European panel radiator maintenance

[britmosh]

Hi all,
I am a renter in an apartment where there are panel radiators made by the Belgian company Radson. My apartment has two radiators. One is working - it is nice and toasty. The second radiator is warm on the right-hand side (where the water enters the radiator) but not throughout the radiator. I tried bleeding the radiator and no water came out. I found a knob on the radiator (see photo) that I loosened, but it didn't seem to release water throughout the system either. (Did I loosen the right part?)

The landlords aren't familiar with the radiators and they are not local, so I am looking for help here. Additional info: my apartment is on the third floor, and the thermostat is on the second floor. This radiator seems to the the only one not working in the whole house.

 

[Dana]

Don't loosen up that valve! It looks like a thermostatic radiator valve with the knob missing. Did it have a thermostatic knob which you have removed? If there's an air-bleeder, it's probably on the other end of the radiator. It's usually a narrow square head vav

< there are a number of different form factors to the valve knobs- this is just one example.

If there's an air-bleeder, it's probably on the other end of the radiator. It's usually a narrow square head valve operated with a special key/wrench, as seen in this video.

I believe the thermostatic valve works by pressing the rod at the end in/out, based on the knob setting. Some will vary a bit in response to room air temperature, others respond only to the radiator temperature. I'm guessing that pushing it in increases the flow through the radiator piping portion to the convection fins, decreasing the flow in it's internal bypass pipe. Letting it out stops the flow through the radiator portion, only allowing flow through an internal bypass pipe. The warm part of the radiator would likely be where the bypass is located. With the knob completely removed it's all going thorough the internal bypass, limiting the output of the radiator. Push on it (with the thermostat turned up), and listen to hear if there is any change in flow.

It's also possible that there isn't sufficient water pressure on the system to get water to the third floor. If the boiler is in the basement 5' below the basement ceiling, the floors (including joist depths) are 12' (x 2= 24' total) and it's another 3' to the top of the radiator that 32', the pressure measured at the boiler level would need to be about 17-18 psi to reliably avoid occasionally air locking the top radiator.




Nice dog-shaped throw-pillow!

 

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[britmosh]

Hi Dana,
Thanks so much for your response. Based on the info you sent, my radiator does seem to have a thermostatic valve. There was a small cap on the valve, which I removed to take the photo. The cap didn't seem to be a real knob, more of a sham covering (see photos). It didn't really seem to "engage" anything (although I was turning it - not pushing it directly in/out). It was the markings on the cap that made me think I was supposed to turn the valve beneath it. All of the other radiators in the house have these little covers on the valve as well.

I haven't tried your solution yet, but will tonight. So basically, just turn up the heat on the second floor thermostat, and then push that little nipple thing inwards and listen? There is a bleed valve on the other side that I can loosen with a screwdriver. I am guessing that I might need to use that once I get the water flowing throughout the radiator? Do you have any other tips/suggestions/words of caution before I try this?


Thanks so much for your response. It has been super helpful.
Brittany

 

[Dana]

This version of the knob isn't thermostatic- it adjusts the flow rate, but doesn't vary the flow rate with room temperature or radiator temperature.

Put the knob back on, and see if turning it all the way to the "+" changes anything. I can't tell for sure from the pictures of the inner & outer pieces of the knob, but I suspect rotating the knob pushes the center rod in when turned to the "+", lets it out when turned to the "-". With the knob off it's probably fully "-". It could be the converse, however.

When you open the bleed valve, does it hiss, pushing out some air? If yes, keep it open until it starts to sputter & spit some water. Eventually it'll be just water, at which point, close the valve.

If it doesn't hiss or spit it means either the zone valve isn't open, or the system pressure isn't high enough to raise water to that level. Have you verified the system pressure?

 

[britmosh]

Hi Dana,
I haven't verified the system pressure, but there is another radiator (same model) on the third floor that works without any issues so I am hoping that pressure is not the problem.

When I last tried to bleed the radiator it did make a very brief hiss, but then quieted to an almost inaudible level. I waited for about 2 minutes and no water ever made it to the valve. This is what led me to believe that water might not be accessing the entire radiator due to some sort of bypass issue.

I will put the knob back on and attempt to adjust as you say, although based on the shape of the cap and how deep it's cavity is, I don't think that it will engage the center rod. It almost seems like the cap was placed on there as an afterthought, to prevent anyone from accidentally tinkering with the center rod. It seems like (based on some youtubeing - skip ahead to the 1:00 minute mark) that the center rod will allow water to flow when it is pulled out, rather than in. This especially makes me think that the knob won't help me, but maybe manually moving the center rod will.

Thanks again - I sure appreciate your help.
Brittany

 

[Dana]

If the other 3rd floor rad is working, you don't have a pressure problem, and should be able to bleed the mis-performing radiator if needed.

If the rod is somehow frozen up and stuck in an in/off position, you may be able to free it up a bit. If it's sticking out the same amount as the other radiator, the radiator probably just needs to be bled.