Tim, 

I am an advocate of the Househeat system. These use digital thermostats mounted on the wall (away from the radiator) that wirelessly control motors that replace the heads of TRVs on the radiators. They allow accurate and timed control of the temperature of each room independently.

 I also use the window sensor in our bedroom, so that when my wife opens the window to air the room, the system automatically switches off the radiator - which she doesn't  :-(

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Monica

Which heat pump is it? And why the Honeywell, which I belive is intended for zone control. It is likely that radiators are on ring circuits rather than zone, so it may be that the control is kicking the heta pump out because one room is up to temperature.  

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I have a water source heat pump which is heating radiators - a retro conversion. We have a digital thermostat/timer in the hall - Honeywell CM907 and TVRs on all radiators. The CM907 is too accurate for the system despite being set at a minimum on time of 4 mins and cycle rate of 3 per hour, which are the oil boiler settings. The heat pump frequently fires for only a short time before the thermostat clicks off again, rather than running for longer and letting the temperature fluctuate more. In principle we like the flexibility of the CM907, (such as allowing the setting a higher temperature during periods of economy 10) which a separate room thermostat and timer would not have. Does anyone have any ideas for a better system of control?

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Alec is absolutely right. Weather compensation is a good idea and a requirement for some local authorities. It becomes virtually mandatory under 2010 Building Regs (to be published in October). But it does not take away from the idea that we need to control the temperature of each room.

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Tims comments are perfectly valid for old systems, but if you are installing a condensing boiler it is advisable to instal it with modulating controls which tell the boiler from either inside the house or outside how much heat is required at any one time, avoiding wasteful over heating. This means the radiator temperature varies.

All boilers have this technology, its called open therm compatibility or weather compensation or modulating controls, its mandatory in Germany and Holland as it saves energy and makes TRVs and on-off controls redundant saving on the install cost.

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The Watersure scheme looks good. It is amazing the number of similar schemes and grants out there for heating, insulation, and the like that all seem to be well guarded secrets. Maybe we should start a campaign to get them all publicised.

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Hi Tim,

Very interesting - old thermos 4 degrees out, will certainley be checking mine!

Not quite the same subject but we have discovered a scheme the water companies are offering to families to reduce their water bills called Watersure. Just a pity they are not advertising the fact.. more details can be found here ...

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