Dead Simple 240v Boil Controller Help

[thekraken]

I want to build a simple 240v boil controller with parts I have mainly lying around. Given the attached diagram, I just need to go out and buy the enclosure and toggle switch.

Can I get a few more sets of eyes on this diagram I whipped up to tell me if things look correct and safe? Is there anything I'm missing?

I intend on using the exact components you see pictured here, simple/common stuff.

(EDIT) The wiring on the switch is wrong! I will post a corrected drawing.

 

[jeffmeh]

I want to build a simple 240v boil controller with parts I have mainly lying around. Given the attached diagram, I just need to go out and buy the enclosure and toggle switch.

Can I get a few more sets of eyes on this diagram I whipped up to tell me if things look correct and safe? Is there anything I'm missing?

I intend on using the exact components you see pictured here, simple/common stuff.

You should use a fuse if you are going to step down from 10awg to 14awg, to protect the 14awg wire.

 

[WI_Wino]

Never mind... Late night, can't read.

 

[thekraken]

You should use a fuse if you are going to step down from 10awg to 14awg, to protect the 14awg wire.

Ah yes, I wanted to ask about that. I debated on the fuse there.

So is that fuse a general best practice kind of thing or is it a requirement?

I genuinely want to have a discussion about it and am not looking for an excuse to cut corners.

So the fuse would be there to protect the smaller wires from overheating and starting a fire, but why would that happen? The load on the other end of those wires is known and relatively static. The whole thing is also contained within the enclosure so no one else is going to be able to come along and change that on me. The wires are a very short run, a few inches.

And finally, what kind of protection do wall warts provide within their own circuitry? I opened up a 12v wall wart just the other day and the internal leads coming off the spades (carrying the 120v) couldn't have been bigger than 22 awg.

 

[neild5]

The fuse is to protect the smaller wiring, pot and wall wart. What if the SCR fried and shorted the 22 g wires? or the wall wart? The fuse should be for just over the input amps of the wall wart.

 

[jeffmeh]

Yes. The fuse is to protect against an over-current situation, like a short. Ideally, it will never blow, but that is preferable to a fire.

 

[lschiavo]

The fuse is to protect the smaller wiring, pot and wall wart. What if the SCR fried and shorted the 22 g wires? or the wall wart? The fuse should be for just over the input amps of the wall wart.

Really? Do you add a fuse to your outlet in your house when you plug in a wall wart?

I figure a UL listed device should not require additional fusing. I emailed auber years ago to ask if fusing was required on their PID's. At that time they said "No. The unit is internally protected". Lots of redundant 1A fuses have been installed in control panels since then.

It certainly does no harm to redundantly fuse things in a control panel. Where to stop though... How about the coil on the contactor, the indicator lamps or the alarm buzzer. For some reason those don't seem to get dedicated fuses.

No question. Fuse the wire.

 

[thekraken]

Really? Do you add a fuse to your outlet in your house when you plug in a wall wart?

I figure a UL listed device should not require additional fusing.
...
No question. Fuse the wire.

Well that was confusing

 

[lschiavo]

Well that was confusing

Sorry. It made sense to me

I guess I'm saying, why fuse a manufactured component that does not specifically require you to do so? And you ONLY need to fuse the wire you use to connect those components. If you're connecting everything up with#14, fuse at 15A. Done.

What many are doing is equivalent to fusing every light bulb in your house or fusing your March pump that is intended to just be plugged in to any 15 or 20A outlet. Or fusing your cell phone charger before you plug it in by your nightstand.

Again, no harm done by it. Lots of happy folks out there making fuses.

 

[thekraken]

Sorry. It made sense to me

I guess I'm saying, why fuse a manufactured component that does not specifically require you to do so? And you ONLY need to fuse the wire you use to connect those components. If you're connecting everything up with#14, fuse at 15A. Done.

What many are doing is equivalent to fusing every light bulb in your house or fusing your March pump that is intended to just be plugged in to any 15 or 20A outlet. Or fusing your cell phone charger before you plug it in by your nightstand.

Again, no harm done by it. Lots of happy folks out there making fuses.

In this particular circumstance you're saying fuse it?

I mentioned before that I opened up a wall wart and saw that the wires connecting the spades to the transformer's circuitry was probably around 20-22 awg, how do they get away with that?

Also, looking at Kal's guide on theelectricbrewery.com he does include a 7A fuse to protect some 14 gauge wire but there are points where there is smaller wire without a fuse behind them, for example the pilot lights: http://www.theelectricbrewery.com/control-panel-part-2?page=13
Without a single complete overall wiring schematic of his panel it's hard for me to follow everything going on with his design...

 

[lschiavo]

In this particular circumstance you're saying fuse it?

I mentioned before that I opened up a wall wart and saw that the wires connecting the spades to the transformer's circuitry was probably around 20-22 awg, how do they get away with that?

Also, looking at Kal's guide on theelectricbrewery.com he does include a 7A fuse to protect some 14 gauge wire but there are points where there is smaller wire without a fuse behind them, for example the pilot lights: http://www.theelectricbrewery.com/control-panel-part-2?page=13
Without a single complete overall wiring schematic of his panel it's hard for me to follow everything going on with his design...

I would put a15A fuse where you drop to #14. That's all you should need the way your circuit is drawn. The wall wart should be UL listed and capable of being plugged into as much as a 20A outlet.

They get away with small wires because they pay big bucks to have the component designed and tested.

It looks like #14 is used to connect the pilot lights. I don't see another option in the legend. Also, if the leads are part of the component you don't need to fuse for them. Just make sure the component is rated as high as the last fuse upstream.

 

[jeffmeh]

Kal uses #22 for the DC signal wires, from PID to SSR. Not a concern...

 

[thekraken]

Kal uses #22 for the DC signal wires, from PID to SSR. Not a concern...

What in regard to?

 

[lschiavo]

Kal uses #22 for the DC signal wires, from PID to SSR. Not a concern...

Not a concern at all if the manufacturer does not specify otherwise. These wires are connected on the downstream side of a manufactured device. No user fusing required. Kal may use #22. That seems like a random selection. Any size wire that fits the terminals will work. I doubt you could even measure the current on these wires.