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NC-v4 EAp2:Minimum energy performance

Water Heater Efficiency per Table 7.8 of ASHRAE 90.1-2010

Hello,

I'm currently working with two (600,000 Btuh, 130 Gallons, 97 EF) boilers for a dormitory building. From my interpretation of Table 7.8 the equation I'm suppose to use is 80%Et(Q/800 +110sqrt(V)) SL, Btuh. From I've what I've read, I'm suppose to disregard the 80% Et and that leaves me for the remainder of the equation to get 2004 Btuh as my standbyloss for my baseline water heater. A few questions I had were:

1. Should I leave this number in the service water heating section as what I calculated asfor the SL or do I need to convert this to an EF ?

2. Is there a way to convert to this to an efficicency (EF)?

In previous projects my co-worker worked on they always left as a % EF and used that to calculate an energy usage in MBH/hr for each water heater. The then plugged that energy usage into Trace 700 for the base utilities for the water heaters.

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Fri, 04/05/2024 - 14:49

I would suggest you model the water heater with the 80% thermal efficiency, and add the calculated standby loss (2,004 Btu/h in your case) to the hourly water heating load. However, you would also need to do the same for the Proposed water heater. 

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