Electric radiator valve control?

[pjbw]

I have scoured Google but I cannot find a simple solution!
My handicapped daughter's room needs accurate temperature control (+- 1C) .
Because of the radiator position TRV's (even with capillary remote sensors) are out.
What I think I need is an electric radiator control valve with a remote thermostat (not necessarily wireless).
When the thermostat is too cold the valve opens slowly to try to prevent overshoot.
When the temperature is correct the valve 'sticks'.
When the thermostat is too hot the valve closes slowly to try to prevent undershoot. (When I was a plant engineer many years ago this was called differential control, I think).
Can anyone suggest a supplier of such an integrated valve and thermostat system, or maybe suggest an alternative?

[SensibleHeatUK]

An Evo Touch controller and HR80 Radiator Controller from Honeywell would achieve this assuming that the valve body is in good condition - it still will not work effectively on a worn or sticking TRV. The Evo Touch controller includes a room sensor which can be used if you prefer not to use the sensor in the HR80 Radiator Controller due to the radiator location. Otherwise there are also separate room sensors that can be used too. The Honeywell system uses "proper" continuous control strategies, that also self-tune to improve their performance in each room automatically, to maximise the efficiency of control.

It also has a wireless receiver that can go back at the boiler to provide a demand signal when the room needs heat to ensure the boiler/pump run as required. This can be wired in parallel with any other controls you already have fitted.

The room sensors and radiator controllers are battery powered so do not require any additional cabling, while the Evo Controller comes with a desktop stand (that plugs into a 13A socket) or an optional wall-mount kit (which powers the unit via a transformer that fits inside a backbox behind the wall mount).

The Evo controller can provide control for upto 8 rooms which also gives you the opportunity to control other room in the house too should you want/need to.

[pjbw]

Thank you SensibleHeatUK,
I get lost in Honeywell's web pages. I don't want zone-control, just an actuator fitted to the radiator valve with a 220V wire to a thermostat with 220V supply. I found an actuator MT4 with options of normally open/ normally closed and two-postion control which looked a possibility. Honeywell recommended Excel 10 and Excel 12 controllers for it and I got lost; 68 PDF pages...
I'll keep looking!

[SensibleHeatUK]

The problem you will have is that you will struggle to find a controller that has the more sophisticated control logic to ensure close control of temperature that can be wired to your thermal actuator without moving to a programmable controller that needs a bespoke program to make it work. Digital thermostats do not usually include this level of sophistication, and most of the controllers (such as the Excel unit from Honeywell) are actually commercial building control systems that are not in any way appropriate for residential homes - if you bought one you would not be able to program it without either going on a training course (if Honeywell would let you attend) or having to pay for a trained installer to set it up for you at significant expense!

The Evo controller and wireless Radiator Controller (and additional rooms sensor if preferred) would achieve exactly what you wanted in an easy to use package that requires no wiring at all. And it is designed using fuzzy logic control strategies to achieve your close control requirements (and monitor/improve their accuracy of control based on feedback from the room) without needing any knowledge of how it works nor any need for custom programming. It is a fully standardised product range so will present no long term issues for maintenance and support, and in terms of total system cost is probably as cost effective as any other solution you could use.

You would be able to buy, install, and set up the Evo system without any need for an electrician or specialist installer as your are only using it for in-room temperature control without any feedback to the main heating system. Don't be put off by the fact it can be a multi-zone control system, it is just as appropriate for your intended application too.

[toscal]

Have a look at HouseHeat

[SensibleHeatUK]

Thinking it through a bit more, if you really want to use a thermal actuator on the TRV valve and don't mind running the cable then you could use the Evo controller with the BRD91 relay too. The important thing with a device that controls the actuator is that you need time-proportional control of the output - ideally you monitor the rates of change of temperature and modify the on-off cycle of the output to modulate the heat into the room for smooth, accurrate response. If you think about the process of heating a room with close control then you have to match the heat input into the room to the heat loss to maintain a stable temeperature. What you don't want to do is to simply have a system where you either are 100% on or fully off as your only control conditions, and time-proportional control does give a much finer degree of control over the on-off cycle to match the required demand. So if you only need 20% of the maximum heat input to maintain the room temperature then time-proportional control will pulse the actuator so that over a particular time period the output is on for 20% of the time and off for 80%. So here you need to combine the measurement of rates of change with error from setpoint in a fairly sophisticated way to achieve close control.

Evo uses this kind of control strategy, and again it is sefl-adaptive too so improves accuracy over time.

However I still think the "best" level of control would be through the Radiator Controller as it uses a stepper motor to provide fully modulated control and accurate positioning of the valve.

[TonySmith]

Thank you SensibleHeatUK,
I get lost in Honeywell's web pages. I don't want zone-control, just an actuator fitted to the radiator valve with a 220V wire to a thermostat with 220V supply. I found an actuator MT4 with options of normally open/ normally closed and two-postion control which looked a possibility. Honeywell recommended Excel 10 and Excel 12 controllers for it and I got lost; 68 PDF pages...
I'll keep looking!

For a single zone/room I think the Honeywell system's going to be well over the top. You don't really get the benefit unless all your important rooms are under its control, so it can bring the boiler on/off in response to the heating load. In you case it sounds as if you just want better temperature regulation. Have a look at some of the wireless radiator valves, where the TRV is replaced by a an actuator but the actual temperature control is from a separate remote sensor and programmer. For example the "House Heat" unit is less than the cost of just one Honeywell radiator controller ...

http://www.discountedheating.co.uk/s...g_Control.html

[TonySmith]

I missed your comments about control algorithms. Possibly Sensible Heat have some insight into how Honeywell's control logic works, but I've not seen any manufacturer come up with hard facts as to what algorithm they actually use for setpoint control. In traditional control speak you are wanting "derivative" control (that's the D in PID) where the controller responds to the rate of change of the controlled variable to anticipate it reaching its setpoint. ("Proportion" responds to how far the variable is from the setpoint, and "Integral" takes account of how long the error has persisted).

I would also love to know how these things work at that level.

[SensibleHeatUK]

I missed your comments about control algorithms. Possibly Sensible Heat have some insight into how Honeywell's control logic works, but I've not seen any manufacturer come up with hard facts as to what algorithm they actually use for setpoint control. In traditional control speak you are wanting "derivative" control (that's the D in PID) where the controller responds to the rate of change of the controlled variable to anticipate it reaching its setpoint. ("Proportion" responds to how far the variable is from the setpoint, and "Integral" takes account of how long the error has persisted).

I would also love to know how these things work at that level.

PID control loops are only accurate if they are tuned to their application though, so will definitely not be the case in most residential controls unless the manufacturer has taken specific steps to deal with this. For example, the Honeywell range uses fuzzy logic routines that are set with strict limits for the boundary conditions, and that can then automatically tune their performance providing they are within certain criteria (no use retuning control loops in summer for example). they can do tis because they use a modular range with known applications, general purpose controllers simply cannot achieve this so have to be manually tuned for best performance.

That said, in my time in comercial building controls I never once saw a system get its control loops tuned, most commissioning engineers simply picked their favourite values and put them into their code and hoped for the best!

[Vangelis]

Try having a look at LightwaveRF http://www.heatandplumb.com/acatalog...tor_Valve.html
Not played with them personally but may do what your looking for. B&Q sell them I think along with all the lighting stuff. If your feeling brave you can link them up to the Internet and control them remotely