Solar Insolation

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.
Next find latitude, the amount of solar insolation, and number of hours of available sunshine at the job site location.
VM can provide you with the expected solar energy figures for any month of the year.


NOTE: The information presented in this page is for guidance only - no part of this may be used for any agreement, whether express or implied, or to form any contract. THERMO TECHNOLOGIES reserves the right to change specifications and prices without prior notice.


To heat 375 liters of water at a job site with a local Annual Insolation of 1400 hours, you need 40 VM tubes. size_b.gif (15778 bytes)

Once the amount of hot water that must be supplied by solar heating system is known, the above chart illustrates how many VM tubes are required. This example suggests 40 tubes.

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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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