central heating actuator/motorvalve

antoinolachtnai

I have one of these, fitted in a house built around 1981 and it just doesn't want to work right for me.

The valve (which is obviously mechanical and prone to failure) stopped working some years ago. So I replaced it.

The way it works is that it is connected to the thermostat. The idea seems to be that the thermostat applies power to the valve when the temperature drops below the thermostat setting.

This is supposed to cut off the flow of water to the radiators. (It still should go to the hot water tank, I think.) As the heat isn't been dissipated, the boiler's thermostat should kick in, and stop heating water. At least that's the theory.

The only problem is that it doesn't work. The heat keeps going, even if you set the thermostat really low.

Any thoughts on what is going wrong? What can I check? I have a meter and a phase-testing screwdriver if that helps.

I really don't know if this has ever worked properly. Do these things ever work?

Pataman

It sounds like its the thermostat. Normally on the top of the actuator there is a light which shows when activated. There is sometimes a junction box between the actuator and the stat. Check to see if the power drops, with a fase tester, when you move the stat temperature.

antoinolachtnai

It sounds like it, doesn't it? I will certainly try that tomorrow.

However, when i played with it last, I think the power was switching.

Should the power be on when the stat is down low or when the stat is up high?

thanks for the help.

Pataman

The light on the actuator is lit when the valve is open

antoinolachtnai

Well, I went working at it and checked some things out.

There is no light or LED on my Satchwell Sunvic actuator.

With no power on it, my actuator valve is closed.

With power on it, it opens (and allows water to flow to the radiators).

The problem is that the thermostat seems to work the other way. When the temperature is higher than the set temperature, the power comes on. When it is lower, the power goes off. (on reflection, this seems like rather an odd way to have a thermostat wired)

Is there a thermostat I can get that will be wired the right way round? (power on when lower than the set temperature, power off when it is above)

I suppose I could rewire this thermostat to work that way (it's a satchwell) or I could get a new one. Is a suitable one available?

Pataman

Most thermostats have 2 wires for this purpose, apart from the earth supply and neutral.

antoinolachtnai

I noticed that my stat wasn't wired with a neutral. I thought having one might sort things out so that i could switch it over to work the opposite way . I wired the neutral where it looked like it was supposed to go, reading the little wiring diagram on the stat.

I blew the fuses and blew up the stat in the process. Had to go and buy another one.

Thanks for all the help and suggestions!
I bought a new one, and fitted it all together, using a neutral, and after sorting out the wiring so the colours made sense. It all seems to work now.

Can't help thinking I was ripped off paying 18 euro for a stat and 48 euro for an actuator. There's not much to them really, particularly the actuators. (Although I must say that the design of the replacement actuator is much better than the design of the original.

a.