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You don't necessarily specify the inlet water temperature to the water heater directly -- you specify the mains water temperature that "replaces" the water going down the drain as part of the WaterUse:Connections object. You can see a diagram of this in the EnergyPlus documentation.

In your case, you want to set the mains water temperature as the desired well water temperature. It's easiest to do this by creating a schedule of the well water temperatures in Celsius, then referencing that schedule for the water system to replenish with. There are multiple ways to do this second step (less effort at the top of the following list):

You can read more about the nuances of mains water inlet temperatures within plant loops (water systems) in an Unmet Hours post.

You UPDATE 1

~~You don't necessarily specify the inlet water temperature to the water heater directly -- you directly~~

You can specify the cold water supply temperature as a schedule for the WaterHeater:Mixed object. See an example of doing that in this Unmet Hours post.

You can also specify the mains water temperature that "replaces" the water going down the drain as part of the WaterUse:Connections object. You can see a diagram of this in the EnergyPlus documentation..

In your case, you want to set the mains water temperature as the desired well water temperature. It's easiest to do this by creating a schedule of the well water temperatures in Celsius, then referencing that schedule for the water system to replenish with. There are multiple ways to do this second step (less effort at the top of the following list):

You can read more about the nuances of mains water inlet temperatures within plant loops (water systems) in an Unmet Hours post.

UPDATE 2

If you want to also account for the pump energy of the well water system, you cannot model that directly since EnergyPlus doesn't allow a plant loop connecting well water to storage tank in the same way your "Service Water Loop" connects the water heater to the water draws. As such, you have two alternatives:

  1. Do a manual calculation after the simulation using results for flow rate of well water used each hour or something similar
  2. Use the EnergyPlus Management System (EMS) feature of EnergyPlus to "embed" such calculations within the model

UPDATE 1

~~You don't necessarily specify the inlet water temperature to the water heater directly~~

You can specify the cold water supply temperature as a schedule for the WaterHeater:Mixed object. object in the OpenStudio application. See an example of doing that in this Unmet Hours post.

You can also specify the mains water temperature that "replaces" the water going down the drain as part of the WaterUse:Connections object. You can see a diagram of this in the EnergyPlus documentation. .

In your case, you want to set the mains water temperature as the desired well water temperature. It's easiest to do this by creating a schedule of the well water temperatures in Celsius, then referencing that schedule for the water system to replenish with. There are multiple ways to do this second step (less effort at the top of the following list):

You can read more about the nuances of mains water inlet temperatures within plant loops (water systems) in an Unmet Hours post.

UPDATE 2

If you want to also account for the pump energy of the well water system, you cannot model that directly since EnergyPlus doesn't allow a plant loop connecting well water to storage tank in the same way your "Service Water Loop" connects the water heater to the water draws. As such, you have two alternatives:

  1. Do a manual calculation after the simulation using results for flow rate of well water used each hour or something similar
  2. Use the EnergyPlus Management System (EMS) feature of EnergyPlus to "embed" such calculations within the model

UPDATE 1

~~You don't necessarily specify the inlet water temperature to the water heater directly~~

You can specify the cold water supply temperature as a schedule for the WaterHeater:Mixed object in the OpenStudio application. See an example of doing that in this Unmet Hours post.

You can also specify the mains water temperature that "replaces" the water going down the drain as part of the WaterUse:Connections object. You can see a diagram of this in the EnergyPlus documentation.

In your case, you want to set the mains water temperature as the desired well water temperature. It's easiest to do this by creating a schedule of the well water temperatures in Celsius, then referencing that schedule for the water system to replenish with. There are multiple ways to do this second step (less effort at the top of the following list):

You can read more about the nuances of mains water inlet temperatures within plant loops (water systems) in an Unmet Hours post.

UPDATE 2

If you want to also account for the pump energy of the well water system, you cannot model that directly since EnergyPlus doesn't allow a plant loop connecting well water to storage tank in the same way your "Service Water Loop" connects the water heater to the water draws. As such, you have two alternatives:

  1. Do a manual calculation after the simulation using results for flow rate of well water used each hour or something similar
  2. Use the EnergyPlus Management System (EMS) feature of EnergyPlus to "embed" such calculations within the model