Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
I have tried - so far in vain - for many months to compare a "VRF with DOAS" system to a "RTU with integrated OA" system and see the roughly 25% energy advantage of the former over the latter that is predicted in other software, such as Trace-700. However, I mostly see a 0% to at most 5% advantage. I used the "VRF with DOAS" measure and even rolled my own Daikin copy from Trace-700. The latter seems to improve energy performance, but fails utterly on unmet hours - so I have put that on ice for now.
Anyway, I did notice that the measure puts in something like 1.3" for fan pressure rise, while, for example, the Daikin systems suggest something more like 0.4". Also, how can I ensure that the terminal (or system?) fans are cycling and not running constantly? Which parameter do I need to adjust for that?
Finally, I noticed in the DOAS part of the "WRF with DOAS" measure, the operation of the air loop shows up as "On/Off", rather than "VAV" - shouldn't it be VAV? Plus, the diffusors on the various thermal zones have "Control for Outdoor Air" set to No rather than Yes, while the thermal zones themselves have "Account for Outdoor Air" set to Yes rather than No. Shouldn't both be set to Yes?
| | 2 | No.2 Revision |
I have tried - so far in vain - for many months to compare a "VRF with DOAS" system to a "RTU with integrated OA" system and see the roughly 25% energy advantage of the former over the latter that is predicted in other software, such as Trace-700. However, I mostly see a 0% to at most 5% advantage. I used the "VRF with DOAS" measure and even rolled my own Daikin copy from Trace-700. The latter seems to improve energy performance, but fails utterly on unmet hours - so I have put that on ice for now.
Anyway, I did notice that the measure puts in something like 1.3" for fan pressure rise, while, for example, the Daikin systems suggest something more like 0.4". Also, how can I ensure that the terminal (or system?) fans are cycling and not running constantly? Which parameter do I need to adjust for that?
Finally, I noticed in the DOAS part of the "WRF "VRF with DOAS" measure, the operation of the air loop shows up as "On/Off", rather than "VAV" - shouldn't it be VAV? Plus, the diffusors diffusers on the various thermal zones have "Control for Outdoor Air" set to No rather than Yes, while the thermal zones themselves have "Account for Outdoor Air" set to Yes rather than No. Shouldn't both be set to Yes?
