Grant Oil Combi Boiler Hot Water Efficiency

26 Jan 2022
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United Kingdom

We have just had a grant vortex oil combi boiler installed and we have two options to heat our hot water; we can have the water on continuously which will keep the very small water reserve in the boiler at a certain temperature. Or we can have the hot water off and then just boost it when we require the hot water.

Which is the most efficient/cheapest option?

If we do have the water continuously on, would the water reserve be big enough to supply hot water for multiple showers without having to boost?
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Cheapest is to just run it when you need it, but at times if high demand you might find the boiler struggles to keep up depending on power and flow rates
This boiler doesn’t store any hot water. The heat store tank pumps hot primary water through a plate heat exchanger on demand. It takes about 15 mins to heat the heat store from cold. It’s designed so that when you draw hot water the heat store provides it whilst the burner fires and starts to put heat back into the heat store. You should never run out of hot water. I would have the hot water on all day and off at night to stop any noise nuisance of the boiler firing once or twice during the night

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