Susan Brown

[Susan Brown]

Haha, we’ve had that question on the quiz for years but only just recently have gotten comments on it. What I’ve done is added the word “only” to the question to remove any ambiguity.

“Which types of dryers run on only 120 VAC?”

[Susan Brown]

Yes, and we had been emailing with you about a month ago about setting up your account at Appliantology so we could upgrade it to the Alumnus membership that you had earned. I just checked and saw that you did set up an account recently, so I just upgraded it. You are now a premium tech member for a year. I’ll send you an email about it.

[Susan Brown]

Hi Trevail (FYI – I moved your question to the Washer, Dryer, Dishwasher Forum)

Here’s a video at Appliantology on heat pump dryers:

https://appliantology.org/topic/105218-whirlpools-hybrid-heat-pump-dryer-system/

[Susan Brown]

Hi Nihar,

I think what he said is that it is a type of closed circuit. A circuit with zero resistance is definitely “closed” (it is not open somewhere) but also is a short circuit, because there is no load (resistance) in it.

Circuits in appliances will always have a load in it by design – an element, fan motor, light bulb, etc. When the circuit is closed, current will flow through it and power the load(s). If a short circuit occurs, that is a fault.

You’ll learn more about these things as you go along.

Does that help?

[Susan Brown]

See the last video, starting around the 20 minute mark. It discusses the water valve being in series with the drain pump, and the implications of that. One thing it means is that if the drain pump winding has failed open, then the water valve would not be able to work. So – if water comes in, that means the drain pump (motor) winding is fine.

Winding: the drain pump is a motor, and motors have windings that the current goes through.

Does that help?

[Susan Brown]

Good catch! We reorganized some things since that video was recorded. Sorry for the confusion! I just added a link to the webinar recording – it is over at Appliantology.

https://appliantology.org/topic/62258-mst-office-hours-362017-neutral-vs-ground-inverter-microwave-digital-communications-more/

[Susan Brown]

FYI – here’s the part of the schematic that shows the circuit:

To get your Appliantology account set up, just go to Appliantology.org and click the red “Sign Up” button in the upper right. Let us know what your username is, then we’ll upgrade your account.

[Susan Brown]

Scott created this sketch for you. First he took the pertinent part of the circuit from the original schematic and drew it as a strip circuit, to make it easier to focus on.

The Heat Sense circuit opens the triac or relay for the test while the motor is running, and uses L1 as the reference for the voltage measurements.

You can see the three conditions that it is designed to sense for below. For the grounded element scenario (where the element has broken and part of it is contacting the chassis), L2 is out of the picture, but there is a circuit from L1 to chassis/ground with current flowing. The resistor in the heat sense circuit has a much higher resistance than the part of the element that is touching the chassis, so essentially all of the voltage will be dropped across it. That is why when you measure voltage at the heat sense location with respect to L1, you get 120v, because you are measuring the voltage drop across that resistor. (Alternatively, if you measured voltage from the heat sense with respect to N, then you would get 0v.)

Take a look and let us know if you have any questions. This is a great example of a modern appliance using some old-school series circuit concepts to accomplish a task. We are planning to do a video stepping through it. Thanks for asking about it!

NOTE – you can right click and open in another tab to get a larger view.

• This reply was modified 4 weeks, 1 day ago by Susan Brown.

[Susan Brown]

Okay, I’ll pass that along to our tech team and see what we can figure out. I understand about your Saturdays. Right now that is the only time we are able to do them. We do post recordings afterwards at Appliantology – did you ever get your membership set up there? I saw that my assistant was working with you to get that set up.

[Susan Brown]

Better to overthink than to underthink! 😀

[Susan Brown]

The correct answer is: Turn on broil and see if you’re getting 120 vac between P20-2 and P1-N at the electronic control board.

[Susan Brown]

When I say “the current here will be different than the current here”, “Here #1” is in the top circuit of the set of 3 parallel circuits, and “Here #2” is in the series portion, as labeled below. As soon as we go past the green dot (up, right, or down), we are in one of the parallel circuits.

The current will be the same along the L1 side of the circuit from the power supply (“L1”) to the green dot. (And, on the neutral side, from the other side of the parallel circuits back to the power supply.) Does this help?

• This reply was modified 1 month ago by Susan Brown.

[Susan Brown]

First I pointed to one of the parallel circuits, then second to the series portion of the circuit, before the set of three. They will have different current.

Is that the part you were looking at?

[Susan Brown]

Hi Andrea,
You are correct. I reset you. FYI – it’s always best to use the Quiz & Exam Reset Request when needed 🙂

[Susan Brown]

Hi Ronnie,

You actually don’t need to calculate the watts to answer this. We know that power is directly proportional to resistance*.

R1 is 5 ohms and R2 is 5000 ohms, which is a 1000 times difference.

The question is “how much work is R1 doing compared to R2?”

The answer is “1000 times less work”

But, to show you the calculation:

I = E/Rt = 120/5005 = 0.024 amps

P1 = I^2 x R1 = 0.024 x 0.024 x 5 = 0.0029 watts
P2 = I^2 x R2 = 0.024 x 0.024 x 5000 = 2.9 watts

* How do we know Power is directly proportional to resistance? One way is that we know voltage drop is (E = I x R) and that power and voltage drop are also directly proportional to each other: P = I x E. The formula P = I^2 x R also shows that P and R are directly proportional.

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