Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Fin tube radiator Heat distribution problems with VEISSMANN 200w

Tonerlow Member Posts: 85
We have retro fitted a Viessmann 200w into our 1250 ft2 split-level bungalow. They plumber this with no low loss header, the boiler feeds 2 heating zones(upstairs /down stairs). With a single circ pump (Grundfos UPS26-99FC). There is a bypass created with a 1/2” ball valve to allow flow when both zone valves are closed.

I am having trouble getting enough heat into the SW bedroom in the upstairs. I assume this is due to it being at the end of the heating loop and too much heat has dissipated the throughout the rest of the house? Thermostat is located in the main hall, nearly deed centre of the upstairs. Or is there too much gycol flowing though the bypass and it is not cycling the heat to that one room? Or is my heating curve/slope not set correctly. 1.3 slope 0 shift. I have closed the majority of the dampers upstairs just now to see if that gets more heat to the last room. Will check that out in the morning. It is typically about 5F cooler than the rest of the upstairs. 

Do I just crank the shift up and sacrifice some efficiency?

Any other thoughts or advise on this issue? Would rather solve this without adding more costs. 

Old boiler was a super hot and got lots of heat everywhere in the house. But that was heating to 190F for all of heating season. This new unit is saving us a TONNE on fuel, but I feel is not running optimally just yet.  

Going to borrow a thermal camera this weekend and shoot temps of radiators while they are cycling. Also can post pics of setup, will do so in comments on this thread. 


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,037
    One option may be to close the damper on the radiators that are the first to receive the heated water. This will reduce the amount of heat those radiators will send out to the room. The radiators at the end of the loop should have the dampers wide open. The dampers in the middle of the loop can be partially closed.

    If you close a damper and the room does not heat as fast, that will leave more run time for the radiators at the end of the loop to heat up. This may take some time and some trial and error to get it just right. As soon as you do get them just right, Someone will try to be very helpful and while vacuum cleaning the dust from the underside of the radiators will open them full, as a favor to you.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • bburd
    bburd Member Posts: 922
    You might check for obstructed airflow through the fin tube in the cold room. Thick carpeting or furniture pushed against the baseboard can do it.