How A Thermostat Adapter "Creates" A Neutral?

Thread Starter

PGB1

Joined Jan 15, 2013
139
Hi All!
I installed a new "smart" thermostat called ecobee3 Lite. Normally, this thermostat requires a "24 volt common" wire from the system's transformer. This way, the thermostat has 24-Line and 24-Neutral. In the kit, there was a magic box called Power Extender Kit that will allow the common to be skipped if none is present at the thermostat.

At the transformer, reading across the secondary, one gets 24 volts AC. For clarity, I call the side heating people call "common" the neutral & the side they call "R" the line side.

One wires the thermostat R (24-Line) G (fan), W (heat) & Y (cooling, if present) to the power extender and wires the power extender's R, G, W and C (24-neutral) to the heating/cooling system control board.

I'm curious how this device can create a neutral for the thermostat to use? Do any of you know how it can supply both 24-Line and 24-Neutral to the thermostat?

Here's a link that shows a wiring diagram: https://support.ecobee.com/s/articl...rmostat-with-the-Power-Extender-Kit-no-C-wire
Click the Drop Down arrow where the page says "Installing the PEK with ecobee3 Lite or ecobee4" Scroll down for the wiring diagram.

Thanks for explaining what my mind can't figure out.

Paul
PS: Since I have separate heating and cooling machinery, I ran proper wiring with the common (skipping the power extender), so I didn't get to test around on the powered device.
 

MisterBill2

Joined Jan 23, 2018
18,388
My guess, based on the fact that when the control switches in the thermostat are open, that there is a voltage across them, usually 24 VAC. My guess is that it uses the heat switch voltage to charge a battery to provide the required voltage needed for operation when the switches are closed. Certainly the electronic thermostat logic and memory do not require very much power.
Actually, it may also use the compressor control and fan control voltages as well, and it might have a "superCap" instead of a battery.
Since heating and cooling are never on at the same time, that could work fairly well. Sneaky but really smart. ALSO, just an educated guess. I have no way toprove it. But what else could do it???
 

Thread Starter

PGB1

Joined Jan 15, 2013
139
Thank You, MisterBill2, for taking time offer explanations.

Does this make sense?:
Since the power extender can operate with only R (24 +), G (fan) and Y (cooling call) and G & Y are energized at the same time, I think your battery or super capacitor thoughts sound logical. The storage will charge during off cycles.

In each of the wiring instructions, "Y" has to be present and you mentioned the compressor control. That board is always energized in cooling season.

Just this morning, I received a junk e-mail telling me about something called a "Common Maker". It does essentially the same as the ecobee power extender, but can use only R & W. (Wonder how they knew I was searching about this topic? Scary, huh?)

It would be kind of fun to tear one apart and see what makes it tick.

Thank You Again,
Paul
 

MisterBill2

Joined Jan 23, 2018
18,388
Thank You, MisterBill2, for taking time offer explanations.

Does this make sense?:
Since the power extender can operate with only R (24 +), G (fan) and Y (cooling call) and G & Y are energized at the same time, I think your battery or super capacitor thoughts sound logical. The storage will charge during off cycles.

In each of the wiring instructions, "Y" has to be present and you mentioned the compressor control. That board is always energized in cooling season.

Just this morning, I received a junk e-mail telling me about something called a "Common Maker". It does essentially the same as the ecobee power extender, but can use only R & W. (Wonder how they knew I was searching about this topic? Scary, huh?)

It would be kind of fun to tear one apart and see what makes it tick.

Thank You Again,
Paul
It is indeed "scary" to see how much the various platforms analyze what you search for. That activity recently lead to some effective legal actions against one social media provider targeting kids with "the wrong stuff" to the point of doing harm. Actually it is more like "pushing dope", except far cheaper to do and targeting a much wider realm of targets.

So I see that Artificial Intelligence will ultimately be more like dumping poison into the water-hole . The damage done by bad-actors using it will outweigh all of the benefits it could supply.
Like a lot of things in the past, the full number of damaging abilities will take a while to become clear and obvious. A bit like FREON took a while to show any bad effects, only this time much worse.
 
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