I work for a company that manufactures commercial appliances which run off of 200-240VAC and draw as much as 40A per machine. For internal wiring purposes, we currently never use anything smaller than 16 gauge wire for the high voltage wires, even in locations where they only carry small fractions of an amp. I was looking at ways to save money, clean up our wiring, make the build process easier, etc. and thought that we could use 18 or 20 gauge wire in some of the low current applications (for example, a solenoid valve that only draws 50mA.) It seems crazy to use 16 gauge wire for current so low that it could be handled with 22 gauge wire.

One of my coworkers says that UL requires that we use at least 16 gauge for anything high voltage, but I've seen much smaller wires carrying high voltage in other machines which I believe are UL compliant. Do any of you know whether or not there's a requirement that high voltage wires within commercial appliances be a certain size? I find numerous references online to small gauge wires that are UL approved for high voltages, but I also know that there could be other limiting factors such that wire is only rated for that voltage in some situations and not others.

Wires that I might be interested in would include UL styles 1007 and 1569, among others:

https://www.nationalwire.com/pdf/UL-AWM-1569.pdf

http://www.standard-wire.com/comparison_chart_ul_wires_cables.html

Thanks in advance for any insights.

 

I suppose you've looked at this?
https://www.ul.com/wp-content/uploads/2014/04/WC_MG.pdf

 

How much do you think you'd save in wire cost?

1. Having to stock multiple sizes has inventory cost implications. More colors and gauges increases costs further.
2. Using more gauges increases chance of using the wrong wire. Worst case is using something smaller than #16 where #16 was actually required. That could trigger recalls.
3. Buying one size, color would give a lower price. If I buy 100 feet of #22 solid wire, I'd pay around $10, but 1000 feet costs about half as much per foot.

One of my coworkers says that UL requires that we use at least 16 gauge for anything high voltage, but I've seen much smaller wires carrying high voltage in other machines which I believe are UL compliant.

I don't know UL requirements, but that's a head scratcher. Voltage rating depends on qualities of the insulator, not wire gauge. What is high voltage? I can't see an appliance routing 240VAC all over the place.

 

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Wires that I might be interested in would include UL styles 1007 and 1569, among others:

https://www.nationalwire.com/pdf/UL-AWM-1569.pdf

http://www.standard-wire.com/comparison_chart_ul_wires_cables.html

Thanks in advance for any insights.

The voltage limits are stated in both those links. As long as you don't exceed those (remember you might have voltage spikes to account for), you are OK using them.

I'm only talking from a spec-sheet look. I am not saying it is 100% OK in your final system design.

 

How much do you think you'd save in wire cost?

1. Having to stock multiple sizes has inventory cost implications. More colors and gauges increases costs further.
2. Using more gauges increases chance of using the wrong wire. Worst case is using something smaller than #16 where #16 was actually required. That could trigger recalls.
3. Buying one size, color would give a lower price. If I buy 100 feet of #22 solid wire, I'd pay around $10, but 1000 feet costs about half as much per foot.

I don't know UL requirements, but that's a head scratcher. Voltage rating depends on qualities of the insulator, not wire gauge. What is high voltage? I can't see an appliance routing 240VAC all over the place.

We already use the smaller gauges for low voltage systems, so we wouldn't necessarily need to add more new sizes. Inventory and cost aspects are well understood - I'm just trying to determine whether or not there are legitimate regulatory concerns.

You make a good point about the risk of accidentally using the wrong size. We use 14 and 16 already and have made the mistake of transposing them before. So maybe it's best to avoid using multiple sizes that are too similar; 16 and 22 poses little risk of confusion, but 16 and 18 might be tempting fate for no good reason.

 

I suspect ebeowulf17 is using the term ‘high voltage’ for mains wiring, and ‘low voltage’ for secondary voltages (isolated from the mains).
So they are using 16AWG wire for all mains circuits, regardless of the current they are passing.

It would make economic sense to use appropriately rated wires, saving costs.
I would recommend you calculate the price of each machine’s mains wiring at 16AWG, then determine cables that can be downsized and the savings that could be made per machine, to see if it is a worthwhile exercise.
Bear in mind that when using a smaller gauge wire, you might need to change the wire terminations, and if these wire terminations cannot be changed you may not be able to reduce the wire gauge.

The only internal wire required to comply with gauge requirements are the earth bond wires. Other than earthing wires, in terms of UL type testing your product, any gauge wire will be judged acceptable (in its application) providing that the wire insulation does not exceed its rating under normal operation. Bear in mind that besides the heating caused by the current, other heat dissipating parts within the machine may impact the wire insulation temperature.

Something else to consider is that although you might reduce wire gauges due to the current – the reduced gauge wire will be less robust, something that could effect reliability.

Note that regardless of the wire gauge, it must be rated for the circuit voltage.