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Acorn Controls® FAQs

Questions Relating To All Products:

Why is my control accuracy not what I expect or what the ASSE standard indicates it should be?

Answer: Product performance depends on many factors beyond Acorn’s® control.  So, in order to confirm that a valve is, or isn’t, operating to Acorn’s specifications and likely to produce ASSE certified results or better, we need to know these site conditions:

  • Inlet temperatures and potential variations
  • Inlet pressures and potential variations
  • Set point
  • Range of GPM draw through the valve, especially the minimum
  • Flow rate of recirculation pump (when applicable)
  • Pump operation (when applicable)
  • Piping diagram (when applicable)

Site conditions are sometimes extreme and outside the range allowed by Acorn’s operating parameters.  Examples of site conditions that can affect a valve’s performance over the long and short term are:

  • Hard Water
  • Stray Voltage
  • Unstable HW temperature
  • Extreme or very rapid changes in inlet pressure
  • Rapid and extreme changes in flow
  • Debris that could restrict the availability of hot and/or cold water by clogging the inlet screens
  • Debris that has made it past the screens or were introduced into the valve during service.  This type of debris could be barely noticeable but could still have a big impact on performance.
  • Improper system piping – some examples: a CW supply that temporarily becomes “hot” or a recirculation pump that isn’t able to function properly due to a missing return connection.
  • Improper maintenance.
  • Lack of, or an improperly set, balancing valve.
  • And more…

Please refer to our installation instructions and elsewhere in this document for a more specific list of issues that affect performance that are beyond the valve’s control.


Is the Acorn Controls Line in ATS?

Answer: The design engineer will have access to Acorn Controls using ATS if he signs up for ATS through the Acorn web site.  Otherwise, Powers is the official tempering valve sponsor and engineers signing up through other methods will only have access to Powers.


Are all Acorn Controls valves supplied with factory pre-adjusted and locked set points and what determined these temperatures?

Answer: YES, except for the SV16

The ST70 valve is set and locked at 105° F, a desirable temperature for hand washing.

The ST7069 valve is set and locked at 105° F, a desirable temperature for hand washing and group showering.

The MV17 valve is set and locked at 120° F, a common recirculation temperature, albeit below our recommendation for Legionella prevention – see MV17 section.

The ET valve is set and locked at 85° F, a very comfortable temperature for safety eye washing.

The SV16 is factory set at a setpoint LIMIT of 110° F by setting the handle rotation stop at that temperature.  The actual user setpoint (bath temperature) can be anywhere from full cold to the 110° F limit.  The SV16 limit stop can be field adjusted to a lower maximum temperature and no less than 105° F would be advisable.  Or, the upper temperature limit can be set higher, but certainly no higher than 115° F.  It is unlikely anyone would be able to shower near that temperature and its still low enough to minimize bather risk.


Are the strainers accessible for all Acorn Controls valves?

Answer: Yes and to our knowledge, this is true of no other shower and tempering valve manufacturer.  Strainers, also referred to as screens, are omitted in some products and some strainers aren’t accessible.  Start up debris is one of the most common problems affecting tempering and shower valve performance, making strainers very important.


What is “pressure drop” and why is it important to selecting the proper mixing valve for the application?

Answer: “Pressure drop” is the inlet pressure minus the outlet pressure and is often stated as psid (pounds per square inch differential) on valve capacity charts.  The highest potentially available pressure drop, which occurs at maximum anticipated user demand, is based on two key jobsite conditions:

  1. Inlet pressure to the valve.
  2. The lowest possible level of backpressure on the outlet, which is determined by water column gravity and resistance to the flow of water through pipe until it reaches the farthest fixture.

For example, assume the CW and HW pressure is 60 psi into the valve and the farthest fixture being supplied is horizontally located and within a very short distance from the valve.  The largest available pressure drop, or psid, would be relatively high since neither gravity nor pipe resistance is having much of an effect on the potential flow of water through the valve to the farthest fixture.  If peak demand is determined to be 25 GPM and the design engineer wants to ensure 10 psi at the farthest fixture, he should look for a mixing valve using these approximate numbers:

60 psi available
Less 10 psi reserved for the final fixture
Less Negligible pipe loss.
Result: 50 psid available for peak demand of 25 GPM

Let’s change our example by putting 3 floors between the valve and the farthest fixture.  With this change the available potential pressure drop is reduced by 3 floors of vertical rise and the effect of gravity on that water.  This added resistance must be overcome before reaching the fixtures.  Now the design engineer should look at valve selection using these numbers:

60 psi available
Less 10 psi reserve for the final fixture
Less 35 psi elevation loss, incl. negligible pipe friction.
Result: 15 psid available for peak demand of 25 GPM

The second example would require a larger valve than the first example, even though the number of fixtures and maximum user demand is exactly the same.

So, selecting the correct valve for the application requires that we know the highest available pressure drop at the maximum potential user demand.  Anytime demand is below the maximum potentially required, it will be met at a lower pressure drop with higher pressure available to the fixtures.  But once you’ve selected the valve based on the toughest challenge it faces, i.e. the farthest and/or highest fixture, the other demands will be met with more than ample pressure available to all fixtures.


Why does Acorn® state the capacity of our tempering and showering valves at 45 psid?

Answer: It has been traditional to do so for many years for these applications, based on a normal street pressure of 60 psi.  Our valves will work properly at almost any pressure differential, but lower available differentials mean lower potential flow through the valve.

Design engineers often select their tempering valves based upon a differential much less than available at the job site.  One reason might be a concern that the street pressure could decline over time and result in lower flow at the fixtures during peak demand.  Whatever the reason, by specifying a valve that’s much larger than needed, they are also sacrificing low flow performance in the process.


I noticed the temperature range on some valves stop at 115° F, yet I was able to get a higher outlet temperature from my valve.  Does that mean it’s not working?

NOTE: This answer doesn’t apply to the ET valve – see that section for the proper answer.

Answer: Not necessarily, the range stated is the functionally accurate range and is intended to limit the use of the product to a range that is both safe and appropriate for the application.  The valve will achieve safe results with typical inlet parameters and a properly set limit stop or set point locknut.  There’s no physical limit that prevents the valve from producing near hot water temperature.  That’s why setting the limit stop (SV16) or setpoint lock (all others) is critical.  All Acorn valves are factory set at safe temperatures for their application. See the next question for another issue related to the highest possible output a valve is capable of producing.

What is “approach temperature” and why is it important?

Answer: Thermostatic valves can’t routinely be expected to produce a setpoint equal to the HW supply temperature.  For example, the SV16 has a 10° F approach temperature, which requires the HW supply to be no lower than 115° F for a 105° F degree shower, under typical site conditions.

We know that HW supply temperatures vary due to many factors, as discussed elsewhere in this document, and it could result in HW that drifts too low to allow the valve to achieve its setpoint, i.e. the difference between the HW temperature and set point is less than the approach temperature.  Also, local codes may restrict a HW supply to no more than 110° F due to the risk of scalding associated with Pressure Balance (PB) shower valves.  This would present a problem if an SV16 was bought to replace a PB valve and the HW supply remained at 110° F.

When a bather is unable to get a hot shower, the SV16 is assumed to be the problem.  In most cases it’s a HW supply temperature that’s too low to cover the approach temperature or inconsistent.  The latter usually means the SV16 can provide a nice hot shower some of the time, but not at the times the HW supply drifts below the approach temperature.

The MV17 and the ST70 have an approach temperature of 5° F, which means that the user needs to ensure that the HW is always at least 5° F above the desired set point.

The ET71 and ST7069 have the same 10° F approach temperature as the SV16.


I closed the CW to my Acorn Valve and saw what I feel is excessive HW still passing through the valve.  Is it defective?

Answer: Probably not.  First, HW leakage under CW failure is allowed under all ASSE standards, but it’s limited to a rate that’s considered safe for the bather.  If the rate exceeds that allowed by the standard, let’s look at the valve setpoint and the HW supply temperature, before assuming the valve is defective.

If the setpoint is within a few degrees of the HW temperature, it’s possible that the valve is allowing a rate of HW it needs to maintain the setpoint or get as close as it can to achieving it.  Reduce the setpoint and if the HW flow also reduces, this is probably the issue.  When CW failure occurs, note both the HW leak rate and the temperature of the leakage before determining if an unsafe condition exists and/or the valve is defective.


Why does Acorn offer Chrome finish on some products and not on others?

Answer: Some applications require a high level of cleanliness.  The normal aging of brass and the surface bacteria it promotes could be difficult to remove and therefore unacceptable.

Under counter exposed lavatory valves, like the ST70, are often paired with chromed or stainless supplies and piping.

The MV17 master mixer might be exposed in areas of a healthcare facility where the design engineer wants the benefits of chrome consistent with his overall need for cleanliness.  In a cabinet, the need for chrome finish is typically not required.

Exposed shower valves (not in the current Controls offering) are almost exclusively chrome for the reason already given as well as general appearance.

Should we find enough demand for the ST7069 and ET71 emergency valves in chrome, we will add it to our standard offering.

Be aware that polished chrome was once the standard chrome finish, but due to cost and quality issues, there are few, if any, directly competing products offered in polished chrome.


How do Acorn cartridge-style checks differ from competing valves?

Answer: Acorn offers unique cartridge style checks (in all products except the SV16) while other manufacturers offer complex multi-function check stops consisting of individual O-rings, stems, springs, poppets and shut-off disks.  Because Acorn checks are a single piece cartridge, they’re quicker and easier to replace.  They are more reliable because the seat is part of the check assembly, not a part of the casting.  Reliable checks are critical to the long-term performance of any mixing valve.


SV16 - Showering:

I’d like to convert my Powers valve to get the benefits of the SV16.  What does this involve and will Acorn warranty the converted product?

Answer: All Powers components and trim, except for the casting, must be removed and replaced with Acorn parts and trim.  Yes, the check stops are included.  The casting should be inspected for defects or damage.  If the casting is clean and sound, install all parts per our instructions shown in document RSV16.  Acorn warranties the converted valve for one year.


Are there issues with sweating the SV16 without removing the check stop components, especially given this product is “lead free”?

Answer: Not if the proper amount of heat is applied.  It’s important that the user apply enough heat for the solder to flow and not much more.  Any shower valve could have check stop failure when excessive heat is applied.  Installation instructions are clear on this issue.


Why can’t I get a hot shower with my SV16?

Please see a related question under the “all products” section.

Answer: The most likely reason is inadequate, or inconsistent HW supply.  This might be caused by debris blocking the HW screen or a HW temperature too low to achieve the setpoint.  Even if the user believes his HW is 10 degrees above the setpoint (which is the minimum recommended on our SV16) all the time, it will vary and at times be too low for his desired shower temperature.  The problem could also be that the handle rotation limit stop is set too low.  In that case, it should be reset a safe upper limit.  Acorn recommends 110° F.


If the installer pipes the SV16 too deep, how does he correct this problem?

Answer: Acorn offers a stem extension just for this purpose.  But be aware that our standard ligature resistant trim is more sensitive to being set to the proper wall depth, which ensures the ligature resistant benefits of the trim.  Installation instructions and the rough-in guide we provide with each valve should ensure that valves are set to the proper depth for the shower enclosure or before the wall and wall finish (typically tile) is applied.


How can your standard Ligature Resistant Trim meet ADA?

Answer: For ADA compliance, it must take less than 5 pounds of force to adjust the temperature of a shower valve without grasping the handle.  ADA does not define the means by which you make this possible.  Since lever handles were always the most advantageous method to achieve ADA requirements, it became common to assume a lever was necessary.  Both Acorn SV16 trim packages, lever or tri-handle ligature resistant, require less than 5 pounds of torque to turn, without grasping, and therefore meets ADA.


What does full range ADA really mean?

Answer: Our SV16’s patented trim and (uniquely designed) ceramic flow control components enable the user to make handle adjustments from OFF to ON and back to FULL OFF, with under 5 pounds of force.  This will remain true whether the SV16 is new or in service for many years.  The SV16‘s design ensures its ADA-compliant closing and opening force will not change over time, even if bathers routinely apply a greater-than-necessary force to close it.

Competing valves rely on user force to compress an o-ring or washer to stop flow through the valve.  As a result, the user may apply, or feels he needs to apply, a high level of force to close the valve drip-tight.  The next user must overcome this higher force to open the valve.  This could and will occur even when the valve is new.  After years of service, higher force may actually be required to close the compression-type valve and, as a result, even higher force is required to open it.

The SV16’s ceramic shut-off components and a non-rising, non-wedging design provides full range ADA compliant operation over many years of service, plus superior reliability.


RSV16 – Showering - Retrofit:

What's involved in installing the RSV16 Retrofit?

Answer: See the video here
Video - Installing RSV16 Retrofit


ST70 – Lavatory Tempering:

Why am I having a problem getting HW at my faucet when I use the ST70?

See related questions under “All Products”
Answer: Dead legs (water that doesn’t move unless there’s actual user demand) are usually the issue in lavatory tempering.  They could be too long for the desired HW temperature doesn’t reach the ST70 and the ST70’s outlet water doesn’t reach the user before the user is finished washing.  This problem can only be addressed in the piping design.  The setpoint could also be set too low.


Can I use the ST70 for both dual temperature and hands-free faucets?

Answer: Yes and you should for all public faucets because it’s not only safe, it’s code.  With dual temperature (single or dual handle, or dual button metering) faucets, the ST70 is feeding the HW side of the faucet only.


Is the ST70 repairable?

Answer: Theoretically yes, but it’s not cost effective, so we don’t offer repair kits.  If the customer needs new screens because of start-up debris, we’ll provide them no at charge.  The user needs a tool to remove and reinstall the retaining ring.


Why do we offer Chrome Finish and what about the fact that it’s not polished?

Answer: Chrome finish was covered in an earlier question, but it’s common in lavatory tempering because it’s frequently used with “P” traps and supply stops that are polished chrome.  Be aware that the quality of Acorn’s standard chrome finish, and the reasons for using chrome, wouldn’t make the need for polished chrome critical for the ST70.  We have no plans to offer polished chrome.


Is the ST70 going to be offered in higher capacity and with 3/4” and 1” connections?

Answer: The ST7069 is certified to ASSE 1070 and offers up to 12 GPM, but we clearly need something in the 18-24 GPM range.  We have plans to offer a higher capacity valve with both 3/4” and 1” connection sizes.


ST7069 – Group Showering:

I’m getting complaints about the time it takes for the user to get a hot shower, is it the Acorn ST7069?

Answer: This is common with group showers and it probably relates to the piping design.  If HW supply (the HW Heater or Tank or the HW recirculation line) is a distance from the ST7069 and/or the user is at a shower that’s a long distance to ST7069, the bather could have a long wait for the bath temperature to reach him.  This problem may not be noticed by bathers closer to the ST7069 or when a multiple showers are in use.  The bathers closer to the ST7069 help deliver the bath water closer (so faster) to the farthest bather at those times.  However, when no one has been showering for a while and the first bather goes to the farthest fixture, the design limitations become evident.

This is one of the first things to consider when troubleshooting this complaint.

Determining the ideal location for the ST7069 relative to the bathers, minimizing the number of ST7069’s in use and getting bath temperature water to each bather quickly, is always a challenge for group showering design.


Can I use the ST7069 for group showering and lavatory tempering at the same time?

Answer: Yes, because it’s certified for both applications and has a low independently certified minimum rate of ½ GPM, so even low flow faucets and showerheads can be used with this valve.

MV17 – Master Mixing:


What happens if I don’t install a “heat trap” as shown in our MV17 piping diagram?

Answer: Maybe nothing, but we recommend one to prevent convection heat from heating up the master mixing valve during long periods of no demand.  This issue could increase the CW supply temperature to valve, because it’s stagnant at times, temporarily producing a slug of dangerously hot water.


Acorn states all minimum flows per the applicable ASSE standard.  So does Powers, but I don’t see this on other competitors flow charts and in their literature or specs.  What’s the difference?

Answer: This is a critical point to understanding the performance of Master Mixing Valves (MMV) under ASSE 1017.  The ASSE 1017 standard temperature control test is performed at an initial flow rate with 10 psid, i.e. the highest flow rate, followed by a 50% reduction on flow, which is the lowest tested flow rate.  Unless stated otherwise by the manufacturer, a design engineer can only assume that any MMV was tested at the flow rates defined by the standard.

Acorn MV17 valves are all IAPMO certified to ASSE 1017 from 10 psid to our advertised minimum flow rates, which are all much lower than the lowest tested rate set by the standard.  For example, the MV17-4 could have legitimately been tested and certified to the ASSE 1017 at a starting flow of 70 GPM, followed by a reduced flow of 35 GPM.  Instead, the MV17-4 was tested by IAPMO to ASSE 1017 from 70 GPM to a minimum flow of 3 GPM.  As shown by this example, the difference in a valve that’s certified to ASSE 1017 and the IAPMO/Acorn listed product certified to ASSE 1017 might be the difference between 70 to 35 GPM and 70 to 3 GPM, for the MV17-4, in other words at 1/10th of the minimum flow rate for competing valves.

This is important because low flow performance is critical to the overall performance of any master mixing valve.  Most of the time, the flow rate through the valve will be relatively low, no matter how big the valve or high the peak demand. During the night the only demand through the master mixer may be the recirculation pump and they are typically under 5 GPM, even for larger facilities.

Powers may state that their flows are “per the ASSE standard”, but this assurance was always based on in-house verification, not the independent lab certification testing.

Other manufacturers, obviously, do not hold themselves accountable to the ASSE 1017 (temperature control) test standards when stating their minimum flow for their master mixing valves.  What they consider acceptable performance at their advertised minimum flow is based on their subjective pass-fail criteria.  If a manufacturer setting his own pass-fail criteria for safety and performance is acceptable to a design engineer, why have ASSE standards at all?


What does High/Low mean and how does Acorn MV valves differ from other High/Low’s on the market?

Answer: The previous question covers the key performance advantage that relates to us calling our valves “High/Low”, but the potential for creating High/Low performance with multiple valves is possible when no single valve is adequate for the application.

Example: A project needs from 1 to 70 GPM (at 30 psid), certified safe to ASSE 1017 and we offer no single valve that meets these criteria.  The closest we come is the MV17-3 with 2 GPM min. to 73.5 GPM at 30 psid.

But, we could build a pre-piped system consisting of two (2) MV17-2’s and achieve 1 to 73.4 GPM, 1 GPM being the certified minimum for a single MV17-2 and 73.4 GPM being the combined output of both valves, at 30 psid.  This assumes that we pipe the valves with a PRV (Pressure Regulating Valve) to block the outlet of one of them during low demand.  With a PRV, low flow demand is met by the valve that’s always open (not blocked by the PRV) while high flow demand is met by both valves, at a rate high enough for both the control accurately.  Therefore, we achieve the 1 to 70 GPM required, fully certified, with a 2 valve assembly using a PRV.  Note that without the PRV, the minimum flow of this 2 valve assembly would be 2 GPM (1 GPM for each MV17-2, since both are open all the time) to 73.4 GPM (the combined output of both MV17-2 valves @ 30 psid).  So, as long as the PRV is set  to open at a flow greater than 2 GPM, accurate control is assured from 1 to 73.4 GPM.

Other two valve assemblies are possible.  Just remember: without a PRV you double all valves min. and max. flow rates, while the use of a PRV means you only double the max. when stating the certified low and high flow performance.


Acorn provides integral checks/strainers and separate full port ball valves with their MV17 master mixing valves.  Why didn’t Acorn include combination (aka ”triple duty”) check/strainers/service stops with their MV17’s, like all other Master Mixers on the market?

Answer: Four reasons:

  1. We wanted to make a reliable cartridge-style check and that would have been complicated by including the service stop function.
  2. Contractors typically install ball valves on their HW and CW inlets so they can service the check stops, which are not known for long-term reliability.  So, we eliminated an extra cost by including them standard.
  3. A more complicated and unreliable check stop would potentially reduce the capacity of our MV valve, while it increases the cost.
  4. Any chance that a contractor/installer might forget to install the separate threaded-on checks and strainers is virtually eliminated.

Full port ball valves are extremely reliable and are trusted to remain so until a major upgrade to the system becomes necessary.  Integral checks and strainer also eliminate a potential leak point.


I’m quoting against a competitor’s valve and since the capacity by model is so different than what we offer, how do I determine an “equal”?

Answer: There are no exact equals since there are very few instances where valves are exactly the same in capacity at the same pressure drop or psid.  Although it’s simple to find the Acorn valve that has at least as much capacity as the competitor’s valve specified, you may be quoting a larger valve than the project needs unless you know the actual site requirements.

For example, if an engineer prefers Leonard as his lead spec and needs 65 GPM @ 30 psid, he sees that their LV-982, with 53 GPM, is too small.  So, he specifies their next size, the LV-983, which offers 99 GPM @ 30 psid and accepts that his peak demand will be met at much less than the 30 psid he determined to be available on site.

Based on a cross reference, you’d quote our MV17-4 since the MV17-3, at only 74 GPM @ psid, appears inadequate against their LV-983.  But it would be a better valve for the project because it offers more GPM than is actually needed on site and it takes advantage of more of the psid available.  It also has an IAPMO certified minimum of 2 GPM against the 5 GPM min. Leonard offers, which is not independent lab certified or based on any 3rd party verification - see earlier question on IAPMO/ASSE 1017 certified minimum flow rates.  Best of all, you’ll be more price competitive, without deep discounting.

So, be careful when you cross reference and understand that meeting or exceeding the capacity of the valve specified may not be the right response. You may not only quote a larger valve than is necessary, you may also put yourself at a cost disadvantage.  It could be enough to cost us the order.


What temperature does Acorn recommend for domestic water recirculation?

Answer: Based on published documents from the CDC and other organizations, keeping the temperature of the recirculated domestic LTHW loop above approximately 123° F helps prevent the propagation of Legionella and other bacteria.  Therefore, we recommend a master mixing valve set point of 130° F or higher, to allow for reasonable variations in set point control and system heat loss without going below 123° F.

A minimum HW storage temperature of 140° F is also consistent with CDC recommendations for Legionella prevention and provides a sufficiently high supply temperature for the MV17 set to 130° F.


ET71 – Emergency Tempering:

What is cold water by-pass and why is it important to Emergency Tempering Valves

Answer: Unlike all other bather applications, for emergency washing cold water is safer than no water at all.  ASSE certification requires that, upon HW loss, CW continues to flow to the safety fixture at a rate advertised by the manufacturer.  Although thermal shock is an important consideration for other applications, it’s not considered a serious risk for emergency showers.  So, if HW is lost, the CW must continue to flow at a rate that maintains the functional benefit of the emergency fixture.


Why does Acorn offer optional lockable ball valves and not integral check stops like other manufacturers?

Answer: Two reasons:

  1. ASSE and ANSI state, “If shutoff valves are supplied for maintenance purposes, provisions shall be made to prevent unauthorized shutoff”.  Check stops that are screwdriver or allen wrench accessible require locking cabinets, some type of locking cover or placement in a locked utility room to prevent unauthorized shutoff.
  2. We want the design engineer to acknowledge that he chooses to include a shutoff device given the first reason, so he also takes responsibility to mandate the lock required to complete the protection these ball valves provide.

The Acorn ET71 is the only valve that meets ASSE and ANSI without additional cost or options.  With or without the lockable ball valve option, we offer a safe and reliable method for preventing unauthorized supply shutoff at the lowest possible cost.


How does the maximum outlet temperature for emergency valves differ from other valves?

Answer: Unlike other Acorn Controls categories, the temperature limit on Acorn ET71 valves is temperature based.  If the setpoint locknut is loosened and the temperature adjustment is turned to its highest setting, the ET71 outlet temperature will not and cannot exceed 100° F.  It achieves this by means of an internal, factory set, limit stop.


Can you recirculate through our Emergency Valves the same as you would a master mixer?

Answer: Yes, but that’s not true of all Emergency Valves on the market.  The advantage is that the design engineer can locate the ET71 near the HW source and recirculate 85° F to remotely located fixtures.  Otherwise, he must recirculate higher temperature HW to the remotely located emergency valves and fixtures, which is less energy efficient.  His only other option is to locate both the HW source and emergency valve at the fixture, which could be cost prohibitive.


Why are Emergency Valves set at 85° F and could the user change the setpoint in the field?

Answer: We set the ET71 at 85° F because this is a very comfortable temperature for eye washes.  It’s also the temperature at which IAPMO tests the valve for ASSE 1071 certification.  Users can change the setpoint in the field, but we caution the user that higher temperatures could accelerate the effects of the chemical being washed from the skin.  Medical consultation is recommended to determine the ideal temperature setting for emergency valves based on type of chemicals being handled.  See our installation guidelines for our medical consultation advisory.