A couple of the radiators in my house have a Danfoss Thermostat on
them (not sure exactly which model of the thermostat but by the looks
of them both I'd say *at least* 10 to 15 years old). Both are turned
up to maximum.

It looks similar to this:

http://www.danfoss-randall.co.uk/Sit...nsor_group.jpg

But mine is of a slightly older design. The principle is the same
though.

Anyhow, the one in the hall works fine - the radiator stays on all the
time and it gets nice and hot and stays that way until the heating
goes off. The one in the lounge comes on okay when the heating fires
up (twice a day) but then goes off when the room reaches what it
thinks is the 'correct' temperature - the thing is I'd like it to stay
on all the time that the heating is on. (Note: there is another
radiator in the lounge that does NOT have a thermostat attached and
that stays on all the time of course).

Is the thermostat likely to have developed a fault? Short of replacing
it, is there anything I can check? I've tried twiddling the setting up
and down, etc but no luck. Don't they have some kind of pin inside
that governs whether the water flows or not based on the temperature?
Perhaps this is sticking at a certain point so causing it to switch
off the water flow incorrectly?

Thanks.

On Fri, 25 Nov 2005 18:54:21 GMT, (galaxi)
wrote:


BTW, on the Danfoss website, the type that I linked to the picture of
is listed as being for the 'commercial market'. The current sensors
they list are the RA2000 range.

galaxi was thinking very hard :
Anyhow, the one in the hall works fine - the radiator stays on all the
time and it gets nice and hot and stays that way until the heating
goes off. The one in the lounge comes on okay when the heating fires
up (twice a day) but then goes off when the room reaches what it
thinks is the 'correct' temperature - the thing is I'd like it to stay
on all the time that the heating is on. (Note: there is another
radiator in the lounge that does NOT have a thermostat attached and
that stays on all the time of course).

The one which shuts the flow off when the room achieves the set
temperature is working exactly the way it is designed to work. If the
room is still cold, the head might be faulty.

If the head is removable, then it should be possible to remove it
leaving the radiator with full permanent flow, as you say you would
like it to be.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Harry Bloomfield" wrote in message
...
galaxi was thinking very hard :
Anyhow, the one in the hall works fine - the radiator stays on all the
time and it gets nice and hot and stays that way until the heating
goes off. The one in the lounge comes on okay when the heating fires
up (twice a day) but then goes off when the room reaches what it
thinks is the 'correct' temperature - the thing is I'd like it to stay
on all the time that the heating is on. (Note: there is another
radiator in the lounge that does NOT have a thermostat attached and
that stays on all the time of course).

The one which shuts the flow off when the room achieves the set
temperature is working exactly the way it is designed to work. If the room
is still cold, the head might be faulty.



"Thermostat" - a device to control heat by turning a device on or off in
response to the needs of the environment.

Why would you want it on all the time if the room has reached the desired
temperature? Try using a thermometer in the room - perhaps you have bcome
accustomed to liking the room to be getting constantly warmer (like my
wife). Bear in mind that there will be a bit of a lag before it opens the
flow again. eg - if set to 21 degrees - that is where it will close - but
the room may have to cool by just over a degree to open it again (Hysterisis
I believe this is called)


John

On Fri, 25 Nov 2005 19:02:16 GMT, "Harry Bloomfield"
wrote:

The one which shuts the flow off when the room achieves the set
temperature is working exactly the way it is designed to work. If the
room is still cold, the head might be faulty.

The room isn't cold, but it's certainly not as warm as we'd like it to
be.

If the head is removable, then it should be possible to remove it
leaving the radiator with full permanent flow, as you say you would
like it to be.

I see, thanks. I'm not sure how to remove it though. Any ideas please?

I notice that at the rear of the sensor there is a small (about 3mm)
allan key head and near that a number moulded into the black metal
that says: 88P (the one in the hall has 82P on it). Obviously not
the price ( ;-)) but a model number perhaps?

I've looked and looked but can't yet see any instructions for this on
the 'net.

On Fri, 25 Nov 2005 19:08:10 GMT, "john"
wrote:



Why would you want it on all the time if the room has reached the desired
temperature?

That's just the thing though - the room, in our opinion, has reached
the desired temperature *but* then it seems to drop a bit yet the
radiator in question stubbornly stays off.

Try using a thermometer in the room - perhaps you have bcome
accustomed to liking the room to be getting constantly warmer (like my
wife).

Possible I guess, I'll have to hunt down a thermometer to check that.

Bear in mind that there will be a bit of a lag before it opens the
flow again. eg - if set to 21 degrees - that is where it will close - but
the room may have to cool by just over a degree to open it again (Hysterisis
I believe this is called)

I see. Okay, thanks - will check the temperature.

galaxi formulated the question :
I notice that at the rear of the sensor there is a small (about 3mm)
allan key head and near that a number moulded into the black metal
that says: 88P (the one in the hall has 82P on it). Obviously not
the price ( ;-) but a model number perhaps?

If you unscrew the allan screw, the head should then slide off. Under
the head there will be a small peg. The peg operates the valve and
should be free to move about 1/8 inch. If not free it off. If you pull
it all the way out water will leak out, so be carefull.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

galaxi presented the following explanation :
That's just the thing though - the room, in our opinion, has reached
the desired temperature *but* then it seems to drop a bit yet the
radiator in question stubbornly stays off.

There is bound to be some temperature overshoot, until it settles down.


Try using a thermometer in the room - perhaps you have bcome
accustomed to liking the room to be getting constantly warmer (like my
wife).

Possible I guess, I'll have to hunt down a thermometer to check that.

That would be the best way, rather than guessing.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Fri, 25 Nov 2005 20:16:23 GMT, "Harry Bloomfield"
wrote:


If you unscrew the allan screw, the head should then slide off. Under
the head there will be a small peg. The peg operates the valve and
should be free to move about 1/8 inch. If not free it off. If you pull
it all the way out water will leak out, so be carefull.

Sorry for the late reply - I'll try your suggestion, thanks.