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# Understanding & Designing Systems With Variable Speed Pumps

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Presented at the 2014 HVAR & Mechanical Conference For Education Professionals, March 4, 2014 in Baltimore, MD

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### Understanding & Designing Systems With Variable Speed Pumps

1. 1. Understanding & Designing systems with variable speed pumps 3/4/2014 1
2. 2. A LITTLE HISTORY LESSON… 3/4/2014 2
3. 3. 1 9 68 3/4/2014 3
4. 4. TYPICAL EUROPEAN SYSTEM Modulating TRV’s Pump runs 24/7 (6k hrs) Small pipe, wide ΔT Low flow, high head
5. 5. TYPICAL US SYSTEM Series loop, fin-tube baseboard  CI bb/radiators/convectors  Radiant floor heating Multiple zones, circs or ZV’s Large pipe, low loads, 200 ΔT High flow, low head
6. 6. STEEP CURVES VS. FLAT CURVES Flat curve = American curve Steep curve = European curve 3/4/2014 6
7. 7. PUMP AFFINITY LAWS 2-4-8 Rule Double pump speed, flow  2X Double pump speed, head  4X Double pump speed, energy consumption  8X 3/4/2014 7
8. 8. SO WHY USE A VARIABLE SPEED PUMP?
9. 9. WHY USE A VARIABLE SPEED CIRCULATOR? Good question… Best applications… Zone valve or RFH Zone pump? Electrical savings?
10. 10. ELECTRICAL SAVINGS???? 5 007’s @ 80W each = 400 Watts 400 Watts ÷ 1000 = 0.4 kW 0.4 kW × 2,200 “on” hrs = 880 kWh 880 kWh × 15¢/kWh = \$132.00/yr
11. 11. WITH ZONE VALVES… 1 007 (80W) + 5 Zone Sentry zone valve (1.44W each)= 87.2 Watts 87.2 Watts ÷ 1000 = 0.0872 kW 0.0872 kW × 2,200 “on” hrs = 192 kWh 192 kWh × 15¢/kWh = \$28.80/yr
12. 12. WITH SUPER DUPER ECM… 1 Pump (20W) + 5 Zone Sentries (1.44W each)= 27.2 Watts 27.2 Watts ÷ 1000 = 0.0272 kW 0.0272 kW × 2,200 “on” hrs = 60 kWh 60 kWh × 15¢/kWh = \$9.00/yr
13. 13. WHAT’S THE REAL COMPARISON? \$132/yr vs. \$9/yr? 93%!!! ≈ \$17.50/mo \$28.80/yr vs. \$9/yr? 55% \$2.80/mo 3/4/2014 13
14. 14. D#^* THIS Traffic JAM! Design conditions All zones calling Max flow, least resistance 15
15. 15. AS ZONES SATISFY… Less flow  flow resistance 3 lanes merge into 1 17
16. 16. SYSTEM CURVES Hydronic “fingerprint” Unique for each system Where do they come from?
17. 17. DO THE MATH, BABY! Need to calc system flow, head Head 1 ÷ Head 2 = (Flow 1 ÷ Flow 2)2 Easier way…
18. 18. MAP IT OUT…
19. 19. NOW ADD THE PUMP… Zone valves close Flow goes down Head pressure 007 Pump Curve goes up Energy In = Energy Out DP = Head  2.31 24 3/4/2014
20. 20. 5 ZONE SYSTEM 70,000 BTUH 7 GPM @ 5’ head Where does system really work?
21. 21. NUMBERS DON’T LIE… • GPM = BTUH DT × 500 • DT = BTUH GPM • DT = 70,000  500 9.5 • < 150  500
22. 22. 1 ZONE CALLING 10,000 BTUH 1 GPM @ 5’ head Where does it really work?
23. 23. NUMBERS STILL DON’T LIE… • GPM = BTUH DT × 500 • DT = BTUH  500 GPM • DT = 10,000  500 2 • 100
24. 24. The Result? And when it’s 350 out?
25. 25. 3/4/2014 31
26. 26. 3/4/2014 32
27. 27. SO BOTTOM LINE.. Zone valve FOR PETE’S SAKE… job - DT TRV job – DT or DP Don’t “oversell” PICK THE RIGHT PUMP FOR THE JOB!!! electrical savings! 3/4/2014 33
28. 28.  John Barba  Taco, Inc  1160 Cranston Street  Cranston, RI 02920  Webiste: taco-hvac.com  johbar@taco-hvac.com  Twitter: @barbajo1  Blog: jbblog.flopro.taco-hvac.com 3/4/2014 34