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Tankless Water Heaters Update

Tankless Water Heaters Update. Ben Schoenbauer, Research Engineer, Center for Energy and Environment MN Blue Flame Gas Association: Natural Gas Conservation Conference October 9 , 2012. Field Study overview. Objectives To determine installed performance of TWH Methodology 10 sites

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Tankless Water Heaters Update

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  1. Tankless Water Heaters Update Ben Schoenbauer, Research Engineer, Center for Energy and Environment MN Blue Flame Gas Association: Natural Gas Conservation Conference October 9, 2012

  2. Field Study overview • Objectives • To determine installed performance of TWH • Methodology • 10 sites • 25 water heaters • 8 Tank Water Heaters (TANK) • 9 Non-Condensing Tankless Water Heaters (TWHs) • 7 Condensing Tankless Water Heaters (CTWHs) • 16 months of operating with 4 week alternating modes • Extensive data logging • Homeowner surveys

  3. How Do Water Heaters Work?

  4. StWH TWH

  5. Differences in Tankless Water Heaters • Size • Residential size (input: 20-190 kBtu/hr) • Max: ~4 GPM in MN winter • Commercial size (input: up to 380 kBtu/hr) • Max: ~7.5 GPM in MN winter • Linked units (input: up to 1000 kBtu/hr) • Max: ~20 GPM in MN winter

  6. Differences in Tankless Water Heaters Condensing Non-Condensing About 90% efficiency about 80% efficiency

  7. Differences in Tankless Water Heaters • Units with storage capacity • Improved water delivery • Decreased efficiency

  8. Hot Water Quality Issues Facing Tankless Water Heaters Delayed delivery time Consistent Supply temperature Minimum flow rate for firing Performance for multiple simultaneous uses

  9. Delayed Delivery Time

  10. Storage Water Heater Outlet Temp • Gas value temperature setting should be used as the primary • Hot water tap temperature measurement can be used to for check extreme errors

  11. Min. Flow Rate for THWs to Start • Minimum flow rate to start is 0.4 GPM (Max. is 0.66 GPM) • 40% of THW require between 0.40 and 0.50 GPM • 60% of THW require between 0.60 and 0.64 GPM

  12. Performance with Multiple Uses

  13. Installation Issues

  14. Mechanical room • Higher input rates than most storage products • May require gas line or meter upgrades • Electric connection is required for each TWH

  15. Venting Non-Condensing Two Pipe Concentric Non-sealed

  16. Venting Lengths Non condensing product Condensing Product

  17. Efficiency and Savings

  18. Be careful of ratings…

  19. Small Draws Reduce TWH Efficiency Only for draws with sufficient idle time prior to draw

  20. Savings grid by GPM and use type? • non cond

  21. Savings grid by GPM and use type? • cond

  22. Occupant Satisfaction

  23. Storage Water Heater Non-Condensing Tankless Condensing Tankless

  24. Residential Water Use by Water Heater • 0 of the 10 sites had a significant difference in daily hot water consumption by WH type. • Water was consumed differently. TWH longer draws at higher flow rates, but less draws per day than tanks Commonly thought that the “endless” capacity or delayed delivery time of tankless water heaters will increase total hot water consumption.

  25. Impact on Gas Distribution

  26. Community Gas Profiles One min. gas input rates at 5 homes on a 0 deg day

  27. Questions? • Full report: • http://mncee.org/twh • Ben Schoenbauer • bschoenbauer@mncee.org This project was funded by Minnesota Department of Commerce – Office of Energy Security Minnesota Statutes § 216B.241, subd. 1e and Center for Energy and Environment

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