Criterion 6.1.1.4 Auxiliary Water Heating Equipment

Criterion text:
A backup system shall be provided such that the combined system will provide the same degree of reliability and performance as a conventional system.

Auxiliary (non solar) water heating equipment shall be compatible with the solar system heat output, temperatures, flow rates and fluid types. Auxiliary equipment shall be listed and labeled by a recognized third party listing agency.

Comments:
This requirement stipulates that all SRCC approved solar systems require an auxiliary tank or auxiliary system to back-up the solar storage tank. In most cases, the auxiliary tank is a conventional electric or gas water heater. For systems that use only one tank, the tank must have a heating element to provide hot water to the load in the event solar heating is not available.

Electric auxiliary water heaters must be listed by UL (See Figure 1) and gas water heaters GAMA listed.

Figure 1

Thermosiphon system storage tanks that incorporate heating elements must also be UL listed.

The installer must make sure that the system installed includes the tank(s) specified in the manufacturer's SRCC approved installation manual.

Figure 2 shows a two tank system. Note the solar tank and the auxiliary gas tank.

Figure 2

Since SRCC system ratings are affected by the selected back-up tank installing the proper tank is very critical.

In the event a tank must be replaced, the installer must make sure that they keep the same tank size (50, 80, 120 gals, etc.) for which the system was certified. In addition, the tank's R-value must be equal to or greater than that of the tank that was originally certified.

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