ASHRAE ECB Heat Source for DOAS with terminal WSHP

asked 2025-05-07 11:27:20 -0500

ivanadriane
321 ●3 ●9

Hello,

Quick question for the community, has anyone dealt with selecting a baseline system using section 11 of ASHRAE when the proposed system type is a DOAS (with gas-fired coils for tempering ventilation air) and terminal WSHP.

Section 11.5.2 j. states that systems with mixed fuel heating sources, a primary and secondary system can be modeled with the appropriate heating source type. Should i map the ventilation system with fossil fuel, and the space heating and cooling system with heat pump? I think this essentially makes my baseline system identical to the proposed (DOAS with gas coil for tempering ventilation air and terminal WSHP)

Thanks,

answered 2025-05-09 10:30:50 -0500

dradair
2498 ●8 ●22 http://google.com/

how is the loop for the WSHP's being conditioned/tempered? The WSPH's can trade heat to/from the loop, but ultimately there is centralized equipment that would need to maintain the loop temperature. That may/should dictate the navigation thru the HVAC system map.

for example - if you have a dry cooler (not a fluid cooler) and an electric boiler(s), those are Air cooled condenser and electric heating. This should make SZ Systems 9's, and MZ system 3's.

Conversely - if this is a fluid cooler - it may depend upon if the capacity of the boiler or the total heating capacity of the WSHPs is larger. (90.1-2022: 12.5.2 j. 2 > mixed fuel heating > largest capacity). If the HPs are larger then it's System 6's. If the boilers are larger it ends up being 5/1 (electric) or 7/2 (fossil fuel).