Hot Water Consumption and Storage Capacity

When designing a VM domestic solar water heating system for a family of five, determine first how much hot water the family will be using per average day. ASHRAE recommends 20 gallons per day per person.


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Recommended solar water storage tank for a family of five is 400 liters. size_a.gif (47940 bytes)

The above graph illustrates a solar water heater storage tank for a family of five with a hot water consumption of 50 liters per day. Consumption per person is 375 liters. In the United States, with higher hot water consumption, a 120-gallon tank is used.
The home may have a dishwasher, washing machine, several children taking daily showers or baths during the day, and all of this water usage must be figured into the total water needs.

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In the following four pages we are going to size a solar water heating system for a family of five. They have a hot water requirement of 50 liters per day, per person, with a local Annual Insolation of 1400 hours. Orientation of the roof is 30° West of South. The local Latitude is 45° and the roof angle 35° (inclination difference 10°). If your property is located in the US, go directly to US Insolation Charts.

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