Forum discussion
NC-2009 EAp2: Minimum Energy Performance
If we convert district steam to hot water for space heating, is there any guideline on the efficiency (of heat exchanger) for baseline model? Or do we assume the efficiency is 100% for both proposed and baseline?
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
March 3, 2015 - 5:11 pm
Whatever the efficiency is of the heat exchanger in the proposed should be identical in the baseline. Whether you count it or not depends on whether it would be considered upstream equipment. A 100% heat exchanger would be the same as not modeling one.
Haojie Wang
Energy ModelerKJWW Engineering
4 thumbs up
March 3, 2015 - 5:21 pm
Thanks Marcus. Is there a guideline to determine what should be downstream equipment? DES v2 says the virtual rate of steam is higher than hot water, does that mean it already takes into account of the heat exchanger efficiency loss in there?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
March 4, 2015 - 10:22 am
DESv2 defines upstream and downstream equipment. If the heat exchangers are in the building or on the site within the LEED boundary then they are downstream.
I do not think that the virtual rate difference is due to heat exchangers. Those numeric factors in the virtual rate calculations have always baffled me. Anyone know where they come from or what they are based on?
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
March 4, 2015 - 11:35 am
Virtual rate...Not sure about US, but there's an ACP for Europe based on a document you can download from the Sweden Green Bulding Council (www.sgbc.se) called "Treatment of Scandinavian District Energy Systems in LEED". It shows how some of these numbers are calculated based on statistics....may give some insight.