Sam Brown

[Sam Brown]

Absorbing heat and chilling the air are really just two sides of the same coin. You can’t have one without the other. In order for the refrigerant to absorb heat, it has to extract that heat from the air, thereby cooling it. In order to chill the air, it has to absorb the heat from the air. That heat won’t just go away by itself!

Let me know if that’s still not clear.

[Sam Brown]

Hi Jim,

You’re right, that was a typo! I’ve corrected it and rephrased that whole paragraph to make it clearer.

Thanks for letting us know about this!

[Sam Brown]

Keep in mind the rule about schematics vs. wiring diagrams: wiring diagrams show the circuit as a human sees it, whereas schematics show the circuit as electricity sees it. Because of this, it’s difficult (if not impossible) to identify EEPs using a wiring diagram, since EEPs are all about the way electricity sees the circuit.

[Sam Brown]

Trust the schematic on this one. That table in the technical data section is just showing what the specs are for the different components — it’s not enumerating exactly how many there are of each in the unit.

Also keep in mind the wording of the question. We want to know how many elements there are in each oven, not how many there are in the unit as a whole.

Let me know if anything is still unclear!

[Sam Brown]

Yes, that’s correct! Since these are parallel circuits we’re talking about, each bulb has its own path to line and neutral, so one is unaffected by the state of the other.

[Sam Brown]

We don’t have a particular brand/kit of wire connectors that we recommend. However, there are some types of connectors that we do recommend having on hand (and some we recommend against!).

For wet environments, wire nuts that already have silicone grease inside them are great. That way, you don’t have to worry about applying the grease yourself after the fact to make the connection waterproof. Click here for an example of these.

For environments that aren’t wet and aren’t super hot (you’ll want porcelain nuts for hot places), we’ve had the best results with crimp-on bell connectors. These actually make for a better, longer lasting splice than the standard screw-on plastic wire nuts. Click here for an example of them.

You’ll still want to have some of the screw-on type around, since you don’t always have the room to crimp on a bell connector.

What we definitely don’t recommend are butt connectors like these. They’re a hassle, and they don’t make for very reliable connections, nor are they as reliably waterproof as the silicone-filled nuts mentioned above.

[Sam Brown]

Hi Phil,

Could you let me know which unit in the course makes reference to that webinar?

Sam

[Sam Brown]

Hi Philip,

In units that have them, the cold control is part of the air flow system, because part of its job is to switch the evaporator fan motor on and off. So yes, repairing a stuck cold control would be part of restoring proper air flow.

[Sam Brown]

Yes, you got the math exactly right!

One small correction: it would be 1352 watts, not volts. Remember that “P” in the equation means power, so we’re solving for units of power (watts), not units of voltage (volts).

Great work!

[Sam Brown]

Hi Steve,

Each of those different prefixes (kilo, Mega, milli, micro, and so on) is just a shorthand name for a certain amount of something.

For example, the “Mega” prefix means one million (as shown on the chart), so 1 Megavolt is equal to 1,000,000 volts. Another example would be a kilometer — since “kilo” means one thousand, 1 kilometer just means 1,000 meters.

And it works the same way with prefixes indicating small amounts, like milli or micro. The only difference is that these are names for fractional amounts. Milli means 0.001 (one one-thousandth) of something. So a millivolt is 0.001 volts, or one one-thousandth of a volt.

The math to convert between these units is (fortunately) very simple. If you want to move down a step in the table, just multiply your amount by 1,000. To move up a step, just divide by 1,000.

Here’s an example: I have 15 Megawatts of power, and I want to know how many watts that is. A “normal” unit (with no prefix) is two steps below Mega on the table. So that means that I have to multiply 15 by 1,000 twice. The first time gives me 15,000, which is the number of kilowatts that I have, and then the second time gives me 15,000,000, which is the number of plain old watts that is equal to 15 Megawatts.

Let me know if anything still isn’t making sense.

[Sam Brown]

Hi Joseph,

Here’s the equation in question: P = I^2 * R

A couple of things I can point out. First, that’s actually the letter “I”, not the number “1”. “I” of course stands for “current”, as it does in every Ohm’s law equation.

Second, the “^” symbol is used to denote exponents. So I^2 means “I to the second power”. In case you’re rusty on your exponents, that just means I * I. If it were I^3, that would mean I * I * I, I^4 would be I * I * I * I, and so on.

Let me know if there’s still anything about that equation that’s confusing you.

[Sam Brown]

Hi Phillip,

This question is about how to calculate equivalent resistance. That was covered in detail in the Equivalent Resistance video from the lesson — the same one I mentioned in my last post. Review that video if you haven’t already.

I’ll give you hint — you don’t even need to do any math to answer question 18. You just need to understand equivalent resistance and the general rule about how large the equivalent resistance is compared to the resistance of the loads in parallel. That rule was also mentioned in the video on equivalent resistance.

If you’re still unsure about the answer to this question after reviewing that video, please write me back telling me exactly what’s still confusing you.

[Sam Brown]

Hi Phillip,

Question 17 is asking why a shunt or a short in parallel with a load is not an example of a parallel circuit. This was explained in one of the videos in that unit — the one titled Equivalent Resistances in Parallel Circuits. I recommend you review that video if you haven’t already.

If you’re still unsure about the answer to this question after reviewing that video, please write me back here in the forums telling me exactly what about the question is confusing you.

[Sam Brown]

Hi Lhodo,

There are a couple of problems with using the temperature display as part of your testing.

First, you would have to determine whether the display is showing the actual current compartment temperature, of if it’s just showing the set temperature. More often than not, it will only display the set temperature.

Second, even if you are able to determine that the display is showing the actual temperature, then you still have to contend with the fact that the display is showing what the control board interprets from the input it gets from the thermistor. Sometimes the sensing circuit on the board can fail in such a way that the thermistor is in spec, but the board doesn’t interpret the data it receives from it correctly.

Long story short, the only way to do a surefire test on the thermistor is to take a measurement on it directly.

[Sam Brown]

Hi Phillip,

Could you please tell me what about question #1 is causing you trouble? I can help you better if I know where your confusion lies.

[Author]

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