I have used various types of countdown timer for my heaters for years. They ensure the heater will be turned off automatically after a set period, usually two hours, so as not to waste power. HPM used to sell specific mechanical countdown timers, and I had several of these. Unfortunately they all stopped working after a time. The next type of timer I had is the Arlec PC900 as referred to in this post. I purchased a pair of these about three years ago and they were used intermittently. Unfortunately one of them has now stopped working reliably, it got stuck on and resulted in huge power wastage as the heater stayed on way longer than planned.
So the next plan is to use electronic digital timers which often have a countdown function. I have owned quite a number of digital mains timers starting with Kambrook brand going back to the 1980s including the KD86 which was an interesting design with a sliding function switch down one side of it. As the picture shows it was capable of being rotated to different orientations in order to try and fit it into different socket configurations/locations.
Before the KD86 I owned other Kambrook timers and since then, a variety including HPM, Arlec and other brands.
HPM make a range of digital timers including the D817 series. Currently there are two quite differently designed models commonly available, the D817SLIM and the D817/2DP. The slim model is designed so that two of them can fit side by side into a double power socket. Reviews on sites suggest these timers are unreliable as they tend to stick on after a while. The countdown function is hard to use as the countdown time has to be programmed into the timer every time you want to use it. So in actuality to engage the countdown function you have to perform these steps every time to use it: in clock mode press UP to set on/off state to the right state; press MENU to access Countdown mode; use UP/DOWN/OK to set hours minutes and seconds; and then Countdown starts automatically.
By contrast the 2DP model whilst somewhat more bulky and clunky in appearance, is very easy to set up for Countdown. To program the Countdown mode, after initial setup of the timer for the first time, press DOWN which will cause the display to show a “d ON” or “d OFF” which indicates the initial on/off state of the timer for countdown mode, and also the display will show the preset delay; press SET so that “d ON”/”d OFF” flashes and then use DOWN to change between “d ON” or “d OFF” initial timer state; use UP/DOWN/SET to enter the hours minutes and seconds; and then press CLOCK to end the programming. Then when ready to use the timer, simply press DELAY to start the countdown; and to cancel, press DELAY again before the end of the countdown period. As implied above, the program settings made for the countdown are retained between uses so that for all subsequent uses, simply pressing DELAY will start the countdown; and on the device’s display you won’t see the hours minutes and seconds counting down, just a flashing “d ON” or “d OFF” as appropriate.
Having purchased both timers to evaluate as they were very cheap (the SLIM currently retails in NZ for around $15 and the 2DP for around $20) I can see the SLIM joining another electronic timer (a Elto) on the shelf. I have not used the Elto for some years and only as a regular on/off timer; these timers have six buttons in two rows and are sold under a wide range of different brand names. See picture below:
As is typical of me I didn’t check to see that I already had this timer and that it was sitting on the shelf ready for use. Like the 2DP HPM timer it retains the countdown settings between uses and all you have to do is to press the CD button to start using it; and it is easy to program, the only trap being the need to press the Master Clear button when it is first set up as the display will just show random rubbish. All of these timers have some form of internal battery to back up the settings in case of power failure, and often times you will see them displaying time in the shop if they have been plugged in long enough to have an initial charge. The Elto timers often go for $10 or similar and can be found in supermarkets and all sorts of places under different names, usually with the same front labeling as you see here and a specific brand name on a sticker on the back.
So there is a precis of some electronic digital timers that can be used for countdown mode and can be a good replacement for mechanical countdown-only timers at a reasonable price. What hasn’t been totally solved is how to limit heaters to a set temperature in the room. As I explained in my previous article there is an Arlec plug in thermostat (misleadingly labelled as a “timer”) from Bunnings that depending on reviews may or may not do the job. I am still using an older Honeywell mechanical thermostat that used to be available attached to a plastic block with a prewired cord on interrupted tapon plug; it functions very well for this but will eventually wear out and then it will probably be a challenge to find a suitable replacement and likely I would have to take the parts of this unit and adapt them to a currently available commercial thermostat. So we shall see what happens in the future.