Hot water and central heating only work together, on full blast, or not at all

[tom2022]

Controller

 

[tom2022]

Diagram of tank. Mine is the one on the left.

 

[tom2022]

Thermostat

 

[mattylad]

This is extremely poor electrical workmanship (but typical of a plumber lol) and liable to failure or worse.
It would be best to power down and redo this connection.

 

[tom2022]

Well pointed out thank you! That might be the issue for the stat

 

[tom2022]

I think this issue has been/will be resolved.

He's going to come round and replace the other valve tomorrow, and I'm going to get a sparky in to fit a a smart stat. All should be working perfectly after that.

 

[ericmark]

Back to basics, the boiler produces hot water, which is pumped around the system, as the room heats up, the TRV's close down, as they close down at first they force more water through those still open, then it lifts the by-pass valve, either way it forces hotter water back to boiler which in turn modulates, (turns down) so heating each room just enough.

This will in fullness of time, reach a point where boiler can't turn down any more, and then the boiler will start to cycle, off/on. So we have a wall thermostat set so when this happens the boiler turns fully off.

So to over heat there needs to be first some thing wrong with the TRV or lock shield valve setting, even if boiler never turns off, it should not over heat.

OK we tend to use the programmable thermostat to switch the boiler down when home not occupied or over night, so above is over simplified. And you clearly have other issues as well as the TRV's and Lock Shield valves not being set up correctly.

TRV is a thermostatic radiator valve, and as the room heat up it reduces flow.
Lock Shield valve adjusts the speed at which the radiator heats up, too fast and there is not enough time for the TRV to close, so it over shoots, and you get a hysteresis. In the start we set lock shield so there is around 15°C drop across the radiator, and with mechanical TRV's marked *123456 the 20°C point is normally between 2 and 3. Easier with digital types, set this type to 20°C and you then only worry about the lock shield valve setting, and also you can program them to change temperature throughout the week.

Clearly the wiring needs sorting out, but although bad wiring may mean no heating, it should not cause over heating, the TRV's should stop that.

 

[ericmark]

I'm going to get a sparky in to fit a a smart stat.

You posted this as I was writing, there are many smart thermostats, and they are not all the same, so the Drayton Wiser TRV head is claimed to work out how long it takes to heat a room, and it will start heating the room before the time set, so it is to temperature required when you come to use the room. I call that a smart thermostat.

But the wall thermostat is really no more than a hub, collecting info from the TRV heads and relaying it to the boiler at least when set to turn boiler on/off.

However some boilers will allow some thermostats to turn the boiler up/down, rather than on/off, the main system seems to be OpenTherm, the Wiser and Honeywell EvoHome the OpenTherm is an add on module, Tado all built in. Nest has OpenTherm but does not link to TRV heads so a bit useless, and Hive does link but can only switch on/off.

EPH is designed to work with motorised valves and OpenTherm, but a motorised valve often turns a group of rooms on/off where TRV's normally control individual rooms, clearly very little need for both, (always exceptions) so EPH wall thermostats don't connect to TRV heads, you just set them as master and slaves, up to I think 10.

Then we look at GeoFencing, some thermostats you can only set the Eco and Comfort setting, others you can set the distance from home. My wife and I spend about 2 hours yesterday getting her phone set up with Nest Gen 3 so it will detect her phone as well as mine to turn up heating when we are at home. Being able to do something is very different from doing it with ease.

I open google home with my phone, and there are 5 thermostats shown, the Nest Gen 3 wall thermostats and 4 Energenie room TRV's but I have 9 programmable TRV's the other 5 are bluetooth, (eQ-3) and can only connect to one phone, but only cost me £15 in 2019, rather than £35 for the energenie.

And with all that, still have heating problems, some where hot water is returning to my boiler and turning it off. And it does not matter if the Nest calls for heat, or if all TRV's are open, unless water is being heated and pumped around, rooms still don't get warm.