How to wire two furnaces to one thermostat? Direct Steps


Some individuals ask if it is possible to wire two furnaces in one thermostat. Is it? Well Yes, you can wire numerous warmers to one thermostat. That is in the case when you’re utilizing 240-volt heaters and a 240-volt breaker. Even so, that does not mean that it is recommended all the time. Indeed, most individuals need to wire numerous warmers to the thermostat for comfort. That bodes well if you have a bigger room with different warmers in it or possibly an open living space where a living room and lounge area are one enormous space. Having one thermostat to control the two radiators will work fine and dandy since you’re managing one bigger space.

On the other hand, it does not work if one thermostat controls two heaters from two different rooms. The temperature in the two rooms would be controlled by the temperate of the room with the thermostat. That just defeats one of the benefits of electric warmth. And that is warming rooms freely to amplify individual solace and limit the electric bill. That most likely means you need to know if how to wire two furnaces to one thermostat? Read on to learn how!

Circuit and Wiring

The quantity of heaters you can join to one thermostat relies upon your circuit and wiring. It will rely upon the size of your breaker in the electrical box, what kind of wiring you are utilizing and the wattage of the individual warmers. 

So a 240-volt circuit running on a 20-amp, two-pole breaker, can have any mix of warmers up to 3,840 watts. For instance, in utilizing the only thermostat, you can either of the following have: (selection)

  • Two 1,500 watt heaters 
  • Three 1,000 watt heaters
  • Five 750 watt heaters

Parallel Heater Wiring


You should wire heaters in parallel, and not in series when utilizing them with one thermostat. 

All warming systems must be wired in parallel. You can either do that by associating every warming system to the thermostat directly. Or you can do so by interfacing every warmer to the next — simply make certain that every warmer is associated with the source wires. 

Selecting compatible thermostat control methods

Circumstances emerge where the inhabitants demand one thermostat to control at least two HVAC units. It might be on the grounds that a gathering room is open over all the module lines, the structure is one huge room, or the end client has essentially mentioned it. Thus, it is vital to choose the most suitable indoor regulator control strategy. As we do as such, we should remember a significant point. 

Each HVAC system has its very own low voltage transformer. Wiring at least two HVAC units together has the capability of wearing out the low voltage wiring all through the majority of the units. To keep this from occurring, ensure the units are appropriately staged. Be that as it may, staging the low voltage framework once at first may not make a perpetual condition. Later on, in the event that anybody switches a wire around, the wiring in every one of the units will burn! This alert applies to the primary control technique beneath and ordinarily is not experienced in strategy number two.

Method 1

Remove the majority of the low voltage transformers in all of the HVAC units, and install one enormous low voltage transformer in one HVAC unit. 

Method 2

Utilize a master control panel. Taking a gander at the primary strategy, aggregate up the volt-amps (watts) rating of the considerable number of transformers, remove them all and put one enormous low voltage transformer in one unit. This first technique will require an HVAC professional contractor. Next, interconnect every one of the units together with a “typical” low voltage leg. Next, bring every one of the wires from the units to one single posse box for the detail. Wire nut all the fitting leads together before the stat. When that is done, the contractor can gauge the setting for the warmth anticipator necessity of the thermostat. Also, remember that some thermostat heat anticipators can’t deal with the heap of more than one HVAC unit. At last, connect with the thermostat and turn on the units. 

Master Controller

The second method includes a master control panel where each HVAC unit’s low voltage wiring is to run separate terminal pieces of that tool. The master control panel requires 110 volts and has its very own transformer for control capacity to the transfers in the device. One thermostat can be surface-mounted on the controller box or it might be mounted remotely. This controller can undoubtedly be installed in the manufacturing plant with little possibilities of wiring mistakes. 

Forced air systems with warmth strips and gas heat HVAC units would require less wiring, fewer transfers, and less space in master controller board box than heat pump would. The succession of activity of this multi-unit master controller would not be similar to that of most master controllers offered available today. Take care not to mistake one sort for the other. The other well-known controller available today is the Lead/Lag master controller. It does not give the two units a chance to keep running simultaneously and includes a limit of two units. 

The Cost

An audit of the expense related with these two techniques would be at least $250 for every unit of a two-HVAC-unit framework, to $ 500 each HVAC unit for a three-to four-unit-framework. A few units constrained by one thermostat in an appropriate establishment shouldn’t present an excessive number of intricacies, yet at least four ought to be audited for potential issues by your mechanical expert. 

Nest Thermostat Zoning


Google Nest thermostats are normally good with the zoned system, incorporating zoned systems with dampers. Be that as it may, some zoned frameworks that require thermostat damper control are not good with Nest thermostats, while other zoned frameworks may require a C or normal wire to be perfect with Nest thermostats. 

In the event that you have more than one thermostat in your home, you have a zoned framework. In zoned frameworks, each thermostat controls warming and cooling freely to warmth or cool various areas of the house. Thermostats in zoned frameworks can control a similar warming and cooling system or each thermostat can control its very own framework. At the point when various thermostats control one framework, the house is partitioned into zones utilizing dampers in the ventilation work all through the house. When one zone needs warming or cooling, the damper for the ventilation work in that zone opens, directing to warm or cool air to that zone. Zoning with dampers is generally organized utilizing zone hand-off boards. 

 Multiple Zones Thermostat


Some homes comprise of numerous zones or spaces for various purposes. You would have a room, front room, kitchen and maybe even an office. Every one of these zones should be warmed or cooled – yet not really simultaneously. When you get up toward the beginning of the day and make your first mug of espresso, you lean toward the kitchen to be warm rather than your room. What is more, also, when you head to sleep during the evening you need not bother with the kitchen and front room to be warmed. The vast majority approach their day by day lives living in various zones, yet we frequently observe individuals treat their home as one single warming or cooling zone, paying little mind to their warming arrangement. 

There are numerous advantages to separating your home into various zones. You can advance for agreeable temperature when you need it, where you need it and spare more energy by taking out inefficient warming. Homes in various districts likewise depend on totally various types of warming frameworks – so recognizing what sort of arrangement your home has is the initial move towards zone warming. 

Two different ways to create zones 

Sensor-based Zoning 

With sensor-based zoning, you utilize separate sensors to streamline the temperature in each zone. This works especially well on the off chance that you have one thermostat controlling the temperature of your home. Normally, the thermostats will analyze the encompassing temperature of the room it is in. And then, it will heat or cool until it comes to the set point. The issue with this methodology turns out to be progressively clear when your thermostats are in perhaps the biggest space – like your lounge room. It likely takes more time to warm your living room than it does to warm your room. 

For instance, some rooms take a long time to warm up or if you need to warm your lounge by 1 degree, your room will have heated up by 2 degrees. With sensor-based zoning, you place sensors in each zone you need to make. These sensors will quantify the temperature of every particular zone, streamlining it for your solace. 

System-based Zoning

System based zoning is a straightforward idea to get a handle on: you have numerous warming zones in your home since you have various warming systems you can control separately. This implies you have more than thermostats. Thus, you will likely one thermostat for every living zone. This is by a wide margin the most effective method for accomplishing energy savings through zoning – in spite of the fact that, contingent upon the warming framework you use, it might be progressively costly to install. 

Warming Systems 

The most noteworthy factor in deciding how you can separate your home into various zones is your HVAC system. It is much simpler to change thermostats than it is to change HVAC frameworks, which may include enlisting more circuit repairmen or contractors. By and large, the voltage yield of your system is the most significant factor in knowing similarity with warming frameworks and the capacity to make zones. Some homes normally keep running on one of two benchmarks: Low voltage and High or Line voltage frameworks.  

Low Voltage Heating 

Commonly, on the off chance that you have a low voltage heating system, you more than likely have a central warming framework with a thermostat. This implies a sensor-based framework is likely your best choice. On the off chance that you need to move towards a system based zoning framework. It presumably implies a decent arrangement of development – new circuits and installations will be required. 

And rarely, there are some cases that low voltage warming frameworks are separated into numerous zones. It is through duplication of warmth sources or use of dampers and channels. Every one of those circuits will require their very own committed through duplication of warmth sources or use of dampers and channels. If so, it is better to have a different thermostat for each zone. With this arrangement, you can spare energy all the more effectively without investing much energy changing setpoints and temperatures for each zone. 

Line Voltage Heating 

On the off chance that you have line voltage warming – 120-240V, you likely have various thermostats –one for each room. All things considered, you are good on your approach to having a framework based zoning framework. Simply supplant these thermostats with WiFi or savvy choices that having zoning alternatives and physically set your zones. 

In other cases, despite the fact that a decentralized warming system is progressively basic for high voltage circumstances, there are special cases. Fan loop thermostats are a sort of central line voltage warming framework, and tragically, there is no keen thermostat that exists for fan loop frameworks. This framework would require a sensor-based system as there is just one thermostat controlling the whole home. 

How about twinning for Furnaces?

There are a few applications where a solitary heater can’t convey enough BTU’s or CFM to warm a space. At the point when these applications emerge, a basic arrangement might be to place in 2 heaters and twin them together. This enables the two heaters to work off of 1 thermostat and be integrated with a solitary pipe framework. 

The rules to remember:

  • When twinning heaters, you need similar twins 
  • Same model, BTU, CFM limit 
  • All engine leads must be on similar taps 
  • All control board settings must be equal 
  • Boards must be indistinguishable part numbers, or else, the sheets will not work appropriately with one another 
  • The power for the heaters must be a similar buss bar in the wire or electrical switchboard 
  • Twinned heaters must be connected on a typical return and supply pipe framework
  • Isolation transfers should be introduced on the slave heater to detach transformers
  • Only PSC engine prepared heaters can be twinned 
  • Furnaces with ECM engines can’t be twinned 

In the event that the majority of the above rules are pursued, fruitful twinning of heaters will work great and give higher warmth limit and blower ability to warm the space. 

One mistake many individuals make is expecting that the blower limit is additive. At the point when heaters are twinned, the consolidated blower limit is just 85% of the all-out CFM delivered by the 2 blowers. This turns into an issue is when temporary workers think they have two 5-ton blowers so they can put a 10-ton climate control system on them. Since the limit is diminished 15% when twinned, those two 5 ton blowers might most likely convey 3400 CFM — enough for a 7 1/2 ton application. 

In furnaces, twinning is made simple with no extra controls. On each board is a terminal stamped twin. By running a solitary wire between the twin terminals on each board and running a wire between the C, or regular terminal on each board, the heaters are currently twinned and will work as one.

The compatible stages

You can give extra comfort by utilizing a 2-stage thermostat and work the warming independently. Also, remember that the two blowers will consistently be running on any call from the thermostat. Furthermore, on the off chance that you utilize 2-stage heaters, you can utilize the organizing clock to really give 4 phases of warming. The most significant thing to recollect however is the way that everything must be similar and, on the off chance that you do that, the activity ought to go easily. 

One final thing to make reference to when adjusting twinned heaters and you have to supplant a control load up, remember to supplant the other load up simultaneously or ensure that the new board is equivalent to the one you are supplanting. 

Can you wire 2 Thermostats in 1 Heater? How?

With a home of any apparent size, there will undoubtedly be regions that are cooler in temperature than others when you need heat, and warmer than others when you need cool. You can help make an all the more equitably molded home by purchasing a different thermostat in another piece of the house. At the point when two thermostats are wired to a warming or cooling system, with zone control and dampers installed in the ventilation work, you have genuine separate temperature zones in your home. 

Install Dampers

  1. Draw a basic graph of your HVAC pipe framework. Recognize the rooms that are fed by every one of the supply air pipes and imprint those conduits with a marker. Find where the conduit branches into the two regions of your home that will have separate thermostats. Measure the channels and purchase zone dampers to fit. 


  1. Cut a gap in the ventilation work with tin clips to fit in a zone damper. It ought to be appropriately measured for the ventilation work. Some zone dampers are drop-in and some are slide-in, so ensure you cut the gap in the best possible area. Secure the damper with screws and seal with silicone caulking. Rehash this progression for the same number of dampers as you are setting. 


  1. Strip the ends and connect 18 gauge thermostat wires to the damper wire openings. Dampers, as a rule, have a few wires. Run the connected wire to the zone control box. 


  1. Strip the parts of the bargains from the damper and append them to the zone control box in the zones stamped Damper 1 and Damper 2. There will be two screws for every damper. Fix the wires down with a screwdriver. 


  1. Mount the zone control box close to the heater, either on the ventilation work or a nearby divider. Run an 18-measure 4-conduit wire from the control board on the heater to the terminals stamped heater on the zone control box.


  1. Strip the parts of the wire and join them to the heater control board. They ought to be joined as White to W, Red to R, Green to G, and Yellow to Y. 

  1. Connect the opposite part of the arrangement in the zone control box to a similar shading coded terminals in the space checked Furnace. 

Install Thermostats

  1. Install a thermostat in every one of the regions being sustained by the zoned channels, adhering to the guidelines for an establishment that are incorporated with the thermostat. Run a wire from each indoor regulator to the zone control box. 


  1. Join the wire from the thermostat being fed by Damper 1 to the terminals stamped Thermostat 1. Rehash for the subsequent indoor regulator, yet connect to the terminals checked Thermostat 2. Again the shading coding of the wires will be as White to W, Red to R, Green to G, and Yellow to Y.


  1. Test the thermostats in every zone to ensure the framework reacts to the demand for warming or cooling.

Can you wire 2 Baseboard Heaters in 1 Thermostat? How?

Baseboard warmer strips originate from the manufacturer with inherent thermostats. They carry out the responsibility that they were intended to do, however, they have downsides. One, frequently utilizing those means getting down on the floor and slithering under or behind tables to change them. Second, on the off chance that you have at least two baseboard warmers in a similar room, you need to modify every one of them independently. It is substantially more helpful and effective to connect the baseboard warmers in parallel and attach them to one wall-mounted, over-the-line thermostats. How?

Steps in connecting 2 baseboards in 1 thermostat

  1. Find a spot on a wall inverse with the baseboard heaters to mount the thermostat. Measure and imprint a spot 5 feet up from the floor. Utilize an electronic stud discoverer to ensure that you won’t penetrate or cutting into a wall stud. 


  1. Imprint the area utilizing the “old work” box as a layout. Draw a layout around it. Drill a 1/4-inch gap in within corners of the blueprint and afterward utilize the convenient jigsaw to wrap up the pattern. 


  1. Drill a 3/4-inch hole through the wall’s base plate, the even encircling part, while working from the cellar or crawlspace. Drill into the wall space where the thermostat pattern is found. 


  1. Switch off the branch electrical switch at the power board and disengage the power from the main baseboard warmer in the circuit. Reroute the power link from the baseboard warmer to the wall pattern where the thermostats will be found. Run another length of 12/2 with ground Romex back to the heater. 


  1. Eliminate 6 inches of the external coat from the two cables and add them into the thermostat box. Push the container into the wall pattern and utilize a screwdriver to turn the screws to tie down the box to the wall. As you turn the screws clockwise, the mounting wings will be drawn facing the posterior of the wall, holding it set up. 


  1. Remove 1 inch of external coat from the parts of the individual wire. Identify the white wires as flow conveying wires by wrapping their uncovered insulation with dark electrical tape. Connect the two wires bringing power from the breaker board to the two-line terminals. Connect the two wires conveying the power from the baseboard heaters to the two load terminals on the thermostat. Attach the two bare ground wires utilizing a wire nut. Install the indoor regulator in its crate. 


  1. Identify the white wire at the connection box of the heater. Connect the insulated wires carrying power to the warmer to the red and black heater wires. Make these grafts three-path joins by associating the wires conveying the power to the second heater to them. Connect the bare ground wires to the establishing screw on the baseboard warmer’s metal edge. Install the spread plate on the graft box and walk out on. 

Keep in mind to always shut off the power at the breaker board before chipping away at an electrical circuit.

Final Thoughts

Instead of doing an expanded review of why each thermostat would be the best alternative for various situations, keep it straightforward. Utilize the choices tree above to settle on your choice – it considers everything talked about above. 

Moreover, controlling at least two HVAC units with one thermostat is a job for an expert or educated adult. Try not to give your children a chance to attempt this at home, not regardless of whether they have been awful! Contact a mechanical designer, HVAC controls organization or your HVAC provider for help on this methodology. Plus, there are also other information mentioned aside from how to wire two furnaces in one thermostat. Each home have different necessities. Thus, you can conveniently use all of those information and decide if which process best fits your home. 




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