Scott Brown

[Scott Brown]

In the the first video for refrigerators it said the suction line bring the refrigerant gas back into the compressor and turns it back to a liquid ?

Watch the video starting at 0:42. It explains that the compressor is a pump that pumps the refrigerant gas into the condenser where it is cooled and converted back into a liquid.

Compressors are vapor pumps and cannot pump liquids. In fact, doing so will destroy it.

There’s a lot packed in that short little video and I recommend watching is several times, pausing it and taking careful notes as you go.

[Scott Brown]

Right, gotta read the questions carefully. Looks like you got it.

[Scott Brown]

Hi Dennis,

I use an iPhone app called Tap Forms. I discussed it in more detail in Episode 5 of our podcast. I don’t think it’s available for Android but I’m sure there are comparable apps for this.

Hope that helps!

Scott

[Scott Brown]

P.S. I’ve unblocked you so you re-take the quiz.

[Scott Brown]

Hi Jason,

That’s right! Motors are all about electromagnetism. We go into this in detail in the Fundamentals course Motors module but you get the gist.

Let me know if you have any other questions!

Scott

[Scott Brown]

Make sure your finger is not blocking the receiver eye when you press the paddle. If the eye doesn’t see the beam, the LED will continue to flash.

[Scott Brown]

Hi Dion,

The capacitor does play a role in the reversal of the motor rotation direction. The main thing that needs to happen to reverse the direction of the motor is to reverse the Line and Neutral ends of the start winding. Doing this combined with the capacitor in series with the start winding changes the direction of rotation of that split phase that needed to get a single phase motor to start rotating from a dead stop.

The Line and Neutral ends of the start winding are typically switched by timer contacts, such as one direction for spin and another for agitate in a washer.

Does that help?

[Scott Brown]

Wow, sorry this one slipped by me! It’s a Swiss Army travel bag. I actually looked into buying another one to have as a backup only to find that they’ve been discontinued! 🙁

I’m sure you’ll find something that’s functionally comparable.

[Scott Brown]

Hi Dennis, sorry for the delay in replying to this one! Somehow it slipped by me.

Anyway, to answer your excellent question, the key is to Take note of the compressor behavior along with your resistance measurement.

Remember that the TSD fails short whereas the PTC device fails open. The key difference in compressor behavior between the two start devices is that, in the case of the TSD device, the compressor will actually start and run for a few seconds. But in the case of the PTC device, the compressor will not actually start but sit there and home while it draws locked rotor current until the klixon opens.

[Scott Brown]

Hi Dennis,

First congratulations for almost completing the Fundamentals course! It’s a lot to learn and big achievement, just one more exam to go!

As for schematics, you probably know more than you think– it’s just a matter of applying what’s already in your head and getting confidence in doing that. I would be happy to review your schematic markups.

You may also be interested to know that we have a course that specifically gives you practice reading all kinds of different techs sheets and schematics as well as going into depth on other topics such open neutrals and appliances with multiple control boards: Advanced Schematic Analysis and Troubleshooting

[Scott Brown]

Hi Matthew,

This a great question and great job for reading the Kleinert material!

Most restrictions in refrigerator sealed systems occur in the high side. High side restrictions are also called liquid line restrictions because, after leaving the compressor, the refrigerant condenses quickly from a vapor to a liquid in the condenser. The cause of the restriction can include a restricted filter-drier, a kinked liquid line, a kinked or bent U bend on the lower condenser coil, a restricted solder joint in the liquid line, or an oil-logged or kinked capillary tube.

A restricted liquid line will starve the evaporator of refrigerant, thus causing low pressures in the evaporator. If the evaporator is starved of refrigerant, the compressor and condenser will also be starved. The evaporator will not be absorbing very much heat for the condenser to reject. However, most of the refrigerant will be in the condenser and not necessarily causing high head pressures because of the reduced heat load on the evaporator.

As a result of the low refrigerant flow through the system, the compressor’s current draw will be lower than normal because there’s just not as much refrigerant vapor that it needs to compress.

Be careful about applying the electric current flow analogy to a the vapor-compression cycle in a refrigerator because there’s some entirely different physics at work here!

[Scott Brown]

Hi Igor,

Please see my reply in your topic at Appliantology: http://appliantology.org/topic/54562-converting-dryer-from-lp-to-natural-gas/

[Scott Brown]

going back to the first half why aren’t we getting voltage across the timer even though cycling thermostat is closed isn’t the load that makes one side of it L1 and the other side L2

Because when the cycling thermostat is closed, L1 is on both sides of the timer– same voltage so no voltage difference. Also, as explained in the lesson, when the cycling thermostat closes, it shunts the timer motor. Be sure to re-watch the lesson screencast. Also watch the other video I posted for you.

let’s put it this way how if I add a load next to cycling thermostat (parallel) circuits won’t we get timer running

For starters, the timer motor is already in parallel with the cycling thermostat. If you added another load in parallel (so the timer motor, cycling thermostat, and added load) all three would be in parallel with each other.

With the cycling thermostat closed, it shunts the other two parallel branches and all the current flows through it. That’s the way shunts work– they by-pass loads. When the cycling thermostat opens, the added parallel load would also have a 240vac supply because it’s part of a parallel circuit. How the heater is affected depends on the equivalent resistance of the timer circuit and the added parallel load. If that equivalent resistance is low enough, the heater output watts could increase to the point that the heater gets warm or even hot (when it’s supposed to be off).

Abe, you’re asking questions about basic electricity and circuits that are covered in detail in the BEBC and Fundamentals courses. The course you’re currently enrolled in, Advanced Schematic Analysis and Troubleshooting, assumes you already have a solid background in electricity and circuits on which to build. While I’m happy to help, there’s only so much remedial instruction I can give in the student forum. Also, the ASAT course lessons are only going to get more complicated. You will be lost without a solid basic electricity background. Let me know if you’d like to upgrade to the BEBC/ASAT bundle so you can acquire those essential circuit skills.

[Scott Brown]

when the cycling thermostat is closed you get no voltage to timer motor

The correct term is that there is no voltage difference across the timer. Each side of the timer has L1 so there’s no voltage difference across the timer to drive electrons (current flow).

but when cycling thermostat is open you would get a voltage across the open “thermostat” even though there is a path (circuit) across the timer now.

I think you may be confusing voltage, current or don’t have a clear idea about what they are. These concepts are covered in detail in the Fundamentals and Basic Electricity Boot Camp course. But as a review: Voltage creates the potential for current to flow– it is the driver. Current flows in a valid, closed circuit as a result of voltage difference between two points.

Back to the problem….

in other words why isn’t considered now as same voltage potential (as when the cycling thermostat is closed which is the reason why the timer motor wont advance)

L1 and L2 are both present on each side of the open cycling thermostat even though there is no current flowing through the thermostat contacts. If you place your meter leads on the cycling thermostat contacts when the dryer is running and the contacts are open, you will measure 240vac.

If you’re unclear of the distinction between L1 and L2, this video will clear that up for you: https://youtu.be/zs4HjHhf0x8

[Scott Brown]

Hi Abe,

You’re asking about the timer motor with the cycling thermostat closed and then about the cycling thermostat with the cycling thermostat open. Did you mean to ask about the voltage across the timer motor with the cycling thermostat open and closed?

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