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Originally Posted by RandallJ.
I just went to trade school but apparently something this elementary is assumed to be known. Dont want to get to work and my lead ask me to check the voltage and i don't know what to do.
Welcome to the trades. And no offense, but I wouldn't take the 'fake it to you make it' approach to electricity and testing. Knowing you just came out of trade school I would encourage you to ask as many questions as you have. I good seasoned tech should be more than happy to answer them.

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Originally Posted by Sooty
Exactly. Electricity doesn't care about colour never forget that it might save your life or at least a control board or two.
X2. A guy I knew from the Philippines told me all the wiring there had black insulation.

I have worked on racks where all the wiring was red.

Other units were all the wiring was white.

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Your black prob is your reference probe when checking DC electricity. When you place your black probe on a point, then use your red probe to test another point, you are determining if that red probe is at a higher or lower potential (voltage) than the black probe. The readout on your display will indicate a voltage that may display a negative symbol in front of it depending on the result. That result indicates the difference in potential between those two points as measured by the red probes position. I suggest you play around with a 9V battery and see how your leads mesure voltage and where they are placed when you mesure a positive vs a negative voltage. 9 V batteries have their polarity clearly marked so it’s a quick and easy experiment.

With AC... well the polarity is alternating (AC = Alternating Current) so your polarity is constantly changing (Hz)

Never try to check resistance on a live circuit. This is where a quality meter may really save you one day. Specially when learning. Have a look at the Fluke 116. It’s a solid candidate as a great beginner meter and will serve many very well through their whole HVAC career.

Depending on your meter, you can sometimes mesure a limited current through your leads (usually 10A Max but changes based on your meters specs and the meter leads you are using... cheep leads... don’t even get me started on those) but you won’t get a proper reading if you are trying to mesure in parallel.

Knowing this doesn’t make using a meter safe. Knowing this doesn’t mean you can troubleshoot anything better or anything at all. This is a drop in the ocean when it comes to the basics of electrical troubleshooting. The interweb has some great beginner electrical kits that you can build and learn electricity on. Battery operated stuff. Not lithium battery (that can pack a punch) but common alkaline type stuff. Safe to learn the basics and gives you something fun to experiment with. Always be careful with things that store energy. Batteries in particular because the amperage they can produce will fry your mind, but capacitors are particularly dangerous because they can hide in circuits and at times keep them live even after you power the unit off.

Have fun, the electrical troubleshooting is an addicting puzzle. Just be careful because it will literally jump out at you if you get too close to it, and it doesn’t offer many second chances when you get it wrong.

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Originally Posted by RandallJ.
I don't know how to use a multimeter. I know reds for hot and blacks for common but for voltage does that mean the red probe goes where the voltage would come in and black where it goes out?
I like the "I KNOW" part. Yeah right! LOL.

You would not touch anything electric, w/ me, until AFTER you explain to me what electricity is. I don't like fried,injured,DEAD, Apprentices. I highly recommend you changing your thinking about your and my safety. You will BE GONE if I catch you lying to me about safety. Not "knowing" is one thing, "knowing" and not "doing" is a whole other subject.

5. Don't ever put your hand on a piece of equipment until you have verified, your journeyman has verified, that it isn't live. Could save your life.

6. Problem is, the first thing you do when you walk up to a unit is: Do not turn the power off.

Don't ever put your hand on a piece of equipment until you have verified, your journeyman has verified, that it isn't live. Could save your life.

7. To the OP:

Safety first. When it comes to electricity, try not to ever touch the unit. Meaning, do not lean on the unit. Do not put your hand on the unit to brace yourself. These are all too easy things to do and can easily lead to an electrocution.

8. OP, have you gotten a job in the trade yet?

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@thatguy thank you that was helpful. I'll take a look at that fluke. What I wanted to do depending on what happened with work was do continuing education for reading diagrams and HVAC specific electrical.

@rider77 No not yet. I graduated 1/29. Getting things lined up to get my EPA and drivers licence and then get ahold of a guy in town that handles the HVAC side of the local union. I do have some shops lined up that take green apprentices. So I'm just getting things ready at the moment .

10. Excellent. If you get into the locals apprenticeship program, you’ll have 5 years of work and night school to teach the fundamentals.
Electrical is a big part of that. I teach several electrical classes in my hall.

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Yeah from the school work I did It was pretty clear that Im gonna need a better grasp of the electrical. My next goal is to be able to read diagrams better.

I didn't realize that there would be more school with the union gig. That's great though. Before I started school I had accepted the fact that it's going to be a lifetime of learning and buying tools and all of that.

12. Originally Posted by RandallJ.
Yeah from the school work I did It was pretty clear that Im gonna need a better grasp of the electrical. My next goal is to be able to read diagrams better.
It all comes with time.

13. Think of a multi meter as an audio/visual reader of electrical! Volts/Amps/Ohms A light switch is a reader of the visual kind.

14. Originally Posted by RandallJ.
Yeah from the school work I did It was pretty clear that Im gonna need a better grasp of the electrical. My next goal is to be able to read diagrams better.

I didn't realize that there would be more school with the union gig. That's great though. Before I started school I had accepted the fact that it's going to be a lifetime of learning and buying tools and all of that.
Absolutely, a good tech realizes they will never know it all.
Most of your issues will be electrical based. A lot of apprentices think it’s all about gauges and refrigerant, but your meter will be your most used tool besides a multi screwdriver.
What area/local are you in?

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Local 404, Lubbock Tx.

16. https://www.fluke.com/en-us/learn/bl...-safety-videos
Not exactly what your looking for, but something for consideration

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