Hi, I've been having some trouble regarding DHW modeling.
Our project is a residential building with no central DHW system, instead, each dwelling unit has its own gas instantaneous boiler (all apartments have the same model), there are 5 apartments by floor, and it is a 40 story building. Therefore we are talking about 200 DHW systems.
In order to keep things simple, the modeling methodology was the same from previous projects, to just model one equipment and the flow would be estimated from the Service Hot Water Fixtures Table from the 1.4 Service Water Heating Tab, consistent with WEp1. (flow=annual hot water cosumption/DHW schedule minutes). This methodology worked just fine for several projects. However there was never a project were the flow was incredibly high, we are talking about 60 gpm for baseline and 50 gpm for proposed (most are 6 gpm or some). So basically the flow exceeds the equipment capacity and when the flow is over 30 gpm the energy consumption remains the same, also the energy cost.
We've been doing some workaround the matter and came up with three approaches:
1.- Model 5 different DHW systems/5 different loops, were each system is one kind of apartment, this way we would be modelling 1 complete floor, and then, manually, multiply the consumption/cost by 40 floors. Make additional narratives explaining the modelling protocol.
2.- Model 1 DHW system that with a flow that account for a whole floor, and same as first approach, multiply by 40 floors. Make additional narratives explaining the modelling protocol.
3.- Multiply the DHW system capacity by the number of heaters, but this doesn't sounds right.
Which would be the most accurate, or are there new ideas here?
System data is as follows: Fuel: Gas instantaneous, Equipment capacity 0.09 MBtu/hr, HIR 1.08. Modeling software: eQuest.
Thanks in advance!