Susan Brown

[Susan Brown]

1. A twisted door boot

2. Broken drum support spider
Failed support shock/shocks

If those don’t make sense, let me know!

[Susan Brown]

Hi Denis,

I think you were saying before that there would be no voltage drop when there is only one load in the circuit.

If you think I said that, I would want to know where so I can see if I misspoke or wasn’t clear, because that is incorrect.

When current flows through a circuit, there will be voltage drop across any of the loads (resistances) in the circuit. The total voltage drop will equal the source voltage. So, if there is only one load, all of the voltage drop will be across that load.

Please rewatch the second video in Unit 4, particularly starting around the 4 minute mark, where I discuss voltage drop and how to calculate it. Can you tell me what the voltage drop would be across the 40-ohm load in Circuit B?

As for the measurements you mentioned that you did (a ring and a heating element), we would need to see the circuit for those items and where your test points were to help.

[Susan Brown]

Asking questions is good and always welcome!

[Susan Brown]

Hi Denis,
It’s good that you are thinking about this – voltage drop is an important concept!

Every valid, functioning circuit will have a voltage drop because it will have one or more loads in it.

[By “valid, functioning circuit” I mean you have a complete circuit, voltage, and at least one load in it. So current is flowing and the load is doing “work” (movement, heat, light, etc.).]

If you have just one load, the voltage drop across that load will equal the supply voltage. So, if we have an L1-N circuit, with one load, it will have 120v drop across it. That is why we draw circuits with Line on one side of the load and Neutral on the other.

If we have two or more loads, then the *sum* of the voltage drops across the loads will equal the source voltage. And the voltage dropped across each individual load will be in proportion to the resistance of that load relative to the total resistance in the circuit.

I hope that helps!

[Susan Brown]

In a gas burner spark reignition system, how does the spark current return to the spark module after it leaves the electrode?

Through the appliance chassis

[Susan Brown]

Hi Carlos,

It’s a challenging Module! Asking questions is good 🙂

When a shunt is present, *all* the current will flow through it instead of going through the path with a load. That is because there is no resistance in the shunt.

So in circuit B, no current will flow through the heater. That is usually the point of shunts – to bring loads in and out of the circuit depending on what is needed at various times.

As for Req: The most important thing to remember about Equivalent Resistance of parallel loads is the Rule of Thumb: the Req will be something less than the smallest resistance. It’s not too often that being able to calculate it would be really important.

See this Forum Post for more, including another video showing how to calculate it.
https://my.mastersamuraitech.com/appliance-repair-course-support/student-forums/topic/equivalent-resistance-vs-total-resistance/

Let me know if that helps.

[Susan Brown]

Hi Denis,

“Voltage is the same in each parallel branch of the circuit.”

Let me know if you have questions about that.

[Susan Brown]

Thanks!

[Susan Brown]

Thanks! That’s helpful. I’ll get our tech team to answer these.

[Susan Brown]

Hi Daniel,
Thanks for the questions! If any of these are connected to information in the videos in the unit, could you please tell us which video(s) and approximately where in the video? That will help us respond to you more quickly. Thanks!

[Susan Brown]

It is a lot! For most of our students this is their first time learning this type of refrigeration material. It definitely takes time and practice to really get a strong grasp of it. We try to keep the quizzes pretty straightforward so you can get through them, but hope that students will revisit the material later so they can continue to get more familiar with it.

[Susan Brown]

I have an appointment this evening, so no time right now for more detailed help. Here are the answers – see if they make sense, and if not, let me know.

You can use the transcript search on the videos to find where we talk about things.

What are some “non-invasive” and zero disassembly methods for half-splitting a warm refrigerator problem between the sealed system and everything else? (Choose all that apply)

I answered this above

Did you mean the iceball question?
Answers: Early-stage leak
Undercharge

With a low side leak, how would you expect the high side pressure to compare to normal?

Higher

Question #6 – With a complete capillary tube restriction, how would you expect the compressor run current to compare to normal?

Lower

[Susan Brown]

Hi John,

Lots of techs in the Appliantology community work on LG refrigerators – the key is to be able to reliably troubleshoot down to the correct component so that when you replace a part, it fixes the problem. This makes it a good value for the customer, and makes sure you are not losing money on jobs.

That is the main point of taking the MST training – to be able to troubleshoot well!

[Susan Brown]

A few high-end fridges have ports for measuring pressure, but for most refrigerators it is invasive – you have to pierce the lines.

Besides amps you can measure temperatures at strategic locations to get information about the sealed system functionality.

Danfoss App: They made a small change to their app that makes the numbers slightly different than what we show. No biggie!

[Susan Brown]

Hi Jonathan,
I sent you answers via email.

More on the thermistor:
If you have only one load in a circuit, it will always drop the source voltage (120v for a fridge), no matter what.

When you have two or more loads in series, the voltage drops will add up to 120v, and will be proportional to the resistances.

Example: If one load is 10 ohms and the other is 20 ohms, you’ll have 40v drop across the first and 80v across the second. But if the 10 ohms load changed to a 20 ohm load, then you would have 60v across each one. (I’m not saying what the typical resistances are with thermistor circuits, but just showing how it works.)

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