Horstmann 425TIARA Programmer, Black

Product Information

Our 425 series of mechanical programmers are the simplest way to control hot water and central heating in the home. The Horstmann 425 Tiara Mechanical Programmer offer a easy to use and simple way of controlling hot water and central heating systems, it uses a 24-hour rotating dial with 2 on/off periods indicated by the red and blue pins. I have got a small problem with my programme, I think, when it's set for CH it comes on but when it's on for HW ( which is what it it is currently set during summer) it Although it says "not user serviceable" I thought I'd have a looksee anyway - I'm not without some skills in the repair and replacement of PCB components - however I can't get the bloody thing off the wall. There's a baseplate which is fixed to the wall/hole in the wall onto which the controller should plug, and is secured with two screws on the top.

There must be something snagging. It's never been removed before. I had to remove plaster from the groove/slot of the two screws from when the house was built (9 years ago). I realised it as the boiler was still on one night when according to the programmer itshould have been off..

The problem only started this week, I have never had any problem before..I have been using set on HW for the past 2 months now that summer is upon us!!!!!!!!!!

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It seems to have a valve on the top pipe that goes into the cylinder. I have 6 cables going to the timer.

So there you go. It's given me some confidence to look at the Heatmiser wifi-connected thermostats next. This would not allow your system to work properly on the CH, so I have to assume you have already 'had a go'. The Tiara has all the capability and features of the 425 Diadem, but without the indicator lights. The Tiara is ideally suited for both gravity systems and fully pumped systems with either mid-position or zone valves.The 425 Tiara is a two circuit programmer for hot water and central heating and is ideal for use with gravity systems and fully pumped systems with mid-position or zone valves. It has 16 programmes available for fully pumped systems, including independent programming of heating and hot water as well as 10 programmes for gravity hot water/pumped heating systems. Obviously this isn't ideal, you get a real mess if you try and use the timers, as each pin does something it isn't supposed to. I also don't really understand how each of the two-way valves operate - whether the timer "job shares" between the two zones and whether two NEST thermostats can replace that functionality. Or if each thermostat demands heat and the timer is on for each zone, both valves just open and they get served with hot water equally. Fitted new one and was slightly irked that the LCD screen on the new one is damaged - faded in places making it hard to read. However the supplier has already accepted the fault and will swap it for me.