Variable Speed System Pumping Theory & Application

1. Variable Speed System Pumping Theory & Application

2. Why use a Variable Speed Circulator? • Good Question… • What do they do? - Vary speed based on changing loads - Use external loads • Best applications - System circulator with zone valves - Radiant with multiple zones

3. Universal Hydronics Formula • GPM = BTUH ÷ ∆T X 500 GPM = Gallons Per Minute BTUH = Heating Load ∆T= Design Temperature Drop • 20˚ for baseboard • 10˚ for radiant 500 = 8.33 x 60 x 1

4. Sample Project • Heat loss = 75,000 BTUH • Design temperature = 0˚ • 3 zones fin tube • 25K BTUH each • 20˚ ∆T

5. Do the math! • BTUH ÷ ∆T X 500 • GPM = 75,000 20 x 500 • GPM = 75,000 10,000 • GPM = 7.5

6. For each zone… • 25,000 BTUH each • GPM = 25,000 20 x 500 • GPM = 25,000 10,000 • GPM = 2.5

7. Pipe Sizing • 2-4 GPM = 3/4” pipe • 4-8/9 GPM = 1” pipe • 8/9-14 GPM = 1-1/4” pipe • 14-22 GPM = 1-1/2” pipe • Min/Max velocity • 2-4 FPS • >4 = Velocity Noise

8. Let’s Pipe ‘Er Up!

9. Head Loss

10. Head Loss • Longest run = 15’ (Including element) • Multiply by 1.5 (to allow for fittings, etc.) • 150 x 1.5 = 225’ • Multiply by .04 • 4’ head / 100’ of pipe • 225 x .04 = 9’ head loss • 7.5 GPM @ 9’ head

11. Pick the Pump… Taco 008 Pump Curve

12. System Curve

13. As Zone Valves Close…

14. As Zone Valves Close… • GPM = BTUH ∆T x 500 • GPM = 50,000 ∆T x 500 • Delta-T is lower than design • Poor heat transfer • Less efficient boiler • Velocity noise

15. What do we do about it? • Ignore it? • “That’s just the way these systems are!”

16. A good solution...

17. A “Flat” solution.

18. A Better solution… Variable Speed pumping! Actual flow rate = 9 GPM

19. Universal Hydronic Formula • ∆T = = 16˚ • ∆T = with 2 Zones = 15˚ • ∆T = with 1 Zone = 12˚ • Under DESIGN conditions! • GPM = BTUH ∆T X 500 • GPM = BTUH x ∆T X 500 • ∆T = BTUH ÷ 500 GPM • ∆T = 75,000 ÷ 500 9

20. But what if Delta-T was fixed? • GPM = BTUH ∆T X 500 • GPM = 25,000 20 x 500 • GPM = 2.5 • The flow will vary!

21. 15 10 5 5 20 10 15 A Better Solution…

22. An important Consideration… • Calculate max flow rate • Estimate Head loss • Length x 1.5 x .04 • Head loss at MAX flow loss • Actual flow rate much less • Can overestimate head by 50% • ∆T circulator “Self-Adjusts”

23. Taco 00-VDT • Variable speed ∆T circulator • Control built in • Simple to install • Simple to program • Simple to understand • 008, 0012, 0013 VDT

24. A simple solution

25. Setting it up • Range Dial • Adjusts to desired ∆T • Dip Switches • Switch 1,3 ON • All others off

26. Supply Sensor Return Sensor Wiring it up… • H-N to ZVC • Supply sensor to S2 & Com • Return sensor to S1 & Com

27. Delta-T vs. Delta-P • ∆T directly related to flow rate • Pump speeds adjusts to required BTU/hr • GPM = BTUH/∆T x 500 • ∆T always runs at lowest required speed • ∆P adjusts only to pressure change • Needs accurate head loss calculation - not estimation • Doesn’t know which zones are open/closed • May not be able to satisfy heat demand

28. 36 33 Energy Consumption 137 kW kW consumed, 2,500 hour heating season Assuming 12.5 hours of operation daily 117 kW 102 kW ECM circulators draw constant 5 kW in “standby” mode to keep memory powered – for 6,260 non-heating hours annually Taco 00 VDT draws NO powerwhen off – runs off standard relay or zone valve controller

29. Cold hard facts...

30. What about system efficiency? • Big difference between Delta-T & Delta-P • Cast Iron Boilers • ∆T circulator controls return water temp. • Reduces short cycling • Uses less fuel • Bigger impact with “mod-con”

31. Delta-T and Boiler Efficiency

32. A quick comparison…

33. Some parting thoughts • ∆T directly related to flow rate • Pump speed adjusts to required BTU/hr • ∆T ensures optimum performance • ∆T does not “flat line” • ∆T always runs at lowest required speed • Many models • EASY to set up!