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I'm teaching an electrical class to our HVAC service and maintenance techs next week. I want to talk to them about common misconceptions about electrical and was looking for some input. What misconceptions have you heard or do you hear most often? What are some of the truths about those misconceptions?

The one's I've got so far are Zinsco/FPE panels will burn your house down if you don't change them immediately. Aluminum wire is illegal and going to burn your house down. Knob and tube is illegal. Your (insert appliance here) isn't working properly because you have a bad ground.

I want to educate my techs to the best of my ability so they are not out there giving our bad or wrong information to our customers.
 

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I own stock in FotoMat!
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Two legs of a 3-phase system is 2-phase.

A 2-pole 40 breaker can have 80 amps go through it and not trip.

If you put a 3-pole breaker in a single-phase panel, you'll get 3-phase power.

Most electrical problems are solved by simply driving a ground rod.

Black is ground, white is hot.

You cannot feed an exterior disconnect with NM.

A 20-amp breaker will trip immediately when 20.0000000000000001 amps go through it.

Circuit breakers last forever, and can be tripped and reset an infinite number of times.

Circuit breakers and fuses provide identical protection.

When shorting out a circuit protected by a 30-amp breaker, there will only be 35 or 40 amps flowing until the breaker opens.

A 15-amp GFCI limits current flow to 15 amps.

If a circuit breaker won't stay closed, you can simply replace it with larger ones until you find one that holds.

Once you use an extension cord or power tool on a GFCI-protected circuit, and it doesn't trip the GFCI, then the cord or tool will never in the future ever trip another GFCI since it's proven itself to be free from ground faults.

You can calculate the ampacity of a panel simply by adding up all the circuit breakers installed in it.

Single-phase power is really 2-phase power with the hots 180 degrees apart.

And the biggest misconception: Electrical is so freakin' easy, you can buy a book at Home Depot and be an expert after you're read it.
 

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Bilge Rat
motors and controls.........
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The high leg of a 120/240 3ø ∆ system is for 3ø only.

All HVAC disconnects must be fused.

The maximum breaker allowed for #14s is 15 amp; #12s is 20 amp and #10s is 30 amp.

Bigger wire is always better.
 

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Explain that wire is sized by amperage, not voltage. That way they don't tell the electrician to just run me a 220 wire. Also explain how to size wire according to the tons of air or KW of the heat strips. I have HVAC guys that I ask how many tons of air are you going with and what size of heat strips and they always tell me, oh just run me a #10 to the condensing unit and a #6 to the air handler, that's what most all electricians run. I'll tell them that's not what I ask, you tell me what size your equipment is and I'll size my own wire. I hate it when people do things by repetition, rather than know how it actually works. When my 19 yr old son first started helping me we were installing switches in a new house and he came to a 3 way and ask me, does the red or black wire go on the black screw? I said no, the switch leg or the hot does, depending on which end of the 3 way your on. I explained to him that I would rather him know how a 3 way works. Don't just put color wires on switches just because that's how I do them. Learn how a 3 way works and then you can troubleshoot a problem no matter who wired the switch or what house you are working on.
 

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I like ceiling fans & EMT
Former commercial, occasional (small) residential
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Ground and neutral are the same thing and/or all electricity goes into the ground.

FWIW I wouldnt discourage people from believing that FPE panels are dangerous. I've seen enough FPE dangers with my own eyes to be a believer.
 

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A lot of people think that water conducts electricity.
Pure water is not a common thing so it's safe for people to assume that. Plus, it's easier to tell them that than to explain what is actually going on with water and electricity.
 
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