This guide walks you through installing two Nest doorbells using a 4-wire setup, ideal for homes with existing doorbell wiring. You’ll learn wiring basics, safety steps, and how to avoid common pitfalls for a reliable, professional-grade installation.
Key Takeaways
- Use existing 4-wire doorbell wiring: Most homes with two doorbells already have the right wiring—two sets of wires running from the chimes to each door.
- Turn off power before starting: Always shut off the breaker to avoid electrical shock when working with doorbell transformers and wiring.
- Nest doorbells need constant power: Unlike older models, Nest doorbells require continuous power, so a compatible transformer (16–24V AC, 20–30VA) is essential.
- Label wires carefully: Mark each wire (front, rear, transformer, common) to avoid confusion when connecting to the Nest devices and chime unit.
- Test before final mounting: Use the Nest app to check connectivity and video feed before securing the doorbells in place.
- Use a doorbell chime compatible with Nest: Ensure your indoor chime works with Nest’s digital signal—mechanical chimes may need a bypass resistor.
- Consider a professional if unsure: If wiring is complex or you’re not comfortable with electrical work, hire a licensed electrician.
How to Install Two Nest Doorbells with 4 Wires
So, you’ve decided to upgrade your home security with not one, but two Google Nest doorbells. Maybe you have a front and back door, or a main entrance and a side gate. Whatever the reason, installing two Nest doorbells using your existing 4-wire doorbell system is not only possible—it’s often the smartest way to go. This guide will walk you through every step, from checking your wiring to final testing, so you can enjoy crystal-clear video, smart alerts, and peace of mind at both entry points.
We’ll cover everything you need to know: what tools to use, how to safely handle electrical wiring, how to connect both doorbells to a single chime, and how to avoid common mistakes. Whether you’re a DIY enthusiast or just looking to save on installation fees, this guide will help you get it right the first time.
What You’ll Need
Visual guide about How to Install Two Nest Doorbells with 4 Wires
Image source: storage.googleapis.com
Before you start, gather all the tools and materials. Having everything ready will make the process smoother and safer.
Tools and Materials
- Two Google Nest doorbells (Wired versions)
- Screwdriver set (Phillips and flathead)
- Voltage tester (non-contact)
- Wire strippers
- Electrical tape
- Labeling tape or colored markers
- Drill and drill bits (if mounting on brick or concrete)
- Masonry anchors (if needed)
- Ladder (for reaching high doors)
- Smartphone with the Google Home app installed
- Compatible doorbell transformer (16–24V AC, 20–30VA)—if upgrading
- Bypass resistor (if using mechanical chimes)
Check Your Existing Wiring
Most homes with two doorbells already have a 4-wire setup. This typically includes:
- Two wires running to the front door (usually labeled “Front”)
- Two wires running to the rear or second door (labeled “Rear”)
- A common wire (often shared between both doors)
- A transformer wire (connects to the low-voltage transformer)
To confirm, remove your existing doorbell button and chime unit. You should see four wires total: two for each door, plus a common and transformer wire. If you only see two wires at each door, you may need to run new wiring or consider a battery-powered Nest doorbell instead.
Step 1: Turn Off the Power
Safety first! Doorbell systems use low voltage, but they’re still connected to your home’s electrical circuit via a transformer. To avoid shocks or short circuits, turn off the power.
Locate the Breaker
Most doorbell transformers are connected to a 15- or 20-amp circuit, often labeled “Doorbell,” “Chime,” or “HVAC.” If you can’t find it, turn off the main breaker to be safe.
Test the Wiring
Use a non-contact voltage tester at the doorbell button and chime to confirm power is off. Touch the tester near the wires—if it beeps or lights up, the power is still on. Double-check your breaker and try again.
Step 2: Remove Old Doorbells and Chime
Now that the power is off, it’s time to remove the old hardware.
Remove the Doorbell Buttons
Unscrew the faceplate of each doorbell button. Carefully pull the button away from the wall and disconnect the wires. Note which wires go where—this is crucial for reconnecting later.
Remove the Indoor Chime Unit
Unscrew the chime from the wall or ceiling. Disconnect all wires, but don’t cut them. You’ll need them for the new setup.
Label the Wires
This is one of the most important steps. Use labeling tape or colored markers to identify each wire:
- Front Door – Label as “F”
- Rear Door – Label as “R”
- Common – Label as “C”
- Transformer – Label as “T”
If your system uses different labels (like “Front,” “Rear,” “Trans,” “Com”), stick with those—just make sure they’re clear and consistent.
Step 3: Check and Upgrade the Transformer
Nest doorbells need a steady power supply to function properly. Older transformers may not provide enough power, especially for two devices.
Check Transformer Specs
Look for a label on your transformer (usually near the electrical panel or in a closet). It should list voltage (V) and volt-amperes (VA). Nest recommends:
- Voltage: 16–24V AC
- Power: 20–30VA
If your transformer is below 16V or under 20VA, it may cause issues like poor video quality, frequent disconnections, or failure to charge the internal battery (even on wired models).
Upgrade if Needed
If your transformer is outdated, replace it with a compatible one. Turn off the main power, disconnect the old transformer, and install the new one following the manufacturer’s instructions. Connect the “T” wire to one terminal and the “C” wire to the other.
Step 4: Prepare the Wiring for Nest Doorbells
Nest doorbells use a slightly different wiring method than traditional buttons. They require a constant power connection, so the wiring must be set up correctly.
Strip the Wire Ends
Use wire strippers to expose about 1/4 inch of copper on each wire. Make sure the ends are clean and not frayed.
Twist and Secure
Twist the exposed copper tightly and wrap with electrical tape to prevent shorts. This ensures a solid connection when you attach the wires to the Nest doorbell.
Step 5: Install the First Nest Doorbell
Let’s start with the front door.
Mount the Base Plate
Hold the Nest doorbell base plate against the wall where you want to install it. Use a level to make sure it’s straight. Mark the screw holes with a pencil.
If mounting on brick, concrete, or stucco, drill pilot holes and insert masonry anchors. For wood or siding, you can screw directly into the wall.
Connect the Wires
Nest doorbells have two terminals: one for the doorbell wire and one for the common wire.
At the front door:
- Connect the “F” wire to the doorbell terminal (usually labeled “Front” or “Doorbell”)
- Connect the “C” (common) wire to the common terminal
Tighten the screws securely. Don’t over-tighten—just enough to hold the wires firmly.
Attach the Doorbell
Slide the Nest doorbell onto the base plate until it clicks into place. Make sure it’s secure and level.
Step 6: Install the Second Nest Doorbell
Now repeat the process for the second door (rear or side entrance).
Mount the Base Plate
Follow the same steps: position, level, mark, drill (if needed), and secure the base plate.
Connect the Wires
At the second door:
- Connect the “R” wire to the doorbell terminal
- Connect the “C” (common) wire to the common terminal
Note: Both doorbells share the same common wire, which is why it’s essential to keep it connected at both locations.
Attach the Doorbell
Snap the second Nest doorbell onto its base plate. Double-check that it’s secure.
Step 7: Reconnect the Indoor Chime
Now it’s time to reconnect the indoor chime unit so both doorbells can trigger it.
Identify Chime Terminals
Most chime units have four terminals:
- Front
- Rear
- Trans (Transformer)
- Com (Common)
Connect the Wires
Reconnect the labeled wires to the correct terminals:
- “F” wire → Front terminal
- “R” wire → Rear terminal
- “T” wire → Trans terminal
- “C” wire → Com terminal
Tighten all screws securely. Make sure no bare wire is exposed outside the terminals.
Mount the Chime
Screw the chime unit back into place. Ensure it’s level and secure.
Step 8: Power On and Test
Now that everything is connected, it’s time to turn the power back on and test the system.
Restore Power
Go to your breaker panel and turn the doorbell circuit back on. Wait a few seconds for the system to power up.
Check the Chime
Press the front doorbell button. The chime should sound. Then press the rear doorbell—both should trigger the chime correctly.
If the chime doesn’t work, double-check your wiring connections. Make sure the transformer is providing adequate power.
Test the Nest Doorbells
Open the Google Home app on your smartphone. The app should detect the Nest doorbells and guide you through setup.
Follow the on-screen instructions to:
- Connect to Wi-Fi
- Set up motion zones
- Adjust notification settings
- Test the video feed
Make sure both doorbells show a clear, stable video stream. Check night vision, motion detection, and audio quality.
Step 9: Final Adjustments and Tips
Once everything is working, make a few final tweaks for the best experience.
Adjust Camera Angle
Nest doorbells allow you to tilt the camera slightly. Use the included tool to adjust the angle so it captures the ideal view—avoiding glare from windows or direct sunlight.
Secure Loose Wires
Tuck any excess wire into the wall or use wire clips to keep it neat. This prevents damage and keeps the installation looking clean.
Enable Smart Features
In the Google Home app, enable features like:
- Package Detection
- Familiar Face Alerts (if available)
- Activity Zones
- Quiet Time
These features help reduce false alerts and improve usability.
Troubleshooting Common Issues
Even with careful installation, you might run into a few hiccups. Here’s how to fix the most common problems.
Doorbell Doesn’t Ring or Chime Doesn’t Sound
- Check wiring connections at the chime and doorbells
- Verify the transformer is providing 16–24V AC
- Ensure the chime is compatible with Nest (mechanical chimes may need a bypass resistor)
Video Feed is Blurry or Disconnected
- Check Wi-Fi signal strength at both doors
- Move your router or use a Wi-Fi extender if needed
- Ensure the doorbell is receiving constant power
One Doorbell Works, the Other Doesn’t
- Double-check the wiring for the non-working doorbell
- Make sure the “R” and “C” wires are connected correctly
- Test the doorbell at the working location to rule out hardware issues
Battery Drains Too Fast (Even on Wired Models)
- This can happen if the transformer is underpowered
- Upgrade to a 24V, 30VA transformer
- Check for loose connections causing power loss
False Motion Alerts
- Adjust motion zones in the app
- Exclude areas like trees or busy streets
- Enable “Quiet Time” during low-activity hours
When to Call a Professional
While this installation is doable for most homeowners, there are times when it’s best to call an electrician:
- You’re unsure about your wiring setup
- The transformer is hard to access or replace
- You need to run new wires through walls
- You’re not comfortable working with electrical systems
A licensed electrician can ensure the installation is safe, up to code, and optimized for performance.
Conclusion
Installing two Nest doorbells with a 4-wire system is a smart upgrade that enhances your home’s security and convenience. By following this guide, you’ve learned how to safely handle wiring, connect both doorbells to a single chime, and troubleshoot common issues. With the right tools, careful labeling, and attention to power requirements, you can achieve a professional-quality installation without hiring a pro.
Remember: always turn off the power, label your wires, and test everything before final mounting. Nest doorbells are designed to be user-friendly, but they do require a stable power source and strong Wi-Fi to perform at their best.
Now that your dual Nest doorbell system is up and running, you can enjoy real-time alerts, HD video, and smart features at both entrances. Whether you’re watching for packages, monitoring visitors, or just checking who’s at the door, your new setup has you covered—front and back.