A mind that is stretched by a new experience can never go back to its old dimensions.

Installing a Thermostat controllable with Wifi

June 23rd, 2011 Posted in home improvement

I recently installed a Wifi Thermostat in my condo. A programmable thermostat is a must, for the following reasons:

  • Turn off the AC / Heat while you’re at work
  • Cool off the apartment before you return
  • Save a LOT of money

A lot of people leave their temperature at the same setting all day and night. This is a terrible waste of energy. It is much more cost effective to cool it when you are returning home, and to turn off system when you leave in the morning. It is hard to remember to do it manually, so a programmable thermostat is significantly better.

I decided to one-up the programmable thermostat and completely geek it out with a wifi thermostat that one can control from their computer, Android or iphone.

The thermostat of choice was this one:

The CT30 from Radio Thermostat Company of America. Despite the cheesy 80’s sounding name which you may liken to other well known institutions like the Peanut Corporation of America or Yokogawa Corporation of America, this is a fine thermostat. The interface is well designed and the software is surprisingly good.



This thermostat was quite easy to install. You need to have a C-Wire in your condo, which is a 24V AC electric supply. It frequently comes from your HVAC unit directly. Most modern buildings have this wire. Our condominium, The Floridian, has a C-Wire ready to use.

Removal of the Old Thermostat

You should remove the old thermostat carefully. In case you find that your wiring isn’t up to snuff and you don’t have a C-Wire, you’ll want to put this back. I had a cheap, builders-grade digital thermometer with only two buttons. I kept it just to have a backup. It had some strange snaps in the back, but can be pried off with a flat screw driver:

Pry it off. It has two weird snaps holding it on:


Turn off the HVAC unit and any A/C Compressors you have. Hopefully they are on individual circuits and individually labeled. The C-Wire carries 24V of electricity and could give you a nasty jolt. It could kill your goldfish but is unlikely to kill you.

Prepare the new thermostat

Remove the old wall plate. Remove this carefully. In our condo, the builder had half-assed the job and hadn’t put any anchors into the wall. I also found out that there was a hidden aluminum junction box immediately behind the drywall which made it hard to add my own wall anchors. I highly recommend using molly bolts in drywall, otherwise any screws you install are apt to fall out with just a light tug.

Wiring and Mounting

Our building has a 5-wire system:

5-wire heat pump system with Auxiliary Heat

This means that a heat pump is used to raise and lower the temperature in the condo. When the temperature needs to be raised by more than 5 degrees, or the heat pump is malfunctioning for some reason, an electric Auxiliary heater kicks in as “emergency heat”. This heater consumes a lot of electricity and is expensive to run. Think about heating with a hair dryer. It is imperative to buy a thermostat that can have a meaningful relationship with the auxiliary heater.

Follow the instruction manual to wire it up and mount it to the wall using wall anchors. You may have to drill up to four small holes to install the wall anchors. They will help to keep the thermostat installed snugly against your wall. I was only able to install two wall anchors because of the pesky hidden aluminum junction box I spoke of before.

Final Product

Total Time: 45 Minutes

Total Cost: $130

Total Savings: $1m, at least. Per week.

In all seriousness, installing a programmable thermostat, even an ordinary one, will save you a lot of money on your energy bill. It will keep the apartment at your ideal temperature when you’re home, and at a more efficient temperature when you’re away. Don’t believe the myth that cooling your home all day while you are away is more efficient than turning on your AC 30 minutes before you come home. Nowadays, I can turn on the AC with my phone anytime I want.

  1. 4 Responses to “Installing a Thermostat controllable with Wifi”

  2. By Kristian Hermansen on Jun 23, 2011

    Check out these cool projects :)



  3. By Rani on Jun 24, 2011

    You have certainly been the busy bee with these home installation projects. You should start your own home improvement show or a blog just for it.

  4. By melissa on Jun 29, 2011

    Extremely useful and witty post!

  5. By rajat on Jul 3, 2011

    thanks for the comments! these posts have been getting a lot of traffic. I’m planning the next project… perhaps a home beer brewing setup. that would be a real home improvement!

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