Review: Filtrete 3M-50 Wifi Thermostat

I came across this particular wifi enabled thermostat a year or so ago, unfortunately they are not available in Canada. I’d guess this is simply the additional headache of bringing an electronic device to market in Canada (yes, different hoops than what is needed in the USA) and the market size. On my last trip to the states I took the opportunity to drop into a HomeDepot and pick one up. There was only 1 unit in the entire city I was in (I had to go to both HomeDepot stores!) – so you may have trouble getting one even if you live in the US, I suggest you call ahead.

The sales pitch on having your home thermostat wifi enabled is to make it simpler to program, and easier to adjust from anywhere in the house or out of the house. When we leave on vacation, turning down the heat and reprogramming the 7 day schedule is pretty low on the priority list. Being able to do so from the hotel over the internet would be handy. I’m looking forward to the ability to pull out more statistics from the device and surface them in graphs, for example yesterday my furnace was on for 4hrs 47mins and today it ran 2hrs 46mins (it was much warmer today).

Most of this post will discuss the installation process, as this is primarily my experience with it so far. Some of this will be specific to my particular install but I’ll try to walk you through the process I used to arrive at a successful result. If you want to stop reading here the short version is that it’s pretty cool, you probably want one.

The first step is to read (or at least flip quickly) through the manuals included. The packaging strongly indicates you need a C wire, the manual lists it as optional. The C wire is required, don’t get confused by the manual. Next take a look the wiring for your existing thermostat.

The good news is that the wire coming out of the wall has more than enough conductors to carry a C wire if I need to add one. The bad news is that I’m standing there scratching my head because I don’t really understand the current wiring.  My existing thermostat is a Honeywell MagicStat CT 3300 for which I was able to easily find a manual online. This helped me identify the wiring that was connected.

Next stop is to go take a look at the furnace, to map the other end of the wires. Unfortunately between the furnace and the thermostat I found this, something I’ll call the mess-o-wires.

The mess-o-wires ties in my A/C unit to the furnace and the thermostat. Opening up the furnace I get to the control board where the wiring starts.

So basically I have my furnace, connected to a wire A, this in turn heads to the mess-o-wires, then connects to wire B, this runs upstairs to the thermostat. Mapping the wire colors and connections results in the following table. The last column is the CT3300 hook ups. I also found a helpful reference to understand what the wiring names were.

Color Wire A Wire B CT 3300
Y orange yellow Y
R red red + black Rh + Rc
W1 white white W
G green green G
C black

This lead to an ah-hah moment. So I’m basically running in a 4 wire mode at the thermostat W Y RH G. The RH and RC are bridged back in that mess-o-wires. Knowing this helped me map to the 3M-50 manual for how to properly hook things up. The solution is that I need to fix the mess-o-wires to allow the C wire to run up to the thermostat using the black wire. Let me stress that this is unlikely to be your solution, but the process of wire tracing and mapping should help you understand your current setup and how to perform the install. If this is over your head, call your furnace service folks to do this part.

Once I was past this part, the actual installation went very smoothly – just follow the manual. The wifi unit ships along with the unit, but is not installed and the manuals don’t seem to reference it beyond providing a URL: I inserted the wifi module while the thermostat was on and running, it seemed to handle that just fine. When you do visit you’ll find a friendly 3 step process:

  1. Register for an account on the web
  2. Verify Thermostat Installation
  3. Use laptop to connect your thermostat to your local wifi, and then to the internet

It’s not really three steps since step three contains more sub steps. My notes are a bit sketchy here, but it didn’t seem to provide much in the way of hand holding – they assume you know what you’re doing when it comes to wireless setup. At this point I’ll deviate from how I did the setup and talk about the iOS app. If you have an iDevice, then you should do step 3 above entirely using it. I’m not sure how smoothly a second iOS device will work out as it seemed that I was forced to re-setup the wifi connection (step 3) on the iPad even though it seemed to be working fine over a web browser. (again my notes are a bit rough as to what happened) I’m certain you can have multiple iOS devices, you just might have to go through the setup phase more than once.

There is also an Android app. This seems to be poorly advertised as I only found it while writing this post, they should really add it to the website. Adding the app to my phone and logging in, I’m able to view my thermostat without any network re-setup required. So my iOS app experience above of needing to re-setup the wifi must have been due to some other issue I was having.

I will say that I really like the wireless configuration approach. Much better than the Logitech HarmonyLink mess with a USB cable and browser plugins. The HarmonyLink could easily adopt this style of setup – creating an ad-hoc network to do the wireless configuration. The thermostat generates a 5 digit verification code to ensure that it’s really you, the HarmonyLink could simply flash the led to give you a verification pattern.

For some reason Chrome didn’t seem to work to create an account. Switching to Firefox solved this. After I had created the account, Chrome worked just fine. In fact, the website has a reasonable mobile layout as well. So a strike against them for doing something odd with account sign ups, but kudos for getting it mostly right no matter what device you visit the website with.

The iOS app is very simple, it lets you control the basic functions: temperature up/down; home/away; fan on/off/auto; heat/cool. You cannot set a schedule with the app it seems. The schedule can be set on the device (but who would do that?) and via a full web browser. The mobile version of the website is limited in a similar manner as the iOS app. The Android app appears to offer the same functions as the iOS app.

Configuration of Celcius vs. Fahrenheit is supported by the web/iOS/Android app in a single setting. The physical display on the thermostat requires you configure this as is shown on this youtube video. This had me puzzled for a bit until I found the video link, it is also mentioned in the FAQ.

There is a developer API available and folks who’ve created impressive private versions of a web UI. Interesting that temperatures are all Fahrenheit in the developer API, so I assume that’s how it is stored internally. I’ll certainly be experimenting in this direction when I have some time. The forums seems to be fairly active and have some good content in them from the quick browsing I’ve done.

12 thoughts on “Review: Filtrete 3M-50 Wifi Thermostat”

  1. Does it speak ipv6?
    Or will you need a port forward so you can get to it from the hotel?
    Or does it call home?

  2. My internal network is IPV4 still – no reason to move to IPV6 with a NAT. The wifi documentation is pretty much all online but poorly, mostly focused on setup issues. I believe this document is for the wifi module, and it indicates it has IPV6 support. Worst case, that’s a starting point to search out more details.

    The device itself calls home to the ‘cloud’ every 5 minutes or so. So when you’re away, the app access the cloud and the thermostat picks up the change on the next call home. [some of this is assumption on my part]

    When you’re at home (on the same TCP IP network), the app will access the device directly – providing immediate updates.

    I’ll likely cook up some additional controls and graphs, allowing me to control it via a protected area of my webserver (hosted locally).

  3. Can you tell me what the lowest temperature setting is for this Tstat. I am trying to find aTstat that can maintain a temperature near the freezing point.

  4. Ray, interesting question. I’m using my to manage the temperature in my home – so my needs tend to stay well above the freezing point.

    You can get manual etc, from here:

    There are also the forums I’ve linked in the main blog post.

    Using the Android software to program the thermostat, I’m allowed to set a temperature of 2C (just above freezing). This may be a limitation (or a feature) of the software and may not reflect reality. You’re best to contact the company for a real answer.

  5. I did in fact contact the company and they tell me that the you can set the Tstat to 35 F. This should work for my requirements. The company I contacted was Current Inovations and the model is CI-500e. Looks identical to the one you have pictures of except for the logos.

  6. I have the CT50 for 2+ years and its been great. Recently however it has started to “click” every 3 -5 minutes and very annoying at night as its in the hall outside the bedroom. It stops when i take out the wi-fi module. I have the system set to heat, not auto, so its not an “on and off” temperature confilict.

    Has anyone ever identified this as a problem?

    Thanks, Dan

  7. I’ve only had my unit a bit more than 1 year. No clicking that I’ve noticed, but it’s in a less obvious location in my home. Hopefully someone else will find your comment and be able to provide a more informative answer.

  8. I’ve had a 3M-50 for less than a year and it started making the clicking sound about a month ago every time the fan would turn on (1 click) or off (2 clicks) very annoying, especially at night since it’s in our master. I’ll try taking out the wifi module as Dan said but that kind of defeats the purpose of a wifi thermostat.

  9. I happened to be in the same room as the unit the other day when the A/C kicked on, and I heard the click sound. It sounds just like a mechanical relay to me, something I wouldn’t be surprised to find inside the unit. I wonder if over time the damping material that kept it quiet has broken down and now it clicks.

    Fortunately it’s in a location that isn’t close to bedrooms or other quiet areas of the house. If I recall correctly, even my old ‘dumb’ control used to click when changing states.

    I they had used a solid state relay (more expensive) then this click wouldn’t be present, but I’m not surprised that they chose a mechanical relay.

  10. I would say that I really like the wireless configuration approach. Much better than the Logitech HarmonyLink mess with a USB cable and browser plugins. The HarmonyLink could easily adopt this style of setup – creating an ad-hoc network to do the wireless configuration. The thermostat generates a 5 digit verification code to ensure that it’s really you, the HarmonyLink could simply flash the led to give you a verification pattern.

  11. The other day I got an email from the “Radio Thermostat Team” to let me know that there is a shutdown plan for the hosted service. The sunset date is May 15, 2023.

    The email references the ‘mobile app’ – but I’m pretty sure that the website will go dark then too. The good news is that local access should still work and there are plenty of solutions that manage things locally. What isn’t clear is how the firmware will deal with the lack of external site, it may be time to look for another device (or build one) – but as long as it keeps working locally I’ll probably just keep using it.

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