Anti-Scald protection at the tankless coil hot water system on a boiler:
This article explains how to install or locate the hot water temperature control at a tankless coil hot water system on a heating boiler. We describe what the tankless coil temperature control looks like, how it works, and how to set the output hot water temperature to avoid scalding burns. This article includes the hot water temperatures you can expect when using this type of mixing valve or anti-scald valve at a boiler.
Page top photo: a Watts anti-scald valve installed at the tankless coil on a hydronic heating boiler.
In this article series 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.
We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Guide to Installing & Setting Tankless Coil Hot Water Mixing Valves
Photo: a Sparco Aquamix AM 100C automatic tempering valve or anti-scald valve. At page top, a Watts automatic anti-scald valve installed at a home heating boiler tankless coil used to provide domestic hot water.
[Click to enlarge any image]
Article Contents
- ANTI SCALD VALVE at TANKLESS COIL
- ANTI SCALD VALVE TANKLESS COIL ADJUSTMENT
- ANTI SCALD VALVE OUTPUT TEMPERATURES
Automatic Anti-Scald Tempering or Mixing Valves at a Tankless Coil – Water Pressure Balancing Type
The Watts anti-scald valve shown above or the Sparco anti-scald valve shown earlier (or an equivalent product) is normally installed at a heating boiler tankless coil outlet or at the outlet of a stand-alone water heater.
This mixing or anti-scald valve contains an internal temperature sensor which permits the valve to add cold water to the outgoing hot water in order to limit the temperature of the hot water leaving the valve.
Our photo at left, taken at a heating boiler in Portland ME, shows a popular Watts™ anti-scald valve made by the Watts Regulator Company.
You can see that the black knob permits the user to set the outgoing hot water temperature leaving the valve, and if you look closely you can see the “HOT” and “COLD” and “MIX” indicators on the three ports of the body of the valve.
Turning this Watts Reg. Co. automatic mixing valve clockwise makes the outgoing water temperature cooler. Turning the Watts mixing valve counterclockwise makes the outgoing water temperature hotter.
Hot water enters the valve’s right side, cold water enters the mixing valve’s bottom, and mixed or tempered hot water leaves the valve at its left side.
Which Way do We Turn the Anti-Scald or Automatic Mixing Valve to Make Hot Water Cooler or Hotter?
Question about tankless coil or other hot water mixing valve operation – example using the Sparco Aquamix AM 102C:
I’m not sure which way to turn my hot water mixing valve. When you turn “down” on valve does it send less cold water or more. I believe it’s less. Let me know. – U.S.A.
Answer:
There should be a direction arrow on the anti-scald valve telling you what it is doing and which turn direction will raise or lower the outgoing water temperature.
The Sparco Aquamix AM 102C tempering valve shown (above-left) is marked to explain that if we turn this valve counterclockwise (the direction of the red arrow) the outgoing water temperature will be hotter.
Turn this anti-scald valve (and most model) clockwise (in the direction of the blue arrow) to make the outgoing water temperature cooler.
Our photo of a Sparco™ Aquamix AM102C anti-scald or tempering valve (above-left) as well as our photo of a Watts™ mixing valve shown earlier in this article both show the arrow that we describe and indicates that turning the automatic mixing valve knob clockwise makes the outgoing water cooler, and turning the automatic mixing counterclockwise makes the outgoing water hotter.
We don’t describe the valve direction as “up” or “down” because these valves can be installed in more than one position, making “up” and “down” a bit confusing.
For hotter output water [on the Sparco or Watts Tempering Valve models shown]: Turn the automatic mixing valve knob counter-clockwise (on the Sparco valve above, in the direction of the red arrow) to make the output water from the system hotter.
For cooler output water: Turn the automatic mixing valve clockwise (on the Sparco valve above, in the direction of the blue arrow) to mix in more cold water and thus to make the output water from the system cooler.
Note that because these mixing valves are automatic, that is once they have been set they maintain a specified hot water temperature for water leaving the water heater, you don’t have to make seasonal changes to the valve adjustment.
The automatic mixing valve, tempering valve, or anti-scald valve approach of installing this safety control at or close to the water heater is discussed further at Thermostatic Mixing Valves.
Watch out: Be sure to take a close look at the indicating arrows on your own automatic mixing valve as some tempering valve models may work differently. And for manual hot water mixing valves that we discuss below, the direction to turn the valve may not be marked, but is easy to determine, as we will explain.
Thanks to readers Bruce Jones and Chris Martino and others for pointing out the need for clarity about about which way to turn the hot water mixing valve or tempering valve.
If your automatic tempering or hot water mixing valve has different instructions or operates differently from those discussed here, CONTACT us and send along a photo so that we can add that information here.
- Watts, INSTRUCTIONS SERIES LF1170 AND LFL1170 HOT WATER TEMPERATURE CONTROL VALVES [PDF] (2013) Watts Regulator Co. (2013), USA Tel: (978) 688-1811, Fax: (978) 794-1848, Website: www.watts.com, Canada: Tel: (905) 332-4090, Fax: (905) 332-7068, Website: www.watts.ca Excerpts: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.Watts Anti-Scald Valve Life To prolong the life of the Model LF1170-M2 or LFL1170-M2 valve, it is recommended that it be trapped as shown (Figure1 – shown above- Ed): i.e. the hot water inlet to the LF1170-M2 valve should be 8″ – 12″ (200 – 305mm) below the hot water supply feed.Period Inspection/Maintenance of the Watts Hot Water Temperature Control Valve This valve requires periodic inspection and verification of the outlet temperature by a licensed contractor. Corrosive water conditions, hot inlet water temperature over 200°F (93°C), unauthorized adjustments or repairs could render the valve ineffective for its intended service. Regular cleaning and checking of thermostat assembly helps to maximize valve life and mixing function. Frequency of cleaning depends on local water conditions.
Tankless Coil Hot Water Mixing Valve Output Temperatures
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:
Notes to the table above
These mixing valves require a minimum supply pressure of 30 psi (207 kPa), and function with hot inlet water temperatures ranging from 120 to 200 °F (49-93 °C ), and with cold inlet temperatures from 40-85 °F(4-2 °C ).
Valve outlet temperature accuracy is +/- 3°F (1.7 °C ). There are other restrictions including a requirement that the difference between hot water and cold water pressures at the valve must not vary by more than 25%. The maximum tolerated pressure is 150 psi (10.3 bar). Lower pressure restrictions may apply when using CPVC or PEX piping & end connections.
Code approvals: CSA B125-certified and Listing: ASSE 10167 & IAPMO UPC.
Source: “Instructions Series LF1170 and LFL1170 Hot Water Temperature Control Valves”, Watts Regulator Co. (2013)
Tankless Coil Anti-Scald 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 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)
Reader Comments & Q&A
On 2020-09-19 – by (mod) –
Thanks for asking, Frank, I wondered the same thing. I’m not sure; the repair kit The Watts LF70A-RK repair kit looks just like the kit for the LF70 – perhaps its brass part is a low-lead version. Some but not all of the listings for LF70 repair kits are described by the seller as “Repair Kit for Watts 70A Series Low Temp Tempering Valve, 1/2″ 70A-RK & 3/4″ L70A-RK (Lead Free)” There are subtle differences in some of the parts photos: the number of round threads/rims on the brass plunger but one can’t say for sure if that’s extant or just how the parts were photographed. I’ll show the LF70A and 70A repair kits below.
On 2020-09-19 – by (mod) –
Thanks for asking, Frank, I wondered the same thing. I’m not sure; the repair kit The Watts LF70A-RK repair kit looks just like the kit for the LF70 – perhaps its brass part is a low-lead version. Some but not all of the listings for LF70 repair kits are described by the seller as “Repair Kit for Watts 70A Series Low Temp Tempering Valve, 1/2″ 70A-RK & 3/4″ L70A-RK (Lead Free)”
On 2020-09-19 by Frank
Does the same repair kit fit that Watts 70a and LF70a?
On 2020-09-17 – by (mod) –
Sounds reasonable; my view is few plumbers you might hire would be interested in repairing the valve – it’s too-small a job and includes some risk of being blamed for a later malfunction or even safety issue; instead they’ll argue that the valve should just be replaced. OPINION even though many components are well-engineered and designed to permit repair, typically people take the approach of simple replacement: less thought, less attention.
On 2020-09-17 by Frank
That is what I am thinking. I might just pay someone, I have never sweated pipes.
On 2020-09-16 – by (mod) –
Frank: Sounds as if it’s going to be less costly to simply install a replacement valve.
On 2020-09-16 by Frank
Mine won’t come apart. It seems to be fused together, I tried to turn it with pliers just to see, and they just slipped. I am probably just going to pay someone to fix it.
Thank you so much, that will be very helpful!
On 2020-09-15 – by (mod) –
Frank Please find your question and my detailed, illustrated procedure for installing the Watts 70A repair kit or LF70A repair kit now near the bottom of the article above on this page. Let me know how that works for you and post photos if you can (one per comment) of what you find in disassembling your valve.
On 2020-09-15 by Frank
I have a Watts 70a which needs the repair kit installed. Are there any detailed instructions out ther, perhaps with pictures?
On 2020-09-15 by (mod) – Detailed Installation Instructions for the Watts 70A or Watts LF70A Mixing Valve Repair Kit
Frank,
This parts explosion, from the original installation instructions for the Watts 70A that I provided below, shows how the replacement parts will be assembled under the control handle.
The Watts 70A or LF70A repair kit involves a simple dis-assembly and replacement of three parts in the valve assembly, performed in these steps:
- Let the heater where the mixing valve is installed cool down – turn it off and wait.
- Remove water pressure from the system
- Unscrew the valve top and remove the assembly by turning the brass ribbed knob under the black valve cap
- Unscrew the top screw that secures the black control knob from the valve stem and remove the knob
- Unscrew the brass nut that secures the mixing valve control assembly to the brass ribbed knob we cited at step 3
- Replace the parts in the original assembly with the new parts from the Watts 70A repair kit – the thermostat, spring and O-ring that’s under the brass ribbed knob/cap
- Re-assemble the parts in reverse order of steps 5,4,3 above
- Restore water pressure
- Check for leaks
- Turn the heater back on
- Set the proper anti-scald temp at the Watts 70-A or Watts LF70A
Below you’ll see the current repair kit parts – these are for the LF70A and consist of a spring, an O-ring, and the actual thermostat that responds to temperature.When you remove the valve parts from the top you’ll also need to un-screw the cap to remove and replace these three parts.
To see details of the valve see these
WATTS 70A MIXING VALVE INSTALLATION INSTRUCTIONS [PDF]Watch out: the older Watts 70A mixing valve has been replaced with the Watts LF70A – a lead-free tempering valve that looks otherwise about the same as the original but has an LF molded into the brass body of the valve – shown below are the old and the newer LF Watts mixing valves
…
On 2020-09-15 by Frank
I have a Watts 70a which needs the repair kit installed. Are there any detailed instructions out ther, perhaps with pictures?
On 2019-12-11 by (mod) – which way do I turn the anti-scald valve?
Thanks for asking about adjusting the Anti-Scald valve, Bob.If your Watts anti-scald control valve looks like the one at the top of this page you should NOT need to loosen the nut atop the valve handle before turning it. That nut just holds the knob in place.Watch out: not all anti-scald valves work the same way; the DIRECTION to turn the valve control knob is marked on the top of the knob to show which way to turn it for cooler or hotter water.For the Watts anti-scald shown at the very top of this page the arrows show that for THAT SPECIFIC VALVE you’d turn the black knob clockwise (to the right) to make the water cooler and you’d turn the knob counter-clockwise (to the left) to make the water hotter.The Sparco anti-scald valve shown near the start of this article has similar arrows and markings.
On 2019-12-11 by Bob
Do I turn the Watts anti scald valve counterclock wise using the knob or do I loosen the set nut before turning the knob
On 2018-01-19 by (mod) – How to adjust anti scald device
Tommy, in the article above see ANTI SCALD VALVE TANKLESS COIL ADJUSTMENT
Set your anti-scald valve so that at the hot water outlet faucet that is closest to the boiler (thus the hottest) the water temperature is 120°F or below to avoid scalding.
and let me know if you have further questions
On 2018-01-19 by Tommy
How to adjust anti scald device
…
Continue reading at MANUAL ANTI-SCALD TEMPERING VALVES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see these
Recommended Articles
- ANTI SCALD VALVES / MIXING VALVES – home
- ANTI_SCALD VALVES & HOT WATER QUANTITY
- ANTI-SCALD VALVE INSPECTION
- ANTI SCALD VALVE PROTECTION, Best Practices
- ANTI SCALD VALVE at TANKLESS COIL
- ANTI-SCALD WATER TEMPERATURE CONTROL TYPES
- MANUAL ANTI-SCALD TEMPERING VALVES
- POINT of USE BUILT-IN FIXTURE ANTI-SCALD VALVES
- POINT of USE ANTI-SCALD WATER TEMPERATURE ADJUST Pfister – how to adjust a point of use anti-scald valve
- SAFETY WARNINGS for ANTI-SCALD VALVES
- HOT WATER ANTI-SCALD REGULATIONS
- WATER HEATER TEMPERATURE ADJUSTMENT CONTROLS – home – all types of water heater temperature controls & adjustment devices
- WATER HEATER TEMPERATURE TOO COLD or TOO HOT
Suggested citation for this web page
ANTI SCALD VALVE at TANKLESS COIL 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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