I bought a house in which one of the radiators (powered from the bottom), as it turned out recently, is leaking at the upper valve. Hence my question: can I close the bottom screw connections (set the position to the horizontal lines) and unscrew the thermostat insert? Will my floor flood? I attach a photo of the insert and ask for help.
First, it will definitely flood. Does "lower screw connections" mean valves on the return branch? In order not to flood, both supply and return must be turned off, and unscrewing the insert causes that the power supply will be a HOLE (after removing the insert, water under pressure will leak). Secondly, to unscrew the insert requires special tools, which are usually only available from Danfoss services (it cannot be unscrewed with ordinary hydraulic tools without damaging it). Where is it leaking, anyway? Whether on the shaft of the gland (this is the pin sticking out of the valve) - then it may be enough to tighten this small nut, or from the flare nut (you can try to tighten the flare nut, but without exaggeration, so as not to break the thread - it is brass, not steel)
When writing about the lower screw fittings I meant:
Closing the valves in this connection cuts the radiator from the installation. Then you only need to drain the water from the radiator through e.g. a vent, when the vent stops flowing from the vent, you unscrew the entire vent, then the water gushes a little more, so you put a small bowl under the radiator, which will take the flowing water. Additionally, you can loosen the bottom cap below the vent to let some more water drop to keep the water level below the liner level. Do everything gently, unscrewing the air vent and bottom plug completely results in the water running out under pressure. 1m of the C22 radiator, 60cm high, has about 6.5l of water in it, so prepare a bucket of appropriate capacity so that you have a place to pour the water out of the bowl. If you drop enough water, you can try to twist the insert. I do not know Danfoss, but I have Oventrop inserts and their replacement is very easy, because an ordinary wrench, probably size 19, fits them, and the presetting is done with a 13 wrench, so you do not need specialized tools and a service technician.
So, with the lower valves closed, I checked the vent on the left side of the radiator. The water was not running. So, armed with a towel and a bowl, I started to slowly unscrew the insert ... and I will write to you that nothing was leaking. I screwed in a new Danfos cartridge (it was slightly shorter). I opened the valves, let some air out, turned on the pump and the radiator started to heat up. Nothing is dripping However, it turns out that when the thermostat is turned to position 0, the radiator still warms up nicely.
as roman 18 wrote, take an old pattern insert and buy an identical one. Under normal conditions, water should only flow through the valve insert, and by closing the valve, no water should flow. Since the new insert is shorter, the water probably flows through the resulting gap, ignoring the insert and hence the heating effect of the radiator despite the head set to "0", i.e. the valve is completely closed. When looking at my brand new insert, I can see the sealing O-ring inside the sleeve, but I cannot see the structure of the radiator. However, on the side of the radiator there must be a suitable pin on which the O-ring will lock, sealing the connection so that water does not flow through the sides. In this case, a shorter insert like yours can make a big difference, because it does not seal the connection.