Taco Comfort

Domestic Water’s Creepy Challenge

It’s a, well, creepy sort of problem.  That is, when hot water recircs lose their ability to govern themselves.  So, there’s the problem.

But, let’s back up just a bit.  Let’s start with an explanation.  Then we’ll talk to the experts.

There’s little debate that residential or light commercial domestic hot water recirculation (DHWR) technology has proven its value in the world of plumbing and mechanical systems.  The devices guard our safety, comfort and health.  Hot water recirc systems move potable hot water to fixtures quickly, without waiting for the water to get hot, so there’s less wasted water, and time.

The key challenge to these simple systems is the problem of “hot water creep.”  Let’s take a closer look, beginning with an examination of the components that have a role in the recirculation of a home’s domestic hot water.

Let’s first define the “system”  After all, the various components, if not connected intelligently and working in concert, would accomplish nothing:

1. Water heater without a tempering/mixing valve. Essentially, an unprotected, full-on arrangement that places anyone at risk.
2. Water heater with a distribution tempering/mixing valve (typically, and ASSE 1017, or ASSE 1070 valve). This is most common, and became the point of introduction for DHWR systems.
3. Water heater with distribution tempering/mixing valve with a DHW recirculation pump and a bypass valve or pump located at the domestic water system’s most remote fixture – with use of the cold water line as a means of returning water to the water heater.
4. Water heater with distribution tempering/mixing valve with a DHW recirculation pump and a dedicated return line from the most remote fixture on that particular hot water zone. Ideally, this is how a DHWR system is installed.
5. Finally, all of the above, to include a control of some means; aquastat, timer or combination control with some kind of logic.

“It takes some, or several of the components above, to make a DHWR system,” explained Rick Mayo, product and applications instructor, Western region, Taco Comfort Solutions.

Most recirc systems, by design, have a tempering valve that continuously adjusts its temperature when water flows through it – while tempering (that is, mixing) it with cold water – to maintain proper outlet water temperature for rapid release at points of use.

The challenge is to maintain the mixed water temp during periods of no demand. The reason for this:  the recirc’s pump enables flow through the valve, even when there’s no demand, or draw, from points of use – such as faucets and other fixtures.  For this reason, recirc pumps must be piped so that the recirc’s returning flow can reach both the cold connection of the valve as well as the cold connection of the heat source.  Some balancing may be required.

Smart, by design

Typically, a water heater’s storage temperature is set for about 140°F for legionella mitigation, and the DHWR’s hot water temperature is reduced to under 120°F at the mixed outlet connection of the valve (with the reduced temp made possible by mixing with cold water, by design).

This cause the valve assembly to adjust temperature; that is, until it reaches the hot water’s set-temp.  The internal thermostat adjusts the piston to open the cold port and close the hot port, allowing hot water to recirculate.  Unfortunately, there can be challenges to the intended function of these systems.

• Creepy situation #1:  If the hot water distribution system isn’t insulated, this can cause the distribution loop temperature to creep down during periods of no demand.
• Creepy situation #2:  Domestic water systems installed with a domestic hot water recirculation pump may cause downstream water to overheat if it’s not piped properly or is running longer than required.  This overheating of temps within the piped system may go unnoticed for quite a while and could cause risk of scalding at points of use.

Mayo offers this insight:  The ASSE 1070 valve does a better job of restricting flow of the hot water than the ASSE 1017 and is more effective at preventing “creep.”  He clarifies:  “Don’t get me wrong.  Those ASSE 1017 valves work as intended in non-recirc systems.  If the temperature is set for 115°F, they regulate the temperature to that point, almost assuredly.  But as soon as you match ‘em up with a (DHW) recirc, problems can begin.”

• Creepy situation #3:  Make sure there’s always sufficient flow to meet the DHWR valve’s minimum flow requirement. All DHWR control valves need a certain amount of flow to function properly.  A properly sized, recirc pump will usually assure sufficient flow.
• Creepy situation #4:  A point-of-distribution, ASSE 1017 mixing valve (or, for that matter, even the ASSE 1070 valve) that does not have a full or completely closed function for its hot inlet port can cause thermal creep if not properly piped and controlled; many mixing valves with an electronic actuator have a fully-closed position so that this doesn’t occur.

Piped conundrum

“It’s often a piping challenge,” said tekmar’s General Manager, Greg Leupin.  “For many hot water recirc ‘creep’ challenges, the challenge has to do with incorrect piping.  When the recirc is off or at rest, thermal ‘ghost flow’ can affect the amount of hot water that makes its way into the [distribution] piping.

Leupin added that many recirc loops lack a mixing valve, causing excessive – sometimes unsafe – temperature in the recirc loop, increasing the risk of scalding.  This can also lead to inefficiency from heat loss, especially when the domestic water lines aren’t insulated.

Smart technology

Manufacturers have stepped in to help negate the risk of domestic water creep when recirc systems are installed.  “Installation instructions are more explicit and the technology’s improved,” said Mayo.

“The problem begins when there’s an inability to dissipate the heat during periods of no demand,” added Mayo.  “As referenced earlier Some [DHWR] devices close the hot side better than others, so both the built-in control strategy may help, as does the installation piping.  Of course, the recirc shouldn’t be running when the distribution system’s already sufficiently full of hot water, readily accessible at taps and other points of use.”

• Taco SmartPlug (which won AHR Expo’s Product of the Year Award in 2017) was developed to eliminate the hassle of a “timer;” because of their design they only allow water to be circulated for short periods of time, this can help fight the challenge of thermal creep.  The small device instantly changes any corded hot water recirc – for instance, those with just timer and on/off function – into a “smart” device by giving it the intelligence it needs to learn a household’s usage patterns to improve and regulate hot water distribution, increasing comfort and efficiency.  It can also be set into a ‘pulse only’ mode for light commercial applications, or for homeowners who don’t have a predictable schedule.

Other hot water recirc solutions include:

• TacoGenie allows homeowners to simply push a button when hot water is desired at a tap, on demand.
• Watts/Premier 500800 – an ideal solution for retrofitting existing domestic water systems with hot water recirc.  The device uses the pump at the water heater (though not tankless systems) and an under-sink sensor valve to create a pressure differential – allowing the cold and cool water in the hot water supply line to bypass into the cold water supply line at a low volume through the thermostatically-controlled sensor valve, keeping the water in the hot water supply line at a “no-wait” temperature throughout the home.

ASSE 1070 valve

As Mayo stated earlier, ASSE 1017 thermostatic valves installed at the water heater or heat source may not close off sufficiently in some instances (while the circulator is running) to stop the outward flow of heat.  If this happens, and a recirc pump continues to run, temperatures within the distribution piping can creep upward – creating the potential for unexpectedly hot water at taps.

In a situation like that one, the need for hot water [in the distribution piping] is satisfied, but if the [DHWR] pump’s running, ‘creep’ can occur,” concluded Mayo.  “Yet another solution protects users from unexpectedly high temps at the tap with or without replacement of the distribution safety valve – and that is the installation of 1016 or 1070 point-of-use valves.  They’re most often used for commercial installations, though there are many residential uses of the valves.”

If you buy an ECM circulator later this summer, you’re likely to see something new stuck to it: an Efficiency Rating label courtesy of the Hydraulic Institute. The labeling represents independent, third-party verification of each circulator’s overall electrical efficiency.

That sounds pretty cool, but what does it all mean?

Well, for starters, it means you don’t have to rely on marketing claims or sales mumbo-jumbo to determine who has the most advanced and efficient circulators. And you don’t have to rely on vague math to determine how much less an ECM circulator will cost to run compared to its standard efficiency counterpart.

In other words, it’s there in black and white.

There’s a lot to unpack here, so let’s get started.

First Off, Just What Is the Hydraulics Institute?

The Hydraulics Institute, or HI for short, touts itself as the global authority on pumps since 1917. It’s an industry association working on behalf of the pump industry and works with the U.S. Department of Energy to establish guidelines and regulations for pumps of all types and sizes. Most recently, its efforts with the DOE led to commercial pump efficiency regulations that went into effect in January of 2020, covering all pumps 1 H.P. and above.

The new labeling on ECM’s under 1 HP can be considered a pre-cursor to DOE regulations that will ultimately phase out standard efficiency circulators. However, don’t expect those regulations to go into effect for at least two, maybe three more years.

While HI is an organization made up of pump and circulator manufacturers, it’s important to note that all of its guidelines and regulations are set in concert with the DOE. In its most basic form, the DOE says, “this is what you have to do.” HI, in turn, develops guidelines, test procedures and processes manufacturers need to follow in order to be rated.

HI also certifies each manufacturer’s test lab, and it fully audits all test results. Yes, manufacturers test their own pumps, but only if their test lab is certified. HI creates all testing procedures and guidelines, including machinery calibration, personnel training and record keeping. Labs are periodically inspected, and all test results are reviewed and audited.

The whole process is set up so there’s no scamming the system. The results are the results.

But What About the Ratings?

You’ve no doubt seen those ubiquitous yellow EnergyGuide stickers on just about every appliance under the sun. They’re not only on fridges, dryers and other everyday items, they’re also on boilers, furnaces, A/C units and heat pumps. The Federal Trade Commission requires those stickers to give consumers an idea of relative energy efficiency compared to similar units.

The new HI Energy Rating stickers on circulators are pretty much the same thing, only different.

Instead of giving you an estimated yearly energy cost, the new HI Energy Rating stickers give each circulator an Energy Rating score, or an ER. It’s a pretty easy rating to decipher: the higher the number, the more efficient the circulator.

For example, an ECM circulator with an ER of 188 consumes 10 percent less energy than a circulator with an ER of 178.

By comparison, a common standard efficiency circulator, such as a Taco 007 or a Grundfos 1558, would have an ER in the neighborhood of 48 to 50.

The math to calculate the ER is fairly detailed, so it would take someone way smarter than me to walk you through it. The ultimate value of ER, however, is to provide a simple way to show a customer how much less an ECM circulator will cost to operate compared to its standard efficiency counterpart based on independent, third-party testing.

Let’s Do THAT Math!

Let’s look at the ER label for the Taco 0015e3. The 0015e3 is a variable speed Delta-P circulator with three settings, two for constant pressure and one for full-speed, fixed speed. It’s the perfect pump to use for zone valve applications and does a dandy job as a zone circulator as well.

As you can see, the 0015e3 has an ER ranging from 152 in its least efficient mode, which is that full speed, fixed speed setting. In its most efficient operating mode setting – variable speed, constant pressure Delta-P – the ER goes to 188.

And not for nothing, Taco has four circulators with 188 ratings (and a fifth rated at 187). Those are the highest rated circulators on the HI database (Armstrong also has a circulator rated at 188. No one else is within six ER points). You can access the HI database here.

The full ratings label provides you with the math to determine how much a particular circulator will save. You first multiply ER by something called WAIP, which stands for Weighted Average Input Power. WAIP represents the average input power in horsepower for an ECM circulator without controls:

188 x 0.071 = 13.348

Next, to convert horsepower to watts, you’d multiply by 7.46:

13.348 x 7.46 = 99.58 watts

From here on it, it’s a simple kWh/cost calculation. To convert watts to kilowatts, you divide by 1000, and then multiply by the estimated number of run hours over a heating season. For this example, we’ll use 2500.

99.58 ÷ 1000 = 0.09958 kilowatts

0.09958 kW x 2500 hours = 248.95 kWh

Last, multiply kWh by your cost per kilowatt hour. That will tell you how much less the 0015e3 would cost to operate compared to a 007 or 1558:

248.95 kWh x 0.15 per kWh = $37.34

Is that a Lot?

Well, it depends. If you’re trying to justify replacing four perfectly good and not terribly old circulators with four ECMs, you’ll save just under $150 per heating season. Depending on how much you charge for the swap out, it might be a hard sell. And there’s nothing “green” about dumping four perfectly good circulators before their time.

However, if you’re trying to show a customer (or yourself, for that matter) that replacing a dead circulator with a more expensive ECM is worth it, you now have something to sink your teeth into.

Say a standard efficiency 007 or 1558 dies and you want to replace it with a 0015e3. Yes, the 0015e3 costs more. But just channel your inner Cosmo Castorini from Moonstruck and tell them, “it costs money, because it saves money.”

Without getting into wholesale costs, profit margins and selling prices (those are your business), it’s fair to say that based on a $37.34 annual savings, the 0015e3’s higher selling price will be offset in less than two heating seasons. After that, the homeowner pockets the rest.

And if you want to talk about how a properly programmed ECM, particularly one that operates on a fixed Delta-T, will help the overall system work better, let’s make an Outlook appointment. There’s a LOT more to discuss.

What’s the Point?

So, why HI is doing this labeling thing in the first place? Simple: to give the industry an easy—and independent—way to show the value of converting from standard efficiency to ECM.

In markets where local utilities do not offer incentive rebates to drive conversion, ECM conversion has been snail’s pace slow. Some of it is a little of the “if it ain’t broke, don’t fix it,” mindset. Some of it has been ridiculous claims of “magic” and the misguided promise that these circulators somehow mean you don’t have to know how to size a pump. No one with half a mind believes that nonsense.

And some of it is, to put it gently, giving new technology a healthy—and distant —respect.

But for the most part, it’s been price resistance.

What the ER label does is give you an easy way to show a customer a fundamental truth: they’re going to be paying for the ECM circulator one way or another. The only question is whether they actually get it or not.

Remember Cosmo’s words.