Rental Home Thermostat Gets Smart Upgrade Without Modifying The Dumb Controller

A problem facing those who live in rental properties comes with two prongs: that such properties rarely have up-to-date facilities such as heating controllers, and that landlords tend to take a dim view of tenants installing their own alternatives. [Andy] wanted to upgrade the heating controller in his home and was in this situation, so he came up with a smart controller add-on for the existing mechanical timer that does not irreversibly modify anything and is easily removable when he moves on.

This sounds like an impossible task, but it’s one he’s done very well by mounting a stepper motor on a 3D-printed frame over the timer switch. It’s the type with a motorised ring onto which plastic fingers can be placed to flip a switch on or off; he’s simply removed the plastic fingers and designed a shaft extension for the motor that simulates their passing the switch. He can now turn his heating on and off at will from an ESP8266, in this case on an Adafruit Feather Huzzah.

Behind it all lies Adafruit IO with a custom dashboard — Hackaday’s [Sean Boyce] took this service for a trial run if you’d like his take on it’s features. For this project, Adafruit IO delivered exactly what [Andy] was after but still left a few teething troubles. The stepper needed to be told not to try to hold its position, and moving a stepper very slowly generated wait periods long enough to trigger the ESP’s watchdog timers. Adding in IFTTT gave him the ability to schedule, as well as Alexa control. All in all he’s replicated some commercial offerings with a lot less cost and all without annoying his landlord. You can see it in action in the video below the break.

25 thoughts on “Rental Home Thermostat Gets Smart Upgrade Without Modifying The Dumb Controller

      1. I clearly meant walk into the apartment, not the cupboard. And if your point is that it’s hidden so the landlord wouldn’t see it anyways, why not just replace the thermostat?

  1. As an HVAC service tech, I deal with alot if tenant/ landlords and I’ve acted as mediator in many thermostat discussions. Most landlords will agree to a smart thermostat on two conditions; Tenant must supply thermostat and must be handy enough to install without causing damage or willing to pay for technician to install. Second, the old thermostat MUST be kept and stored BY TENANT and reinstalled at end if lease OR smart thermostat stays in place.

    1. I seem like there was just one complaint, and the tenant took it upon himself to get some kind of heat, using something like a mobile app that connect to outside servers, to produce heat to his residence, something like Intuit Things;

    2. There’s always the issue of the IoT lightbulb with smart thermostats or any home automation product.

      It’s simply more work for no real benefit to anyone. After all, once the tenant who wanted the smart thermostat gets bored of fiddling with the temperatures in about a year or two, the smart thermostat usually ends up being set to some fixed schedule like a regular dumb thermostat and that’s it.

      If they keep the thermostat, the landlord inevitably has to deal with the third party service provider that gives you the fancy web/phone app, and deal with the account management when the tenant goes away, assuming the company hasn’t folded or pulled support for that particular product already. These things are supposed to last for up to 50 years, but the business reality of any “smart appliance” is about 5 years and then the company has to figure out how to sell the next thing.

      1. Also, landlords have to deal with insurance providers, and if it turns out someone can fiddle with the heating system remotely over the internet, your premiums may just need some re-calculation…

      2. My regular dumb thermostat doesn’t have any options for different days of the week, daylight savings, occupancy, etc. I’m not saying I want something that lasts 5 years, but there are definitely benefits to ‘smart’ appliances.

  2. I am pretty sure I would not be happy with something sticking out of the wall like that. I think a cleverer hack would be to use a peltier device to fool the thermostat. You could have one module with and esp8266 and a switching device and the peltier device and perhaps a foam box over the thermostat and an esp8266 with a temperature sensor someplace more central in the room. You talk to the remote thermostat and it talks to the peltier device. This would also let you adjust the temp for where you sit, not some random place on the wall.

    1. That sounds like asking for a whole of of trouble with thermal mass messing up your control. The easy solution is just to talk to the landlord, or just swap the thing and swap it back neatly and nicely whenever you leave. Any dim views they have likely come from people clumsily tearing their property to shreds, instead of people making solid improvements without it costing him a dime.

      1. Na, there is not a lot of mass there. In college I lived in an old house, the landlord was too cheap to split up things so he paid the utilities. He put in a fixed 68 degree thermostat right over a heat duct. SOP was hang a bag of ice over the thermostat. It worked real well. When you got warm enough, you took the bag off.

    2. I did something like that once with a fancy electronic thermostat meant to control a window A/C and an incandescent light bulb. The thermostat was obviously designed to turn on the A/C when it got warm enough. In the winter, I used it to turn on the incandescent bulb when it got warm enough. The bulb was situated under the baseboard heater’s thermostat. With the bulb off, the heater would turn on. Once the room was warm enough, the bulb would turn on, making the thermostat turn off the heater. But of course, I could keep the heater off even when the room got colder, just by setting the fancy thermostat appropriately.

      1. In the case of wanting to make the thermostat call for heat, you need to cool it off, when you want it to call for A/C you need to warm it up. A resistor would work for cranking the A/C, but you need something to chill the thermostat to make it call for heat. Thus the peltier device. Drive it by an H bridge and it does both.

  3. This hack deserves more appreciation.

    I can’t tell you how many rentals I’ve lived in that I could have saved hundreds if not thousands in heating bills because I didnt have something like this, one, because I couldnt have bought this- and 2- because Im dumb enough on electrical stuff that I couldnt have made this.

    Too many ancient rentals in Pittsburgh where I live, with absolutely zero insulation or windows newer than 40 years old.

    This screams make it and sell- renters would love this! If it were an official product, these could be retrofitted with more acceptance, and a lot of people would save serious $

    1. I wonder if a part of the problem is the same that tends to affect my area; “all or nothing” building codes. I forget what the standard has crept up to now, R-40 insulation I think… which in a lot of older homes is unpossible without tearing it half apart and completely rebuilding it. $100,000 worth of work to stick $2000 worth of insulation in. They’ve probably got about R-12 and doing the best they can probably get R-40 in some bits but only R-20 in dormers and storey and a halfs where the beams aren’t deep enough to do more…. and that would save quite a bit of energy…. but no, code says if you touch it, it has to be R-40 or nothing, so it’ll just go on costing energy and emissions.

      1. Yeah, agree with that. Similar in Australia – if you touch it, you have to bring it into line with the latest building codes. Solution: either don’t touch it, or if you do, make it look as if you didn’t.

  4. It’s an ancient trick to place a nightlight (7 watt) incandescent bulb on the wall under a thermostat, then connect the bulb to a timer for a timed-reduction thermostat. Did it myself in the 80s and it worked very well. Adjust the position relative to the thermostat to adjust the degree(s) of temperature reduction. Probably not very good with modern LEDs :-)

      1. At the risk of making a dumb mistake here, but… wouldn’t a 7W LED produce less heat than a 7W bulb because it’s more efficient, i.e. outputs more light and less heat from the 7W of power it dissipates, than its incandescent counterpart?


          A 7W Incandescent bulb will have an overall luminous efficacy of around 1%, whereas a 7W LED will be around 20%, both depending a lot of their quality, but yeah, a 7W LED will put out closer to 5.5W of heat and the incandescent would still be very close to 7W.
          BUT :
          This assumes the LED itself consumes 7W of electricity. Some measure how much power goes through the LED-chip itself and some measure total power consumption, which includes the driver-circuit. The driver may very well produce more than 1.5W (~80% efficiency, which i believe is VERY optimistic), which may make the LED-bulb output more heat overall

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