Sam Brown

[Sam Brown]

if there is an issue with return current where does the burner head come into play?

We’re seeing the spark make it all the way out of the electrode, so an educated hypothesis is that something after that point in the circuit is interrupting the current flow. And the burner head is the first step on the current’s journey through the appliance chassis back to the DSI board; it’s the big hunk of metal that the spark wants to jump into.

If that burner head isn’t properly seated, or maybe if it’s covered in gunk that insulates it from the rest of the chassis, that could certainly mess with your return current.

Make sense?

[Sam Brown]

Sorry for the slip up calling you Scott last night.

No worries! Happens more often than you would think. 😉

[Sam Brown]

Gauge, as its name suggests, is what you would see if you used a gauge for measuring the pressure, so it’s the more practical one for us to use in a real-world situation like this. But Scott could have just as well used absolute instead of gauge. It doesn’t really matter which you use, as long as you make sure you don’t get them mixed up.

[Sam Brown]

Make sure to use inHg gauge, not absolute. If you do that, you’ll get around -1.5 inHg in the Danfoss app, which is almost exactly the same value that Scott got in the video, except negative.

Why didn’t Scott include a minus sign in the video? Because he’s talking about inHg Vacuum — “Vacuum” meaning the negative end of the inHg gauge scale.

[Sam Brown]

It’s hard to talk about this without looking at the schematic together, so I’ll go ahead and show this schematic markup — see if it makes sense to you.

[Sam Brown]

I think you might be looking at the heater PCB (control board), not the heater itself. The heater itself is connected to the heater PCB at 32-2. See if you can trace out what the other end of the heater is connected to and deduce which side is line and which is neutral.

[Sam Brown]

WAIT, I think I am beginning to see it now. Sorry for the inconvenience, I was getting a little frustrated with myself. I just reviewed the schematic and found something I did not realize. Part of learning I suppose.

Great to hear! Sometimes a little persistence is all it takes to have that “aha!” moment.

But if you still have any specific questions about these units, let me know!

[Sam Brown]

Hi Darren,

Yes, differences like that between your results and Scott’s are just due to tweaks that have been made to the app since that video was recorded. Those are very small variances which would not make a difference in an actual troubleshooting scenario.

[Sam Brown]

The relays are open as shown, you are only measuring N-N.

That’s exactly what EEPs are — two points in a circuit that have the same electrical potential. In this case, both of those points have 0 volts of potential, regardless of whether the relay is open or closed.

Does that make sense?

[Sam Brown]

What that question is asking about is devices like triacs and relays, both of which allow the board to use low-voltage DC power to open or close a switch — thereby switching AC power on and off. That’s why you can say that they’re controlling AC loads using DC power.

Does that make sense?

[Sam Brown]

Another question has formed in my mind…watching the Practical Sealed System Thermodynamics video…the term Cap Tube separation is mentioned as a possible reason for the shift in the vertical line down to the Evaporator Coil…what does Cap Tube separation mean..? Thx

I believe what that’s referring to is how the capillary tube separates the two different pressure zones of the sealed system. There’s the high-pressure side located after the output of the compressor (that’s where the condenser is), and then there’s the low-pressure side before the input to the compressor (that’s where the evaporator is).

Make sense?

[Sam Brown]

Good question! There’s an important (and slightly unintuitive) rule for situations with parallel loads: equivalent resistance. If you don’t remember how it works, you should review Module 3, unit 5 of Core. We have a video there that explains how it works.

[Sam Brown]

Yes, one timer motor operates multiple cams. That’s how they manage to use one motor to operate all the timer switches in the machine.

[Sam Brown]

Scott just threw that out as an example of a clamp-on thermocouple — he didn’t mean for it to be a hard and fast recommendation. In fact, he doesn’t use that kind of thermocouple himself. Usually what we use are K-type thermocouple probes — like this one: https://www.grainger.com/product/1T322?gclid=EAIaIQobChMI8MPL5cbs6wIVivHjBx2XzAt9EAQYASABEgLugvD_BwE&cm_mmc=PPC:+Google+PLA&ef_id=EAIaIQobChMI8MPL5cbs6wIVivHjBx2XzAt9EAQYASABEgLugvD_BwE:G:s&s_kwcid=AL!2966!3!264955916540!!!g!436873882546!&gucid=N:N:PS:Paid:GGL:CSM-2295:HRLBWZ:20500731

The point with thermocouples is not the specific type you use, but rather that whichever you use, you make sure it makes solid contact with whatever you’re trying to measure. Whether that be with a clamp or with a thermocouple probe that’s securely taped on to the condenser coil is up to you.

[Sam Brown]

A cam is a very simple mechanical device that you find in many different applications, from sewing machines to car engines to timer motors. All it is is an oval-shaped disc attached to a shaft. If the shaft rotates so that the long part of the oval is facing an actuator, the actuator will get pushed down. In the case of a timer motor in an appliance, this actuator would be a switch contact.

This demonstrates their action pretty well:

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