How to model service hot water for midrise apartments

edit

(I realize this is in the gray area between a comment and an actual answer)

@Julien, thank you very much for the helpful information, I will study these options carefully. However, I did not find any measure for service water heater in BCL library, could you please provide a link to this measure? In addition, this is a LEED project and the baseline model should be consistent with ASHRAE 90.1-2007 modeling protocol, hence I have to provide answer to the entire question that you mentioned from the standard for the baseline model, is this correct? Thanks again for all your help!

If there's no mesure in BCL you have to create it. It'll be a simple mesure though.

Not sure I understand what's your actual question about the LEED and ASHRAE protocol

Julien, thank you for your response. I am not quite familiar with creating measures, so thought using following procedure to model SHW for the apartment units of the model: 1. Create a new plant loop with a water heater and water use connections 2. Select an unconditioned space in the underground parking garage that is not part of the building total floor area 3. Select a multiplier equal to the number of apartment units within the building for the Thermal Zone of the selected space. 4. Select this space as “Space Name” for each of the Water Use Equipments Is this procedure correct?

You actually don''t have to specify a space name in the water use equipment. This is optional, to account for heat gains (latent).

This would work if you only care about getting hot water heating consumption in your model, but keep in mind it's a simplification

Julien, thank you for the confirmation and additional information, the only purpose of selecting a space name for the water use equipment was to use multiplier (total number of the residential units), is there other way(s) to select multiplier for water use equipment?

just play with the GPM. For example I usually end up with something like 20 GPM with a schedule to model DHW consumption of an entire multifamily building.

Thank you very much for your help, your guidance solved my problem. I revised the peak flow rates of the fixtures in Loads tab per total building flow and simulation results showed the expected values.

I still need some advice on this subject. When you set the Max Loop flow rate to 20 GPM and run the model what was the percentage of annual SHW energy consumption compared to the whole building annual energy consumption? In my model, the Max Loop Flow Rate is 47.137 gpm and annual energy consumption of SHW is only 2% of the annual energy consumption of the building, which is not realistic. With the same fixture definitions: lavatory faucet 2.2 gpm, shower 2.5 gpm and kitchen sink 2.5 gpm I changed the Max Loop Flow Rate to Autosized, but this did not change the simulation results.

Max loop flow rate doesn't have to be set. I usually use one water use connection with one linked water use equipment definition where I set a flow rate and a schedule multiplier. Based on that, you should be able to calculate the water heating consumption you expect and make sure it matches more or less. One thing to beware is whether your consumption will be categorized as water heating by E+ or not (if you use a waterheater:mixed it will, if it's a boiler (via a HX or not) it probably won't).

Thank you very much for your response. This process works, I can get the expected energy consumption related to SHW.