Amazon Smart Thermostat not powering up

JeffDIY

Hoping someone can help.

I have been trying to get my amazon smart thermostat to power up. This is a brand new zone. I have an 18/3 wire to the thermostat. Red to R, White to W, and green to C at the thermostat.

On the other end, it is connected to a TACO SR506 zone controller. The red to the right T, the white to the left T, and the green to the common side of the 24v connection on the left side of the panel.

This is my second thermostat so I know it's got to be something wrong with my wiring. I've tested all my wiring so I know my connections are good. I did notice something that might be the issue, and maybe someone here will know.

When I test the red wire, I show 29.2 volts. I know systems can put out more or less, and this is normal from what I have read. However, I cannot find anything on this. On the entire 24v side of the this panel, all the common wires, in the case, where my white is wired, and where the green is connected all show 3 volts. Should there be and voltage on the common side? Is that the issue why the smart thermostat won't power up?

Another thing I noticed is as soon as I plug in the thermostat which does not power up, the zone turns on. I moved the red and white to zone 6 and it still does it. I disconnected the wiring to the circulator to prevent it from coming on as I have not yet filled that zone with water.

Thoughts?

Jamie Hall

You should have 24 VAC, more or less, between whatever is connected to the R terminal on the thermostat and whatever is connected to the C terminal. Note that I say "whatever": electricity is colourblind, and just because the wire is red doesn't mean it's constant on hot. Two wire thermostats don't care which is which, so my bet is your red and white are switched, although it doesn't look like it on the switching relay board. Check at the thermostat.

EdTheHeaterMan

It looks like the green wire is connected to R on the 24 V pair. Try changing the green wire to COM on the 24 V pair

JeffDIY

EdTheHeaterMan said:

It looks like the green wire is connected to R on the 24 V pair. Try changing the green wire to COM on the 24 V pair

So, that creates a bigger question. The first thermostat I tried, I had hooked to the com side. I believe I fried it, because when I put a voltage meter to both sides to a ground, the 24v side reads 3 volts and the com side reads 24 volts. Which is why I'm on the other side.

JeffDIY

Jamie Hall said:

You should have 24 VAC, more or less, between whatever is connected to the R terminal on the thermostat and whatever is connected to the C terminal. Note that I say "whatever": electricity is colourblind, and just because the wire is red doesn't mean it's constant on hot. Two wire thermostats don't care which is which, so my bet is your red and white are switched, although it doesn't look like it on the switching relay board. Check at the thermostat.

I agree about they color blind. Wires don't care what color they are. The right post on the thermostat is hot when I put a voltage meter on it. It's connected to the correct terminal on the thermostat. I am correct that the r on the thermostat base if for the hot wire, yes?

EdTheHeaterMan

JeffDIY said:

So, that creates a bigger question. The first thermostat I tried, I had hooked to the com side. I believe I fried it, because when I put a voltage meter to both sides to a ground, the 24v side reads 3 volts and the com side reads 24 volts. Which is why I'm on the other side.

Then you connected the R and W on the thermostat incorrectly.
When you have a 2 wire thermostat then the R and W are just two sides to a switch. So you dont need to know which one is which.

However, when you need to add a C wire then the R wire on the thermostat must be connected to the R on the transformer and the C on the thermostat myst be connected to the C on the transformer. that leaves te W on the thermostat to be connected to the W on the control. With that Taco Relay, the left T is the R and the Right T is the W. They don't tell you that on those old controls. The newer controls do tell you the difference between R and W.

JeffDIY

EdTheHeaterMan said:

JeffDIY said:

So, that creates a bigger question. The first thermostat I tried, I had hooked to the com side. I believe I fried it, because when I put a voltage meter to both sides to a ground, the 24v side reads 3 volts and the com side reads 24 volts. Which is why I'm on the other side.

Then you connected the R and W on the thermostat incorrectly.
When you have a 2 wire thermostat then the R and W are just two sides to a switch. So you dont need to know which one is which.

However, when you need to add a C wire then the R wire on the thermostat must be connected to the R on the transformer and the C on the thermostat myst be connected to the C on the transformer. that leaves te W on the thermostat to be connected to the W on the control. With that Taco Relay, the left T is the R and the Right T is the W. They don't tell you that on those old controls. The newer controls do tell you the difference between R and W.

I hear what you are saying, and I appreciate the input. I did try to connect the R to the voltage side of the transformer and blew the fuse. As I mentioned above, on the transformer post, I am getting 3v on the left and 24v on the right. That's opposite of how they are labeled. Could the transformer be the issue? Could something else in my wiring be reversing those posts? Why would it blow the fuse? Thanks!

SteveSan

@JeffDIY Morning Jeff, how many Nest are you trying to wire to our older SR control? If more than two please see the wiring diagram attached. You will need an external transformer to do so. If 1 or 2 please make sure your t-stat W goes to the left T and R goes to the right T. Your com will go to the com side of the 24vac/com terminal to the left of the board. Any questions please give us a call at Taco Technical Support during normal business hours Mon-Fri 8am-5pm EST 401-942-8000. Just ask for Technical Support.

Jamie Hall

On the voltage measurements at the thermostat -- what you are looking for is 24 VAC between R and C, and anything (it's floating) on W when the thermostat is not calling. When the thermostat is calling, it should be 0 volts (sometimes 0.5 on a digital) between R and W.

Voltage to ground is irrelevant.

EdTheHeaterMan

When ever one of my customers is experiencing trouble with a WiFi thermostat, I would isolate the thermostat from the system with a relay. look at this discussion about the way to install an isolation relay. https://forum.heatinghelp.com/discussion/comment/1713260#
Here is the isolation relay on that diagram in the left. See how there is only a set of contacts (2 wires) from the relay in the original circuit to replace the the 2 wire thermostat?

This is how it might look on your system



Read the entire discussion to see the parts I recommended and the learning curve of the person with the problem.

This might help solve your problem.

Alan (California Radiant) Forbes

One thing that can be confusing on older Taco SR controls is that the "R" terminal is on the right side and the "W" terminal is on the left. This will make a difference when trying to connect a resistor from the "C" terminal to the "W" terminal for 2-wire thermostats.

SteveSan

@Alan (California Radiant) Forbes please see below on the older SR controls. Depends on the model you have makes the difference when using it with a 3-wire t-stat. If a two wire stat it doesn't matter where you land the R-W to the T connection.

SR502-503
Red=left “T”
White = Right “T”
SR504-506
White = Left “T”
Red = Right “T”

EdTheHeaterMan

This set up will help keep the smoke from leaving a 24VAC 40VA transformer

JeffDIY

SteveSan said:

@JeffDIY Morning Jeff, how many Nest are you trying to wire to our older SR control? If more than two please see the wiring diagram attached. You will need an external transformer to do so. If 1 or 2 please make sure your t-stat W goes to the left T and R goes to the right T. Your com will go to the com side of the 24vac/com terminal to the left of the board. Any questions please give us a call at Taco Technical Support during normal business hours Mon-Fri 8am-5pm EST 401-942-8000. Just ask for Technical Support.

Hi Steve! This worked! Thank you so much for monitoring this forum and coming through with a solution. I was ready to pull my hair out.

Thank you to everyone else for their input as well. It is greatly appreciated!

Jeff

SteveSan

@JeffDIY You're welcome Jeff, glad Taco Technical Support was able to help you with your issue. Please give us a call if you ever need any assistance. Have a great day!