With a combi boiler why not just use the roomstat to control the TRVs? I've always wonder why TRVs work when there is feed back from the rad close by.
Not having any experience of combis; what does the combi sense, return water temperature? How does it know if the demand is from DHW rather than central heating?
AJH
Apart from how do you switch mode? Software runs the risk of "random button pushing" changing it so a switch round the back is called for ie needs deliberate action to alter. There isn't any difference between a 7 day set with all days the same and a 1 day. Programming might be a PITA if there isn't a "copy" feature.
Our Danfoss clocks are quite good both in programmers and the RF programable stat. couple of mins in 6 months (ie between BST/GMT time changes). The programmers may actually be mains locked, ISTR that the clocks were miles off after spending 6+ hrs on the generator the other month. The stat is set to show actual temp rather than the time so unless it gets really wrong (hours) the time on it doesn't matter.
Be easier to use the standard existing programable stats and put the "smarts" in the central box. Stat 1 controls valve 1 when that's open box runs pump and fires boiler, repeat for Stat 2 etc. Holiday mode is just "off" for n days the box can do that. Adding frost protection to hoilday is a bit harder but not impossible. Frost stat in box when that demands fire boiler one could also link it with the remote stats so that they all have to be demanding heat as well.
By first going into a "service" mode which would require simultaneous pressing of multiple buttons. This makes it less likely to be activated by accident or by "unqualified" users. OK it makes the mode switch more complicated to achieve but it's not the sort of thing that needs doing very often so isn't much of a nuisance if you need to get out the instruction book to do it.
LOL! Yes - that may be the answer...
11 years ago, I was traveling out to the US many times a year, usually for a couple of weeks each time. I built a heating controller which I could access over the phone or Internet. I could turn the heating back on as I touched down at Heathrow. Even when I was working in this country, I would switch the heating on just as I left the office for the journey home.
At the time, I remember thinking all heating systems will be like this in a few years. How wrong I was - 11 years later, and domestic heating controls basically haven't changed at all.
I have since installed similar controls into another family member's home, which I can fully monitor and control remotely, including letting me know instantly if the system goes wrong.
Heating for an elderly person probably wants no user-accessible controls, and instead wants to be expertly programmed so that no day-to-day adjustment is necessary, and a remote alarm is generated in case of a fault (boiler lockout, room temp outside allowable range, etc). Such systems do exist for commercial premises, but I'm guessing the costs are too high for residential use.
Then you would have no interlock to turn the boiler off when the house is warm enough. (that and TRVs are not usually electronic things that can be connected to room stats)
There is a flow or pressure sensing switch in the hot water path. So when you turn on the hot tap it trips the pressure / flow switch and that then usually switches an internal diversion valve to direct the boilers primary flow through the HW secondary plate heat exchanger rather than the rads. It also demands heat and hence causes the boiler to fire.
There's a "low energy" house conversion near here, a demo for seeing what can be done by the social housing landlord, this has TRVs with wireless receivers and electric (battery) actuators. If a pressure switch can be used on the DHW side why not in the heating circuit, when all TRVs close then the pump reaches pressure? Though I can see that one might as well use the wireless roomstat to switch the boiler with the TRVs just being zone controls.
Their development adjacent has solar PV in the form of large slate like tiles incorporated into the roof, whilst still noticeable they are not conspicuous.
Thanks
AJH
On 19 June, 06:11, andrew wrote: . If a pressure switch can be
So presumably the pump switches off when the pressure indicates all the TRVs are in a closed state. But how does the switch then determine that a TRV has opened, as the pressure will have dropped when the pump turned off. To do so would mean cycling the pump to check that the TRVs were still closed, which is not a good thing. :-)
John
This already happens with modern smart pumps. They sense the back pressure increasing as TRVs close, and reduce the pumping rate in response.
The Honeywells already have this. You can set things from 12 or 24 hour clock through optimum start to parameters limiting number of times the controller will switch on and off per hour, for boilers that don't like rapid cycling.
I'd guess that too. This would make a fine open-source collaborative project given choice of suitable basic hardware.
I fitted one of those a few years ago and as I recall it was quite nice. One slight niggle with it was that you couldn't program a time after midnight, so if you wanted a period of, say, 10pm to 1am, you had to do midnight to 1am (at the beginning of the day) and another of 10pm to midnight (at the end of the day).
Interesting, Not actually tried that...
Also thinking about it, the 7 day one has a better display than the
24/hr one.(IIRC it has up to 6 sets of on/off times per day, so that's not too much of a limitation)
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