Hi,
We have been getting the following comment from several reviewers:
"It is not clear if the preheat controls have been modeled as required by section G3.1.2.3. Note that the proposed case RLT heat recovery is considered preheat in the energy model. Therefore. the baseline should also be modeled with a preheat coil."
This is is usually happening in situations where there is a heat recovery unit in the air handling unit in the proposed building design while a heat recovery unit is not required in the baseline according to table 6.5.6.1.
We have tested to run the baseline model by inserting a preheat coil that has the following:
- supplied with hot water from the same source as the heating coil available in the same air handling unit
- controlled to acheive the same air temperature levels the exhaust energy recovery unit in the proposed building achieves at each time-step
- placed uppstream of the economizer
This leads to the baseline building model performing worse than it would without the preheat coil. Is there something I am missing here or is the reviewer's comment uncalled for?
Tyler Thumma
7GroupLEEDuser Expert
61 thumbs up
December 16, 2022 - 8:32 am
Yes, I would expect the addition of a preheat coil to the Baseline system to increase the Baseline energy use and therefore improve your savings.
The PNNL 90.1-2010 Performance Rating Method Reference Manual (https://www.pnnl.gov/main/publications/external/technical_reports/PNNL-25130.pdf) goes into greater detail about preheat coil modeling, so I would recommend following the guidance in Section 3.6.6.2 of that document.