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Help with new viessmann boiler

mitkrow Member Posts: 1
Hey guys. Need some advice on my new boiler system. The local plumber are far from useful at this point and until I have a direction to point them in there is no point in talking to them.

My system consists of a veissman 222f-35 with 6 zones. Five of the zones are radiant in floor in concrete slab run off a single circulation pump. The remaining is my garage loop, which is also in floor pex but isolated by a heat exchanger and with its own pump as it is a glycol loop. I have a low loss header (not a veissmann) which I feel acts as a primary loop? Then the remaining zones are all on a secondary loop. The boiler is set up for outdoor reset control with a slope of 0.7 and a shift of 5K. All zones are on thermostats with zone valves. The stats are wired to the external circulation pump which only turns on when there is a call for heat. The stats and the pump are not connected to the boiler at all.

The problem I'm having is that the boiler is firing upwards of 80 times in a 24 hour period. Because there is no communication between the calls for heat and the boiler, the boiler seems to just be doing its own thing. The local plumbers initially had it wired with the pump and the stats to the boiler but they couldn't get the external pump to stop circulating so they spoke with the viessmann representative who told them to do this instead. I've looked through the manual for some of the coding but non of it seems to apply to my scenario. Anybody out there have any suggestions? I cant go back to the local guys without having a direction to point them in. Thanks and sorry about the wall of text. Let me know if you need any more info.


  • ChasMan
    ChasMan Member Posts: 459
    edited January 2018
    Well, the usual references to a dogs early morning meal aside, that boiler has about 1.5 gallons of water in it so every time a thermostat calls it is going to fire. If your system was designed properly the boiler would fire less for longer periods. Getting there will require more than a couple of wiring amendments. More pictures and diagrams would help people here to better address the issue.
  • Paul Pollets
    Paul Pollets Member Posts: 3,509
    To work correctly, the Viessmann LLH should have been used with the LLH sensor. The existing hydraulic separator looks too small and the ports are not offset, not to mention the lack of sensor. The installation manual comes with schematics with all piping possibilities. Why wasn't it followed? If these systems are installed and wired correctly, they work without short cycling.
    EBEBRATT-Ed Member Posts: 12,023
    In addition to what others have mentioned above it is probably also a water content issue. With only a partial load on the system the boiler short cycles due to low water content. Adding a buffer tank will help if this is the issue. Need more pictures of the entire system

    How does everything heat? If it heats ok a buffer tank may solve this