How to add extra 24VAC wire (C wire)
#1
Member
Thread Starter
Join Date: Apr 2015
Posts: 1
Upvotes: 0
Received 0 Upvotes
on
0 Posts
How to add extra 24VAC wire (C wire)
I have recently bought a Honeywell rth9580 programmable WiFi thermostat. Unfortunately I have old electric heating/cooling system probably from 70's. The system is based on two relays (I guess heating and cooling). Since transformer doesn't have 3rd wire (C?) by default I would like to make one by connecting extra wire to transformer chassis. Having terminal C I would like to connect wire G to terminal C and jump terminal G with Y. I measured the voltage between transformer chassis and Rh wire: idle 34VAC, calling for heating/cooling 24VAC. Here are my questions:
1) Is this setup will work?
2) Is it safe to connect thermostat since voltage on idle is a bit higher than it supposed to?
3) Am I right to assume that transformer won't overheat because thermostat will try to drain to many amps?
1) Is this setup will work?
2) Is it safe to connect thermostat since voltage on idle is a bit higher than it supposed to?
3) Am I right to assume that transformer won't overheat because thermostat will try to drain to many amps?
#2
34 volts is not correct.
A 24vac HVAC transformer only ever has two terminals. One terminal is technically connected directly to the R terminal. The other terminal can be a blind connection.... like just a crimp or wirenut... and may just connect to ground.
If you know where the two wires that go to the outside unit are...... one connects to the Y and the other is the C connection.
Can you post a pic or two of the existing wiring ? http://www.doityourself.com/forum/el...rt-images.html
A 24vac HVAC transformer only ever has two terminals. One terminal is technically connected directly to the R terminal. The other terminal can be a blind connection.... like just a crimp or wirenut... and may just connect to ground.
If you know where the two wires that go to the outside unit are...... one connects to the Y and the other is the C connection.
Can you post a pic or two of the existing wiring ? http://www.doityourself.com/forum/el...rt-images.html