Nest + Islandaire
Connect a Nest Learning Thermostat to an Islandaire PTAC unit
Ever wanted to install a smart thermostat to your apartment’s floor unit? This post will guide you through a quick and easy method of hooking up a Nest Learning Thermostat (but really, any type of thermostat) to an Islandaire PTAC unit.
What’s involved?
- Look for the operating and maintenance manual for your PTAC unit.
- Order the necessary connectors and parts to build a custom cabling harness.
- Assemble the cabling harness with a connector, thermostat wire, and cable sleeving.
- Mount your thermostat near the PTAC unit.
- Attach the cabling harness and test your thermostat.
Where do I find the manual for my PTAC?
The operating and maintenance manual for your PTAC unit can generally by found on the manufacturer’s website. For Islandaire PTAC units, here is a generic manual for their models.
So, why do you need a copy of the manual? Well, the manual will help you determine if your PTAC unit has remote capabilities to begin with. If so, it can help you understand how to use the remote interface to interact with the unit. Within the Islandaire manual, page 16 describes and provides a detailed pinout of the interface available. This port will be used to connect your thermostat to the PTAC unit.
What parts do I need?
This is the tricky part. Most manuals will likely not provide the part number of the interface on the PTAC unit, since this information is generally not useful for the end user. You will have to dig around and do some research to find the exact connector that you’ll need for your PTAC unit.
For my Islandaire unit, the remote thermostat interface uses a TE Connectivity MATE-N-LOK connector. In particular, I needed a male, 1-row, 8-pin connector, with compatible pins for 18 AWG thermostat wiring.
As mentioned above, you’ll also need some 18 AWG thermostat wiring. The length here depends on how far away you’ll be placing the thermostat from the remote thermostat interface. I would suggest leaving a foot or two of slack, since most of the wiring is easily hidden within the PTAC unit.
Note that since the wiring won’t be in-wall like a traditional setup, there will be at least some wiring that will be exposed and visible. This is where you’ll need to plan out how to hide those wires. In my application, I used cable sleeving and heat-shrink tubing to keep it nice and clean (as well as designed a 3D-printed stand that neatly covers the wiring as it exits the Islandaire unit).
How do I put this together?
Now that you have all the parts that you need, it’s time to piece them together! This process will differ depending on the parts you needed for your particular PTAC unit.
With my Islandaire unit, I started with the 18 AWG wiring. The Nest thermostat only needed 6 of the 8 pins, so prepared 6 wires by cutting them to 3 feet each. The wires were then sleeved and stripped on one end facing the thermostat. For the end facing the PTAC unit, pins were crimped onto the wiring, then inserted into the MATE-N-LOK connector. With everything in place, the cable sleeving was secured with heat-shrink tubing on both ends.
At this point, plug in the cabling harness to both ends just to test and ensure it works properly. You’ll have to consult both the PTAC and thermostat manuals to determine which pin on your PTAC connects to which pin on your thermostat.
