Resistor control of individual central heating radiators

[Brian A]

Currently I don't have a central heating system. I want a system which allows me to control each radiator separately. This will then allow me to only have rooms heated when they are likely to be occupied and to properly control the temperature with wall thermostats. Rather than employ 2 port motorised valves I thought about trying a different system of control. What would happen if a standard thermostically controlled radiator valve was set to full temperature and then a resistor placed in the vicinity to facilitate temperature control. By applying a voltage to the resistor it would heat up and, hopefully, cause the valve to close. Has anyone tried this method of control? If so:-

1. With what type of thermostically controlled valve?
2. What power dissipation was necessary in the resistor to achieve the necessary control?
3. Where, precisely, was the resistor placed?
4. What sort of hysterysis was evident?

(I am aware that at one time capilliary/bulb systems were used but having not found them on appropriate web sites I assume that they are no longer used. I need a system which employs current proprietary parts.)

Remove 'no_spam_' from email address.

[Jim]

Why dont you just use a standard thermostatic valve on each radiator???

jim

[chris French]

In message , Jim writes

I think he wants a remote/centrally or automatically timsd operated system (well I assume so)

might find the Honeywell CM-Zone system of interest?

[Andrew Gabriel]

I did it with a Grugasar gas wall heater which had a capilliary/bulb providing modulating/proportional control, but no timeswitch or remote control capability built in.

I taped 3 resistors to it. I had originally intended to drive these directly from the alarm/home-automation system, but found I needed more power than I wanted to drain from its battery backed supply, so I used a wall-wart to power it, controlled by the HA system.

You can callibrate it by driving the resistors at a certain power, and measuring the corresponding setback in room temperature. This then scales linearly to increase or decrease the setback temperature required. Then you set the thermostat (TRV in your case) to the normal room temperature, and drive the resistors to create the appropriate setback. I had two setback levels -- one for night time of a few degrees setback, and one for frost/damp protection.

One thing is I'm not conviced by the accurancy of TRV's. The Drugasar I had would maintain the room temperature to an accuracy of 0.1C (it had a very long bulb, which made it both accurate and responsive), but I don't think TRVs come close to that, which might make the calibration difficult, and the final result a bit more hit and miss.

I vaguely recall finding a web page somewhere showing how someone had done this with TRVs, so you could try searching that out.

[Autolycus]

You've invented the boneless sausage!

Google this group for much earlier discussion about home-made and commercial versions.

I bought Sauter actuators, sold as Prefect 9500 Wet Radiator Valve Drives from Prefect Controls

for about 23 quid each. Still waiting for the tuit for my own house, but I installed them successfully in my mother's place. The ones I bought don't have auxiliary switches, so I'll need to use the changeover switching of my roomstats for boiler control and have the actuators in their normally-open mode.

For a completely new installation in my son's house, I went for the manifold principle, with a valve farm of conventional motorised valves - except that to minimise the initial cost they're all just plain lengths of pipe at present. Pipe sizes to individual radiators depend on length and required flows - only one needed 15mm in our case - and there are a couple of places where returns are commoned. As funds permit, motorised valves and programmable room stats will be added with no disturbance to floorboards and pipe runs.

[Doctor Drivel]

This is probably the cheapest method, running all stat and zone valves cables back to a junction box. The problem is it takes up space. But is does give more precise temp control of rooms and time zone can be selected from just one to every room being a zone. Using the sauter valves does the same, but a stats are required about the house, controlling each chosen zone.

When constructing a manifold install good quality full bore isolation valves to isolate the battery of zone valves on the manifold, and use a Grundfoss Alpha variable speed pressure sensing pump.

[:::Jerry::::]

That has got to be one of the worst web sites going, it's quicker to watch paint dry!

'Design' over accessible content... :~(

[Christian McArdle]

You can buy them ready made (obviously not from B&Q!). However, you can also get motorised heads, which are more reliable, if a little more expensive. I can't remember the supplier, unfortunately.

Christian.

[dennis]

You must have gone to a different site. I was looking at the installer diagrams after about three clicks.