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AGE of WATER HEATERS
APPLIANCE DIAGNOSIS & REPAIR
AQUASTAT CONTROL Functions
BACKFLOW PREVENTER, HEATER WATER FEEDER
DRAIN a WATER HEATER TANK
ELECTRIC WATER HEATERS
FLOODED WATER HEATER REPAIR
GAS FIRED WATER HEATERS
HOT WATER EXPANSION TANKS
HOT WATER SUPPLY
HOT WATER IMPROVEMENTS
HOT WATER DELIVERY SPEED UP
INDIRECT FIRED WATER HEATERS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
NO HEAT - NO HOT WATER: HEATER DIAGNOSIS
NOISE, WATER HEATER
RELIEF VALVE, WATER HEATER
SOLAR HOT WATER HEATERS
TANKLESS WATER HEATERS
THERMOSTATS, WATER HEATER
TIMERS for ELECTRIC WATER HEATERS
WATER HEATER ALTERNATIVES
WATER HEATER ANODES, DIP TUBES
WATER HEATER AIR INLET
WATER HEATER DEBRIS FLUSH
WATER HEATER DRAIN PROCEDURE
WATER HEATER EFFICIENCY
WATER HEATER FLUSH PROCEDURE
WATER HEATER NOISE DIAGNOSIS, CURE
WATER HEATER PROBLEM DIAGNOSIS
WATER HEATER COMPARISONS, PROPERTIES
WATER HEATER SCALE
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER ODORS, CAUSE CURE
WATER PIPES, Clogs Leaks Types
WATER PRESSURE TOO HIGH: DANGERS
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
Safety & functional inspection of anti scald valves & mixing valves.
This article describes key safety inspection points that should be examined when inspecting building hot water supply anti-scald protection and tempering valve or mixing valve or temperature compensating valve installations.
We discuss temperature or scalding safety, valve adjustment, and leak concerns at mixing valves, and we include manufacturer's instructions & warnings about mixing valve installation, safety, and periodic inspection & maintenance.
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Safety First: are there temperature control devices installed on the building hot water supply system? In most jurisdiction scald protection is required for residential properties but it may not be specified by local codes for commercial properties.
When you find the temperature mixing or anti-scald device, check to see if the temperature controls properly set?
Check the temperature control settings on the device and where appropriate, actually measure hot water output temperature at the fixtures closest to hot water supply in order to assure that the mixing valve has been set to protect the building occupants from scalding.
Remember that while these valves may show a target temperature on the valve setting knob, the actual water temperature that comes out of a building faucet or tap will vary and may be hotter or cooler than the actual temperature set.
[Click to enlarge any image]
This is not precise lab-grade equipment capable of controlling water temperature precisely, and more, the length of pipe run between the hot water source and the building faucet or fixture will affect the temperature of water received there. A long run of un-insulated hot water pipe will deliver cooler water than a well-insulated water supply pipe of any length.
Leaks Second: See TANKLESS COIL / HOT WATER COIL LEAKS for a detailed discussion of how to recognize, evaluate, and repair leaks at tankless coils on heating boilers
At above left we illustrate the typical piping arrangement into and out of a tankless coil water heating system. Cold water is piped to an inlet marked "COLD" and building hot water supply piping is connected to the tankless coil outlet marked "HOT".
This tankless coil piping example from Crown Boilers indicates the use of a mixing valve or anti-scald valve right at the heating boiler. The company includes an interesting warning reading as follows [Quoting - Crown BDS Installation Manual]
Typical Hot Water Supply Temperature Control Valve Operating Range & Adjustment Settings
The following table is excerpted from ANTI SCALD VALVES / MIXING VALVES the home page for this topic:
Using the modern Watts Regulator Co. Series LF1170 / LFL1170 Hot Water Temperature Control Valve instructions as an example, these valves control water temperature in the following ranges:
Look for the presence of anti-scald protection at the point of use of hot water in buildings and make the same inspection and tests of temperature we just cited above.
At the plumbing fixture outlet hot water temperature must be at or below the highest temperature allowed by local building codes. These temperature specifications vary by U.S. state and in Canada. Though 120 °F is a common upper temperature limit at the fixture, some states such as California specify a lower number (105 °F) and prison sytsems also have specific requirements.
See TABLE OF SCALDING TEMPERATURES & TIMES - where we explain how long it takes for hot water to cause a burn and where we cite regulations about water temperature control and anti-scalding requirements.
Watch out: it can be confusing listening to plumbers, home inspectors, and building supply sales staff who toss around terms like "mixing valve", "tempering valve", and "pressure-balancing valve" a bit loosely, all referring to ways to avoid scalding burns at plumbing fixtures, but not all working the same way.
There are several approaches to controlling hot water temperature to avoid scalding burns:
The high temperature limit control on the water heating device itself can be set to prevent scalding water from being produced. Below at Table of Scalding Temperatures & Times we include a photo of a typical water heater label warning about scalding temperatures, implying that this option is one to consider.
A point of supply pressure balancing valve or automatic mixing valve (or a manual mixing valve) can be installed at or near the water heater, or at the tankless coil or other hot water source so that scald protection is provided even if the water heater is set to a high temperature. This approach is sometimes used to obtain more total hot water as we discuss at Mix Valve Improves Hot Water Quantity and detail at HOT WATER IMPROVEMENT.
An temperature-sensing thermostatic mixing valve or anti-scald device can be installed at or near the water heating device so that even if the water heater is set to a high temperature (to obtain more total hot water as we discuss at Mix Valve Improves Hot Water Quantity and detail at HOT WATER IMPROVEMENT).
MIX VALVE SCALD PROTECTION, Best Practices, includes excerpts or adaptations from Chapter 6 of Best Practices Guide to Residential Construction, adapted courtesy of Wiley & Sons and written by Steven Bliss.
If cold water is diverted to a flushing toilet or other appliance and the pressure drops, the valve automatically reduces the hot water flow proportionately to maintain the temperature.
If the cold water pressure plummets or stops altogether, the flow is reduced to a trickle.
To guard against someone accidentally turning the shower valve to scalding temperatures, these valves typically use a temperature limit stop that prevents the user from turning the shower control past a set point—typically set at or below 120°F.
A check valve is required on the cold water side to prevent backflow, and a hot-water expansion tank is recommended to prevent excessive pressure on the hot water side.
The unit will compensate for changes in either pressure or temperature to maintain a constant delivery temperature and flow rate.
If the cold water fails or the tempered water is still too hot for any reason, the unit will shut off the flow.
As with the pressure-balancing valve, the installer sets a temperature limit stop to prevent the user from turning the shower control to scalding temperatures.
We illustrate this approach as it is installed in a modern bathroom in Molde, Norway at Built-in Fixture Anti-Scald Valves.
In retrofits, point-of-use devices can be installed by a plumber or homeowner to limit water temperatures to 120°F. These include antiscald showerheads, as well as point-of-use devices that fit into individual plumbing fixtures, such as showerheads and bath and sink faucets.
For example, MemrySafe and ScaldShield (Antiscald Inc.) are inexpensive retrofit devices that reduce the water flow to less than 1/4 gallon per minute when the water temperature at the faucet or showerhead exceeds 120°F. These devices do not regulate temperature or pressure, but do offer protection against serious burns.
Mixing Valve Installation Safety Warnings From the Manufacturers
Watch out: read the installation instructions from the manufacturer of the product you are installing, both to make sure it's installed properly and thus will work as expected, and also so that you understand what to expect by way of hot water temperature control the product handles.
At TANKLESS COIL INSTALLATION PROCEDURE where we recommend the use of mixing valves we quote this warning from the Crown Boiler Company:
Similarly, the Watts Regulator Company's instructions for the installation of the Series LF1170 & LFL 1170 Hot Water Temperature Control Valves includes this warning: [Bold font is our emphasis]
Other Mixing Valve Warnings - using Watts instructions as an example, include :
Anti-Scald & Hot Water Safety Articles
Continue reading at ANTI SCALD VALVE PROTECTION, Best Practices or select a topic from the More Reading links shown below.
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