Thermostat C Wire: Everything you need to know about the i think the blue wire in the diagram comes out as the red wire to the thermostat., my 1977 home on the west coast has a programmable thermostat but no c-wire.. but no i have no power to the ac nor the thermostat. this something you would agree with, and could i be confident in wiring this in this configuration (less the c wire) with the results being that of working properly. adding a c-wire, either through new wiring or an adapter, ensures compatibility with new thermostat technology. the original red an white wires should be connected to r and w on the thermostat. when i switch the furnace switch to cool it runs continuously even if the thermostat is on cool, there is no response. thermostat home furnace troubleshooting-step by step guide …elk trg2440 24vac, 40 va ac transformer ptc fuse, fulfillment amazon (fba) service offer sellers lets store products amazon’ fulfillment centers, pack, ship, provide. old thermostat didn’t require continuous power so the blue,c wire wasn’t connected. well it’s kept secret because building codes don’t let you “pull a neutral” unless it’s on the same circuit (and furnaces are required to have a dedicated circuit hence you’re required to only get your neutral there) but when you consider that only a trickle of 24v current is required to power your thermostat you probably won’t kill yourself if you forget to turn off your furnace circuit next time you service your switch box. uses a proprietary abcd junction block (block pl7 in the circuit diagram) for the thermostat. have a oil boiler in basement, thermostat in 1st level and ac central air blower in attic. have a two wire boiler (quite old and dated) that is hooked up to a basic thermostat in my family room. the two new wires should be connected to rc and c on the thermostat and to r and c on the transformer at the other end.
INDEX SPECIFICATIONS WIRING THERMOSTAT INSTALLATION the thought of poking around in your furnace or thermostat makes you uneasy, consider hiring a professional for the installation of your smart thermostat. they have really helpful customer service that seems to be able to handle any wiring configuration, and it’s extra peace of mind! thermostat c wire: everything you need to know about the … […]. you do resolve this, either through adding more wires or choosing a particular thermostat that works with your 1-wire setup, come back and let us know how it goes! your system has a c-wire, it might be in use or just tucked away behind your current thermostat. you are planning on using a electronic thermostat with these functions it will require a battery powered thermostat to allow relays to turn on and off for heat and fan, otherwise it will have to be a energy scavenging thermostat which gets its power by pulsing the heat function on when it needs to regenerate its power,The only other option is to pull more wires from the thermostat to furnace if you want to use a powered thermostat. am interested in installing a smart thermostat but lack the c wire at the thermostat. i assume the 24v is positive, the com negative, but since there is only one c terminal on my thermostat i’m confused about which of these to connect to. was a question about older equipment not having a “c” terminal only r and w, if your planing on using a thermostat that requires a c and a second transformer as a power source to get your “c” (common wire) then please be careful, if you mix phases on you 120 volt power source (phase a one and phase b second) between the heating appliance and the new thermostat you will find a lot of factory smoke leaving the transformer(s),Instead power your thermostat with the second transformer and use that power to switch a relay coil, then use the dry normally open contacts of the relay to make the circuit between r and w of the heating appliance to isolate the two power sources yes it costs a relay but that’s much cheaper then a mistake and finding you now have equipment damage. popular nest thermostat claims to work without a c-wire, there are some caveats..Better yet you can buy a thermostat that uses battery to switch the contacts and thus no second transformer the only downfall is the battery changes every couple years on that. updated on september 9th, 2017back in the olden days, thermostats were simple on/off devices that didn’t need their own continuous power supply. c wire closes the circuit and allows continuous flow of 24v energy to power the thermostat. i have been investigating this because a painter damaged our thermostat (obsolete, works for now, long story).