For this edition of Working Pressure magazine, I would like to discuss three standards that are not familiar to many people and whose applications are often misunderstood.
I will begin by discussing ASSE 1069, Performance Requirements for Automatic Temperature Control Mixing Valves, and ASSE 1070, Performance Requirements for Water Temperature Limiting Devices. Then I will discuss ASSE 1071, Performance Requirements for Temperature Actuated Mixing Valves for Plumbed Emergency Equipment, and how it relates to the other two standards.
Before we get into the details of these standards, we need to discuss terminology. The terms in question are temperature limiting, temperature control and thermal shock.
Temperature limiting is a means of protecting the end user from extreme temperatures. Devices using this principle are designed with an upper temperature limit that the outlet temperature cannot exceed. These devices are generally set to a specific temperature limit of 120 degrees Fahrenheit or below. This provides anti-scald protection.
Temperature control devices are another means of anti-scald protection by which the temperature is controlled by automatically compensating for pressure and/or temperature variations in water distribution systems. When there are changes in the supply pressure of either the hot or cold side, the devices will adjust the mix of the water to produce the same outlet temperature (setpoint).
Thermal shock is a phenomenon where the user/bather experiences a sudden change in temperature. (Note: Humans can sense a temperature differential of about 3 degrees.) As the user reacts to this sudden change in temperature, there can be a risk of slips or falls. Protection against thermal shock is a safety feature sometimes incorporated into plumbing devices.
Both ASSE 1069 and 1070 devices are used to supply tempered water to the fittings of multiple devices, such as lavatories, showers and bidets. A common use is in public spaces where there is a duplication of fixtures (e.g., a series of lavatory sinks). In this setup, a single ASSE 1069 or 1070 device is used to supply water at a setpoint temperature to all fittings. Each device protects against anti-scald but uses different means to achieve this. ASSE 1069 devices use automatic compensation, while ASSE 1070 devices use temperature limiting.
A major difference between the two types of devices is that the ASSE 1069 device also protects against thermal shock. The ASSE 1070 does not. ASSE 1069 protects against thermal shock by controlling the outlet temperature to within ± 3 degrees Fahrenheit. All automatic compensating devices — including ASSE 1069 devices — also protect against an extreme condition of thermal shock caused by a loss of supply pressure in either the hot or cold water line. An example would be a situation in which the cold water supply pressure suddenly drops to 0 psi. Without automatic compensation, the outlet temperature would go suddenly to full hot. As you can see, protection against water supply failure is a very important aspect of the ASSE 1069 device. When a water supply failure occurs, the device slows the flow of water to a trickle.
So, what are the applications for each type of device? ASSE 1069 devices are intended to be installed where the bather has no access to the temperature adjustment means, and where no further mixing occurs downstream of the device. Typically, these are used in gang shower applications, but their use is not limited to this. ASSE 1070 devices are intended to be used where there is a need to limit the tempered water supplied to a fitting. These are often found to be used in conjunction with sink and bathtub faucets.
As I mentioned, I was going to discuss how an ASSE 1071 device relates to these products. Specifically, I will discuss the means of controlling temperature. ASSE 1071 devices are used with plumbed-in emergency equipment such as eye wash stations and showers. For this application, it is imperative that there is a flow of water. These devices shall be capable of supplying water with an adjustable range which falls within 65 to 95 degrees Fahrenheit and the outlet temperature shall not exceed 100 degrees Fahrenheit under normal operating conditions. So, you can see that these devices limit the outlet temperature under normal conditions.
While ASSE 1071 devices are not automatic compensating devices, they do protect against water supply failure. What is unique — due to the emergency aspect — is that during a water supply failure, the flow of water is not shut off.
In the event of a hot water failure, the device reduces the flow rate but continues to supply cold water. Depending on the initial flow rate, the flow rate is reduced to 1.5 gpm with a 30 psi differential for devices initially flowing under 20 gpm; for devices flowing greater than 20 gpm the reduction is to 15 gpm with a 30 psi differential.
When a cold water failure occurs, the outlet temperature cannot exceed 100 degrees Fahrenheit before the flow is significantly reduced. Again, the reduced flow rate is determined by the initial flow rate, typically decreasing to a range of 0.5 gpm to 1.0 gpm. This reduction helps protect the user from potential scalding.
In conclusion, the three standards discussed provide minimum performance requirements for the devices they cover. These standards include important safety requirements, as extreme temperatures or drastic changes in temperature are real hazards associated with plumbing systems. These standards ensure that code required products are available to protect the public from these hazards.
