Circuit help

Thread Starter

jtm311

Joined Jun 2, 2020
8
I hope this is the right place to ask. I'm looking for a way to handle the following circuit.

power goes from H to R and power from AC to RC and I have also have a single lead (C) going to AC & RC.

Now what I need when the switch is in up position power goes from H to R and and "C" is cutoff from R "C" stays on RC and power cutoff between AC to RC
When switch is down power goes from AC to RC and "C" is cutoff from RC and stays on R and cuts power between H to R
Sorry wish I could draw this.
H AC
R RC
C
I think it is a flip flop?
 

BobTPH

Joined Jun 5, 2013
2,391
I have no idea what you are talking about.

What are H and R? AC usually means alternating current and RC usually means resistor- capacitor, but these make no sense in your post.

Try again without assuming we know what you mean by those terms.

Bob
 

Thread Starter

jtm311

Joined Jun 2, 2020
8
Sorry those are terminals points this is for a thermostat so I have a two transformer one controls heat and the other is for AC and the "C" is common and my goal it to flip between the two transformers.
H- heat and RC is for Air.
 

Thread Starter

jtm311

Joined Jun 2, 2020
8
So you see below are the two thermostats I will be joining them into the one and the primary is the white one.
Not sure how much everyone knows about them but I had to add an external transformer to make it work to get a common "C" connection which now occupies the RC connection which is needed for the AC "R" connection from the old thermostat. So my idea is to come up with a flip flop switch of some kind. What I have to do today is remove the R take the wire from the RC and move it to the R then connect the other thermostats Red wire to the RC. Sure hope that is clear :)
 

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Irving

Joined Jan 30, 2016
402
I don't see two thermostats, i see some sort of programmer/controller on the left and possibly a thermostat backplate on the right. Is this part of a central heating system? If you need a transformer you've probably fundamentally misunderstood how these things are normally wired (I've done 100's and never used a transformer yet). How about some wider shots of the actual items (with and without covers on) so we can see what they actually are, as I don't think your terminology is correct...
 

Thread Starter

jtm311

Joined Jun 2, 2020
8
I don't see two thermostats, i see some sort of programmer/controller on the left and possibly a thermostat backplate on the right. Is this part of a central heating system? If you need a transformer you've probably fundamentally misunderstood how these things are normally wired (I've done 100's and never used a transformer yet). How about some wider shots of the actual items (with and without covers on) so we can see what they actually are, as I don't think your terminology is correct...
Sorry I don't need a transformer and yes this is Heat/AC the face plates will not help. Every new style smart thermostat needs to have a C - common connection which was never used in older thermostats, I've already taken care of that problem by adding an external transformer. I appreciate all the help.
 

Thread Starter

jtm311

Joined Jun 2, 2020
8
all thanks I got the message I was looking for and just wanted to share how it was solved.

What you could do is get a 24v normally open SPST relay (about 10/15 dollars) from your local HVAC supply or Amazon.
Remove the Rh and W1 wire from the thermostat and set aside for now… Take your 24v transformer put one wire in Rh the other in C. Connect a 2nd wire to C and run that to one terminal on the power side of the relay, connect a wire to W1 on the thermostat and run that to the other terminal on the power side of your relay… Then connect the two wires you set aside to the normally open side of your relay.
When your thermostat calls for heat it will just send 24v to the relay and close it, when the relay closes it will turn your heat on. Meanwhile the Transformer you plugged in being connected to Rh and C will let your thermostat slurp all the power it wants and not need batteries.
 

Irving

Joined Jan 30, 2016
402
Are you sure you mean 'common'? Every 'dumb' thermostat I've seen has two sides to the normally open switch contact marked variously as L1, L2 or COMMON, L1, or COMMON, NO and sometimes a 3rd terminal marked respectively L3, L2 or NC for the normally closed contact. The later smart thermostats then add a NEUTRAL connection and sometimes a secondary LIVE as they need constant power if they can't get it from L1/COMMON. All plus protective ground of course.

Adding 24v circuits into a normallly 220/240v setup is dangerous for the future - you know what/why but someone else servicing it later may not...
 

Thread Starter

jtm311

Joined Jun 2, 2020
8
Are you sure you mean 'common'? Every 'dumb' thermostat I've seen has two sides to the normally open switch contact marked variously as L1, L2 or COMMON, L1, or COMMON, NO and sometimes a 3rd terminal marked respectively L3, L2 or NC for the normally closed contact. The later smart thermostats then add a NEUTRAL connection and sometimes a secondary LIVE as they need constant power if they can't get it from L1/COMMON. All plus protective ground of course.
not an expert but this is what they say.
The C wire, or “common wire” enables the continuous flow of 24 VAC power to the thermostat. ... If your system doesn't have a C-wire, you'll need to run a new cable from your furnace to your thermostat to install most of the modern smart thermostat models. Thermostat wire is just a big spool of bundled, color-coded wires.
 

Irving

Joined Jan 30, 2016
402
Ah, if you'd said you needed to get 24v ac to a NEST style thermostat on an older 220v system in post #1 - or posted that last statement this would have been so much simpler... not all Smart thermostats use 24v Connection to boiler
 

Thread Starter

jtm311

Joined Jun 2, 2020
8
Ah, if you'd said you needed to get 24v ac to a NEST style thermostat on an older 220v system in post #1 - or posted that last statement this would have been so much simpler... not all Smart thermostats use 24v Connection to boiler
I didn't say that because it is not what I needed :) all good thanks for the help. They guy which sent me how to flip the 24 av in post 9 is just what I needed..
 
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