Saturday, Nov 29, 2014 at 14:26
When you say "quite hot" how hot is that.
warm to the touch
hot as the outside of a coffee cup
so hot you can hold it for long
so hot it burns on contact
the insulation is melting
There are a number of reason why things arround terminals and fuses get hot.
A high resistance can produce heat that travels some distance in wires, giving a false impression of where the exact cause is.
The standard of workmansip across the trailer industry is not good and far from consistent....there are a only few out there who know their business and do nice work.
Poorly cripmed lugs can produce hot spots....a properly crimped lug should be "as good as welded" and should not represent a high resistance point.
Even though passable ratchet crimpers can be had for under $20, there are many persisting with pressed tin crap.
Good quality lugs have never been as easily avaiable and as cheap...but there is still crap put there.
If a good quality lug of the correct size has been crimped on a wire with the correct cripmer it should be as good as welded and should not present any problem.
The #1
test for lugs and one that people consistently fail to do is....try to pull it off.....the wire should break before the crimped union fails.
Apply the pull
test to your lugs.....if the lug pulls off the wire it needed recrimping anyway.
Blade fuses are far more reliable in an automotive setting than any of the previous options...but people push them too far.
If you have a 40 amp blade fuse it should be a maxi blade fuse.....anything above 25 amps is hard to get in a standard blade fuse, I will not use over 30 amps in standard blade fuse.
My limits are
nothing over 20 amps on a mini blade fuse
nothing over 30 amps on a standard blade fuse
and unless there is no other choice either a circuit breaker or an ANL fuse for anything 60 amps and over.
Even IF the bade fuse it self is adequate for the job the fuse holder may not be rated for the fuses fitted to it. Some standard blade fuse blocks and holders are only rated for 20 amps continuous on a single circuit and an 8 way block may have a total rating of 60 or 80 amps continuous.
Many people fail to even consider the rating of the fuse block or holder.
Failures here manifest as hot points where the fuses contact the holder terminals....the terminals may not have sufficient tension or current carrying capacity..even if they do the surrounding plastics may not have the capacity to handle the heat.
Some heat arround fuses can be quite normal under full load situations.
Light cables can be a problem.....but in automotive the voltage drop becomes a problem before the curret carrying capacity becomes an issue.....that said I have seen some very light cable used.
There may be some issues with screw terminals not being tight enough....remember no wire should be soldered before putting in a strew terminal.
There may also be issues with spade and bullet lugs lacking tension..a squeeze with pliers on the femal lug can fix this.
SO
If you have a 40 amp fuse and the cable runs the length of the trailer I would expect to install at least a maxi blade fuse if not an ANL or a circuit breaker.
I would expect to install at least 6mm2 twinn ( not 6mm automotive cable 4.6mm2) if not 10mm2.
This would mean I would not be using insulated lugs as 6mm2 wont go onto a yellow lug.
I'd be using non insulated lugs and heat shrink.
I' d expect to see some sort of sub fuse block at the rear.
so what does this all look like.
cheers
AnswerID:
542328
Follow Up By: The Bantam - Saturday, Nov 29, 2014 at 14:31
Saturday, Nov 29, 2014 at 14:31
If the problem on a 40 amp circuit is present woth only 3 to 8 amps flowing ether something has been damaged due to high current flow at a previous time or there are some very real resistance issues.
cheers
FollowupID:
828604
Follow Up By: Allan B (Member, SunCoast) - Saturday, Nov 29, 2014 at 14:36
Saturday, Nov 29, 2014 at 14:36
My head hurts! lol
FollowupID:
828606
Follow Up By: The Bantam - Saturday, Nov 29, 2014 at 14:54
Saturday, Nov 29, 2014 at 14:54
best go back to bed then.
cheers
FollowupID:
828607
Follow Up By: Allan B (Member, SunCoast) - Saturday, Nov 29, 2014 at 14:56
Saturday, Nov 29, 2014 at 14:56
Now that's sound advice!
FollowupID:
828608