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Melting wires & smoke from panel

 
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mbiskup




Joined: 09 Jun 2014
Posts: 26
Location: Massachusetts


PostLink    Posted: Sat Nov 04, 2017 2:25 pm    Post subject: Melting wires & smoke from panel Reply with quote


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Hi, Kal

Yesterday I noticed that there was smoke coming out of my panel when I finishing my brew day. I did some investigating and found that one of the 120V lines coming from the main 30A receptacle was melting (photos attached). Also, one of the female disconnects on the boil contactor was beginning to discolor as well. The screws on the right side of the main supply contactor also discolored (black).

I used the correct size wires to the receptacles, correct sized power line, and everything is grounded. Are the ways the lines run an issue? Are the sharp turns a stress riser for that high of a current? Or is there an issue that I cannot see or should investigate further? I have had this panel for roughly 3 years and about 50 brews.

Thanks for the help.



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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Sat Nov 04, 2017 2:56 pm    Post subject: Re: Melting wires & smoke from panel Reply with quote

Hi!

I take it this is a panel you built yourself and you sourced your own parts? I ask because I'm seeing things in there that we don't use like wire marrettes, certain wire colours are incorrect, friction fit spades, etc.

In your case I'm pretty confident your issue is because there's a poor connection between the two points from using friction fit push on spade connectors. Don't use these on high current connection points. Use the screws on bare wire as it'll give you a much tighter fit.

You can use these push-on spades on posts for low current stuff like the contactor side coils or when you need to pull low current off one of the contactor inputs or outputs for element lights or the amp/voltmeter - basically anywhere you're using 14 ga or thinner wire as there's very little current pulled. Use the contactor screws directly on wire with the high current devices which is any of the fatter 10 ga wire. That's what the screws are for. See here for pics of our of our 30A pre-assembled panels as an example: http://www.theelectricbrewery.com/forum/viewtopic.php?t=27330

Note that we use push-on spades for the low current stuff connected to the contactors but use the screws for the fatter high current wiring.

mbiskup wrote:
Are the ways the lines run an issue? Are the sharp turns a stress riser for that high of a current?

No - don't worry about that. While you're not supposed to have really sharp turns because creating those can damage the wire inside (effectively reducing the gauge), it doesn't affect the flow of current as long as the strands inside are not broken.

I hope this helps!

Kal

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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Sat Nov 04, 2017 3:43 pm    Post subject: Reply with quote

Just to add to why this happens:

Heat is created when current flows through an area that is too small to handle that amount of current. This can happen:

(a) with a loose connection where only a few strands are making contact because the wire is not properly tightened/fastened, and/or
(b) a wire that is too small to handle the current is used, and/or
(c) when a properly sized wire is used but some of the copper strands were cut/trimmed to get it to fit (this should never be done), or
(d) if an electrical socket or blade is dirty or charred or if the plug is not pushed and locked in properly with the receptacle.

All of these cases effectively reduce the contact area meaning that more current flows through a smaller area which in turns creates more heat which can melt the insulation on wires and damage nearby components.

It could also be that you’re actually pulling too much current by using oversized heating elements. This would only be possible if an incorrectly sized breaker was installed in the electrical panel (larger than 30 or 50 amps, depending on your control panel size) as otherwise the breaker would pop if more than 30A or 50A was pulled. A 30A or 50A breaker must be used (sized for your control panel) per our control panel instructions.

In this case the spades may not be rated to handle the current, or over time the subtle heating/cooling expansion and contraction of the metal has lowered the surface contact area which reduces the amount of area that the current can flow through requiring the current to flow "faster" in that one spot to compensate since current is pulled by the elements.

Think of a 6-lane highway that has a one lane bottleneck for a few hundred feet. On the highway the entire road will slow down to compensate but current doesn't work that way. If the current is like the cars moving across the road, the current has to flow 6 times faster during that bottleneck where only one lane is available. This in turn creates heat which travels across the wire on the inside and is melting the wire insulation.

Note: This analogy is not entirely accurate so please no comments from other Electrical Engineers). Wink

So I would redo any 10 ga wire connections to NOT use push-on spades (go directly into the screw and tighten). Not every point has melted, but what you've done isn't safe so I'd redo all high current points (anywhere a 10 ga attaches). Any wire that is melted should be replaced. The contactors are likely fine.

Good luck!

Kal

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We ship worldwide and support our products and customers for life.
Purchasing through our affiliate links helps support our site at no extra cost to you. We thank you!
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