I have had this problem with combination boilers in two different properties:
When showering in the first property, the hot water temperature fluctuated wildly. The water was hot for 2 min, then fell to cold for 1 min, then got hot for 1 min, then cold for 1 min, then hot for 2 min, etc. The fluctuations stabilised after around 10 minutes. It was in the summer and no radiators were on.
In the second property similar problems arise when the boiler pressure (Worchester, Greenstar 28i Junior) is too low (0.4 bars) or too high (1.5 bars). When the pressure is around 1.1 bar the problems are somewhat less intense.
For the first three months in the property, the hot temperature was reasonably stable and the boiler delivered +55 degrees hot water, as it should. Perhaps every third week, the hot water turned cold for around a minute once or twice before going back to stable temperature.
When the fluctuations started, the cycle began with hot water for 2 min, then cold for 1-2 minutes, and then hot with overshooting (way hotter than +55) for 1 min, and then with hot water at around +55 for a minute before going cold again for 1-2 minutes, back to hot with overshooting, etc. After around 10 - 15 minutes the fluctuations went away. During this cycle the boiler sometimes turns itself off for around one minute and then turns on very high for one minute before going back to normal burning. However, sometimes the hot water temperature drops even though the burner in the boiler is running.
I get similar but much smaller fluctuations in the bathroom sink when running the hot water tap but have not noticed any fluctuations when running hot water in the kitchen sink.
None of the taps has a thermostat though the shower mixer (Mira Combiforce 415) is a pressure balancing mixer.
This is a mystery. Has anyone encountered something similar? What is the problem?
When showering in the first property, the hot water temperature fluctuated wildly. The water was hot for 2 min, then fell to cold for 1 min, then got hot for 1 min, then cold for 1 min, then hot for 2 min, etc. The fluctuations stabilised after around 10 minutes. It was in the summer and no radiators were on.
In the second property similar problems arise when the boiler pressure (Worchester, Greenstar 28i Junior) is too low (0.4 bars) or too high (1.5 bars). When the pressure is around 1.1 bar the problems are somewhat less intense.
For the first three months in the property, the hot temperature was reasonably stable and the boiler delivered +55 degrees hot water, as it should. Perhaps every third week, the hot water turned cold for around a minute once or twice before going back to stable temperature.
When the fluctuations started, the cycle began with hot water for 2 min, then cold for 1-2 minutes, and then hot with overshooting (way hotter than +55) for 1 min, and then with hot water at around +55 for a minute before going cold again for 1-2 minutes, back to hot with overshooting, etc. After around 10 - 15 minutes the fluctuations went away. During this cycle the boiler sometimes turns itself off for around one minute and then turns on very high for one minute before going back to normal burning. However, sometimes the hot water temperature drops even though the burner in the boiler is running.
I get similar but much smaller fluctuations in the bathroom sink when running the hot water tap but have not noticed any fluctuations when running hot water in the kitchen sink.
None of the taps has a thermostat though the shower mixer (Mira Combiforce 415) is a pressure balancing mixer.
This is a mystery. Has anyone encountered something similar? What is the problem?
