All I want is a room somewhere, far away from the cold night air...

December 10th, 2011

The very pretty Nest thermostat has justifiably attracted a certain amount of attention recently. But it has a few failings, too:

It's expensive - someone quipped that the Apple-inspired design comes with Apple-inspired prices
It's a single point of temperature measurement, and what most houses need is multiple thermostats, or at least sensors
It isn't available in the UK and wouldn't work with most UK heating systems anyway,

So, it's not for me. But I am keen to upgrade my heating controls: we have pretty substantial fuel bills even for our small and fairly well-insulated house.

So I'm after recommendations. Here's my ideal system:

You could set the temperature you want in each room, and control the times of day at which you want it. Or, even better, it would learn the pattern for each room. (And not get too confused by daylight savings time changes)
We have radiators in each room, so it would need to manage the radiator valves. (i.e. replace the TRVs)
The temperature sensors would not necessarily be on the radiator valves, but could be elsewhere in the room.
The timing of the boiler ignition would be based on the combined needs of the house, and not on the temperature of a particular thermostat in the hall, or of the time programmed into a separate heating controller.
Ideally, it could be programmed through a wife-friendly app or web interface.

Anyone know of anything that satisfies a significant number of these? I don't expect to get them all. But I also don't want to spend a lot of money and time on a system which does some of them, only to discover that another would have been a better choice.

Oh, and I'd rather not have to do any major plumbing...

Any suggestions welcome!

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Pilgrim Beart December 10, 2011 at 1:26 p.m.

Working on it!

Richard Morrison December 10, 2011 at 3:51 p.m.

Also working on it! Although not to entirely the same set of ends as Pilgrim, I suspect! The Google Calendar method for controlling things looks to have significant merit. I wonder if it counts as friendly?

John Lawton December 10, 2011 at 6:53 p.m.

Hi Quentin, good thoughts on ideal heating control, which echo mine. Some control systems also take account of the outside temperature in order to determine the heating switch-on time, and also possibly the boiler temperature. Reducing boiler cycling would also be a useful characteristic of the controller. However I don't expect it to be particularly cheap to implement with a lot of control valves and sensors required. Keep us posted!

Jason December 12, 2011 at 4:01 p.m.

I've had many similar conversations with Andy F and AvdH on this very topic. One day when I have time I'll solve this.

qsf December 13, 2011 at 7:14 p.m.

Mmm. These look interesting - Zigbee radiator valves. http://www.adhoco.com/homepage/produkte-en/aktoren/adhocov1 100 quid a pop, though...

Rod Williams December 13, 2011 at 9:06 p.m.

Rather than looking at control systems you may find it useful to focus on the building fabric. If you have a very well insulated/airtight house, following the Passive House pattern, the whole building is a single zone and heated to a pleasant temp (typically 19-21 degrees) for the whole heating season (i.e. 24 hours a day Dec-Feb) and it uses less than 20% the space heating needed for a standard new build, which are just heated morning and evening. This typically translates to ~15 kWh/m2 per year for space heating. There are UK companies building new houses to this standard and there are also some example UK retrofits to the same level. When the heat demand goes below ~10W/m2 even on the coldest days then its possible to do away with a radiators or underfloor heating and instead use the ventilation air to carry the heat into the building. Fresh air slowly flows through the building from the bedrooms/living rooms to wet rooms and the is expelled from the building, but before it leaves the heat is reclaimed so the stale air leaves the building only a couple of degrees warmer than the external air temp. So there is a constant supply of fresh air but the heat is conserved. The heating control system is typically very simple: a wall stat that switches on the heat source in the air supply duct when the building air temp falls below 21 degrees. If you haven't looked at this type of building they are worth reviewing as they change the playing field.

qsf December 14, 2011 at 12:13 a.m.

Thanks, Rod, but my house is 100 years old! So there're various things we're going to bring it up to spec, but some of them are quite expensive. By the time we've replaced all our sash windows with new double glazed versions it might have been cheaper to buy a new house! Still, I'm always interested in alternatives! Q

Rod Williams December 14, 2011 at 2:10 p.m.

There is a summary of a "100 year service" which updated a similar age building: http://www.peterwarm.co.uk/1st-enerphit-in-uk-andy-simmonds-grove-cottage/ I am not advocating everyone does this as the economic benefits aren't clear cut, but the building will also be more enjoyable as there will be no cold areas or drafts and the air will be constantly fresh. Re:your original requirements, if you are interesting in open-source hardware for the room monitors it may be worth considering WiNodes and a central NanodeRF to run a web service and demand heat from the boiler: http://sustburbia.blogspot.com/2011/12/building-blocks-for-internet-of-things.html The WiNodes could monitor more than temperature (for example humidity or a motion sensor) and potentially control the rad (if you find a rad valve containing a servo). Google tells me there are commercial systems that cover the above and more: http://www.siemens.cz/siemjet/en/home/press/releases/all/Main$pageletManager$PressList$AssetGrid-gotoItem/38890.jet

qsf December 14, 2011 at 2:19 p.m.

Thanks Rod - All interesting links - I'll check them out! Q

Jason December 14, 2011 at 4:48 p.m.

It could be fun devising energy harvesting systems for the valve. There is the heat diffential as well as the pressure drop, so the potential for harvesting energy to power a low power RF receiver is there. How to actuate the valve using mere mW of power, that is the challenge. A plumber's FET is needed. Do I need to use RF? Could I modulate the pressure from the boiler to encode a command to the radiators, or send an acoustic signal down the radiator pipes? It's a fun problem to consider.

Krisztian Flautner December 16, 2011 at 9:58 a.m.

This is what I have: http://living.danfoss.com/ ... It uses z-wave, batteries in actuator valves use 2xAA batteries, supposed to last a few years, there is a central control unit that allows me to set temperatures in each room separately.

qsf December 16, 2011 at 11:15 a.m.

Kristian - Thanks - the Danfoss stuff looks really interesting - I'll check it out! Quentin

Aideen January 21, 2012 at 5:25 p.m.

Related to Nanode (above), check out http://openenergymonitor.org/ Their emoncms software can be used to gather and graph data from any sensor. They've recently released v3 and the project feels like it's gaining momentum.

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All I want is a room somewhere, far away from the cold night air...

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