Bleeding Radiators: Proper Venting Techniques, Screw Positions (A, B, C), & Ideal Temperature

Hi, I have a problem like this when venting - radiator cold (other radiators in the flat work without a problem) - I have turned off the head at the thermostat, unscrewed the valve and water is pouring like mad (more than half a bucket so far), the radiator remains cold. I've added pictures, can you advise anything? I didn't move those tubes at the bottom, I'm throwing in just in case, they just happen to be slightly warm, but nothing else.

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After this venting, has the head been opened (at least to a temperature that is higher than the current temperature in the room where the radiator is located)? If so (the best way to check this is to open the heating head to maximum), then there is a problem with the flow through the radiator. It's worth checking how the so called presetting is set (it acts as an orifice) and this can be checked by removing the thermostatic head (it looks like a Danfoss to me on the photo, so it should be quite simple). If it's a Danfoss (which it looks like it is), when you remove the head there will be a metal ring with numbers from 0 to 7 and then an N on it. The higher the number, the higher the flow of the heating medium through the radiator (N is the maximum flow - as if without an orifice and this setting is generally only used to flush the valve). On the brass body (on the screw side) there is a dot - a reference point - whichever number is opposite the dot indicates the setting. To change the setting, you have to pull the metal ring a little towards you and turn it (if it is not stained, you can do it with your fingers, if it is dirty, you may need to use e.g. a pair of pliers). In any case, if venting does not help (all indications are that there is no air), the cause is a lack of heating medium flow or a very weak flow. If the setting was on a low value and, in addition, the head was in the closed position all the time, the valve may have become silted up. If this is in Krakow (especially near the Ugorek housing estate) - I could come.

Unfortunately, Warsaw. I changed the setting, but it doesn't do anything. I've left it on 'N' and nothing happens to the radiator temperature either. Another thing - shouldn't it be the case that when I turn the head down to zero, the water in the radiator is not topped up? I've done this, unscrewed the vent valve and a strong stream of water is pouring out of it. On the one hand, it's good that there is no air, but according to the diagrams in this thread above, I would have thought that with the head turned to zero, there would be no supply of new water to the radiator and the pressure would go down to zero (i.e. the water jet would get weaker and weaker until it stopped flowing).

kubackiandrzej wrote:

that when I turn the head to zero, the water in the radiator is not topped up?

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The pressure is coming from the return side.
There is still the stem coming out of the thermostatic insert screwed into the valve to check if it moves at all. Check after unscrewing the head to see if it pushes inwards.

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This is what it looks like when the head is removed. Apart from being able to adjust between 'N' and '7' (turn that red knob) nothing moves there (at least not without tools / a lot of force and I'm afraid to try so as not to deform anything).

This protruding pin should be able to be pushed in using a small amount of force.

>>21261767 Something is jammed. It should be able to be turned from 0 to N and all around. You may have to try turning it with a pair of pliers (first pulling the red part towards you), but make sure not to crush or deform it. You should also consider whether the valve at the bottom is choking the flow (photo on the right in the first post) - the left screw is not quite parallel to the inlet. You might also want to chamfer those other radiators a bit (maybe throttling them will induce flow through the faulty one). And is this a bungalow, townhouse or block of flats? Is it the top floor or, for example, the ground floor (if it's a larger building - several storeys high, then maybe the floor below should be slightly chimneyed with radiators).

It can be spun from zero to N (you don't have to pull it off), while this protruding pin doesn't move at all (doesn't go in). It's a block of flats, top floor.

kubackiandrzej wrote:

while this protruding pin does not move at all (does not go in).

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It is the insert that is to be replaced. It is supposed to move.

The insert is not necessarily replaceable. You have to try to move this pin with pliers. First try pulling it out (you should be able to pull it out e.g. 2 mm if it is baked closed), then push it in (if it was baked open, you should be able to push it in about 2 mm). Probably the radiator has been many years in the baked-on position, which is why this pin (and the valve) got blocked. As it is possible to completely shut off the radiator from supply and return at the bottom, it would be theoretically possible to replace the insert.