Upgrading Room Thermostats Analog to Digital

there are two issues here: the first is the accuracy of the unit against a reference temperature

As 2011 says, for accuracy, I don't think a 50 dollar mass produced unit will be +/- 1

The other point is that the actual temp and the accuracy of the temp at wall stat is largely irrelevant as its the temp that folk feel when sitting in the room is what matters, for older folk I use a large garden thermometer which I place beside their chair to see what they need at the chair and set the wall stat to deliver that.

Then the kids/grand kids come in and see the stat at say 30 and say, grandad, thats too high and turn it down!

The second issue is what is the gap between the upper and lower set points, so in a heating system,

it closes the circuit, fires the boiler, at 18 and opens at say 21

The mechanical ones, by the nature of the bimetal stat, would have a wider set point gap and therefore there would be less on/off cycling of the boiler.

A set point gap of 1 will be a nightmare for cycling.

What's the set point gap on the kit you bought, I dont see it listed.

Don't bother.

You are simply renovating old tech.

Do a full digital system (individual rad control)and save yourself cash in the long term.

Controling zones instead of individual radiators is Flintstone technology.

Not sure why you are being unnecessarly disagreeable and pernickety here?

I'll spell out what is obvious.

"Gross" zone heating design championed in the 80's consisting of upstairs-downstairs-Hot water zones c/w static TRVs might have been cutting edge and have had value where heating systems were cheap and energy cheaper, but those days are gone.

Technology has rapidly progressed, boilers are far more complex and energy much more expensive.

Wasting energy and boiler hours heating rooms, zones, radiators not in use is untenable now.

You can't give whatever name you want to modern heating systems, i care not but "Digital" is as good as any.

Most modern boilers are high efficiency and capable of modulation, meaning that the old inefficiency of the on-off boiler no longer hobbles the approach to low load heating (single rads vs a full zone).

Wiser is as good an example of a fully digital system. Easy to switch the old inefficient and inflexible 2-3 zone S-plan to something much more granular and controllable.

Replace the controller, add the trv heads to each rad, add a room stat to main rooms as/if required and you are good to go in the 21st century.

You can heat individual rads, rooms, zones as requested and at the press of a app.

Not difficult. Saves money and works perfectly.

No brainer.

It is really something to needs to be assessed on an individual basis.
You are adding significantly more complexity with individual radiator controls, and justification for this will vary between houses.
This equipment will also need to be purchased and installed initially and then maintained over time.

In terms of efficiency, adding controls like will actually reduce overall system efficiency as a boiler will be running to heat individual rooms, with associated boiler and distribution losses rather than heating a complete floor together. You will likely have increased boiler on time, yet reduced condensing hours as this will be impractical during such low heating loads.

Many gas boilers have modulation, but most oil doesn’t, so that also will be a consideration.

It’s something that would need to be looked at on a case by case basis. In many houses, having regard to the individual use cases, I wouldn’t recommend something like that. Certainly not as a retrofit solution.

It’s not that they can’t have individual control, and in some cases it may be desirable. But in many others, the negatives outweigh the benefits.

In most domestic premises all rooms are within the same thermal envelope; I.e they are in the same heated space, so having them at significantly different temperatures isn’t really feasible in any case.

Just asking, what heating you are using ? Oil, gas, other(please specify) ?
Thanks