Odd boiler cycling?

7 Aug 2008
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United Kingdom
I have a Vaillant ecoTEC+ 937 boiler connected to a VRT360F.
In the morning the boiler fires up and stays on for about an hour without cycling until the house has reached the desired temperature, then the boiler cycles to maintain the temperature. I found this strange as on other systems the boiler cuts off when the demand is satisfied and when the room temperature drops by 1 degree or so then the boiler will fire up. On my system the boiler cycles to maintain the temperature, the temperature is always steady.
Is this how it is supposed to work?
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yes it is. Have you range rated it in d 0? How many rads do you have?
I expect that your heat demand is not that high and the boiler's minimum heat output might be about 11 kW.

In that situation the boiler cannot modulate down any further and 11 kW is more power than is needed to produce the heat demand.

The result is that the boiler cycles on/off at 11 kW to maintain the set temperature.

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That's fine then, the boilers modulation range is 12kw-28kw I have 11 radiators and a Myson Kickspace, the boiler is rated at 25kw.

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