Thermostatic mixing valves

Every year, thousands of people suffer serious Thermal Shock or Scalding injuries in their bathtubs, sinks and showers. Often, injuries in the shower are caused by slips and falls in reaction to a sudden increase or decrease in water temperature. Ideally, if the supply of cold or hot water is lost, the water flow would be shut down immediately. Termination of flow would eliminate the instinctive but dangerous reaction to move quickly away from a too hot or cold water stream.

Water at temperatures above 106 degrees F are painful. At a temperature of 131 degrees F, a child can be scalded in less than 4 seconds.

Many shower and combination mixing valves in today's homes use a pressure balanced design. Unfortunately pressure balanced type valves do not automatically control outlet temperatures, nor do they automatically limit outlet temperatures should the supply temperatures dramatically increase or decrease. Such limitations are potentially dangerous.

Further, to prevent users from adjusting the valve beyond a safe operating temperature, pressure balanced valves require adjustment of the limit stop by the installer. In addition, to accommodate future changes in the hot or cold water temperature, the limit stop would need to be re-set.

Upon use of tempered water, a thermostat in the mixing chamber of the valve senses the outlet temperature. The thermostat automatically positions a shuttle or valve which controls the flow of hot and cold water supplied to the mixing chamber. A mechanical adjustment permits selection of the desired outlet water temperature within range of the valve.

• The water temperature that is discharged directly from a water heater can vary + / - 10 degrees F or more. This can be due to tolerance of control devices, inlet water temperature changes and stacking (higher water temperatures at the top of the water heater). Use of a hot water extender or mixing valve assures constant outlet water temperature even with variations in hot or cold water supply temperature.

• If a water heater is operated at lower temperatures, high flow Demand situations can result in a reduction of hot water supply Temperatures if the recovery time of the water heater is not sufficient for the flow demand. Using a hot water extender or mixing valve allows the water heater to be operated at higher temperatures, extending the effective system flow rate.

• To be able to supply peak demands for domestic hot water it is often necessary to provide high capacity water heaters with high recovery rates. Use of a hot water extender can reduce the size or BTU requirements needed to provide capacity for peak system demands.

Heat loss in the system piping can result in varying temperatures of the hot and cold water supplied to fixtures. The use of thermostatic mixing valves assures constant safe hot water temperature at the point of delivery to the fixture.