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Lead ASHRAE Article Identifies AFUE Alone Fails to Indicate Performance and Deep Energy Savings Potential
The industry’s preeminent heating, air conditioning and refrigeration engineering society, ASHRAE, has published "Performance of Combination Hydronic Systems" by Thomas Butcher, PhD, as the December 2011 cover story in the ASHRAE Journal. This article highlights that the current practice of labeling heat and hot water appliances with AFUE alone fails to indicate the actual annual performance and to identify the deep energy saving potential possible with a system upgrade.
Energy Kinetics has always been focused on delivering the best efficiency, and System 2000’s performance stands out in the study with the highest annual efficiency and the lowest idle loss (0.15%). System 2000 significantly outperforms the 95 AFUE modulating condensing boiler and all other systems tested from around the globe. Our unique purge control strategy, low mass design, and high performance water heating system results in the top rating, and virtually eliminates the effects of oversizing. The next best system in the study had an idle loss of four times System 2000, which resulted in higher annual fuel use and significantly lower efficiency during hot water production.
| Thermal Efficiency (%) |
Idle Loss (%) |
Calculated Annual Efficiency (%) |
Estimated DHW Production Efficiency (%) |
72
|
4 |
51 |
20 |
83
|
2 |
68 |
36 |
88
|
1 |
77 |
53 |
88
|
0.5 |
80 |
67 |
88
|
0.15 |
83 |
80 |
Note the effect of small changes in idle loss on annual efficiency. Example Analysis of the Performance of Integrated Hydronic Systems. Location: Albany, NY. Design Day Maximum Heat Load = 40,000 Btu/hr. Hydronic System Rated Maximum Output = 110,000 Btu/hr. *
About Oversizing: Low idle loss also virtually eliminates the effects of oversizing heating equipment. This means that the heating system can be upgraded before building envelope improvements, without an adverse effect on efficiency. Very high efficiency homes with very low design day heat loss may require significantly higher output to satisfy domestic hot water needs. With low idle loss, small and large heating demands can be satisfied with near steady state thermal efficiency.
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Note the substantial reduction in performance with only a small change in idle loss.
Example results. Effect of system oversize on annual efficiency at two different idle loss levels. Assumed thermal efficiency = 86%. Location = Albany, N.Y., design day heat load = 40,000 Btu/hr, domestic hot water load = 64.3 gal/day*
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Note the substantial reduction in performance with only a small change in idle loss.
Example results. Effect of system oversize on annual efficiency at two different idle loss levels. Assumed thermal efficiency = 86%. Location = Albany, N.Y., design day heat load = 40,000 Btu/hr, domestic hot water load = 64.3 gal/day*
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Figures and tables source: ASHRAE Journal, December 2011, pp 39 – 40.
[ Read the Article ]
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The summary concludes "In addition to steady state, full load thermal efficiency, the idle loss is an extremely important parameter which impacts the performance of the system during low load periods, including DHW only, as well as the annual efficiency. These idle losses can be controlled through a combination of better insulation of boilers and indirect tanks (where used) and control strategies."
Energy Kinetics leads the industry in optimal boiler and tank insulation, and with integrated control strategies for the best delivered performance in a highly reliable package, all made in the USA.
Contact us for your next project – you’ll be glad you did!
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