by ericmark »
Fri Sep 18, 2020 12:34 am
I fail to see and earth wire in the existing thermostat wiring, I know Nest say the earth is only required when the thermostat is powered from the heat link, but the British Standard BS 7671 since 1966 has required that an earth wire is run to all installed equipment even if not used, before 1966 there was an exception for lights.
I have looked for the double insulated sign, and can't see it, it is unlikely to be a problem, or danger, unless the property is rented, in which case the EICR could show a C2 due to no earth, personally I would not worry but it is up to the inspector.
I say this as may be better to mount near the boiler now with new cable than have to do job twice is some inspector fails it.
It would seem the CH and HW connections are not used with a combi boiler, just the LS LR N E L. So Black, Grey, Blue, Green/yellow or bare sleeved green/yellow and Brown.
The literature on website says very little, in my old house we had an open plan and an old gas boiler with no modulation controls and this unit would work well, but if the boiler can modulate and is the condensing type, then it is important the thermostat does not use mark/space to stop hysteresis. It will work with the mark/space controls, but not efficiently.
I had this problem with mothers house some one had fitted wrong type of thermostat, with for example Nest it works out at what point to switch off so the stored heat in radiators will get room to correct temperature without over shooting, or it can also connect with opentherm and turn boiler up/down rather than on/off. But cheaper thermostats turn the boiler off/on repeatedly as it approaches the target temperature which is all well and good with non modulating boilers, but with modulating it causes the boiler to restart at full output each time so more energy is lost through the flue.
It may seem odd, but for a modulating boiler either very cheap or very expensive thermostats work well, it is the middle range which cause the problem.
Since I have Energenie MiHome TRV heads I can see the temperature of rooms independent to Nest, so I know Nest geofencing is working, however since I am not there when it turns off and then back on, other wise I would not know if it worked automatic without my needing to go onto some web site to manually alert it.
My daughter tells me her system will turn off with phone, but she has to manually go into an app to do it. If it was me I would forget.
So would like a report on how well the Heatmiser works, as at £42 it is very cheap, and would consider fitting it to our flat.
