Supply air temperature reset based on return air temperature on eQuest

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Hi all,

I am trying to model supply air temperature reset based on return air
temperature on eQuest 3.64.

HVAC Input function samples on DOE2.2 Vol3- Topics provides a sample input
function for Cold Deck Supply Air temperature reset using return air
temperature.

I am new to eQuest input functions. Does anyone know how code for HVAC
input functions should be entered to the program, is there someplace that I
can paste the sample code ? BDL file or INP file.

Some basic insight in to HVAC input functions will be highly appreciated.

Or is there an easy way to model supply air temp reset based on return air
temp.

Thanks,

Gamage Lakshan,

EE Engineer

LEED AP BD+C, BEMP, B Eng

Gamage Lakshan's picture
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Gamage,
Input functions are not implemented in DOE2.2. This is made clear in the DOE22Vol3-Topics manual:

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Sustainability & Energy

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Jones, Christopher2's picture
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Hi Jones,

Thanks for the quick reply.

Do you know about another way that I can control the supply air temperature
based on return air temperature. Note - The HVAC design requires the AHU
fans to run at constant volume all the time to maintain room pressure.

Thanks,
Gamage

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Hi Gamage,
I don?t know of a direct way to control SAT based on RAT in eQUEST. Here are some approaches to consider:

1.) Set the ZONE keywords for THERMOSTAT-TYPE, THROTTLING-RANGE and (in eQUEST 3.65/DOE2.3) THERMOSTAT-LOCN to best approximate your control strategy. You should use a PROPORTIONAL or REVERSE-ACTION thermostat type if you want to adjust the heat addition/extraction rate in proportion to the difference between the zone set point and the zone temperature (which should match or closely match the RAT).

2.) Set the SYSTEM:COOL-CONTROL to WARMEST to adjust the cold deck temperature based on the highest zone temperature (highest RAT).

3.) Set the SYSTEM:COOL-CONTROL to SCHEDULED and create a COOL-SET-SCH and/or HEAT-SET-SCH to force the cold/hot deck supply air temperatures. You could set the SAT in these schedules to be consistent with the thermostat schedules, space loads, cooling/heating season, or whatever else is driving your control strategy.
Note that you can select a SYSTEM:TYPE of PVAVS or VAVS to enable the COOL-CONTROL keywords, even if your actual system is constant volume. You would just want to set the system for constant volume FAN-CONTROL and 1.0 for MIN-FLOW-RATIO.
Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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T: (585) 698-1956 F: (585) 325-6005

bbishop at pathfinder-ea.com www.pathfinder-ea.com

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Hi Gamage,

As per me at the higher return air temperature the supply leaving air
temperature should be set to the higher values among all. It can be kept as
lower temp among all but it will have to cool the air drastically.
Also at lower return air temperature the supply leaving air temperature
should be higher value among the two supply leaving air temperature.

In eQuest the following method is used to have the reset temperature in the
Air side.

The outside temperature can be used as supply air temperature.
Here is the snapshot for that which you can link in the cooling side in th
Air side as the Cold deck schedule.

[image: Inline image 1]

The line graph obtained from the above supply temperature and supply
leaving air temperature is like this:

[image: Inline image 2]

As per this reset the temperature above and below the reset behaves with
no temperature change. It will have another cooling side aspects
controlling it.
But as per ASHRAE 90.1 it ill be a linear functioning the SAT reset.The
temperature shall be functioning in a linear proportional way to have
increase in the temperature.
It is just an example. There can be several go around.

Thanks,
Sharad.Kumar.

........................................................................................................................................

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Gamage Lakshan via Equest-users
*Sent:* Monday, December 11, 2017 10:35 PM
*To:* equest-users at lists.onebuilding.org
*Subject:* [Equest-users] Supply air temperature reset based on return air
temperature on eQuest

Hi all,

I am trying to model supply air temperature reset based on return air
temperature on eQuest 3.64.

HVAC Input function samples on DOE2.2 Vol3- Topics provides a sample input
function for Cold Deck Supply Air temperature reset using return air
temperature.

I am new to eQuest input functions. Does anyone know how code for HVAC
input functions should be entered to the program, is there someplace that I
can paste the sample code ? BDL file or INP file.

Some basic insight in to HVAC input functions will be highly appreciated.

Or is there an easy way to model supply air temp reset based on return air
temp.

Thanks,

Gamage Lakshan,

EE Engineer

LEED AP BD+C, BEMP, B Eng

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