amp feeder line idea... Leaves room for adding another device (with its own fuse)

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

I required the guy installing my dashcam and rear camera in my truck (I didn't want to take the dash apart myself) to put them each on their own fuses and the 3.5 inch rear camera monitor is on its own fuse.

The cell phone chargers that plug into the cig lighter ports... have a fuse in them.

If you get a "splitter" to plug 4 devices to the cig lighter, it has a fuse and then each device has its own fuse.

This is ALL done for a reason.
__________________

__________________
TurninTurtle is offline   Reply With Quote
Old 14-06-2016, 04:54   #18
Registered User

Join Date: May 2010
Posts: 666
Re: 5 amp fuse keeps blowing?

separate fuses might be ok as long as you remember where they are. If all of the components go back to the original fuse it will still kepp on blowing. the ratings you are quoting might be average use and don't consider the occasional surge such as what happens when you turn a device on or the dvice loads up to operate a relay or other piece of equipment. So go with a small panel of fuses(like your car) just to keep them together but put the lot through a larger circuit breaker (aka fuse) to cope with total load
__________________
dlymn is offline   Reply With Quote
Old 14-06-2016, 06:08   #19
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?

There are lots of different fuses with different time/current ratings. One example is old style panels quite often had AGC fuses in them. This fuse is called a fast acting fuse. From page OC83 of this link - http://www.cooperindustries.com/cont...ne_Catalog.pdf
- we see that a 5 amp AGC fuse will take 100 seconds to blow with 6 amps of current, 1 second with 10 amps, 0.1 seconds with 23 amps
__________________
cal40john is offline   Reply With Quote
Old 14-06-2016, 09:34   #20
Registered User

Join Date: Feb 2011
Posts: 2,105
Re: 5 amp fuse keeps blowing?

Fuses need spare capacity. Breakers already have that built into them. Rated amps per appliance is an average, not a constant. Start up amps usually more than operating amps. And yes, not just an ideal, but a wise move to have everything separately fused, ideally with breakers not fuses. Easier to track down the short, isolates the problem so other systems can still operate, and easier to replace.
__________________
reed1v is offline   Reply With Quote
Old 14-06-2016, 09:58   #21
Senior Cruiser
 
CLady's Avatar

Cruisers Forum Supporter

Join Date: Jan 2013
Location: Seattle
Boat: C&C40T 1980
Posts: 178
Re: 5 amp fuse keeps blowing?

What size wire on the power side?
__________________
CLady is offline   Reply With Quote
Old 14-06-2016, 09:59   #22
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 5,798
Re: 5 amp fuse keeps blowing?

skipmac summed it up correctly. I think the first thing is to identify the wire gauge to and from the switch and fuse. It could be all you need is a larger fuse because you have increase the load. Just don't fry an inadequate wire size.
__________________
Cadence is offline   Reply With Quote
Old 14-06-2016, 10:08   #23
Registered User

Join Date: Apr 2011
Posts: 2,196
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by smac999 View Post
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
That's what I used when installing new instruments. Works great.

The wire from the breaker to the fuse block should be rated for more than the breaker, and also for less than 3% voltage drop with all the instruments on.

There's a good voltage drop calculator, here :

Voltage Drop Calculator Genuinedealz.com

For example, although 18 gauge will handle the current, you need 14 gauge to stay under 3% over a 10ft length at 5A.

Don't forget that the voltage drop from breaker to fuse block, and from block to instrument, is accumulative, and the total should stay under 3%.

I've always got a good length of 14 gauge two core boat cable, as it's so useful - a great general cable to have around.
__________________
Bristol 31.1, SF Bay.
MarkSF is offline   Reply With Quote
Old 14-06-2016, 20:27   #24
Registered User

Join Date: Jun 2013
Location: canada
Posts: 1,603
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by Cadence View Post
skipmac summed it up correctly. I think the first thing is to identify the wire gauge to and from the switch and fuse. It could be all you need is a larger fuse because you have increase the load. Just don't fry an inadequate wire size.
each of the devices will have inadequate wire size. that is why they each need a proper sized fuse. among other reasons. you can't just put one big one for everything.
__________________
smac999 is offline   Reply With Quote
Old 15-06-2016, 05:44   #25
Marine Service Provider

Join Date: Jan 2012
Location: Lake Ontario
Boat: Douglas 32 Mk II
Posts: 1,642
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by Hoohaa View Post
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
Refer to ABYC E11 - AC and DC electrical systems on vessels.

The panel current limiting device should be sized to protect the wire, not the devices connected to it. Each instrument should be protected by a current limiting device that will not disable other devices connected to the branch circuit.

Fortunately, based on your description, the wiring errors you have introduced into your system are not likely to start a boat fire (like many of the DIY wIring mods I see). When it comes to vessel wiring, don't guess; follow the standards or hire a pro, your life or the life of loved ones may depend on it.
__________________
ramblinrod is offline   Reply With Quote
Old 15-06-2016, 06:49   #26
Registered User

Join Date: Feb 2011
Posts: 2,105
Re: 5 amp fuse keeps blowing?

Still not clear why fuses and not circuit breakers? Is there some advantage to having fuses?
__________________
reed1v is offline   Reply With Quote
Old 15-06-2016, 08:36   #27
Registered User

Join Date: Mar 2011
Posts: 156
Re: 5 amp fuse keeps blowing?

There could be another issue... What is the Voltage that the stuff is running on?
As your voltage drops ( due to use of battery ) the current could be more then specified, (as the Power requirements are a function of Voltage: P=VI).

What is the state of your battery health? Does this happen while hooked to shore power?
__________________
EzzyD is offline   Reply With Quote
Old 16-06-2016, 22:30   #28
Marine Service Provider

Join Date: Jan 2012
Location: Lake Ontario
Boat: Douglas 32 Mk II
Posts: 1,642
Re: 5 amp fuse keeps blowing?

Quote:
Originally Posted by EzzyD View Post
There could be another issue... What is the Voltage that the stuff is running on?
As your voltage drops ( due to use of battery ) the current could be more then specified, (as the Power requirements are a function of Voltage: P=VI).

What is the state of your battery health? Does this happen while hooked to shore power?
While the formula you referenced is correct, the application may not be.

Reducing applied voltage usually reduces current drawn.

Most devices represent a fixed impedance regardless of the voltage applied.

In that case P = E^2/R

e.g. A device rated 60 Watts at 12 Volts represents a 2.4 Ohm load and draws 5A.

If the voltage is reduced to 10 Vdc, P = E^2/R = 100/2.4 = 41.7 W. The current is actually I=E/R = 10/2.4 = 4.17 A.
__________________
Rod Brandon
Sheen Marine
ramblinrod is offline   Reply With Quote
Old 16-06-2016, 22:40   #29
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 ramblinrod View Post
While the formula you referenced is correct, the application may not be.

Reducing applied voltage usually reduces current drawn.

Most devices represent a fixed impedance regardless of the voltage applied.

In that case P = E^2/R

e.g. A device rated 60 Watts at 12 Volts represents a 2.4 Ohm load and draws 5A.

If the voltage is reduced to 10 Vdc, P = E^2/R = 100/2.4 = 41.7 W. The current is actually I=E/R = 10/2.4 = 4.17 A.
This is correct except for devices with switching power supplies built in.
__________________
cal40john is offline   Reply With Quote
Old 16-06-2016, 23:45   #30
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?

Quote:
Originally Posted by ramblinrod View Post
While the formula you referenced is correct, the application may not be.

Reducing applied voltage usually reduces current drawn.

Most devices represent a fixed impedance regardless of the voltage applied.

In that case P = E^2/R

e.g. A device rated 60 Watts at 12 Volts represents a 2.4 Ohm load and draws 5A.

If the voltage is reduced to 10 Vdc, P = E^2/R = 100/2.4 = 41.7 W. The current is actually I=E/R = 10/2.4 = 4.17 A.

Works for a resistance based incandescent light bulb... not for most electronics.

Generally its a bad idea to feed electronics the wrong voltage. While most "12 v" devices can tolerate 10.5 to 14.0 v (some a little wider range) due to expected output range of automotive alternators and batteries, some can't tolerate being outside 11.0 to 13.0 v.

Electric motors will attempt to deliver the power demanded by the load. Reduced voltage applied invariably results in increased current demand. Reduced voltage results in lower operating RPM which means lower "counter-electromotive force" which is the main "resistance" to current flow while a motor is spinning.

Actually the "fixed impedance" is mainly seen in lights (and not LED or fluorescent lights...)
__________________

__________________
TurninTurtle 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


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:00.


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.