Susan Brown

[Susan Brown]

The fact that I’m reading 0 across the heating element means that there is an issue with one side of the 120s

That is correct, although you can be more specific about what you mean by “issue”.

240 being direct current only reading 120

I’m not sure what you mean here. This is an AC circuit, not DC. Is any current flowing in this circuit anywhere?

When we measure L1 wrt N or L2 wrt N, we would expect to read 120v each, because we’re just measuring one phase of power.

Where would we normally expect to read 240v in an L1-L2 circuit?

L2 is not present. When you disconnect it it’s just reading L1 threw out the circuit . l2 is open

Are you looking at the diagram on the Midterm? (It is a little different than the similar one in unit 6.) Which measurement changes after we disconnect one side?

[Susan Brown]

Correct! I moved your topic on Question 9 to a new topic

[Susan Brown]

Okay, good!

The Safety is 120v.
The Main Coil is [answer hidden]

How does this leave the Ignitor and the Booster?

• This reply was modified 3 months ago by Susan Brown.

[Susan Brown]

Main coil igniter and booster 40 vd each due to being in series

There are several reasons this is not correct. For one thing, voltage drop is proportional to resistance, and we haven’t given you any information on the resistance of these loads. Second, if all 3 of these loads are getting current, this is a series-parallel circuit scenario, which would require some complicated calculations.

However – none of that is necessary. Big hint: One of these loads is not getting current.

The key is to recognize the function of the closed detector switch.

Do you have any ideas about that?

[Susan Brown]

Okay. If you haven’t, see the Appliantology 101 short course, specifically units 2 and 3.

[Susan Brown]

Hi Jacob,

Question #4 – What does an oven’s gas valve need in order to open and release gas?

From the unit:

The gas valve has a specification for how much current must flow through it in order for it to release gas into the burner. The ignitor’s resistance lowers the hotter it gets, letting more and more current through. Once it is hot enough to allow the current to reach the valve’s spec, the valve opens,

I bolded the pertinent parts – heat is involved, but not the key component.

• This reply was modified 3 months ago by Susan Brown.

[Susan Brown]

Correct!

Now the next step is to figure out what is going on with the other 3 loads, if they are in series or parallel with each other.

The Main coil is wired in series with the Ignitor and Booster, which are in parallel with each other. Normally, when we have a series-parallel configuration, the voltage drops are impossible to determine unless we give you the resistances so you can do some calculations (like I show in one of the videos for Unit 5).

***But that closed detector switch changes things significantly, and allows us to know the voltage drops without needing to do any calculations.

Do you have any idea what that might be, or do you need another hint?

[Susan Brown]

That is not quite right.

Only loads in series will split voltage up (Kirchhoff’s Law)

The important thing to remember about parallel circuits is that they are independent circuits that happen to be tied together at the power supply. Other than that, what happens in one does not affect the other.

Also remember that if a circuit just has a single load in it, the voltage drop for that load will equal the source voltage.

So, for example, the Safety is in parallel with the other circuits in this scenario. It has full, independent access to L1 and N. What will its voltage drop be?

[Susan Brown]

Hi Kevin – have you activated your Appliantology membership yet? That is usually where we want students to post questions about specific repairs that they are working on. The Ask the Teacher Forums are mostly for questions directly about the course content or quizzes.

[Susan Brown]

Okay – you’re all set!

[Susan Brown]

I can reset the quiz for you so you can retake it – there’s always another chance! I assume you’d like me to do that?

[Susan Brown]

Hi Ronald,

The two answers that are not invasive and do not involve disassembly are:
Temperature
Amps

Measuring pressure is invasive and looking at the frost pattern requires disassembly.

Let me know if you have any other questions.

[Susan Brown]

Hi Dale –
I assume you are talking about the “Kleinert” book that we have some assignments from. See the Orientation module, unit 1, Preflight Checklist item 4.

Also see this topic here in the Forums:
https://my.mastersamuraitech.com/appliance-repair-course-support/student-forums/topic/link-for-the-pdf-textbook/

[Susan Brown]

Basically:
While the fridge is running, you would use the schematic to find the pin locations for the sensor so you could measure the voltage across it (DC voltage). You would need to know the specifications (from the service manual/tech sheet) so you would know how to interpret the number you get. Not all manufacturers give voltage drop specs.

[Susan Brown]

Hi Zachary,

When looking at schematics, it can sometimes be hard to see if a load is in series with other loads or in parallel. Some people are good at tracing the voltage lines out by just looking at them, but for some it’s helpful to think of it the way we describe – imagining that we are the load, and reaching out with each hand to touch Line and Neutral at the power supply (or L1 and L2 if it’s a 240v circuit). We will take the easiest route – if there is a shunt (often a closed switch), we will take that to avoid going through another load. It’s just a little visual trick to help us out.

As you get more into the Troubleshooting material, you’ll learn more about why it’s important to be able to see how a load is laid out in a circuit, relative to other loads in the appliance.

Does that help?

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