Temperature Controller, 2 Wire Room Thermostat Heating Thermostat Digital Thermostat with Large Screen LCD Display Wall Hanging for Control Room Temperature (White)

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If your O or B terminal shares a label with another wire — typically W —identify whether you have a heat pump system or not. A heat pump runs your compressor for both heating and cooling. If you don’t know your system type, place this wire in the W terminal. If you have a heat pump system, put it in the O/B terminal. O” or the orange thermostat wire is for reverse valve cooling. Most bigger heat pump manufacturers like Trane, Goodman, Lennox, and so on have the orange wire that goes to the condenser (located in the outdoor unit of heat pumps). Overall, the Nest thermostat is a very smart and useful gadget that allows you to keep an eye on your home’s temperature at any given moment. 2. Ecobee Smart Thermostat (5th Gen)

What if there is no C wire for the thermostat?” (Older thermostat; you can leave it without or add it) In addition to heating (2 wire thermostats) and C or fan (3 wire thermostats), 4 wire thermostats include the cooling wire, usually in blue or yellow color. Here are the wires in 4 wire thermostats with terminal codes and color codes (also referred to as 4 wire thermostat wiring color code): Take off the motherboard and secure the wires; if you don’t hold them, the four wires will get lost in the wall. HVAC technicians know the color-coding by heart; they can just remove any Honeywell thermostat, replace it with the new one and reconnect the terminals.These thermostats are typical for heat pumps: HVAC devices that can cool and heat. To produce the airflow, a fan is needed (green wire). If your thermostat doesn’t look exactly like this, or even anything like this, don’t worry. We just need to get a grip of what each color wire is and what it does. If you are DIY thermostat wiring, here’s the easiest thing to do before removing the old thermostat: required when using a radio module”. It is interesting they say a 24V DC can be used and in other place they indicate the polarity of connection is immaterial (The CT32 can be externally powered with a power source rated from I've had a shifty on t'net and Satchwells of this ilk seem to have common wiring terminals as follows:

Many 2 wire thermostats are suitable for mains voltage, however some are not, so care is required when selecting a 2 wire thermostat for mains use. In all cases, we will use this basic Honeywell thermostat for reference: This is a standard Honeywell thermostat; perfect for learning the ins and outs of thermostat wiring. The protocols apply to Honeywell thermostat wiring as well as for other thermostat wiring. The Nest 3rd Gen thermostat has 10 terminals, say Rh, Rc, W1, W2(aux) Y1, Y2, O/B, G, C, etc. You just need to connect ‘red’ wire from the furnace to Rh and ‘white’ wire to W1. These 2 connections will set the Nest thermostat as a ‘smart 2 wire thermostat’ taking care of your home heating ‘smartly’. These are more common. In addition to the line and switched line, a neutral is also required. This is used to power a small heater inside the thermostat, to improve response times. Without this, the temperature difference between the thermostat switching On and Off (hysteresis) will be excessively large, resulting in the room temperature fluctuating significantly.

There are several solutions to your problem. Some might just want to install a new 6 or 8 wire thermostat wire to your thermostat. (the proper but usually more difficult way) This might mean relocating your thermostat. Or they might bring a product like the one that you have, to wirelessly connect the thermostat to the furnace, and then use the builder installed 2 wires to power the thermostat. B” is for reversing valve heating. Some producers like Rheem energizes the reversing valve when the heating mode is on in heat pumps. A dark blue “B” wire is needed for the t-stat terminal. Thermostat Green Wire (“G” Wire) Knowing how to wire a 3-wire thermostat is fairly easy compared to 4 and 5-wire thermostats: 4 Wire Thermostat Wiring (Heat Pumps, HVAC)