DIY Doctor UK DIY Forums

Hello,

Old boiler had a physical timer-clock on it, this was controlled by a simple dial thermostat downstairs. Boiler broke down and had to get in replaced with a Worcester Bosch Greenstar. Installer did mention about thermostat, but I thought the boiler itself would have a timer function (maybe I was more concerned about how much it was already costing me thus far!) and decided to stick with the dial.

It's nice to have a working boiler, but not nice waking up to a cold house every morning! A friend recommended the Beok BOT-313 thermostat. I'm stuck with how to replace the dial one with this one.

I've attached images of the dial and the wiring, as well as the wiring installation extract from the Beok manual. The L to L and N to N seems straight forward, but it's how to engage the switch which has snookered me.

Any help would be much appreciated!

It seems you have no neutral so to use that thermostat you need to wire in a neutral, Flomasta 22199SX Wired Digital Programmable Thermostat Screwfix number (6259G) is battery powered so will work without a neutral.

Top of range for two wire is likely the Nest e, this is wireless and one of very few where the base does not need a neutral.

I think this http://www.free-instruction-manuals.com ... 457824.pdf is instructions for old thermostat, there should have been a neutral connection to terminal 2, this worked a small heater in the thermostat that reduced the hysteresis (over shoot) however they would work without it, and often with a modulating boiler it was actually better without that neutral connection.

I will try to explain, with a modulating boiler instead of the boiler switching off/on it turns up and down to match demand, the main control is the TRV (thermostatic radiator valve) as it closes the by-pass valve opens sending hot water back to boiler which in turn reduces its output (modulates). Until it can't turn down any more, then it starts to cycle off/on.

However it has one big problem, in the summer it will continue to cycle, so the old wall thermostat is used in a cool room so in summer it will turn the boiler off and stop the cycling, and a large gap between off and on temperatures is good for that job.

As you say you want the temperature at different levels in each room through the day, to do that there are simple replacement heads for the TRV's like the eQ-3 at around £10 each so you can set different temperatures for each room to match time of day, no wiring involved, unscrew old wax head and replace with electronic head.

So bedrooms allowed to cool in the day, and living rooms cool at night, and you set the temperature in degrees C not silly *12345 which is really hard to work out.

Also they have some extra features, like window open detect, I use that in kitchen so when we unload shopping from car, the radiator stops heating the room while we are doing it.

Simple dial allows you to alter the temperature, but you can also set the eco and comfort temperatures as swap between two by pressing one button, plus a boost button.

Pay a little more and you can get bluetooth version so you can program with your phone, there is also the Terrier i30 which is very similar.

You can get £50 versions that connect to wifi and link to a wall thermostat, likely Honeywell EvoHome is the best, but I am talking about using cheap £10 models.

To use the thermostat your talking about you will need a neutral, but there are others which are battery powered, I have the Horstmann one in front of me at the moment, Flowmasta also make one, the latter three events per day. If you want wireless neutral free, the Nest e is the only one I know.

Thanks for the above information ericmark- much appreciated as it has shed a lot of light on the current set-up I have.

I think I will obtain some quotes for installing efficient wiring to a smart thermostat. Then make an informed decision.

Nest e uses just two wires, so you can fit one of those easy enough, note it is Nest e not Nest 3rd gen only the Nest e is battery operated.