House Radiator Thermastat Question

  babybell 21:38 30 Nov 2010

This might be a bit long winded but I've been left scratching my head about a problem with our bedroom radiator and was wondering if anyone could answer my question.

The radiator wasn't heating up, so I was told to remove the thermastat and press the little metal button down on the valve using a pair of pliers and bingo, the radiator began to heat up.

Upon closer inspection of the thermastat, there is a little black plunger in the middle. I spun the temperature control round and this plunger didn't move. I removed and looked at a thermastat on another radiator that DOES work, and noticed that the plunger moves up and down when you select the temperature you want. So I've ordered a new thermastat and this should solve the problem......but this isn't whats puzzling me.

The puzzling thing is, when playing around with the working thermastat, I noticed that when I select a low temperature on the thermastat, the plunger is sticking out, but when I select a hot temperature, the plunger moves back inside the thermastat? I would have thought that if the metal button on the valve needs to be pushed in to let hot water in the radiator, then a hotter setting would push the plunger OUT of the thermastat and down onto the valve?

This probably makes no sense, but here's hoping!

  peter99co 21:41 30 Nov 2010

It would depend which side the valve seat was on. Upside or downside?

  Forum Editor 21:54 30 Nov 2010

in a clockwise direction a smallish pin on the valve head is pushed in a downward direction, reducing the flow through the valve.

Turn the head anti-clockwise and a spring in the valve pushes the pin back up, increasing the flow, and thus the heat exchanged into the room.

There's a small rubber cone on the other end of the pin, and this closes onto the valve seat, cutting off the flow. When you set the valve head at a chosen setting a heat sensor in the head expands and contracts depending on the room temperature, and this causes the spindle to be depressed or raised automatically.

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