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Discuss Viessmann boiler short cycling in the Central Heating Forum area at PlumbersForums.net

OP
V

Valdas

I have attached the log file containing data for full day when the outdoor sensor was disconnected. I think Baxi uSense thermostat doesn't include TPI software.
 

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J

John.g

I had a similar problem, for me it was the flow rate sensor, and this was with 100w as well.
I was wondering why you mentioned this but I now know (I think). The boiler has a flow switch which will shut down the boiler if the heating flow rate falls below 200l/h (3.3LPM) but with no alarm. I am assuming that this is a heat boiler only and that its not a combi and that they are not referring to the DHW flow? , but they do refer to the "heating" flow rate.
 
M

MCornish

Hi,

I have noticed my boiler Viessmann Vitodens 100-W(B1HC-26) makes a series of short cycling before starting to heat. Boiler is controlled by Baxi uSense room thermostat connected via Opentherm. I installed some monitoring equipment to get the better understanding of the problem. Bellow is the illustration of the problem:
View attachment 42946

I will explain the graph from the top to bottom:
  • Green bar indicates heating pump is on
  • Red bar indicates flame is on
  • Black line indicates max relative modulation level (%)
  • Orange line indicates DWH temperature (Celsius) (not relevant in this problem )
  • Red line indicates boiler water temperature (Celsius)
  • Grey line indicates setpoint temperature (Celsius)
The graph reveals that it took 10 times for the boiler to fire up until it started to run. Water temperature inside the boiler reaches ~40 degrees very quickly after boiler fires up and then it switches off.

I would appreciate any ideas of how to solve the short cycling.
If the temperature rises too quickly then cuts burner out it sounds like the plate heat exchanger is blocked in turn locking out as it’s overheating. Had this recently on the same boiler.
 
D

doitmyself

If the temperature rises too quickly then cuts burner out it sounds like the plate heat exchanger is blocked in turn locking out as it’s overheating. Had this recently on the same boiler.
The OP hasn't replied for five months, so his problem has probably been solved. In any case, he has a system boiler, not a combi, so there is no plate hex.
 

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