by ericmark »
Mon Nov 15, 2021 11:33 am
Sorry DHW is domestic hot water.
It seems likely you have a combi boiler so domestic hot water is on demand, no timer for that.
New gas boilers (not oil) are modulating (that means it can turn down output) and gain the latent heat, (energy used to turn water into steam) and to do that the return water temperature is critical.
So basic idea is water to all radiators and as they heat up room to connect temperature the TRV (thermostatic radiator valve) turns down and finally off, and the water is either forced through remaining radiators or lifts the by pass valve, so the return water would if the boiler did not turn down get hotter and hotter, so the boiler monitors return water temperature and reduces output (modulates) until it can't turn down any more, then it starts to switch off/on (mark/space ratio) further reducing output.
The anti-cycle software monitors how fast hot water is returned when it turns on, and adjusts the off time depending on that.
So in theory you don't need a wall thermostat, the TRV does it all, however.
For the TRV to work also the lock shield valve (tap other side of radiator) also needs setting correctly, if open too much the radiator gets stinking hot before the TRV can close, and also likely some radiators will not get hot.
The plumber uses a differential thermometer to set the lock shield valve so 15 degs C difference between in and out pipes, not really some thing you can do DIY.
However closing the lock shield valve completely starting with radiator closest to boiler letting pipes cool then opening little bit at a time until just feel a little warmth, and slowly moving away from boiler will normally get them near enough.
With a TRV marked *123456 normally half way between 2 and 3 will be around 20 degs C I have swapped my heads [attachment=0]61dmtMm13BL.jpg[/attachment] and I can set temperature in degs C and also the time, the advantage is the heads shown cost just £15 and they simply screw on instead of originals so easy to fit, and also easy to remove and refit old type when you go.
Not ideal would be better to get timer working, but even with boiler cycling when you are away, still likely cheaper than using electric to heat with. Mine called eQ-3 there is also Terrier i30 prices seem to have gone up since brexit, the eQ-3 I have is bluetooth so can adjust with phone, but so easy to adjust direct, I only use phone to set schedule, easier with phone but can be done without.
It does depend on the home, my three story house takes long time to heat and cool, and I am retired, so don't turn heating off, last house had a 3.5 kW fan assisted radiator plus 3 kW standard radiator and a 4.5 kW gas fire in the living room, from stone cold to 20 degs C less than 20 minutes even on coldest day, often less than 10 minutes, so we never bothered with timers or geofencing (heating turns on automatic as your mobile phone gets close to home) we just turned it one when we got home.
A fan heater is fast, but an inferred heater is instant, but line of sight, also if pointed at windows it goes through windows without heating room, but a fan heater or inferred heater while waiting for central heating to warm home may be worth thinking about.
Since this house is mine, I fitted Nest Gen 3 thermostat, not the best, but it does auto turn on heating before I get home, and auto turn it off when it detects both mine and wife's mobile phones are not in the house. But at over £200 not something you would want to fit, if even permitted.
All central heating is a compromise, yes we could have all fan assisted radiators with a heat pump which both heats and cools the home as required, but the installation cost is silly, so we use near enough engineering.
My heating is not perfect, but much improved since buying house, how the last owners put up with if I don't know, had to go outside down a set of steps and back into flat under main house and plug in the pump, there was no thermostat, and the timer did not turn pump on/off only the boiler.
I likely spend around £800 to get it all working, now I can sit at this laptop and turn the heating on/off around the world, but can't really expect a landlord to pay out that sort of money to automate the system.
But the moes thermostat is quite cheap, that is also wifi enabled, £20 approx, so maybe you can strike a deal, you buy it, he gets it fitted, if he things he is getting some thing free he may go for it?
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