I have a system that produces hot water with a heat pump. Now I want to add a hot water tank to soften the peaks in demand.
I'm using: WaterHeater:Mixed with 0W but I don't understand the difference between "Use side inlet node name" and "Source side inlet node name".
Source and Use side nodes are meant to represent the water heater used as a source (provides hot water to a component) or where there is heat exchange between the tank and another fluid (a use of the tank as a sink/source). In reality there is no real difference since each of these nodes adds or extracts heat to/from the tank in the same way mathematically.
@rraustad There appears to be a difference. I modeled a stratified air source water heater in OpenStudio. Both source (the heat pump) and use (Plant Water Loop) were connected to the same two nodes (Use Side Inlet and Outlet Nodes). This left the Source Side nodes unused with the result:
** Severe ** InitWaterThermalTank: Detected problem for stratified tank model. Model cannot be applied.
** ~~~ ** Occurs for stratified tank name = HPWH TANK
** ~~~ ** Tank volume = 0.1893 [m3]
** ~~~ ** Tank use side volume flow rate = 4.7685E-003 [m3/s]
** ~~~ ** Tank source side volume flow rate = -99999.0000 [m3/s]
** ~~~ ** Nominal tank change over rate = 39.70 [s]
** ~~~ ** Change over rate is too fast, increase tank volume, decrease connection flow rates or use mixed tank model
** Fatal ** InitWaterThermalTank: Simulation halted because of sizing problem in stratified tank model.
Asked: 2022-06-06 05:19:52 -0600
Seen: 247 times
Last updated: Dec 05
