Fuse on hot bus

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kokonutz

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I have a hot bus that I want to connect from my contactor, but I'm having a little con-FUSE-ion (sorry...I'll stop)

All the wires on the bus are 18 awg (switch for actuating another contactor and PID) - I have the understanding I should add a fuse between the contractor and the bus. However I am not clear how large that fuse should be according to the chart here


it sounds like nothing bigger than 4.6...so 3 amp fuse? I only have 1, 5 and 10 on hand, so if that's the case, I'll have to go for a drive today.

Also, my inline fuse holder is 14 awg. Can I use a larger gauge wire on my holder with a fuse that is more appropriate for the lower gauge wires down the line?

IMG_4919.jpg
 

RedRyderr

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Disclaimer - I'm not an electrician. Just a random person on the internet, take this for what you will! I just finished a control panel, only one brew on this system so far (with no electrical problems!). But I used 20AWG for all the small stuff (power to PID's, contactor actuation, etc), and protected with a 1A fuse. Knock on wood, no blown fuses yet.
 
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kokonutz

kokonutz

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Disclaimer - I'm not an electrician. Just a random person on the internet, take this for what you will! I just finished a control panel, only one brew on this system so far (with no electrical problems!). But I used 20AWG for all the small stuff (power to PID's, contactor actuation, etc), and protected with a 1A fuse. Knock on wood, no blown fuses yet.
was that a fuse per hot wire, or one fuse on a terminal bus?
 

RedRyderr

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was that a fuse per hot wire, or one fuse on a terminal bus?
I very closely followed a couple of Doug293CZ's diagrams (adjusting as needed for my panel). I have a 1A fuse that feeds from the power on side of my main power contactor that distributes to all of the PID's, the main power on switch, and the element switches.
 

doug293cz

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I have a hot bus that I want to connect from my contactor, but I'm having a little con-FUSE-ion (sorry...I'll stop)

All the wires on the bus are 18 awg (switch for actuating another contactor and PID) - I have the understanding I should add a fuse between the contractor and the bus. However I am not clear how large that fuse should be according to the chart here


it sounds like nothing bigger than 4.6...so 3 amp fuse? I only have 1, 5 and 10 on hand, so if that's the case, I'll have to go for a drive today.

Also, my inline fuse holder is 14 awg. Can I use a larger gauge wire on my holder with a fuse that is more appropriate for the lower gauge wires down the line?

View attachment 719958
Not sure where your reference got their ampacity table, but it is different than what's in the electrical code. Here's a link to an ampacity table from the 2017 NEC. The NEC requires the following maximum fuse/breaker ratings based on wire size:
14 AWG - 15 A​
12 AWG - 20 A​
10 AWG - 30 A​
Not sure why the NEC does provide a max ampacity for 16 AWG, but it is good for 10 A, and that's the fuse/breaker size I recommend for 16 AWG.

For wires smaller than 16 AWG, the table you provide gives a safe, conservative allowable ampacity. You can always use a smaller fuse than code requires, but you cannot use a bigger one.

Brew on :mug:
 
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kokonutz

kokonutz

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thanks all...and the last question I asked...my inline fuse holder is 14 awg, but the wires I am intending to protect are 18. Can I use a larger gauge wire on my holder with a fuse that is more appropriate for the lower gauge wires down the line? can I put a 1amp fuse in this holder, and then connect and 18 awg to the 14 awg that is part of this fuse holder?
 

doug293cz

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thanks all...and the last question I asked...my inline fuse holder is 14 awg, but the wires I am intending to protect are 18. Can I use a larger gauge wire on my holder with a fuse that is more appropriate for the lower gauge wires down the line? can I put a 1amp fuse in this holder, and then connect and 18 awg to the 14 awg that is part of this fuse holder?
Yes.

Brew on :mug:
 
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