Viessmann radiator cold at bottom, warm at top—using Vitopend 100, 2.5 bar pressure

Hello,

I have Viessman heaters in my apartment. In the bathroom and in 2 rooms, the radiator warms very well, while in the third room, the radiator is cool downstairs and warm upstairs. All this is handled by the Vitopend 100 2-function stove (pressure currently set to 2.5 bar). What may be the cause of incomplete heating of one radiator? I will add that they are all vented.

Thanks in advance for your answer

generally, the room is very large and is connected to the kitchen (area approx. 40 m2) and taking into account that there is only 1 radiator, which is 140 cm, it is always cooler in this room (approx. 19.75-20.5 degrees, the rest of the rooms approx. 22.5 -24 degrees)

krecikno1 wrote:

Hello,

I have Viessman heaters in my apartment. In the bathroom and in 2 rooms, the radiator warms very well, while in the third room, the radiator is cool downstairs and warm upstairs. All this is handled by the Vitopend 100 2-function stove (pressure currently set to 2.5 bar). What may be the cause of incomplete heating of one radiator? I will add that they are all vented.

Thanks in advance for your answer

First, drain the water from the system because you have too much pressure.
If the radiator is not equally warm vertically (left, right side), there is air in it, if horizontally (up, down) there is too little flow of the heating medium.

I will stick to the topic.
Network pressure 1.8 - 1.9
On one side of the apartment 2 heaters (boiling)
On the other side, there are 3 radiators - the first bathroom is hot, the next two are warm at the top, summer or cold at the bottom. Temp. on the stove set to 70 ° C.
Boiling water comes to the two faulty ones, because the tube is hot and it splits into two radiators. Cold return tube. Radiator bottoms barely lukewarm. Where is the cause of underheating of the pits? All radiators are bled, of course.

Second question. Can the supply and exhaust pipes be connected to the radiators on the same side or should they be connected diagonally to the radiator?

Hello,

maybe the radiators are just too small?
Maybe the flow in the installation is too weak, e.g. a collapsed filter, traps in the installation ...
If you have thermostatic valves, check what are the settings - if possible, set them to higher values.

The method of connecting the heater affects its power, but most manufacturers allow different configurations.

Regards

Thanks for the hint.
They are certainly not too small. They were warming normally last season. I will check the settings and I think I will also bet on the muck in the installation on this side of the apartment because I know that it has not been flushed for a long time.
I will fight again ...

It is especially unpleasant when the radiator is cold from the bottom and warm from the top (it does not heat the legs and the back is hot). If this is the case, it means that there is a small flow of the heating medium in relation to the size of the radiator. First of all - as it was written in the previous post - check the initial settings (orifice) and increase the flow in those radiators that heat badly (they are cold at the bottom). In those that are very hot, slightly reduce the presetting. The presetting is not what is set with the thermostatic head, but what replaces the cladding. To do it, you need to disassemble the thermostatic head (under the head there is usually a setting ring - if Danfoss - or a special nut - if other valves - with numbers corresponding to the setting value and there is a dot on the valve body - a reference point. One more thing. is the bottom cold also when the temperature is set to the maximum by the thermostatic head? Maybe the head is damaged (defective / worn).