Are we moving into the analogue age.

[ericmark]

It seems with central heating analogue is replacing digital (on/off open/closed) control. The boiler turns up/down (modulates), the wall thermostat turns up/down (OpenTherm), the old motorised valve is being replaced with the wifi connected TRV head.

But does this new analogue control really work? I look at my TRV heads and so often I see this

as you can see dinning room greyed out, as to if still working not a clue, if it was sending info to control central heating rather than simply just telling me what is going on, would I have a cold dinning room when heating failed to run, of hot house when it failed to stop.

As it is I have not fully gone analogue, my old oil boiler simply switches on/off it does not modulate, so even though my Nest Gen 3 has OpenTherm my boiler doesn't so still digital (on/off) but son with gas fired boiler will I assume need to use all analogue controls which is good of course, but so many of the analogue controls seem to be wireless, with digital easy to check, turn up thermostat hear boiler start, turn down thermostat hear boiler stop, but how do you check with analogue?

My mother had a modulating boiler, and I knew it was running, but there was nothing to say if running at 20% or 100% I had not a clue if working as it should.

 

[bernardgreen]

Does the average home really need the complication of analogue controls ?

As a retired design engineer I thought I would love to have a control system saturated with functionality and information displays for this cottage. I got as far as creating the PCBs A master control PCB and two versions of a temperature sensor PCB that would communicate with the master via RS484 network. One single channel for room temperatures and one quad channel for hot water cylinders ( how deep is the hot water ). The cottage layout is best served by two hot water cylinders to reduce water wastage and time before hot water reaches the tap.

Then I though what the hell am I doing. I want to sit and relax in a warm cottage rather than spend time managing a complex control and monitoring system.

If I feel warm and cosy then that is all I need to know. I don't care one bit if the temperature is 0.01% above or below the setpoint for the room.

 

[ericmark]

It just seems strange, for most things we go digital, but for central heating analogue, I remember as a lad laying the fire, and lighting it, and house was freezing until fire lit, and mother for ever saying cau'r drws (think it was only Welsh she knew then) and shutting the doors allowed us kids to play in the draft and the air was sucked through every gap as the chimney sucked the air out of the room.

The main advantage with central heating was not sucking air out of the rooms, so it got rid of the drafts, dad still said put wood in hole, (he was English) but the need to close doors was no longer there, mother even when in a wheel chair still always closed doors, but we moved to an open plan house, only one internal door down stairs. So even when we moved, we still never bothered with doors, maybe close so I could watch a different TV program but not for heat.

Now with TRV heads every room has different settings, so doors are again important, raising butt hinges on the living room door, and a Father Christmas doll to keep it open when carrying coffee. The idea is good, when one is due home from work the radiators heat in sequence, kitchen, dinning room, living room, then a gap then bedroom, just one little problem, I don't work. Well OK if it was not for Covid I would be at the railway, but wife still at home, and there is another point.

Cool down time, back in the 1950's no double glazing or plastic doors, and the house cooled fast, today turn down heating at 10 pm and up again at 7 am and although set to 17°C the boiler never cuts in. 3°C between 20°C and 17°C and it does not drop that much in 9 hours most nights. I prefer it cool at night, but the question is if the average when heating is off is 18.5°C just 1.5°C lower than when at home, is that really saving energy?

We are told when the gas modulating boiler is running at less than 100% that it extracts the latent heat, but that does not happen when running at 100% output, so each time we turn the boiler off with a thermostat or programmer it then turns back on at 100% output until the water starts to return warm, I have looked to see how much energy difference there is maintaining temperature using mark/space to modulating control, but have been unable to find it.

We are told you should allow the boiler to modulate, as it runs more efficient that way, then to fit zone valves with digital wall thermostats which stop it modulating. It seems the government and heating industry can't make up their mind? EPH make wall thermostat that work Master/Slave so you can have OpenTherm with zone valves, but they don't connect to the TRV heads.

So one minute we are told go analogue, then we are told fit this digital device, not that it makes much difference to me, I still have a digital oil boiler, not moved to analogue yet.

 

[bernardgreen]

We are told

What we are told and what is factually accurate may be different

We are told when the gas modulating boiler is running at less than 100% that it extracts the latent heat,

It can only extract latent heat if the temperature of the water coming to the boiler to be heated is below the dew point temperature, The dew point temperature for water vapour in combustion products is about 55°C

We are told you should allow the boiler to modulate, as it runs more efficient that way,

It would be interesting and informative if manufacturers and/or their "independent" test laboratories would produce graphs of efficiency against modulation level

It seems the government and heating industry can't make up their mind?

Add science into the equation and maybe minds could be "made up" to agree on a logical and realistic result.

 

[Harry Bloomfield]

If I feel warm and cosy then that is all I need to know. I don't care one bit if the temperature is 0.01% above or below the setpoint for the room.

Modern heating control systems do cope very well indeed, with their ability to predict and calculate just how much modulated boiler output is needed to restore a building just to bring it to set temperature. I find I tend to notice when the set temperature is just 0.5C in error.

The one thing which seems to be lacking in all domestic heating controls, is solar sensing - some means of detecting solar radiation arriving via windows. Perhaps more essential in a car with so much glass, but even my cars have had solar heating detection for years, to auto-adjust their climate control systems. Solar heating makes quite a difference to how warm it appears to be.

 

[ericmark]

@Harry Bloomfield makes a very good point, late mother's house with bay windows seen room temperature rise to 32°C when sun came out and the old wax TRV heads were slow to respond, I will guess the valve was fully open when sun came out, and slow closing, the electronic TRV was much better set at 21°C it would still hit 24°C when sun hit the windows, but likely would hit that even with no heating, so looking at two things which may be different, one temperature of radiator, and two speed of the TRV head.

Since one can hear the motor and every Saturday at mid day the TRV exercises I know one cycle takes around 4 minutes, so not really fast, and a hot radiator takes time to cool. Say another 15 minutes so takes around 20 minutes for heating to turn off.

So I think more down to radiator not being at full temperature to start with, the any hysteresis software on the Energenie TRV head I was using in her house was a little OTT, set to 20°C at 7 am and it was 11 am before room at 20°C, so I cheated, set to 22°C at 7 am and 20°C at 8 am and it did seem to then stay at 20°C.

So at 10 am when the sun hits the bay window the radiator is only warm, maintaining the temperature rather than heating the room, so if the radiator is only at 50°C instead of 70°C when sun comes out, then both speed and stored energy both come to play.

But to be frank never tried connecting a sun sensor to the TRV, since the TRV is IFTTT enabled it should be possible to have a sensor which turns down the temperature when the sun comes out, however I was not really impressed with IFTTT, I could not see how to write my own program, all I could do is select one already written, the same applies with geofencing.

It seems to me that Nest does not use a fixed point to start reheating house, I know it has cooled as looked at the app for the TRV which shows when away the house has cooled, and when I return the house is warm, as to if Nest looks for one getting closer, or within x miles, and if that x miles changes with outside temperature I don't know, but Nest does work.

However with the TRV again using IFTTT so it is down to who wrote the program one has selected.

However my old house, my son has it now, in living room had a 4.5 kW gas fire, a 3 kW myson fan assisted radiator and a 3 kW double panel radiator and within 15 minutes of getting home the room was warm, and I can stand 15 minutes in a cool room, there was simply no need to geofencing, come home to cold house and you turned on gas fire and the inferred from gas fire soon made one warm, and once myson kicked in the warm air was circulated. And once room was warm turned off fire, myson would auto stop blowing and the panel radiator maintained the heat.

 

[ericmark]

I wanted to work out if my late mothers boiler was working efficient, but there was nothing to show how much it had used, other than the gas meter. The oil boiler in this house cycles off/on, and again nothing to record how long it has run for, Nest sends reports, but useless, it says how long boiler turned on, but that does not relate to output, it racks up hours even when it has tripped, and the TRV heads means there is not relation between being switched on and output.