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What is the Thermostat Setpoint Temperature at Peak Load [C] in OS's Results Summary?

asked 2021-04-12 09:29:56 -0500

wjsjch gravatar image

updated 2021-04-12 09:31:12 -0500

In my model, I have set the temperature schedules as 26℃. While in the simulation results, the indoor temperature seems to comply with the thermostat setpoint. But I don't think I've made such a setting. Because I used the VRF system and there's no thermostat at all.image description

For the heating scenario, there's also a thermostat setpoint and make the room temperature deviate from my design temperature.

Looking forward to your help!

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answered 2021-04-13 09:44:06 -0500

The report you're referencing is the HVAC Sizing Summary report, which shows summary information for the HVAC system during the summer and winter design days. Note the column that says Design Day Name. During the design day sizing calculations, EnergyPlus will use the thermostat setpoints that correspond to the "SummerDesignDay" and "WinterDesignDay" day types during these design days; see the Day Types documentation for more information.

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Yes, your answer is right! I directly modified a schedule provided in OS but I found that I forgot to change the settings in design days. Thank you!

wjsjch gravatar image wjsjch  ( 2021-04-13 18:48:39 -0500 )edit
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answered 2021-04-12 11:43:11 -0500

The Thermostat Setpoint Temperature at Peak Load listed in the HVAC Sizing Summary is the zone's setpoint temperature at the time of the peak load. In your case, the setpoint temperature at peak cooling is 24C, which is being met by the system. I'm not sure exactly what you're asking; were you expecting this to be 26C instead of 24C?

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Yes, I hope it can follow my schedule (26℃) that I set before. And I'm also confused about where does the setpoint of 24℃ comes from because I think I haven't made a setting of 24℃ in my model.

wjsjch gravatar image wjsjch  ( 2021-04-12 19:01:56 -0500 )edit

Most likely you have a ThermostatSetpoint:DualSetpoint object that lists a heating setpoint schedule and a cooling setpoint schedule.

ericmartinpe gravatar image ericmartinpe  ( 2021-04-12 19:34:00 -0500 )edit

@ericmartinpe Thank you for your reminder first. In the Inspector in SketchUp, I really find several thermostats called *Thermal Setpoint Dual Setpoint +number * which have been assigned to my thermal zones.

But I have no idea how these thermostats are generated and I want to modify them. However, I'm not able to find them in OS. So would you please tell me how to modify them in OS?

wjsjch gravatar image wjsjch  ( 2021-04-12 20:37:53 -0500 )edit

I don't use OS so I can't tell you how to modify them in OS. I recommend looking at your IDF directly in a text editor to see which schedule is assigned to which zone. Though it appears, based on your screenshot, that all zones are set to 24C (cooling setpoint) during the daytime.

ericmartinpe gravatar image ericmartinpe  ( 2021-04-12 21:02:12 -0500 )edit

OK, I'll try to look into the IDF file. Thank you!

wjsjch gravatar image wjsjch  ( 2021-04-12 21:43:41 -0500 )edit
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answered 2021-04-12 22:32:58 -0500

wjsjch gravatar image

updated 2021-04-12 22:33:54 -0500

I've looked through the IDF file and found the details of the thermostat setpoint. But it seems that nothing goes wrong. They are using the setpoint that I set before (26℃ for cooling and 22℃ for heating). But the simulation result shows that the setpoints are 24℃ for cooling and 26.7℃ for heating respectively. So weird.image description

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I'll bet if you look at the Summer/WinterDesignDay in those heating setpoint temperature schedules, you'll see the temperatures listed in the HVAC Sizing Summary report, as @shorowit indicated. The screenshot you provided isn't very helpful, because it doesn't show the Summer/WinterDesignDay temperatures in the setpoint schedules. Alternatively, you can set the SimulationControl to simulate for the sizing periods, and output the schedule values for your setpoint schedules.

ericmartinpe gravatar image ericmartinpe  ( 2021-04-13 17:23:01 -0500 )edit

Yes, I forgot to change settings in design days. It's a stupid mistake. Thank you for your help!

wjsjch gravatar image wjsjch  ( 2021-04-13 18:49:47 -0500 )edit

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Asked: 2021-04-12 09:29:56 -0500

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Last updated: Apr 13