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Honeywell 6006 guide Mixing Valves & Anti Scald Valves
Temperature Limiting Valves & Controls on Hot Water Supply or Radiant Heating Systems

Anti-Scald protection for water heaters:

In these hot water temperature control articles, we explain how to buy, install, adjust and inspect anti-scald equipment to prevent hot water burns. We explain what a mixing valve, tempering valve, or anti-scald valve is, where and why these valves are installed on hot water systems, and how they work.

This article series answers most questions about Heating System Boiler Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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Guide to Mixing Valves and Anti Scald Valves on Heating Equipment & Plumbing Fixtures

Sparco tempering valve (C) Daniel Friedman

Here we will describe and illustrate various types of automatic and manual mixing valves, anti-scald valves, or compensating valves.

Photo: a Sparco anti-scald valve or tempering valve installed at a hydronic heating boiler. Other texts refer to these safety controls as mixing valves or compensating valves or temperature compensating valves.

[Click to enlarge any image]

Article Contents

Anti-scald valves used with water heaters are also called tempering valves or mixing valves. An anti-scald valve mixes cold water in with the outgoing hot water (or regulates pressure, or uses another approach) to assure that hot water exiting a building fixture is at a temperature low enough to be safe.

In the sketch shown below, courtesy of Carson Dunlop Associates, an anti-scald valve (also referred to as a tempering valve , a compensating valve or an automatic mixing valve) is shown installed at the hot water piping and tankless coil on a heating boiler.

The drawing illustrates that hot water leaving the tankless coil has been heated to 180 °F. by the coil which is itself immersed in hot boiler water. The 180 degree F. water leaving the tankless coil is mixed with 55 °F. water inside the tempering valve. This produces outgoing hot water from the valve cooled down to 140 deg F.

Sketch of a tankless coil tempering valve or anti scald valve

In the U.S., most authorities consider hot water at or below 120 deg F to be safe from scalding. Some facilities limit water temperatures to 100 deg. F.

How Long Will an Anti-Scald Valve Last?

Anti-scald valves typically are warranted for just 12 months from the date of installation. Plumbers report a typical tempering valve life of five years. (Moley 2022)

Kitchen and bath faucets themselves have a typical life expectancy of 15-20 years.

Really? We're uncertain about how various plumbers or others have defined the service life of these plumbing components. For example, a bathtub faucet may begin to drip after 2-8 years but may need nothing more than replacement of a faucet washer: a part costing less than $1.00 U.S. and a job within the capacity of many homeowners and most handymen.

Some plumbing faucets and valves, such as models using a ceramic cartridge, may last the lifetime of the building even if the faucet's finish and trim do not last that long.

Moen 1200 faucet cartridge replacement at InspectApedia.com

Watch out: ease of replacement of faucet parts and even the cost of replacement faucet cartridges varies enormously. A typical brass Moen 1200 one-handle kitchen or bathroom faucet cartridge like the one shown above costs about $30. U.S. but we were quoted over $100. when trying to buy a ceramic faucet cartridge for a Kohler-brand bath sink faucet.

Other Kohler faucet cartridges currently sell for around $18.

Definition of an anti scald valve or compensating valve - to avoid hot water burns

Anti-scald valves are used on heating and plumbing systems to avoid hot water burns at plumbing fixtures such as sinks, showers, and tubs.

An anti-scald or mixing valve mixes cold water with the outgoing hot water either automatically or manually to make sure that a person using the plumbing fixture won't be scalded.

Definition of anti-scald valve vs. mixing or tempering valve: manufacturers recommend point-of-use anti-scald protection

Limit switch on a steam boiler tankless coilWatch out: different definitions of mixing valve, tempering valve, anti-scald valve: most likely because of a combination of product liability concerns and because the manufacturer of a mixing valve cannot control what other plumbing installation or operating details are followed at individual buildings, heating boiler manufacturers recommend point-of-use anti-scald protection.

For example, Crown Boiler Co. discussed

at TANKLESS COIL INSTALLATION PROCEDURE

and mixing valve manufacturers described here, all take care to refer to products like the Sparco control shown above and the Watts mixing valve shown on this page as a mixing valve or tempering valve. They are not promising that the device will prevent burns from scalding hot water.

In fact, manufacturers (Watts for example) typically add that point of use scald protection should be installed:

ASSE standard 1016, 1069 or 1070 listed devices should be used at fixtures to prevent possible injury.

That advice means that besides mixing valves or tempering valves that are typically installed at the water heater or tankless coil, separate anti-scald protection devices are available for and should be installed at the point of use: sink, shower, or tub etc. Those sorts of anti-scald devices are also discussed in this article.

Above, in our photograph of a more traditional single-function heating boiler limit control, the limit switch is being used on a tankless coil, serving as an upper limit on the temperature to which the boiler is to heat its water. This temperature may and usually is well above 120°F and so is a scalding burn hazard.

Confusion About Names, Types & Features of Scald Protection Devices

Really? In my experience with plumbing and heating installers, home inspectors, and consumers, these terms: automatic compensation valve, mixing valve, tempering valve, anti-scald device, automatic pressure regulating valve, pressure balancing valve, pressure compensating valve are thrown about in a blizzard of usages that treat the words as synonyms.

In the course of inspecting several thousand buildings between 1976 and 2014, I have almost never found anti-scald devices at individual plumbing fixtures in private homes. The only water temperature control we typically find are mixing valves at the hot water source. Worse, sometimes there is no hot water scald protection at all.

When a heating boiler uses a tankless coil to produce domestic hot water, a third single-function control may be installed for that purpose. In our photo, a Honeywell limit control switch is being used to monitor hot water temperature at the tankless coil which is in turn mounted on a steam boiler of an older home in Portland, Maine.

You can see the black-handled mixing valve in the lower right of the photo above.

Cold water from the building is entering the tankless coil via the bottom pipe (green corrosion) and hot water, heated by the coil is leaving at the upper part of the tankless coil, where it turns downwards to enter the left side of the mixing valve.

Additional cold water is permitted to enter the bottom of the mixing valve, and tempered (non-scalding) hot water then leaves at the right side of the mixing valve in that photo,

Photo of an anti-scald tempering valve

and in the enlarged version of the same installation and given just above, you'll see that the temperature limit on the control is set to about 140 °F. Scalding!

Types of Anti-Scald Controls

Temperature control purposes

  1. Avoid scalding burns

    on someone using the plumbing appliance - generally by trying to prevent water temperature at the device from exceeding a safe limit either set by the manufacturer or adjusted by the installer or user.

    Note that once a temperature limit or stop has been set, water temperature might still vary both above or below that setting, depending on the type of limiting device and on the causes of variation of water temperature entering the building or of hot water produced by and exiting the water heater itself.
  2. Avoid or minimize variations in water temperature -

    generally by monitoring water pressure, flow-rate, or temperature to avoid surges of hot or cold water.
  3. Sanitation:

    commercial applications such as a restaurant kitchen dishwasher must maintain an adequately high temperature to meet sanitation requirements.
  4. Economy:

    in some applications, avoiding unnecessarily high water temperatures is desirable or necessary for energy conservation and economic reasons.

Locations of Anti Scald or Temperature Control Valves: Define POS & POU

Separately and in more-detail at TYPES of ANTI-SCALD WATER TEMPERATURE CONTROLS

we describe six different approaches to controlling water temperatures in a building:

  1. TEMPERATURE CONTROL ON the WATER HEATER - POS or point-of-source control
  2. THERMOSTATICALLY CONTROLLED MIXING VALVE AT the WATER HEATER - POS or point-of-source control
  3. MANUAL MIXING or TEMPERING VALVE AT the WATER HEATER - POS or point-of-source control (or possibly elsewhere)
  4. MECHANICAL STOP TEMPERATURE LIMIT at FIXTURE - POU or point-of-use control
  5. PRESSURE COMPENSATING CONTROL at FIXTURE - POU or point-of-use control
  6. THERMOSTATIC HOT WATER TEMPERATURE CONTROL at POINT OF USE - or POS - point of source for some devices including TAFR - Temperature Actuated Flow Reduction devices as well as others.

For a complete inventory of all of the methods used to control water temperature in buildings, please

see WATER HEATER TEMPERATURE ADJUSTMENT CONTROLS - home

Watch out: as you'll read here and in the article topics we have listed, various water temperature control devices have different purposes, and not all of them are designed to prevent scalding burns.

So it is important that you select the proper temperature control device and that it is installed where its manufacturer intends, and that it is adusted as required.

Sources of hot water scald burn risk at buildings without adequate anti-scald device protection

Watch out: Where no anti-scald valve is installed, the risk of a person being badly burned by hot water can be significant in buildings for a variety of reasons that we will explain here, including:

Automatic compensation valves in new homes protect against severe changes in water temperature when the pressure drops; but these systems are only required to be tested at a flow rate of 2.5 gpm.

It follows that when the new 1.75 gpm showerheads have no matching automatic compensation valve, anyone in the shower runs the risk of being scalded when the pressure abruptly changes. -Koeller [6]

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.

Watch out: every anti-scald device, mixing valve, temperature control device whose instructions we reviewed includes a collection of safety warnings that explain the limitations of the device and its vulnerability to improper installation, improper adjustment, or to external causes of water temperature variation that are outside the scope of the control.

The installation instructions for these devices are very specific about the temperature settings, periodic maintenance, and other adjustments that are required for safe, reliable use. Be sure you read and follow the instructions for the specific brand and model anti-scald or temperature control device you are installing.

Mixing Valve Safety Warnings

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 that 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:

WARNING: Thermostatic mixing valves are intended to increase the supply of hot water available from the coil. They are not intended to prevent a scald hazard.

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]

WARNING: FAILURE TO COMPLY WITH PROPER INSTALLATION AND MAINTENANCE INSTRUCTIONS COULD CONTRIBUTE TO THE VALVE FAILURE.

This Hot Water Master Tempering Valves cannot be used for tempering water temperature at fixtures. Severe bodily injury (i.e., scalding or chilling) and/or death may result depending upon system water pressure changes and/or supply water temperature changes.

ASSE standard 1016, 1069 or 1070 listed devices should be used at fixtures to prevent possible injury.

These Hot Water Tempering Valves are designed to be installed at or near the boiler or water heater. They are not designed to compensate for system pressure fluctuations and should not be used where ASSE standard 1016, 1069 or 1070 devices are required. These valves should never be used to provide “anti-scald” or “anti-chill” service.

The components of the system must be of materials with a construction capable of withstanding the high limit output temperatures of the water heating source. - Watts (2013)

Question: repair parts for Danfoss Mixing Valve

Danfoss anti-scald TMV mixing valve repair (C) InspectApedia.com GS

I am looking for repair kit for this Danfoss TMV mixing value or O-rings for use in my building in Nova Scotia, Canada - Anonymous by private email, 2017/04/03

Danfoss anti-scald TMV mixing valve repair (C) InspectApedia.com GS

Reply:

I can see why you asked, Anon, as it's difficult to find repair parts for Danfoss TMVs in Nova Scotia.

The first document below lists the components and parts of the mixing valve you describe - or a model close to it. The second provides instructions for a newer Thermostatic Mixing Valve or TMV from Danfoss, the Series 30 HR/HV.

Danfoss does not sell directly to the public. To buy Danfoss equipment or repair parts, check with your local plumbing and heating supplier or with one of the online Danfoss TMV repair part kit suppliers we'll list below.

Links to Danfoss mixing valve installation guides are given below.

Anti-Scald Valve Installation Manuals

Products listed here include thermostatic mixing valves of several types including valves that are installed at the fixture or point of use (POU thermostatic mixing valves), valves that are installed at the water heating source, and other products.

Watch out: as you will read in the individual product specifications, some thermostatic mixing valve instructions take care to mention that the valve does NOT provide scald protection and should not be used where ASSE 1070 devices are required.

Caleffi 5231 Thermostatic Mixing Valve internal operation cited & discussed at InspectApedia.com

Cash Acme Heatguard 110 temperature-activated mixing valve at InspectApedia.com

Delta scald guard cartridge for a shower faucet control illustrates anti-scald device cited & discusse at InspectApedia.com

Photo: a replacement Delta Scald Guard cartridge. This is a rotational stop device. Detailed instructions on how to adjust this Delta scald guard device are given just below as a PDF download from the company.

Honeywell AMX300 DirectConnect mixing valve hot water temperature control cited & discussed at InspectApedia.com

Tempera pressure compensating valve or shower/bath water temperature control cited & discussed at Inspectapedia.com

Precision Plumbingt Products Tempera-Therm Thermostatic / Pressure Balance Control Kit meeting ASSE 1066 temperture control / anti-scald standard, illustration adapted, colored, by InspectApedia.com

Symmons TempControl 7-series Hot Water Temperature Controller - Mixing Valve cited & discussed at Inspectapedia.com

Symmons MaxLine water temperature limiting valve cited & discussed at Inspectapedia.com ... Symmons water temperature limiting valve cartridge replacement instructions cited & discussed at InspectApedia.com

Watts POU Point of Use Thermostatic Mixing valve, Minimixing cited & discussed at InspectApedia.com

Photo of an anti-scald tempering valve

Photo of an anti-scald tempering valve

Above: The Watts LF1170-M2 hot water mixing valve used for either domestic hot water temperature control or in radiant heating system temperature control systems.

How the Watts LF1170 or LFL1170 is plumbed and trapped when used to control the temperature of domestic hot water supply - cited & discussed at InspectApedia.com

Above: Watts illustration (edited by IAP) showing how the LF1170 or LFL1170 mixing valve is "trapped" 8 to 12 inches below the hot water outlet from the water heaterr when used to provide tempered domestic hot water (washing & bathing).

Below: Watts illustration (edited by IAP) showing how the LF1170 or LFL1170 is plumbed when used to control temperatures in a radiant heat system.

How the Watts LF1170 or LFL1170 is plumbed when used to control temperatures in a radiant heat system. - Cited & discussed at InspectApedia.com

 

Inspection of Mixing Valves or Anti-Scald or Tempering Valves

This discussion has been moved to a separate article now found

at ANTI-SCALD VALVE INSPECTION

Can an Anti-Scald Valve Improve the Hot Water Volume & Quantity?

Moved to HOT WATER QUANTITY IMPROVEMENT via ANTI-SCALD VALVE at the water heater

Tables of Scalding Temperatures & Exposure Times that Cause Hot Water Burns, Laws, Regulations

We have moved this scalding temperature table.

See TABLE OF SCALDING TEMPERATURES & TIMES for a table of safe temperatures for residential hot water

See HOT WATER ANTI-SCALD REGULATIONS for a table of Hot Water Anti-Scald Limits, Hot Water Anti-Scald Laws & Hot Water Regulations

Guide to Installing & Setting Tankless Coil Hot Water Mixing Valves

This discussion has moved to ANTI SCALD VALVE at TANKLESS COIL

Which Way do We Turn the Anti-Scald or Automatic Mixing Valve to Make Hot Water Cooler or Hotter?

See ANTI SCALD VALVE TANKLESS COIL ADJUSTMENT

Tankless Coil Hot Water Mixing Valve Output Temperatures

See ANTI SCALD VALVE OUTPUT TEMPERATURES

Guide to Using a Manual Hot Water Tempering Valve on the Domestic Hot Water Supply

This discussion has moved to MANUAL ANTI-SCALD TEMPERING VALVES

Point of Use Anti-Scald Valves, Guide to Bath Fixture Anti-Scald Valves, Automatic, Thermostatic Mixing Valves, or Tempering Valves to Avoid Hot Water Burns

This topic has moved to POINT of USE BUILT-IN FIXTURE ANTI-SCALD VALVES

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-11-21 (mod) - water not hot enough after installing a mixing valve

Jac

I can but guess because there is other information about your plumbing system that I don't know, but it's possible that you are anti scald device is installed at the water heater and that there is too much distance between that point and the nearest hot water Plumbing fixture.

In that case you're regulating the water temperature at the source but the water continues to cool off on the way to your tab.

A solution would be to install the anti scald device right at your plumbing fixtures. It's more expensive in the landlord may not want to do that. OR the mixing valve output temperature is simply set lower than necessary. Temperature can be set as high as 120F. but no higher at the fixture or there'd be a scalding burn hazard.

On 2019-11-21 by Jacquie

A mixing or equalizer valve was just installed on my hit water tank by the landlord. I am finding that the water isn't hot enough for us. We were told the temperature would be set for 110°F and would not be allowed to be higher.

We also pay for our own hot water usage through the gas company and it isn't being paid for by the landlord. We are not using any cold water for showers or for anything other than drinking at this point. I would like to know if there is a way to increase the amount of hot water.

There is no risk of scalding in this house as we are adults who know how to live responsibly while using the water without harm to ourselves and others within the home.

On 2019-11-17 - by (mod) -

How do I adjust my GE boiler water temperature

Moh

If we are talking about a domestic water heater that produces hot water for washing and bathing, there will be a thermostat (or two of them) on the water heater; the thermostat controls vary depending on whether the heater is fueled by oil or gas or electricity.

See ELECTRIC WATER HEATER THERMOSTATS if your water heater is electric

See THERMOSTATS, WATER HEATER if you're talking about a home heating boiler or a gas or oil fired boiler that uses a tankless coil for hot water

A photo guide to types of oil or gas fired water heater and heating boiler aquastats is

at AQUASTAT SELECTION GUIDE

See also TEMPERATURE of HOT WATER is TOO LOW

On 2019-11-17 by Moh

How do I adjust my GE boiler water temperature


...

Continue reading  at ANTI-SCALD WATER TEMPERATURE CONTROL TYPES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see ANTI SCALD VALVES / MIXING VALVE FAQs - questions & answers posted originally on this page

Or see these

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Suggested citation for this web page

ANTI SCALD VALVES & TEMPERATURE CONTROL / MIXING VALVES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER HEATERS

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