Setpoint Manager OpenStudio

asked 2016-01-21 06:38:12 -0600

Dustin
1065 ●3 ●16

updated 2016-01-21 08:04:35 -0600

I am wondering which setpoint manager I should be using for AHU supply air temperature. Basically I originally modeled the building with a SetpointManager:Scheduled for a constant temperature supplied by the AHU for the entire run period. I know have further information that the supply air temperature directly from the AHU can be between 13 and 18°C. Basically the temperature supply would depend on the zone requirements as expected.

Should I be using the SetpointManager:ScheduledDualSetpoint? If so will the program automatically determine the supply air temperature based on the zone requirements? ie. will it supply the 18°C during the heating requirement days and 13°C on the cooling requirement days?

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answered 2016-01-21 07:57:47 -0600

Julien Marrec

29726 ●94 ●76 http://www.effibem.com/

SetpointManager:ScheduledDualSetpoint is designed to work with PlantLoop objects, not AirLoop.

As stated in the [documentation]:

Currently the DualSetpoint Manager will be used with PlantLoop when the Plant Loop Demand Calculation Scheme is set to DualSetpointDeadband.

As far as what SetpointManager you should use, you need to get the actual proposed sequence of operation from the MEP and really understand it.

If you know that your building will be equipped with a Building Management System (BMS) and that this system will be polling information from the zones themselves to get for example the position of the VAV boxes and reset the temperature accordingly so that the worst zone VAV box is fully open, then I would use a SetpointManager:Warmest object (doc). Set the minimum Setpoint temperature to 13°C and the maximum setpoint temperature to 18°C.
If you won't have such a system, then it's likely that you should use SetpointManager:OutdoorAirRest (doc). Set it to dry bulb and then pick low and high outdoor air temperature and it'll interpolate linearly between the two. For example, it might be define that if outside air dry bulb temperature $OAT_{DB}$ is 10°C (low cooling load), then $SAT$ is 18°C, and if $OAT_{DB}$ is 18°C then $SAT$ is 13°C. It would result in the following behavior.

Outdoor Air Reset

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Thanks for the answer. I will try the first option because there is a BEMS in place. Will let you know if this works the way I am wanting it too.

Dustin ( 2016-01-21 08:15:01 -0600 )edit

The first method didn't work as I expected. It still kept the temperature pretty well constant near 18C. Will try the second option now. I am wondering how you determine what temperatures I should use. I am in a northern climate where the temperatures can range between -20 and 30. Just wondering what I should use then? Thanks again.

Dustin ( 2016-01-21 08:55:36 -0600 )edit

That just means that it didn't have to supply 13°C ever...

What's your building type? If residential I'd say Lo 60°F Hi 75°F, for an office it'd shift it lower because its got a lot more internal gains.

Julien Marrec ( 2016-01-21 09:14:55 -0600 )edit

I know the building would have had 13C air supplied to the space during the summer months.

The building is an office building. I will try again.

Dustin ( 2016-01-21 09:25:37 -0600 )edit

Still no luck. I should be using the SetpointManager:Warmest and not the SetpointManager:OutdoorAirReset. But it is not working in the way I would expect it to. Is it possible to use the Warmest and Coldest SetpointManagers at the same time on the same node? Or would that cause some errors?

Dustin ( 2016-01-21 13:50:47 -0600 )edit

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