HoneywellST9400C Thermostat Programmer. 7, 2-Channel, 3 on/Off per Day, 24 V, White, 1

Genuine part and so easy to set upI had to replace the existing controller because the buttons became "tired" and matter how hard I pressed I decided to bite the bullet and buy a new unit.I didn't even have to set the clock because it had retained the time and date in the memory.The buttons are working fine now. I should have replaced it sooner and saved myself a few months of grief!

I brought the ST9400C to replace the ST6400C which had seen better days. The ST9400C is a direct replacement for the ST6400C and as such has been cleverly designed to sit on the same back plate as the ST9400C. This means no need to rewire, drill new holes or the need to call a plumber. All you do slacken two securing screws at the bottom of the ST9400C hinge the unit up to separate the backplate and main body of the ST9400C into two halves. You do the same process on the ST6400C, switch off your electricity supply at the mains and simply fit the ST9400C main body onto the existing ST6400C backplate. It is as simple as that, jobs done, hassle free and quick.The ST9400C unit comes complete with a simple to follow ‘quick programming guide’ which really makes light work of programming your hot water and heating needs. From start to finish I had replaced my old ST6400C with the new ST9400C and programmed it in no more the 15mins. I love the fact that the ST9400C even adjusted itself when the clock’s went back for winter.If I had to criticise anything it would be that the buttons do sometimes tend to stick behind the plastic body of the ST9400C, however pressing the buttons delicately seemed to solve the issue. I highly recommend the ST9400C. I have read issues about reliability of the ST9400C but since installing the unit about a month ago I have not had a single problem.

Simply turn off the power at the fuse box, undo two screws and snap out the old unit from the backplate, click in the new one and tighten up the screws again and put the power back on. Job done. 15 minutes tops, including opening the box and fetching the screwdriver.Well done Honeywell. What a clever design.

Brilliant. - worked straight out of the box - a life saver - simple easy to follow instructions

I had an old ST9400S which would no longer function as the relays kept clicking and it was turning on and off every two seconds, meaning the system could never reach temperature. Tried temporary fixing by turning the backlight off and making heating and hot water come on at different times but eventually stopped working all together.Read somewhere on the Honeywell forums that the ST9400S and ST9400C used the same backplate so decided to purchase this as offered more programming and was cheaper. Installation was relatively pain-free apart from having to dremel off some of the plastic at the bottom as I do not have it mounted flush but rather with a wire running up the wall in the boiler cupboard. Ensured safe installation by turning off the mains as well.When turning mains back on, immediately came on with right date and time and immediately fired up the system again. Home back up to temperature and nice hot water; perfect!

Bought as a replacement for a simpler (and possibly even prehistoric) Honeywell controller that had died rather suddenly after many many years of service (and left us without heating or hot water until we figured out the problem).The controller is simple to install (I used a wiring chart that I found online that detailed how the wiring on the new controller related to the wiring on the old controller) and even simpler to operate. The LCD screen is bright and clear and informative - the default setting is to have the screen lit, but it will remain lit at all times (a little disconcerting initially). There are a host of settings that can be tweaked (including whether the LCD display is lit or not), and even the programming of the device is simple, making it easy to have different settings for each day or to copy the settings from one day to the next. There are even built in programs that you can use if you don't want to set your own.Simple to use, not unpleasant to look at, quick and easy to fit (at least as a replacement) & (so far at least) reliable.

This product is for normal 240 volt household mains electricity supply and NOT 24 volts as indicated in the description.

Compared to my previous Honeywell programmers, with easy to use sliding switches, this is much more attractive......and that is where the improvement ends! It is so difficult to set, unless you want to leave the same settings every week, all year, that we just use the "extra hour(s)" feature all the time and never set it to auto. OK, I'm not young, and my reading vision is poor now, but I'm not the only one by any means who will find this fiddly and exasperating to use with b...r all advantage over the previous units (except that it is so bright you don't have to turn the light on in the same room)!