A thermostat operates much like the wall switch that controls your lights. Obviously there are differences, but the main one is that the thermostat opens and closes the circuit all by itself. You don't have to do a thing except, of course, set the temperature. A two-wire thermostat is the most basic type. It has only one internal pathway, so it can handle only a single appliance. Most people use a two-wire thermostat to control their furnace or a room heater, but you can also use one to control an air conditioner.
Thermostat technology is constantly advancing, and digital battery-powered models are becoming more common than mechanical models, many of which contain mercury. When you replace a mercury thermostat with a digital one, remember that mercury is toxic.
Handle the old thermostat with care and dispose of it as hazardous waste. Most household thermostats operate at 24 volts, which is supplied by a transformer connected to the heating or cooling appliance that the thermostat controls. Inside the thermostat is some type of heat-sensing device. In electronic models, this is often a thermistor, a device that responds electrically to changes in temperature. The sensing device in mechanical models is usually a bi-metal strip that responds mechanically to temperature changes.
Some models contain a small vial of mercury that tips one way or the other in response to the moving coil. Mercury conducts electricity, and when the vial tips far enough, the electrical circuit closes and the appliance goes on. That's basically all there is to a two-wire thermostat. There are no wires to control fans, compressors or heat pumps, which are the usual components of sophisticated heating and cooling systems.
You can use a thermostat with more than two wire terminals as a two-wire thermostat, but the reverse isn't true. If your furnace has an auxiliary fan, you need a thermostat capable of accepting more than two wires. Check your furnace wiring diagram if you aren't sure. The terminals on a two-wire thermostat are labeled R and W.
If you use a thermostat with more terminals, but you only have two wires, you can ignore all the other terminals except for these two. The colors associated with these terminals are red and white, so if the wires coming out of your wall are these colors, simply connect the red one to the R terminal and the white one to the W terminal. If the wires are different colors, you may have to check the furnace control panel to find which wire is connected to which terminal. The terminals on the control panel have the same letter designations as the thermostat.
Be sure to turn off the power to the furnace before wiring the thermostat. You won't get a serious shock from handling volt wires, but you'll still get a shock, and getting no shock is better than even a mild one.
Location matters when it comes to thermostat installation. If you're installing one for the first time, avoid putting it in a sunny location or above a heat register. In either place, it will sense a temperature higher than that in the room and won't come on when the room is cold. Conversely, it shouldn't be in a drafty place, or it will come on too often, and the room will be too warm. The best place for it is usually at shoulder height next to an interior passage door and out of direct line of the main entry door.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience.
An avid craftsman and musician, Deziel began writing on home improvement topics in Thermostats vary in the features they offer, and there are also differences when it comes to wiring one to control your home's heating and cooling system. If you check the Honeywell thermostat ct31a wiring diagram, you'll see that it requires only two wires. This is because it's a very basic thermostat designed only to control a heating system.
If you have a system that both heats and cools your house, you need a more complex thermostat with more wire terminals, and if your system incorporates a heat pump, you need even more wire terminals.
You can use a multifunction thermostat to control a simple system, but not the other way around. It helps to have a basic understanding of your home's heating and cooling system before you buy a thermostat to control it.
If your HVAC knowledge is limited, you can also simply count the wires connected to your old thermostat. Your new Honeywell thermostat should be able to accommodate the same number of wires. Honeywell thermostats follow the industry standard for terminal identification. Each terminal is marked with a letter that usually corresponds to the color of the wire that should be used to connect it. Here's a list of the basic terminal letters and their functions:.
Some thermostats may have additional terminals, including W2 for the second-stage heater, Y2 for the second-stage cooler and X2 for the second-stage indicator lights. The wire colors for these extra terminals aren't specified. Other thermostats have fewer wires. Again referring to the Honeywell thermostat ct31a wiring diagram, you can see it requires only two wires, R and W. It doesn't control cooling and, because it's a mechanical thermostat, it doesn't need power for internal functions, so it has no C wire.
If your system has both heating and cooling functions, you'll need to connect both the Rc and Rh terminals with a red wire. Because many thermostats come with a pre-installed thermostat jumper wire that connects these terminals, you only need one red wire, which could be the thermostat Rc wire or the Rh wire. If this jumper wire isn't present, you can install one yourself. If you don't, you'll need two red wires so you can connect each terminal separately to the system transformer.
When installing a thermostat, many people — even HVAC pros — don't always pay attention to wire colors, so you can't assume that the colored wires sticking out of your wall perform their standardized functions. The best way to identify the wires is to look on your system control panel.
It has the same terminal designations as the thermostat does, and you can simply note the color of the wire attached to each terminal. If you're replacing an existing thermostat, note the color of the wire attached to each terminal before you disconnect it, and connect the wires to your new Honeywell thermostat in the same way.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in Hunker may earn compensation through affiliate links in this story.
How to Wire a Honeywell Thermostat. W white controls the auxiliary heating elements.
How to Install a Honeywell CT87K Thermostat
Y yellow controls the compressor on the cooling system. G green controls the fan. C blue or black provides a return path to the transformer. This terminal is needed when the thermostat uses 24V power from the system control panel. This terminal won't be present if the thermostat has batteries or operates mechanically. O orange controls the reversing valve on a heat pump to switch the pump back and forth from heating to cooling.
Rh red supplies 24VAC power to the thermostat and switches the heating system on and off. Rc red supplies 24VAC power and switches the cooling system on and off. Share this article.One useful feature about Honeywell t-stats, is that they generally use the same wire labeling as their older models. Their remote access functions need no other connections. Through this wire, it gets its 24 volt AC power for running its WiFi, internet, and program functions.
Not a problem if you replace another programmable thermostat with this one. Indeed, most of those also use the C wire.How to Replace an Analog Thermostat with a Digital (HD)
But if you upgrade from a non programmable model that not use the C wire, then you may have to improvise. You may have to run the C wire power to your new t-stat. We discuss how to do this in more detail below. A level, to check that the mounting plate is plum and completely horizontal. Check this before marking the places on the wall for the anchors. Hammer for tapping pilot holes at the chosen spots on the wall where the anchors will go, prior to drilling.
But sometimes, furnace installations provide a separate power switch for this purpose. Our furnace has a standard volt AC mains plug that interrupts mains power to it when pulled out. Verify that power is off by inspecting any pilot lamps on furnace or old thermostat. These should all be dark, and no hum or other running sounds from the furnace should be heard.
Remove the old thermostat unit from its holder plate. Most thermostats nowadays detach from a wall mounting plate. This allows simple wire hookups, with low risk of thermostat damage. New thermostats usually come with a sheet of wire labels. They often print these with the wire letters found in most t-stats. Also, do not let the wires to fall inside the wall. Doing so will create major headaches for you.
So to prevent losing the cable into the wall, wrap it around a pencil or nail. This should hold it in place until you install the new wall plate. Without one, this t-stat will not work in your setup. If you cannot add a C wire, then return it for a refund. We discuss next some options for adding a C wire. Check for any unused conductors single wires in your existing thermostat cable. They bundle these wires into a single cable four, five, seven, or eight wire cables.
See the picture above that shows a common seven wire thermostat cable.
Often, installers use a cable with extra free wires to permit easy expansion later. To find an unused wire, look at the wire layout at your thermostat wall plate. See the example shown above for our old t-stat.
How to Hook Up the Wiring for a Honeywell Thermostat RTH111B
If so, pick one, and note its color.InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website. This article gives a table showing the proper wire connections for Honeywell brand wall or room thermostats used to control heating or air conditioning equipment.
Our page top sketch, courtesy of Honeywell Controls, illustrates the wiring diagram for a traditional Honeywell T87F thermostat used for 2-wire single pole single throw control of heating only in a typical gas-fired heating system. Do not use C, C1 or X wire. Do not use B wire if you already have O wire. Wrap bare end of wire with electrical tape. This thermostat cannot be used if your old thermostat had [and used] any two of the following wires: R, RC, RH, 4 and V.
Shown here is the company's orginal traditional T87 round, non-programmable thermostat and its contemporary, digital replacement that will be wired identically: Honeywell's TC These thermostat T87F models vary by the operating temperature range they support and a few other simple features such as the presence or absence of a thermometer. Functionally and for wiring they are similar.
How to Install a Non-Programmable Thermostat
Some thermostats will be supplied with a jumper wire or clip between the thermostat RH and RC terminal and will not provide a simple R terminal such as the 3M Filtrete. Connect the red wire t. Remember that ultimately a thermostat is simply an on-off switch, or provides several on-off functions. But with multiple zone heat, you should expect to provide a thermostat for each individual zone - else they're not heating zones at all. In a traditional hot water heating system that does not use the Azel i-Link controller, the first thermostat is wired directly to an aquastat that controls the first zone; the second two thermostats are wired to individual circulator relays if individual circulator pumps are used or to individual zone valves if a single circulator runs the whole system.
Where zone valves are used, an end switch closes to turn on the circulator a logical inclusive OR function with the other zone valves when the zone valve opens to allow hot water to flow. And the company makes clear that their controller is compatible with standard thermostats:. ALL - controls are compatible with 2, 3 or 4 wire type thermostats. Calling Honeywell with the right product number Tel: might produce better results.
Honeywell has done a great job making installation and operations manuals available for their equipment, but you've got to search with the right product number. Searching the Honeywell site for the corrected thermostat number delivers a single product that's probably yours, the Day Programmable Thermostat - RTHB In fact this thermostat is widely sold including at Home Depot stores, and I've installed and used this very model myself to control an add-on hot water heating zone and Taco circulator in an older home.
According to Honeywell, this thermostat is compatible with:. Here are details from that manual's instructions for wiring the Honeywell RTHB Day Programmable Thermostat beginning with the inspection of the existing wires:.
Identify and label each of the existing thermostat wires by using not the wire colors someone could have made a wire color error and violated convention but rather, identify each existing thermostat wire by noting the letter next to the old thermostat wiring block terminals where each wire was connected to a screw.
Identify and label the wires that are connected as. If any wires are not attached to your old thermostat or are attached to a terminal marked C or C1, they will not be connected to your new thermostat. Wrap the bare metal end of each of these wires with electrical tape, so it cannot touch and short other wires. Watch out : since here we are focusing on connections, I am leaving out some important procedure and safety details like removing and taping each wire end to avoid shorting, etc.
Honeywell Day Thermostat Wiring Table : If the wire labels from your old thermostat hookup don't match the above, Honeywell offers additional advice that we adapt in table form provided in detail. If the wire labels from your old thermostat hookup don't match the above, Honeywell offers additional advice that we adapt in table form:. Be sure that you label the wires before disconnecting them from the old thermostat, or if you are installing new equipment, identify the incoming wires from the equipment terminals and its manual.
Below are alternative wiring connections for the Honeywell RTHC thermostat along with an explanation. Watch out : if your wires do not match the above see several alternative wiring installation hookups on both of the thermostat wiring manuals given just below.
Hi, I have a setup that I think is probably common, at least in the northeast, but that I found very difficult to get straight. I have a boiler with a hydronic zone valve that controls two zones. The thermostat I was replacing was an old White-Rogers mercury switch.
It's a 3-wire configuration. The new t-stat is Honeywell RTHThe Honeywell RTH series consists of battery-powered, basic programmable thermostats suitable for controlling a number of household heating and cooling configurations.
You can use the Honeywell RTHB in a two- or three-wire configuration to control a gas, oil or electric furnace or an air conditioning system. You can also use it in a four- or five-wire configuration to control a heating system with air conditioning. However, this model is not suitable for controlling a heat pump or a system with second-stage heating or cooling.
If you're replacing your old thermostat, note the terminals to which the existing wires are connected and connect the wires to the same terminals on the new thermostat. If this is a first-time installation, you may need to match the thermostat terminals to those on the system control panel.
There is a color standard for thermostat wiring, but you can't always depend on it. It's best to double check by looking at the connections on the control panel. Take a picture if necessary.
Although RTH thermostat wiring is not as complicated as that for many other thermostats, you should take the time to read the installation manual before you start. That way, you can familiarize yourself with the idiosyncrasies of this model. One of the most important is the fact that, since it gets its power from batteries, it doesn't use a common wire, which is usually blue or black and labeled C, C1 or X.
If your old thermostat used this wire, simply tape off the end and push it out of the way. You don't need it. These supply power to the heating and cooling systems respectively. If you have only one power wire which is usually redleave the jumper in place and connect the wire to either Rc or Rh.
However, if you have separate Rc and Rh wires, remove the jumper and connect each wire to the appropriate terminal. If the thermostat is going to control a furnace, you'll have at least two wires. One is the power wire, labeled R redand the other controls the furnace. It should be labeled W white. Connect these wires to the appropriate terminals.
If the system has a separate fan control, you'll see a third wire labeled G green. Connect it to the G terminal and set jumper JP1 on the back of the thermostat to the HE position if the furnace is electric.
Leave it in the HG position for a gas or oil furnace. If the Honeywell thermostat installation is to control an air conditioning system, you'll have an R wire for power and a W wire to control the air conditioner.
You may also have a Y wire yellow to control the compressor motor. Attach this to the Y terminal. It's for the reversing valve, and it's usually labeled O orange.When wiring the new thermostat, ignore the color of the wires; wire the thermostat only according to the terminal designations. For new installations or unmarked wires, consult the installation manual in the References section.
Ensure that power to the heating system and thermostat is disconnected before attempting to replace or service the thermostat. If you've started to notice a rise in your heating bills, uneven heating, or your heating system switching on and off more frequently, it may be time to replace your thermostat.
New thermostats are more accurate and more reliable than older thermostats and can save you considerable money over their lifetime. Replacing your old thermostat with a Honeywell CT87K thermostat can be accomplished using only basic hand tools and some preparation.
Switch the breaker or remove the fuse that supplies power to the existing thermostat or heating system. Remove the existing thermostat but leave the wall-plate with the wires attached intact. Mark each wire according to the terminal it's connected to on the wall plate. Disconnect the wires from the wall plate using a screwdriver and remove the wall plate from the wall. Pull the wires through the large opening in the base of the new thermostat and hold the base against the wall in the desired mounting location.
Mark the location of the mounting holes using a pencil. Remove the base from the wall and drill holes in the marked locations using a drill and appropriately sized drill bit. Insert the included wall anchors into the drilled holes and lightly tap them with the hammer until they are flush with the wall surface. Pull the wires through the large hole in the base of the new thermostat and align the mounting holes with the wall anchors.
Insert the included screws into the anchors and tighten them firmly with a screwdriver. Insert each wire into the terminal on the new thermostat that corresponds to the terminal it was connected to on the old thermostat.
Tighten the terminal screws snugly with a screwdriver. Line the tabs on the faceplate up with the slots on the base and press firmly until the faceplate snaps into place. Restore power to the thermostat and test system operation.
Recheck all connections, fuses and breakers if the system fails to operate. David Young has written for the website for the Save Darfur Coalition and is currently writing articles for various other websites. Hunker may earn compensation through affiliate links in this story. Tip When wiring the new thermostat, ignore the color of the wires; wire the thermostat only according to the terminal designations.
Warning Ensure that power to the heating system and thermostat is disconnected before attempting to replace or service the thermostat. A new thermostat can help keep you warm and keep your power bills low. Step 1 Switch the breaker or remove the fuse that supplies power to the existing thermostat or heating system.
Step 2 Pull the wires through the large opening in the base of the new thermostat and hold the base against the wall in the desired mounting location. Step 3 Insert the included wall anchors into the drilled holes and lightly tap them with the hammer until they are flush with the wall surface. Step 4 Insert each wire into the terminal on the new thermostat that corresponds to the terminal it was connected to on the old thermostat.
Step 5 Line the tabs on the faceplate up with the slots on the base and press firmly until the faceplate snaps into place. Share this article. David Young. Show Comments.A non-programmable thermostat is the most basic type of heating and cooling control system available. Inexpensive but useful, these manual thermostats lack the automated functions of more advanced thermostat models — but can be installed to work with nearly any heating and cooling system.
Newer non-programmable thermostats are commonly produced by Honeywell. Although the company sells a number of newer, programmable models in addition to the base-level manual thermostats, one Honeywell thermostat works as well as any other of its models in terms of core functionality.
Honeywell thermostat older models lacking the advanced features are just as effective at running heating and cooling systems. By following the Honeywell thermostat directions included in your manual thermostat's packaging, you can easily uninstall an old thermostat and replace it with your new manual unit without professional help. To begin, go to your breaker box and turn off the power to your heating and cooling system to prevent any risk of taking an electric shock later on in the thermostat installation process.
Remove the old thermostat from its mount, then unscrew the old thermostat mount, being careful to not harm the thermostat's wiring. Once you've exposed the wiring of your old thermostat, you can begin the process of wiring up your new one.
Honeywell non-programmable thermostat wiring and installation are functionally universal: Wires are inserted into unit terminals based on color. If your old thermostat's wires aren't labeled already, take note of which terminal each wire is plugged into, using masking tape to label each wire as you remove it from the old thermostat's mount.
When all wires are labeled and removed from the old mount, thread them through the wire hole on your new thermostat's mounting panel. Then, use a drill, screws and drywall anchors to install the new panel on the wall. Connect each wire to the appropriate terminal on the new thermostat's panel based on the instructions printed on the panel and the wire labels. Use a screwdriver to tighten each wire into its appropriate terminal on the panel.
With the wiring complete, finish the thermostat installation process by plugging your new manual thermostat into its base, then restoring power to your home's heating and cooling system.
Press your unit's power switch if necessary and then follow the instructions in your Honeywell digital thermostat manual to begin using your new, fully-installed manual thermostat. Blake Flournoy is a writer, reporter, and researcher based out of Baltimore, MD. As a handyman's apprentice operating out of the Atlanta suburbs, they made a name for themselves repairing appliances and installing home decor.
They have never seen Seinfeld and are deathly scared of wasps. Hunker may earn compensation through affiliate links in this story. How to Install a Non-Programmable Thermostat. Climate Control Corp: Programmable vs. Share this article. Blake Flournoy. Show Comments.