We have a 1965 Austin-Healey replica that we have had for about 7 years. I have gotten the chassis and suspension sorted out and all is well there. However the windshield washers have never worked, and the wipers do. What I did find was a 5 amp glass fuse was blown which I replaced and they now work after I cleaned the gunk out of the nozzle. I am not very electrical savvy and have not found the fuse call out for the different circuits. One as a 14 gauge and another at 16 gauge. Am I right in thinking this fuse per the wire size should be 7 or 10 amp? The length of the wire run is about 24 inches. Thank you for your input.
duehew
fusing
The wire is sized per the load of the device that is being powered. The fuse is sized to protect the wire.
There are many factors that establish the wire size and fusing. Such as:
Load in amps. Here are some examples.
Headlights are ON for a long duration and the wire must not add resistance so even though the load may be only 12 amps, I would use #12 wire to make sure the voltage is maintained at the headlights.
The electric windows may only be 12 amps but they are only used for short duration so #16 wire is adequate even if the voltage drops a little it won't effect the window operation.
The length of the wire is usually not an issue because the wire lengths are short. A LIMO might be an exception, however.
Once the wire is sized then the fusing is sized.
#12 = 25 amp fuse
#14 = 20 amp fuse
#16 = 15 amp fuse
#18 = 10 amp fuse
vicrod
The wire is sized per the load of the device that is being powered. The fuse is sized to protect the wire.
There are many factors that establish the wire size and fusing. Such as:
Load in amps. Here are some examples.
Headlights are ON for a long duration and the wire must not add resistance so even though the load may be only 12 amps, I would use #12 wire to make sure the voltage is maintained at the headlights.
The electric windows may only be 12 amps but they are only used for short duration so #16 wire is adequate even if the voltage drops a little it won't effect the window operation.
The length of the wire is usually not an issue because the wire lengths are short. A LIMO might be an exception, however.
Once the wire is sized then the fusing is sized.
#12 = 25 amp fuse
#14 = 20 amp fuse
#16 = 15 amp fuse
#18 = 10 amp fuse
vicrod
fusing
protecting the wire is 1/2 correct.. if u used a 14 wire to power something that takes 5a to run.. would u fuse it for 15a or 5a ?
both need to be considered when wiring up the sys. thats just the way i look at it.. i've wired 4 st rods and i consider each device and wire size.. i don't go smaller then 14ga. my winter project will be complete new wiring on my p/u, don't need it but safe then sorry.... if i don't sell it first
protecting the wire is 1/2 correct.. if u used a 14 wire to power something that takes 5a to run.. would u fuse it for 15a or 5a ?
both need to be considered when wiring up the sys. thats just the way i look at it.. i've wired 4 st rods and i consider each device and wire size.. i don't go smaller then 14ga. my winter project will be complete new wiring on my p/u, don't need it but safe then sorry.... if i don't sell it first
The NEC allows derating fuse for wire size, you just cannot go the other way. If that 5 amp device shorts it can draw far more that 5 amps. I would use a 15 amp fuse on a 14 awg circuit no matter what it is powering.
Vince
Vince
Thank you Vince. I did stumble on a chart that showed what fuse for what wire size. The chart shows 7.4 amp fuse for 16 ga. wire. I am using 16 ga. because this is one of the wire sizes shown so I will go with the smaller wire size. Once again thank you for your response.
:thumbup:
:thumbup:
I agree with Bill. If a wire could handle a 20 amp load and you fused it for 10 amp........ the wire would never come close to frying before the fuse blew.
Agree with the math....... however IMO....... why would I protect a 14g wire with a 15 amp fuse if the max draw was 5 amps?
It would work well in providing a 15 amp load to a shorted item until the 15amp load was reached and the fuse blows.......... possibly overheating and melting something else etc..... where as if I put a 5 amp fuse in the circuit it would blow a lot sooner and there-by protect from the melting issue etc.....
It would work well in providing a 15 amp load to a shorted item until the 15amp load was reached and the fuse blows.......... possibly overheating and melting something else etc..... where as if I put a 5 amp fuse in the circuit it would blow a lot sooner and there-by protect from the melting issue etc.....
Thank everyone for their input as it is very helpful. I guess what I will do is continue to run with the 5 amp fuse and see if it blows and then determine what will have to be done. My guess is for as much as the nozzle was clogged, the person who had the car before me was running water that cristalized in the nozzle and kept pushing on the washer knob which blew the fuse. When I finally got around to checking it out, I first changed the blown fuse. When pushing on the washer knob I now heard the pump. I removed the fluid line at the bottom of the bag where the pump outlet is and water squirted out when pushing the knob. I then removed the hose from the nozzle and fluid came out there which pointed to the nozzle. After cleaning the white crud out of the nozzle all was well. This prompted me to ask as to fuse size requirements. I do not know the amp requirements of the washer pump. Once again thank you all.
Not asking you Denny, I know how to properly calculate length to gage to load etc.....
IMO blowing a smaller fuse is preferable to melting the wire (in your example of a cut wire/direct short)
IMO blowing a smaller fuse is preferable to melting the wire (in your example of a cut wire/direct short)
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