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Water Heaters Used for Temperature Control 

Three New Standards Anchor This Technological Trend

A key, long-standing assumption is being upset in the codes: these water heaters can control final POU water temperature.

Standards are the final stopping point for innovation in our industry. For all the great new products you see at trade shows, the ones that spawn a competitive space become the signal to create minimum performance requirements. Of those, a subset of the water heater market has been able to control their output temperature precisely enough such that there is no need for redundant downstream mixing valves. Current model code language in the 2018 Uniform Plumbing Code (UPC)® and 2018 International Plumbing Code (IPC)® assumes that the temperature output control for a water heater operates the same as it did 50 years ago. ASSE International has released three new standards: ASSE 1082, Performance Requirements for Water Heaters with Integral Temperature Control Devices for Hot Water Distribution Systems, ASSE 1084, Performance Requirements for Water Heaters with Temperature Limiting Capacity, and ASSE 1085, Performance Requirements for Water Heaters for Emergency Equipment, which create the equivalent performance and safety requirements of ASSE 1017, Performance Requirements for Temperature Actuated Mixing Valves for Hot Water Distribution Systems, ASSE 1070/ASME A112.1070/CSA B125.70, Performance Requirements for Water Temperature Limiting Devices, and ASSE 1071, Performance Requirements for Temperature Actuated Mixing Valves for Plumbed Emergency Equipment, respectively.

A Brief Background

The impetus to create these standards comes from the instantaneous1 (i.e. tankless, on-demand) water heater industry. These products are capable of controlling water temperature within the tolerances of the ASSE 1017 and 1071 standards, but the model codes require that the water heater not be the point of final control. At the same time, many water heaters have control designs that compete with the control features of downstream mixing valves, resulting in potentially inconsistent temperatures at point-of-use. To combat this, some manufacturers (both tank and tankless) have provided a bundled system with the appropriate temperature control/limiting valve for better performance. A more elegant solution for the benefit of the plumbing system is to avoid that workaround altogether – which is where these standards fit. ASSE 1082, 1084, and 1085, therefore, optimize plumbing designs by requiring the same levels of protection from thermal shock and scalding on the heaters themselves as the current mixing valve standards.

From the beginning of development at the working group, it was quickly observed that the best route would be to mimic the structure of the existing 1017, 1070, and 1071 standards. This is so the standards can be easily adopted and accepted by the model codes. Mirroring the scope of the existing standards and adding the heater control performance requirements allows for an easy sell to authorities having jurisdiction and plumbing designers.

Those heater requirements themselves are already well documented in other safety standards (e.g. ASME Boiler and Pressure Vessel Code, ANSI Z21.10.1 and .3, and many UL standards). The working group allowed for flexible product designs, as the goal was to be technology-neutral. While those safety standards are referenced in ASSE 1082, 1084, and 1085, they are non-mandatory, as existing code requirements will drive this continually evolving need.

What do these new standards cover?

Temperature Performance
ASSE 1082, 1084, and 1085 make the assumption that the worst controls a heater will have will be at the maximum energy output at the maximum flow rate, and also at the minimum flow rate. This same assumption is made in the ASSE 1017 and 1071 standards and is made explicit in these standards – the maximum flow rate drives the appropriate tolerance band. For both ASSE 1082 and 1085, those same tolerance bands are paralleled. A new temperature control requirement had to be given for ASSE 1084 (for point of use) that parallels ASSE 1085 (for emergency fittings). While ASSE 1070 (for point of use) is written for temperature limiting, those requirements would not be sufficient for a product that adds energy into a system.

Where can each be installed?

1082 Installation
Intended for installation near the beginning of a hot water distribution system to increase and regulate the output water temperature during steady state flow. Not intended for direct connection to plumbing fixtures – there are no scald prevention requirements for the controls.

1084 Installation
Intended for installation near, or at, plumbing fixtures in order to increase and regulate the output water temperature. This product limits the maximum temperature to 120°F or less to prevent scalding.

1085 Installation
Intended for installation before an emergency shower or eye wash station fixture to increase and regulate the output water temperature in order to comply with ISEA Z358.1. These water heaters limit the maximum temperature to 95°F (35°C).

Where are We Now?
Proposals associated with these standards were submitted for consideration in the 2021 IPC code cycle that began in Jan. 2018. The Final Actions Results from the ICC are out2. Not all proposals passed, but all three standards will be referenced in the 2021 IPC.

We will need to wait for the 2021 IPC to be published for the final language, but you can get an understanding of the changes by reviewing the particular proposal numbers in the Group A Public Comment Agenda3.

Proposals were also submitted for consideration in the 2021 UPC. The UPC process is still underway with the next Technical Committee meeting scheduled for April 29 – May 2, 2019 in Denver.

When the ASSE 1082, 1084, and 1085 standards were beginning development, the first conversation was with respect to scope. In those initial conversations, it was heavily debated as to whether the outcome of the working group would be one standard or three standards. The result is a set of three standards meant to correspond with existing valve standards so that industry can easily understand and accept them into plumbing codes. While some products in the market have capabilities that allow them to be recognized as all three types of water heaters, there is a salient need for products that only correspond with one of those standards for distribution, point-of-use, or emergency fixtures. When choosing a water heater for installation, it is important to consider the intended application and use of the associated standard.

“Instantaneous” meaning having <2 gallons of rated storage volume for consumer electric and gas-fired water heaters per 10 CFR 430.32(d). For commercial gas-fired, this means >200kBTU/hr and ≥4kBTU/hr per gallon of stored water per 10 CFR 431.102.
Final Action Results on the 2018 Proposed Changes to the 2018 Edition of the International Building Code, Group A.
2018 / 2019 ICC Code Development, Group A.