4 Responses to “Is ASHRAE Getting It Right With Solar Thermal System Design?”


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  1. Dr. Ben, Help.. In a word!
    Im wording on a job and spec’ed American Solartechnics 430 gal. atmospheric tank. Drainback. They wanted a “Cert” on the tank . The plumbing inspector, asked for an SRCC cert on the tank. This is a 6-Apricus AP-30 in to 430 gallon tank.
    This has gotten out of hand.
    I have been putting in and/or designing systems, since 1983.
    I have never been asked for something, that i dont know were to find.
    Could we talk ear to ear? My cell is 503-807-1349.
    This is no way to get solar affordable…being ‘stuck-up’ by the plumbing inspector

    • Dr. Ben

      There is no such thing as a certification on the tank. SRCC does not have anything to do with tanks. They do certify collectors (OG100) and some small pre-engineered residential DHW systems (OG300). Maybe that is what the inspector is thinking.

      For example, the City of Palo Alto Utilities Solar Water Heating Program Handbook- Modification v2 58 (www.cityofpaloalto.org/) sets requirements for their program which defines,
      OG-100: Operating Guidelines 100 (OG-100) is a certification and rating program for solar collector developed by the Solar Rating and Certification Corporation (SRCC). The purpose provides a means for evaluating the maintainability of solar collectors and a thermal performance rating characteristic of all- day energy output of a solar collector under prescribed rating conditions.

      OG-300: Operating Guidelines 300 (OG-300) is the SWH system rating and certification program developed by the Solar Rating and Certification Corporation (SRCC). The purpose of this program is to improve performance and reliability of solar products and is based upon the determination by SRCC that the system successfully meets its minimum criteria for design, reliability and durability, safety, operation and servicing, installation, and operation and maintenance manuals. OG-300 is a comprehensive certification of the entire SWH system.
      And requires the owner/installer to certify as below

      Solar Water Heating Contractor Participation Application CITY OF PALO ALTO UTILITIES

      (g) I understand that all single family residential systems installed for incentives must be SRCC OG300 certified, and that all commercial systems require collectors that are OG100 certified, or if appropriate, systems that are OG300 certified, and that all systems must have automatic freeze protection. I agree that I will not substitute components, or change configuration of systems from data submitted to SRCC for system or collector certification. I understand each system requires an Owner’s Manual, a 10-year Collector warranty, five year warranty on other parts, and a one year Labor warranty. I agree to allow my warranty to be published to facilitate comparison by customers.

      The problem with OG300 is that there are so many combinations of tanks, pumps, exchangers, and collectors, that it is impossible for all small systems to be OG300 certified. I think this is overreaching, and is designed mainly to line the pockets of SRCC. Especially if a dealer is used to assembling various components to make their own system.

      There is one distinction above vs your system. That is, the rules above apply to someone applying to a specific city incentive program. If you are not applying to a specific incentive, then all you should have to meet is the state code for solar equipment (usually OG100 for collectors), and any local plumbing codes for safety. Many inspectors are simply not up to speed on solar and you can bump into all kinds of hassle depending on where you are.

      The best approach I have found is to calmly educate the inspector with descriptions and definitions. That frequently does the trick. If not, find out what the procedures are for an official hearing on the matter. I used to refer obnoxious inspectors to the State Department of Insurance (the codes section) who knew about my systems and would straighten out any errant inspector.

      Good luck!
      Dr. Ben

      • bruce dike

        Dr. Ben,

        What approvals (if any) are commonly required for atmospheric tanks? What do we tell inspectors who have no idea what they’re looking at and want to see ‘something’? For example, in Mass. they want to see the Mass. Association of Plumber’s approval.

        Thanks in advance.

        • Dr. Ben


          Approvals are the mine field of any “new” technology. Even though commercial solar products have been sold in the USA since the 1890s, the technology is completely foreign to many code officials.

          For example, I sold thousands of systems all over the country in the ’80s with little code troubles. We used only UL labeled components and the tank was not a pressure vessel. A little chit chat with the code officials usually fixed the concern. I never had a system rejected by a code official.

          Now, times are changing. We still use only UL listed components, and the tank is non pressurized, but some jurisdictions want to see a package certification, usually electrical in nature. So, we are proceeding with an electrical certification for all our products.

          I don’t know any approval or ratings needed for non pressurized tanks. ASME rating kicks in at 15psi. There are different rating levels according to the intended service pressure. Ordinary residential water heaters are rated for about 120 psi. They fall under a residential section of the code that limits the size to 120 gallons. That is why you see solar dealers installing multiple 120 gallon tanks to get enough storage on a pressurized system. You can’t walk out and buy a 250 gallon pressure vessel without getting into the boiler code area and 5-10x the price. This is big reason why we don’t do pressurized systems.

          So, what to do. I recommend a pro-active approach. Sit down with the code officials during the planning stage of a project. Show them what you intend to do and the equipment you want to use. Go over the characteristics of the equipment and get agreement that they will accept the design and the equipment. This avoids on-the-job confrontation with an inspector who has no idea what he/she is looking at and simply falls back on code rules that may not apply to your system.

          We have had many long distant conversations with inspection departments, describing our equipment and methods. This is also one reason we give seminars on solar design and invite code officials to come, so we can all be on the same page.

          I hope this helps.
          Dr. Ben

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