Honeywell ST9400C ST9400C1000 7 Day or 5/2 Day Two Channel Programmer for Central Heating and Hot Water. 3 On/Off per Day. White Programmable Controller - Combines with Thermostat. (S88608F)

This was bought as a like-for like replacement for one in which the relays had failed. It was easy to replace. The screws to undo the old one had been plastered over but once I dug them out it was easy enough to loosen the failed controller. The replacement just slots on the top. No work at all really.I've given only four stars for two reasons. First, the retaining screws were hard to access even after I dug them out of the plaster. You can say this is the plasterer's fault and that might be true, but I'd have preferred a design where even a crap plasterer can't mess up the installation.Second, the whole concept of sitting a controller next to the boiler and programming to switch on or off at certain times just seems a bit dated. I really want to control the temperature in each room by time of day using my phone. I know this product isn't designed to do that but combined with the other problem I'm only going to give four stars.

My very old ST3200A 2 channel 1 day Honeywell needed replacing after the hot water became permanently on due to broken slider.Had a look round, and this ST9400C was the latest in a line of incremental replacements release by Honeywell.It uses the same backplate, so ordered it on that basis, having checked the wiring online first was unchanged.MAKE SURE YOU TURN OFF THE ELECTRIC FIRST.Remove old controller from the backplate.Recommendation is usually to replace the backplate, with new enclosed one.. I didn't.However, what I did do was spray the old backplate electrical contacts with electrical contact cleaner, and wait 10 minutes to dry..I then put the ST9400C on the old backplate, switched electric back on. and everything up and running first time.

Easy replacement of previous item

My programmer started clicking on and off repeatedly and I had no hot water. Apparently this is a known fault with this model which can be rectified with a new front plate. The item arrived promptly. Changing the face plate involved only removing 2 screws and swapping the face plates over, very simple. Heater was up and running again in no time. Problem solved and no need to call anyone out. It is very simple to programme and apart from this fault has been very reliable for years.

This unfortunately was not compatible with our heating system

This programmer is easy to install, easy to program and easy to use. The only slight downside is the longevity of the 'power supply'. I say power supply because it could really do with a proper switch-mode power supply. In fact, the mains voltage is dropped to the required voltage by a polymer film capacitor, which does not have the life expectancy of a proper power supply. That said, I was happy to replace the original one (which failed for that very reason) with a like-for-like unit. The original one will be repaired (quite easily with the help of YouTube videos) and kept as a spare (sorry Honeywell!!)

This was to replace one that a plumber had brought in 7 years ago and was not fully operational , so got this one ordered and swapped it out , and it is fully operational now . Works as expected , could do with changing the thermostat now to a more modern one though.

vgood