1. Variable Speed Pumps Theory and Application

2. What Is Variable Speed Pumping?
Pump changes speed based on load
Curve shifts on both head and flow axis
More speed – more flow and head
Set point or outdoor reset
Zone valve/TRV or fan coil systems
Variable speed injection mixing
In 2004, Taco introduced the very first variable speed cartridge type circulators to the US market. These “00” circulators have controls built-in to provide varying degrees of variable speed control for a variety of different purposes. These types of circulators have been available in Europe for years, and as a concept, variable speed pumping has been around for quite a while. But just what is “variable speed pumping?” Well, as the name suggests, the on-board controls vary the speed of the circulator based on some sort of feedback, typically a target temperature. The pump will either speed up or slow down based on the temperature input compared to the temperature target. The pump curve will shift on both the horizontal, or flow axis as well as the vertical, or head axis. The faster the speed of the circulator, the more flow the circulator will produce and the more head loss the circulator will overcome. Conversely, the slower the speed, the lower the flow and head.
Variable speed pumps are available in either setpoint or outdoor reset versions. Setpoint variable speed pumps will strive to maintain a fixed water temperature, or a fixed Delta T depending on programming, within a system, and will speed up or slow down based on system needs. The most useful applications for setpoint would be in zone valve or TRV (thermostatic radiator valve) jobs. The more zones that call, the faster the circulator will run. We’ll have more on this application later. Setpoint variable speed pumps can also be used to protect non-condensing boilers and also for fan-coil systems to vary the speed of the pump based on air supply temperature. For outdoor reset, a variable speed pump is used for variable speed injection mixing in radiant heating systems

3. Universal Hydronics Equation
GPM = BTUH ¸ DT x 500
Change heat load, change GPM needed
Change DT, change GPM needed
BTUH = GPM x DT x 500
Change GPM, change BTUH output
Change DT, change BTUH output
Variable speed pumping is based on the universal hydronics formula – GPM = BTUH divided by Delta T x Basic math tells us that if we change the heat load required while the Delta T and the 500 constant remain the same, the GPM requirement to deliver the heat will change. It will go up if the heat load increases and go down if it decreases. In addition, if the Detla T should change, but the heat load and constant stay the same, then the GPM will also change. If the Delta T goes down, then the required GPM will go up. If the Delta T goes up, then the required GPM goes down.
If we multiply both sides of the equation by (Delta T x 500), we find that BTUH = GPM x Delta T x So if we change the GPM – by changing the RPM of the motor – we can change the BTU output – increasing the output if we speed up the motor, decreasing the output if we slow down the motor. By the same token, if the Delta T should change, the output would also change.

4. Variable Speed Pumps Setpoint – 00-VS Outdoor reset – 00-VR
Maintain specific water temp
Maintain specific Delta T
Outdoor reset – 00-VR
Injection mixing
Change supply water temp based on outdoor temp
003 thru 0014
Taco offers two residential variable speed circulators. The first is the 00-VS, for Variable Speed - Setpoint. The VS is designed to maintain either a specific water temperature in a secondary piping arrangement. It has a couple of other uses as well -- it can be used as a bypass pump to maintain a minimum return water temperature for a non-condensing cast iron boiler, or it can be used to maintain a specific Delta T in a zone valve or thermostatic radiator valve job.
The other model is the 00-VR, for variable speed - Reset. This is a 00 circulator with a variable speed injection reset control built in, and is used for injection mixing for radiant floor heating applications. The circulator will speed up or slow down based on the required supply water temperature and the outdoor temperature.
Both pumps are available in all 00 sizes, ranging from the 003 all the way to the 0014.

5. The Many Uses of the 00-VS Fixed set point Optional boiler protection
Adj. set point 30°- 210°F
RFH, radiators
Fan coils
Optional boiler protection
Program with dip switches & range dial
The 00-VS set point circulator is a very versatile pump. When piped as an injection circulator in a primary-secondary arrangement for radiant heating, the 00-VS can maintain a fixed water temperature for the radiant system, much like a 3-way tempering valve or an iValve can. The setpoint is adjustable from a low of 30 degrees (for chilled water applications) to a high of 210 (for high temperature applications). The set point function can also be used in a fan coil application with the sensor placed on the outlet for outgoing air temperature. The sensor will read the air temperature, and tell the circulator to speed up or slow down to maintain the desired temperature.
There’s also an optional boiler protection function on the 00-VS – simply connect a sensor to the S3 terminal on the wiring board and connect it to the return piping of a non-condensing cast iron boiler. The control will automatically monitor the boiler return temperature – it’s set to a low limit of 135 degrees. If water temperatures start approaching that temperature, the control will tell the circulator to slow down. The circulator will stop taking as much hot water out of the primary loop, allowing more hot water to return to the boiler to keep it from condensing. This function is disabled if S3 is not connected.
All programming is done with a series of dipswitches, sensor connections and the range dial. S1 and dipswitch 2 determine whether the circulator works at the low temperature range (30 to 120 degrees); while using S2 instead of S1 and changing the dipswitch position will allow the circulator to work at the higher range – 120 to 210 degrees. The range dial will allow for further fine tuning of the control.

6. Injection & Primary-Secondary
Perfect for multi-temp, multi-load systems
Key is tee spacing
6” or 4 pipe diameters
At least 6” straight pipe on either side of tees
1’ thermal traps
The 00-VS set point pump should be piped in a primary secondary fashion, as shown here. In this drawing, the circulator will inject hot boiler water from the primary loop into the lower temperature secondary loop as needed, with the circulator running faster or slower depending on what the radiant supply sensor reads. This type of piping arrangement is perfect for multi-temperature, multi-load systems that we see in modern hydronics. These types of system may include an indirect hot water tank, a fan coil or two, some high temperature radiation – such as baseboard, some high temperature radiant – such as between the floor joists, some low temperature radiant, such as a basement slab, and a snowmelt system. That’s five separate water temperature off one boiler – primary-secondary boiler piping is the easiest way to pipe it all up so that it makes sense.
The key to primary-secondary piping is in the tee spacing – on both the primary and on each secondary. The tees should be no more than 6 inches or 4 pipe diameters apart, to minimize pressure drop between them. That way, the only way hot water could pass from the primary into the secondary would be for the secondary pump to actually turn on.
Other things to remember, if you look at note 2 in the drawing – there should be at least 6 inches worth of straight piping on either side of the set of tees. This will prevent the momentum of the water in the primary from pushing flow into the secondary. And finally, note 3, there should be a thermal trap of at least 12 inches in the injection loop piping to prevent any convective heat transfer from the primary into the secondary.

7. Multi-Temp, Multi-Load
Here’s an example of a multi-temp, multi-load system – going from left to right we have the boiler and the primary circulator. Then there’s some high temperature radiation using straight boiler temperature. The next two water temperatures use the 00-VS and injection mixing to maintain fixed water temperatures in each secondary. The first may be high temperature joist heating, while the second may be for the basement slab. Note the two boiler return sensors installed, so that each circulator may use its boiler protection function.

8. Bypass – Boiler Protection
Here we show another in set point mode. The top picture show the 00-VS used as a bypass pump to protect a non-condensing boiler from flue gas condensation. In this example, the set point sensor is placed on the boiler return piping, and the circulator is placed in a bypass loop. The sensor monitors the return water temperature and if that temperature starts getting too low, the circulator will speed up to keep the water temperature above the condensing point. This may be used with larger residential boilers, where even small amounts of condensing will adversely affect operation, efficiency and life of the boiler.

9. In The Delta T Mode For zone valve systems Set for 200 DT
All zones calling – full speed
As valves close – slow down!
Maintains 200 DT
Reduces noise, smoother operation
Perhaps the most useful application of the 00-VS circulator is in the Delta T mode. In this application, the circulator uses two sensors and will monitor the Delta T, or temperature difference between the supply and return. The circulator will then speed up or slow down in order to maintain the programmed Delta T. In this case, the 00-VS is trying to maintain a fixed temperature drop across a distribution system containing a number of independently controlled zone valves as shown here. This figure shows a typical zone valve system. The distribution system would be designed for, say, a 20 degree temperature drop under design conditions. So when it’s the coldest day of the year out, and all zone valves are calling, the 00-VS would run at fairly close to full speed.
When a zone valve closes the load instantly drops. This will cause the temperature drop between the supply and return side of the distribution system to decrease. The 00-VS circulator senses this decrease and reduces its speed to maintain a constant temperature drop. This not only saves electrical energy, it also reduces the chances of both high differential pressure across the circulator and flow noise when only one or two zones are operating.

10. Same Thing Only Different…
Panel radiators, baseboard or zoned radiant
TRV’s or valve actuators
00-VS speeds or slows based on heat calls
The 00-VS circulator can also be used in combination with panel radiators, baseboard or radiant heat connected to a home-run type distribution system through a radiant manifold as shown here. The panel radiators may be controlled by either thermostatic radiator valves as shown, or they could be controlled by manifold actuators provided by the manifold suppliers. Those actuators are essentially zone valves, and the system will operate in exactly the same way as the system shown in the previous slide.
As the valves open or close, the 00-VS circulator would sense the increasing or decreasing load and increase or reduce the speed of the circulator accordingly.

11. How Does It Work? All zones calling – lowest flow resistance
As zones close, flow resistance increases
System curve “backs up” pump curve
Noisy traffic jam!
00-VR is traffic cop!
Under design load conditions, all space heating zones will theoretically need heat, and thus all zone valves will be open. When this happens, the distribution system exhibits its lowest flow resistance. You can think of the distribution system as a multiple lane bridge with all lanes open. As the zone thermostats reach their set point temperatures, and the associated zone valves close, the distribution system as a whole develops increasing flow resistance. The overall system flow rate decreases, while the flow rate through each
open zone circuit increases. Some of the lanes on the bridge are now blocked off, and it’s simply not possible to get the same amount of traffic across, even though traffic moves slightly faster along each open lane. The system head loss curve of the distribution system gets steeper each time a zone valve closes. All hydronic systems constantly seek equilibrium between the mechanical energy (head) input from their circulator and the head loss due to fluid friction in the piping. When represented on a graph, the system always operates at the point where the system head loss curve crosses over the pump curve.
Anything that changes the flow resistance of the distribution system causes the system head loss curve to either steepen, (for increasing flow resistance), or flatten (for decreasing flow resistance). As the system curve shifts so does the point where it intersects the pump curve.
When a zone valve closes the system head loss curve gets steeper forcing the operating point to slide upward along the pump curve. This increases the pressure differential imposed on the zones that remain open. The increased pressure differential increases the flow rate through these zones. At some point the increased flow velocity will probably cause noise in either the zone valve or the piping. In some systems, the increased differential pressure generated by several inactive zones can partially open what are supposed
to be closed zone valves. This can cause heat input to zones that are supposed to be off. (Note that the Taco EBV Zone Valve with its ball valve design and 125 psi shut-off pressure eliminates this possibility). Imagine a system having several space heating circuits and a separate circuit supplying an indirect water heater. All the circuits
are controlled by zone valves. In warm weather, the domestic water heater is likely to be the only zone operating. It’s entirely possible that a high differential pressure across the circulator when the DHW tank is the only operating zone could allow hot water to “ooze” through the closed zone valves on the space heating circuits. This situation is sure to
result in a call back.
With the 00-VS in a zone application – the pump will speed up or slow down as zone valves open or close – in effect creating new pump curves to handle the increasing or decreasing load. When a zone valve closes, that means the zone is satisfied and less heat is needed. Therefore less heat is released through the distribution piping. As a result, the Delta T between the supply and return will decrease. When this happens, the control running the circulator will sense the change and tell the circulator to slow down – less RPM producing less flow -- until the Delta T increases back the desired point. In essence, the control is making the circulator smaller by creating a new, lower pump curve It’s basically acting as a traffic cop at the bridge.

12. Variable Speed– Outdoor Reset
Perfect for radiant jobs
“Delivery” reset
Changes SWT based on outside temps
Comfort and economy of operation
Lots of features…
Adjustable heating curve
Adjustable min/max SWT
Adjustable boiler protection
System pump relay
The 00-VR is a variable speed pump with an outdoor reset control built in, to provide the installer with variable speed injection reset for radiant systems. Injection reset is one of the most common, and versatile methods of providing delivery reset – meaning the heat delivery, or the radiant system itself – is being reset, not the boiler. Commonly used with a cast iron, non-condensing boiler firing up to its high limit, variable speed injection reset will change the radiant system water temperature based on changing conditions outside. The colder it gets outside, the warmer the radiant system water will be. The warmer it gets outside, the cooler the water will get in the system. This resetting of the water will enhance the comfort of the system as well as its economy of operation. Wear and tear on all the components will be decreased, as well.
The 00-VR has lots of features, including an adjustable heating curve to dial in the reset ratio. It also has an adjustable minimum and maximum supply water temperature function for radiant applications. The minimum may be set for 85 degrees, which is useful for floor conditioning applications. The maximum water temperature setting is useful if the radiant system has, say, hardwood floors and you would like to make sure the surface temperature doesn’t exceed guidelines. It also has automatic boiler protection with an adjustable temperature –either 120 or 135 degrees. All programming is done with dipswitch settings.
The 00-VR also has an on-board relay for the radiant system circulator – so that both the injection pump and the system pump may be turned on through one control.

13. Understanding Reset
To fully understand the application of outdoor reset, and the benefit to the homeowner, it’s important to realize that the goal of any heating system is to maintain a constant room temperature during the heating season. Now of course, the heating system is designed to heat a given room under design conditions – the “coldest day of the year.” In a radiant system, the radiant design calculations will tell you, based on the heat load of the room, the floor covering, the installation method and the tube spacing what water temperature you’ll need to heat the room under design conditions. Controls such as a 3 way tempering valve, the Taco Setpoint iValve and the 00-VS setpoint circulator will provide that water temperature for you – but that water temperature will be fixed all winter long. But what happens when the outdoor temperature changes?
It should be obvious that the heat loss of a structure is based on the outdoor temperature. The colder the outdoor temperature, the greater the difference between the indoor room temperature and the outdoor temperature. The greater this Delta T, the greater the heat loss of the room will be, so as the outdoor temperature goes down, the room’s heat loss will go up. Conversely, when the outdoor temperature increases, the room heat loss will decrease.

14. Changing Conditions Heat Loss Heat loss change every day
Fixed SWT
Variable SWT
Heat loss change every day
Fixed water temp = variable run times = cycling in mild times
Variable water temp = fixed run times = less short cycling = greater efficiency
Heat Loss
Variable
SWT
Fixed
Run Time
So how does this apply to water temperature? Well, obviously if the heat loss of a room goes down as it gets warmer outside, the room doesn’t need as much heat. Since we’re not going to add or remove radiant tubing to a room during the course of the heating season, we’re left with two choices for maintaining comfort and preventing overheating. We could provide either a fixed temperature system with a tempering valve, Setpoint iValve or a 00-VS circulator, or we could provide a variable water temperature system using the 00-VR reset circulator.
With either option, it’s clear that the heat loss will vary every day based on how cold it is outside. With a fixed water temperature system, the water will always stay the same temperature. The only way to prevent overheating would be to vary the run times – shorter run times in milder conditions, longer run times with it’s colder. This, unfortunately, leads to short cycling of the boiler which leads to lower overall system efficiencies. More on/off cycles will also lead to more wear and tear on all the moving parts in the system.
With reset, however, the supply water temperature will vary in lockstep with the outdoor temperature – the colder the outdoor temperature, the warmer the water will be. If both the heat loss and water temperature vary together, then the run times for the system, in theory, would have to fixed all winter long. The system will always think it’s the coldest day of the year out, so system on-times will be constant. This will lead to greater system efficiency since the boiler won’t short cycle, and will also lead to less wear and tear on system components, leading to longer life and lower maintenance costs.

15. How Does It Know? Four key numbers Reset ratio = Outdoor Design Temp
Mix Design
WWSD
Mix Start
Reset ratio =
Mix Design Temp - 720
How does a reset control know what water temperature to produce? It’s all based on three numbers used in programming. The first number needed is the outdoor design temperature, or the temperature upon which the heat loss has been based. This is the so-called “coldest day of the year.” The next number needed is the Mix Design number – this is the water temperature the radiant system requires when it’s design conditions. This number will be determined during your radiant design calculations. Next is WWSD, or Warm Weather Shut Down – this occurs when the outdoor temperature is equal to the desired indoor temperature. When that happens, the heat loss of the building is ZERO, and no heat is needed. In warm weather shut down mode, the valve won’t enable, preventing heat from being supplied to building accidentally. The final number required is Mix Start – that’s the water temperature you’ll want running through the system at the warm weather shutdown point. The 00-VR defaults to 72 degrees, although that number is adjustable up to 85, if needed.
Using these numbers, we can determine the “reset ratio” needed to program the 00-VR. Use this formula:
Reset ratio = Mix Supply Temperature – 720
720 – Design Outdoor Temperature
720 – Design Outdoor Temp

16. Let’s Do One… Mix Design = 130, Outdoor Design = 0 130 – 72 58 =
72 - 0 = 72 =
0.8
Let’s do an example – Let’s say we had an aluminum track radiant system that required 130 degree water at an outdoor design temperature of 0 degrees. If we do the math we find the following:
130 – =
72 – 0
= Reset ratio of 0.8 72
We can verify this by looking at the chart – First, find 130 degrees on the supply water temperature axis on the right, and then find the outdoor design temperature on the bottom. Follow the lines to where they intersect, and it should be at the diagonal line representing a ratio of 0.8.

17. What Does 0.8 Mean?
Radiant water temp increases 0.8 of a degree for every 1 degree drop in outdoor temperature
To program:
Move dial on VR control to correct ratio
So, what does the reset ratio of 0.8 actually mean? Well, by setting the ratio to 0.8, the control will know to follow the line in the chart represented by When the outdoor temperature changes, the radiant supply water temperature will change as well, along that line. In essence, the 0.8 means that the radiant water temperature will increase 0.8 degrees for every 1 degree drop in outdoor temperature.
Programming the 00-VR is very easy --- simply adjust the dial on the control head so the arrow points to the desired ratio.

18. 00-VR Piping Arrangement
The piping arrangement for the 00-VR is the same as the piping arrangement for the 00-VS set point circulator when used for radiant floor heating. We use primary-secondary piping, and make sure the supply and return tees on both the primary and the secondary are no more than 6 inches or 4 pipe diameters apart. In addition, there should be at least 6 inches of straight pipe before each supply tee and after each return tee so there won’t be any accidental flow. And finally, there should be at least a one feet thermal trap in the injection supply and return to prevent thermal migration between the primary and the secondary.
You’ll also note there is a balancing valve on the return leg of the injection piping. This valve is critical to the performance of the injection system, because it adds pressure drop to the piping and makes sure the injection circulator doesn’t short cycle, which would cause erratic water temperature control. A globe valve – similar to a stop and waste – should be used. A globe valve provides linear throttling – a half valve turn has the same effect no matter how much the valve is open or closed. A ball valve should not be used here, since it is designed to be either open or closed and does not provide linear throttling.

19. Pipe & Pump Sizing Radiant system – 30,000 BTUH, 100 DT
6 GPM, 5’ head loss
1300 SWT, 1200 RWT
RFH supply pipe - 1”
Injection pipe sizing:
GPM =
GPM =1.00
Injection legs = ½
Taco 003-VR
Valve 30% open
1300 Radiant Supply
1800 Boiler Supply
30, x 500
Here’s a sample radiant job –30,000 BTU’s worth of radiant, designed to a 10 degree delta T. Using the universal hydronics formula, we can determine the GPM flow rate for the radiant system. As we all know, GPM – BTUH divided by (Delta T x 500). If we do the math, we find that the radiant system requires 6 GPM. Let’s assume the radiant design calculations tell us the overall head loss on the secondary is 5 feet. The radiant supply water temperature is 130 degrees, so at a 10 degree Delta T we can surmise that the return water temperature, under design conditions, would be Piping guidelines tell us the radiant supply piping on the secondary side would be 1” to carry the 6 GPM for the radiant. The radiant circulator would need to provide 6 GPM at 5 feet of head, and would most likely be a Taco 007.
To pipe up the 00-VR injection circulator, we need to figure out the actual injection flow rate, or how much 180 degree water we’ll need to inject from the primary into the secondary in order to maintain 130 degrees in the radiant side at design conditions. Again, to determine flow rate we use the universal hydronics formula:
GPM = BTUH divided by Delta T x 500.
In this case, the BTUH is 30,000, but the Delta tee is the temperature difference between the water coming in off the primary loop – 180 degrees in this example, and the radiant return water heading back to the primary – in this case it would be 120 degrees. Since we’re sizing the injection legs, we’re concerned about the Delta T not in the radiant system, but between the supply injection leg and the return injection leg. The boiler water coming from the primary in this example is 180 degrees, and the radiant return water is 120 degrees, so the Delta T we use to find the injection flow rate is 60 degrees. So the math would look like this –
GPM = 30,000 divded by (60 x 500) or 30,000.
If we complete the equation, the injection flow rate would be 1.00 gallos per minute. At that flow rate, ½” pipe would be perfectly adequate. And if we check the chart that comes with the 00-VR, we find that indeed the pipe size would be ½” and that a circulator as small as the 003-VR would be perfectly adequate. Remember, we only need to circulate 1 gallon per minute through the injection legs at design conditions. Whenever the temperature is above design, the required injection flow rate would be less. In addition, the chart tells us the globe valve used for balancing on the injection return leg would need to be only about 30% open.
1200 Radiant
Return

20. Wiring This Bad Boy…
Here we show the internal wiring of the 00-VR. You see the three sensors – outdoor, radiant supply and boiler return – wired to the appropriate terminals. Zoning for the heat delivery – zone valves or circulators – would be wired through a separate Taco Zone Valve Box or multi-pump relay. Both Taco zoning packages have 2 sets of end switches – one set would go to TT on the boiler, while the other set would go the injection circulator to turn it on when there’s a call for heat.
If zone valves are used, then the radiant system circulator could either be wired to the zone valve box or to the injection circulator control, which has a separate switch to enable a circulator.