Sam Brown

[Sam Brown]

We covered it earlier in the Oven and Range course — Click here to review that unit.

[Sam Brown]

This question uses terms that are all introduced in the video for this unit. Before we go any further, I recommend that you rewatch the video, since it essentially gives you the answer to this question.

If, after rewatching, you’re still not clear, let me know and we’ll go over it some more.

[Sam Brown]

Flame rectification is an important part of how reignition systems detect the flame at the burner. We have a video that goes into it in depth in module 7, unit 4 of the Oven and Range course (which I think you’re just about to start on). So stay tuned for that!

[Sam Brown]

Correct! Since it’s not trying to sense the presence of a flame, there’s no need for the spark current to return to the spark module in a regular ignition system.

[Sam Brown]

You’re correct that, in the first question of this unit’s quiz, we’re just talking about an ignition system, not a reignition system.

With that in mind, does it even make sense to talk about a “return path” for the spark current?

[Sam Brown]

For the exam unit 5 question #5 asks about the test point I choice L1 to N because there’s a fuse in series with that side of that capacitor so I would measure those 2 points first to indicate I’m still getting my line voltage input then if I do I can precede to check L2 to neutral to see if the noise filter is putting out the voltage I just find it better to follow sequence in order.

Remember that in question #4 it’s stated that all those components of the noise filter (including the fuse) are contained in a box — and therefore inaccessible. You’ve also been told that you have a good power supply to the noise filter. Your next logical test should be to measure the output of the noise filter.

Also for the video in this unit 5 the half splitting master Samuria was able to demonstrate getting 120v L1 to ground chassis with the dryer running and 0v through L2 to chassis and motor not running did he do this demonstration having the door open ? And then closed it to get the motor to run and get that 120v.

That’s most likely what he did, yes. He started up a heated cycle, then opened the door to switch off the motor while he checked for voltage at L1.

[Sam Brown]

so if we measure after R For example bk to orange we will get a voltage reading since there is a open?

Yes, with the thermal fuse open, you would read 240 volts between BK and OR (assuming the machine is set to run). This is because you’re simply measuring the difference between L1 and L2.

lets say we measure across the heating element on this circuit with nothing open we will get 240v?

Yes, we would also measure 240 volts in this situation. If all the various switches and controls are closed, that means we have a good circuit with current flow. Since current is flowing, all of our 240 volts will drop across that heating element, and so your meter will show a voltage difference of 240 volts when you put your probes on either side of the element.

but for instance let’s say the thermofuse is open or the contacts between bk and R is open we wilL read 120v across the element because we will only we getting 120v from L2?

This is where it gets a little bit tricky. With the thermal fuse or the timer contacts open, you would not read any voltage difference when you put your probes on either side of the element.

The reason for this is that with the circuit open, there’s no current flow, and therefore no voltage drop across the element. Assuming you have the machine set to run, you would in fact have 120 volts present at that element (from L2 through the centrifugal switch). But you won’t measure any difference across the element, and therefore would read 0 volts on your meter.

Things making more sense now?

[Sam Brown]

An excellent observation!

Keep in mind that, whenever you make a voltage measurement, you’re measuring the voltage difference between two points. This means that if you measure across a closed switch, you’re going to read 0 volts no matter how much voltage is present there, since your two measurement points are electrically equivalent. That’s why we could make that test regardless of whether L2 was present or not.

Let me know if it still doesn’t make sense.

[Sam Brown]

Both of these questions are actually addressed in the video on electronic commutation, so I recommend that you give it another watch. Make sure to take notes so you don’t forget any important bits!

If, after rewatching it, anything that’s covered in the video still isn’t clear to you, by all means post it here. Make sure to include what timestamp in the video your question pertains to.

[Sam Brown]

Yes, simple as that! It’s the thing that’s not doing its thing, so it’s our LOI. Now that we’ve identified that, we can move onto figuring out why it’s not working properly.

Make sense?

[Sam Brown]

The short definition of an LOI is just “the thing that’s not doing its thing.” We’re not trying to conjecture about potential causes of the problem at this point — that’s getting ahead of ourselves. Right now, we just need to focus in on the load that’s not doing what it’s supposed to be doing.

Given the information from the previous two units in this case study, which load would that be?

[Sam Brown]

In fact, here’s an image of a split-phase motor taken directly from a dryer schematic. You can see the two windings and the three terminals, like we’ve been talking about:

On this particular schematic, the common terminal is the one on the left-hand side of the motor. You can see that it’s connected to both of the windings (which is what makes it the common terminal).

The image also shows the centrifugal switch, which takes the start winding out of the circuit after the motor has started spinning.

[Sam Brown]

So on a compressor motor there are three windings

No, there are only two windings on any split-phase motor — start and run. But there are three terminals, one particular to each winding, and then one that is common to both.

This is not specific to compressors. Split-phase motors are configured this way across various appliances.

[Sam Brown]

Here’s a helpful picture showing the windings of a split-phase compressor motor:

You can see that there are three terminals on the motor: the start terminal, the run (or “main”) terminal, and the common terminal. As you might expect, the start terminal is connected to one end of the start winding, the run terminal is connected to one end of the run winding, and the common terminal is connected to the other end of both windings.

To measure the resistance of the windings, you would simply make your measurements between all three terminals. Even if the terminals aren’t labeled, you’ll be able to tell which is which by simply comparing your resistance measurements, since the start winding’s resistance will always be higher than the run winding’s.

Just to make sure you’ve got the concept, see if you can figure out which terminal is which on the image where the terminals are just labeled as X, Y, and Z.

[Sam Brown]

Sorry for the delay in getting back to you, Phillip! Could you copy and paste the text of the question you’re having trouble with and post it here? I’ll be able to help you best that way.

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