My guess, based on the components visible in the picture, is that the original intention was to have the CH controlled by the wireless receiver with a remote smart thermostat (i.e. thermostat and programmer combined) acting as the sender somewhere else in the house. The single channel programmer should have been wired to to control just the DHW.
If I'm right, all that's happened is whoever wired the wiring centre made a mistake and didn't check/test their work carefully enough. Depressingly common these days...
Is this the same system you asked about roughly a year ago?
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Yes. Exactly. It's a loooooong story that I won't go into in full depth.
But this tale might be of use to others who come here so I will document the problem.
I will be as brief as I can be.
The complaint can be summed up by the phrase : The CH seems to be doing what it likes. Coming on even when the timer has it switched off.
I initially suspected a wifi RF frequency conflict and altered the dip switches and that seemed to make a difference according to the owner.
But just recently, end of summer, she complained about the amount of oil being consumed even in the summer. She also complained about the heating coming on in the middle of the night which was annoying for two reasons i) too hot in bed and ii) the noise from the boiler which is located below her bedroom.
So I decide to do a full survey of the system.
First thing that revealed is that the room thermostat receiver and the timer are connected to the installation in parallel so they are capable of making independent demands on the boiler for heat. The owner was expecting the timer to be in total control of the boiler ie: when the timer is OFF, in accordance with the program settings, the boiler was OFF and when the timer ON the boiler ON.
I had verified that the timer was working as it should during the previous intervention btw.
The owner's perception or expectation is not unreasonable by any means from a consumer's perspective. It makes sense.
What she had discovered by trial and error was that turning the room stat to ECON mode turned off the boiler. She didn't understand why but she became accustomed to using that as an ON/OFF switch so to speak.
That still didn't completely eliminate the problem of the boiler coming on at night. And it got worse as summer turned to autumn and so on.
But once you understand this independence between the timer and the room tstat you realise that the equipment is not at fault and it is just doing what it is supposed to do.
In ECON mode the default room temp setting is 10C. So the reason the boiler was coming on at night, even in ECON mode, is because the room temp was falling below 10C.
Now there is an ANTI-FROST mode on the tstat unit that has a default of 5C. Had she happened upon that as her ON/OFF choice that would no doubt have stopped the overnight boiler requests.
That's the way she has been manging the CH for almost a year.
The upshot of this is that the way the controls were at the point, due to the parrallel wiring, the room tstat is in charge as it overules the timer settings.
So what I decided to do was to replace the room tstat, which was only controlled by temperature, with a programmable one that controls room temperature on a time line.
This is what I did and it. Replaced BOSS TPSRF31 with BOSS TPSRF51.
The TPSRF51 works by letting you control the room temperature on a time line. The temperature range is 5C to 30C so
setting the temperature to 5C for a period of time is tantamount to switching it off. If the room temperature happens to fall below 5C during that time it's probably not a bad idea to turn the heating on. So it makes sense.
In order to test the new room stat I switched the timer to MANUAL OFF ie permanently off, and just observed over 24 hours.
The new room stat worked fine with the boiler coming on and off according to the new tstat time schedule.
It was next day that revealed the HW wasn't working.
So I dug deeper and determine the CH is S-Plan, looked at the programming capabilities of the existing timer, looked at the wiring of the rest of the equipment and reached the conclusion documented above.
As I said earlier I was a little bewildered as to why it wasn't installed as an S-Plan installation initially.
That lead me to the forum to see if anyone could point to something I was missing.
But now I know what's going on the above changes should bring it to normalcy.
Having said that the owner will still need to understand that in the summer the room tstat will still need to be switched to OFF mode in order to have just HW.
