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Great question! From a technical perspective, a capacitor in a circuit is an open. And in a DC circuit, this is always true in the practical sense as well.
In an AC circuit, things get a little more complicated. Because polarity is constantly reversing, you can still have current flow in a circuit with a capacitor. However, the capacitor must be rated for the frequency of the voltage in the circuit. Otherwise, there still won’t be any current flow.
In summary: current can never flow in a DC circuit with a capacitor. In an AC circuit, current can flow if the capacitor is sized for the frequency of the voltage in that circuit.
Every voltage measurement just boils down to the meter detecting the difference in electrical potential between your two probes. We quantify electrical potential as volts.
Line should have a potential of 120 VAC when compared to neutral, and neutral should have a potential of 0 VAC when compared to line. That 120 volt difference between the two is what your meter picks up.
So if you want to confirm that you have a good neutral, you have to check if that neutral really has 0 volts with respect to line. The way you check for this, of course, is to simply put one probe on line, the other on neutral, and then see if your meter detects a 120 VAC difference between the two points.
Doing this kind of measurement is very common — it’s not peculiar to this particular diagram.
Is that any clearer?
Don’t worry, we’re not in the business of shooting our students! As for your question:
At minute 13:44, Scott said that if we get 120v between Connect 5- Pin2 and COnnector 7-pin3. Can you explain why it was good to measure 120v? I thought getting 120v there means there is an open, and getting 0v means there’s continuity?
Whenever you make a measurement, you always have to keep in mind exactly what you’re measuring for. What you’re thinking of is measuring across a switch — in other words, putting one lead on one side of the switch and the other lead on the other side. If that were the case here, then you’re correct that 120 VAC would mean open and 0 VAC would mean closed.
What we’re doing with the measurement at 13:44 is not reading across a switch. Rather, we are checking for the presence of a good neutral at connector 7, pin 3, with respect to a known good line at connector 5, pin 2. In this case, a reading of 120 VAC indicates that you do indeed have a good neutral, since that’s the expected difference in electrical potential between a good line and a good neutral.
Make sense?
In the video it says its an unintentional electric path between a power source and a grounded surface
That’s one definition of a ground fault. Another definition is when there is less current on Neutral than there is on Line. If you think about it, this is just a follow-on effect of current flowing to ground — if you have some of your current flowing into ground, then you’ll have less current flowing through Neutral. And the current on Line will be the sum of the current flowing through both Neutral and ground.
This current imbalance between Line and Neutral is a ground fault, and it’s what a GFCI device detects.
Hi Shawn,
Sorry that didn’t get back to you — you’re right, the error that the Sperry is showing is undocumented. I can’t find anything on what three lights means. Either the Sperry has gone whacky or something is seriously messed up about that outlet.
Speaking of which, your readings with your meter don’t make much sense either. Were you using the LoZ function, or just the normal VAC function?
Refrigerator and AC sealed systems work in fundamentally the same way, but there are some key differences. A big one is that refrigerators have defrost heaters, whereas AC units usually do not — there’s no need for them to have them, since their saturation temperatures aren’t low enough to cause frost accumulation.
The failure you’re describing (frost buildup on the evaporator coil when there is a lack of airflow) does happen in refrigerators too. However, it’s usually less noticeable because the defrost system mitigates it.
The meter leads that we use for getting into tight connectors can be found on Amazon. If you search for “Pamona meter leads”, you’ll see a bunch of different lead sets containing fine-tipped leads like those.
The spark module produces the spark, not the electrode. The electrode is just where the spark is supposed to come out of. Let’s say that you yank the spark wire out of the electrode, but leave the other end connected to the spark module, and then touch the spark wire to the chassis. You’d get quite a spark — no electrode required!
Remember the findings in one of the previous units:
To verify the problem, you trying lighting all of the surface burners. All light except for the LF. You do hear sparking when the LF burner is turned on, but it sounds much softer than the other burners. You also smell gas coming out.
This told you that the spark module is doing its job and sending out the spark voltage, but the spark isn’t reaching the electrode. And the component that’s between the spark module and the electrode is…?
If a refrigerator has a full-blown computer board, then all the defrost functions will be built in to that. They will definitely not have an ADC board.
ADC boards are only present in models that do not have a more sophisticated computer board.
We cover just about everything there is to do with sealed systems and getting certified for them in Module 3, unit 5 of the Refrigeration course. If you have a specific question about the material of that unit, let me know.
I’ve noticed that a lot of your forum questions recently have been about things that are directly answered in the course material. We’re always happy to help you out, but you need to put in the effort to absorb what’s taught by the course before asking. Otherwise we’ll just direct you back to the coursework!
Make sure to always reread the text and rewatch the videos in the relevant part of the course before posting here. Make lots of notes, too. Odds are that your questions will be answered in the coursework, and that will end up saving you time and improving your information retention.
Assuming that you’re referring to the last video in that unit, then no, it would not mean that something is necessarily wrong at your 240 VAC outlet. The schematic drawn out there is very simplified, because it is focused on just the heating element. The most common cause of a missing line to one side of an electric heating element is a failed control somewhere in that circuit, such as a thermal fuse.
So yes, the scenario shown in that video is a failure that happens pretty commonly in electric dryers, and the culprit is usually a failed control component in the heating circuit.
Remember what the purpose of a start device is: it’s to take the start winding out of the circuit once the motor has started. If it doesn’t do that, then the motor will draw excessive current, so much so that the overload protector will go open, shutting off the motor.
TSDs almost always fail shorted, meaning that they are no longer able to take the start winding out of the circuit. So yes, as the video said, the compressor will run for 10-15 seconds, and then get shut off by the overload protector.
How do you check the amp draw? Just like you would for any other circuit. Put your amp clamp around one of the wires and see what it tells you!
Check out the last video in module 1, unit 10 of the Refrigeration course — it goes into detail about the differences between TSDs and PTCs and how to troubleshoot them both.
What kind of start device are we talking about here? Is it a TSD on a refrigerator compressor?
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