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Water Usage from Well/Storage Tank

asked 2021-12-23 21:29:21 -0500

JR460's avatar

updated 2021-12-24 10:01:01 -0500

I'm trying to setup a model with the cold water from on onsite well. I've made my own measure to add the swell and tank, and connect the storage tank to the waterUse:Connections objects, and that seems to work fine.

However, I can't seem to figure how to to get the well water to be used for the water heater.

Now in the long run it would be nice to be able to do it all in Open Studio. I'd think I should be able to on the blue water showing the water supply and change that from Utility to some water storage tank, or other source. But for right now, even if having to hand edit an .idf file, I'm not sure how to make it happen.

Added the one plant loop image.

C:\fakepath\Screen Shot 2021-12-24 at 10.47.43 AM.png

Next shot shows the water equipment. The source water, the blue tank to the right, I've made a measure to change that for from a blank field in the model to the well storage tank, and that works, what I can't figure out is where in the model to change the upper left blue makeup water for the hot water plant loop. I've yet to figure out the field in any object that it might be.

C:\fakepath\Screen Shot 2021-12-24 at 10.55.35 AM.png

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answered 2021-12-24 09:08:30 -0500

updated 2021-12-24 10:44:39 -0500


~~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.


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
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Thanks, but that is not really the question. Yes I know I can set water mains temp, and I can set the well water and storage tank temp. I can connect the storage tank to water use connections objects just fine, and they pull cold from the well. The questions is with the plant loop around the hot water heater,, by default the makeup water comes from WaterMains, and I see no way to change that.

I needs to come from the well and power usage of the well pump and then later any pumps used as part of water treatment get counted in the total electrical usage.

JR460's avatar JR460  ( 2021-12-24 09:16:51 -0500 )edit

@JR460 can you update your post to include a diagram or other image of the system you're trying to define? It sounds like you have two plant loops: one with a storage tank for well water and another with a water heater that delivers hot water to the water draws. Is that correct? If so, does the well water storage tank feed water into the water heater?

Aaron Boranian's avatar Aaron Boranian  ( 2021-12-24 09:28:18 -0500 )edit

@JR460 thanks for updating the question, that helps. I've updated my answer above. I should note that the Site:WaterMainsTemperature object ALSO applies to the cold water makeup temperature entering water heaters or storage tanks in addition to the hot water going down the drains after water draws.

I also didn't realize that you needed to account for pump energy from drawing well water, since you didn't mention that in your question. I've added some thoughts on this at the bottom of my answer.

Aaron Boranian's avatar Aaron Boranian  ( 2021-12-24 10:37:14 -0500 )edit

Thank you for the answer Aaron. It seems like this should end up being a feature request for E+. The ability to provide the makeup water source for a water loop to be from storage tank, rather than just defaulting to water mains. Once E+ can deal with it, then getting OS to understand it is a later issue.

JR460's avatar JR460  ( 2021-12-28 19:02:44 -0500 )edit

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Asked: 2021-12-23 21:29:21 -0500

Seen: 75 times

Last updated: Dec 24 '21