Horstmann 425TIARA Programmer, Black

Product Information

Our house experiences brief power outages from time to time. The heating controller's "life-long" battery must be dead (9 years old) because it regularly displays the incorrect time, leading to cold water at bath/shower time. So there you go. It's given me some confidence to look at the Heatmiser wifi-connected thermostats next.

I could buy a new programmer and change it but i want to be certain this is what the cause of the problem is... Tiara, two channel programmer with 16/10 programme setting for fully pumped or gravity hot water/pumped CH systems.Select ON/OFF twice a day, ON all day,or permanently ON or OFF with advance switch and 9 pin wall fixing plate. 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. Removal *should* be simply the removal of the screws and a firm pull of the unit to unplug it from the baseplate, however even pulling with all my 100Kg, I'm not shifting it.

Product Specification

If this isn't sensible for somebody with little experience like me, what should I do - cut my losses and buy a real H27XL? Or is there a cheaper alternative? Thanks - I read that earlier but even trying that suggestion feels like I'm pulling the baseplate off the wall too. HORSTMANN (SECURE) 425 TIARA PROGRAMMER - Now use 4210051 or 4210056 Our Part No 4210005 MPN NU0550301000 Some people will, incorrectly, refer to your type of system is a "gravity" one. The term should really be used only for systems where the circulation through the HW coil is due to the change in density of the water when heated; i.e it is not pumped through the HW coil. There are way too many options out there, so we have taken on ourselves to find the 10 absolute best reviewed central heating controllers.

Sounds like a 2 port motorised valve, yes a valve to stop the HW from getting hot. Sounds like you have gravity circulation for the energy supply circuit to the hot water which can be stopped with the valve. And a pumped circulation for the energy to the radiators which is controlled by the pump being on or off. 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. What I really want to do is to install a NEST in place of the two thermostats, and a single timer for the water but I don't yet understand what wiring my system employs and how I might convert that for NEST. The Tiara is ideally suited for both gravity systems and fully pumped systems with either zone or mid-position valves. They use the same wiring. Coronet uses terminals 456 for CH changeover (5 is common/live). Diadem/Tiara use 123 for the HW changeover and 456 for the CH changeover.

For instance, I *hope* the cabling to each thermostat allows for me to install the NEST power supply (supplies?) in the hot tank cupboard (where the timer currently lives) and power each thermostat (remotely) that way. 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.