The National Voluntary Laboratory Accreditation Program (NVLAP) is a US federal program run by the National Institute of Standards and Technology (NIST) that provides third party accreditation to laboratories in the USA. NVLAP tests laboratories and not products, for accordance with ISO/IEC 17025:2005. NVLAP accreditation is available, but it is not required for commercial university and federal laboratories.
It is important to note that NVLAP accreditation to ISO/IEC 17025:2005 is no longer recognized as of November 30, 2020. As a result, NVLAP has developed a transition plan to ensure all NVLAP-accredited laboratories meet the requirements of the 2017 version of the ISO/IEC 17025 standard within the required time frame.
Competitors include this requirement as part of their specifications with the sole purpose of eliminating competitors. It adds no additional value to the performance of the product or the ability of a supplier to achieve excellent performance, accuracy and reliability for the end-users application.Competitors still calibrate their Venturi Valves to the NIST Policy on Metrological Traceability standard same as Johnson Controls with the same accuracy of ±5% or 10 CFM, whichever is greater and use NVLAP certification to prevent competition. It is important to educate the customer and ask a few questions to clarify for the engineers involved, and explain that the NVLAP certification is not a true requirement for the performance, accuracy and reliability of the Venturi Valves
Data points and the calibration process
The factory calibrates each individual Venturi Valve to 49 points, across the entire operational flow and duct static pressure range of the device, to ensure it meets the published performance specifications.
Some competitors use a 48 point calibration at only one static pressure, whereas Johnson Controls calibrates at least seven different static pressures to ensure pressure independence across the entire operating range of the Venturi Valve.
Venturi Valve certification
The electronics on the Johnson Controls Venturi Valves are UL certified.
Venturi Valve duct static pressure change response
Venturi Valve actuator control signal and air flow response
The fast acting actuators respond almost instantly to the controller signal and begin to move to the required position to meet the change in airflow requirement. The time it takes for the actuator to go from 0% to 100% is less than three seconds.
Venturi Valve air flow control accuracy
All Venturi Valves have an industry standard accuracy of ±5% or 10 CFM, whichever is greater.
Venturi Valve pressure drop
The pressure drop across a Venturi Valve is dynamic and not static. It can be anywhere between 0.3 in. W.C to 3.0 in. W.C for low pressure and 0.6 in. W.C to 3.0 in. W.C for medium pressure Venturi Valves. As long as the pressure does not fall below the minimum of 0.3 in. W.C for low pressure and 0.6 in. W.C for medium pressure, or exceed the maximum of 3.0 in. W.C, the Venturi Valve will maintain pressure independent flow control and function as intended. In order to get a true pressure drop reading across the valve, it must be measured during its operation conditions. When you calculate the pressure drop to determine the required Fan static, use any value between 0.3 in. W.G, or 0.6 in. W.G for standard pressure, and 3.0 in. W.G as the value across the valve. Typically the lower value is used plus some margin for static fluctuations.