Worcester heatslave 20/25

16 Aug 2018
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United Kingdom
2 questions !
1. Should the water pump on a worcester heatslave 20 / 25 oil boiler be hot when running ?
2. What does the thermostat knob on the front of the boiler actually regulate ?
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Yes, the pump runs to keep the heatslave tank hot. The thermostat keeps the oil burner running for a little longer than previously set.
John :)
So the hot water from the tap isn't regulated by the thermostat then ?
The pump will run whilst there is a demand for hot water or from the heatstore (DHW) thermostat. The DHW thermostat controls the temperature of the heatstore, which directly dictates the temperature from the hot water tap.
What has prompted the question? Do you have a problem which you are trying to solve?
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Although the temperature control on the outside of the boiler is on minimum the water from the taps is red hot. Is that right ?
The DHW thermostat may be out of calibration, or there may be a problem with the flow switch. Without doing tests and observations, it is difficult to be specific. Don't forget, like any combi, when the incoming water is as warm as it is at present, your hot water will be hotter than in winter.
As oilhead says. The manufacturers instructions state that the hot water may need a thermostatic blending valve after the boiler to regulate the temperature. Modern oil combis are thermistor controlled on the heat store so burner fires on temp drop rather than on flow switch call

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