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Trane Trace Energy Modeling Ventilation OA hourly amount

asked 2020-02-12 15:51:15 -0600

KLim gravatar image

updated 2020-02-12 17:25:47 -0600

Hi. I am working on energy modeling with Trane Trace 700, so I have proposed model and baseline model. Based on the code, I am using the minimum OA for thermal zones in both models with same amount. However, the result from Trane Trace shows me different outdoor air amount in hourly. The total amount of OA is same in Airflow report however, in hour Ventilation chart shows me dramatic difference between baseline model and proposed model. How that hourly OA amount is calculated? Is that space peak? or coil peak?

Thank you.

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answered 2020-02-12 21:03:26 -0600

tj.olson gravatar image

Hi KLim, I would suggest you contact CDS support. 608-787-3926

Since you are speaking of a specific project file you are working on it would be useful to send in the archived (.taf) file attached in your email so we can understand your question better. Also if you have screen shots showing the differences in your reports that would also be helpful.

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Hello, I am not sure if you were able to contact CDS support. If you haven't I would still recommend you reach out so they can look into your question at a deeper level. In TRACE 700 the VRF system is allowed to modulate down to 10% airflow for low load operation. PTHP systems are constant volume only. This more than likely explains the large difference in cfm between the two. However, to answer the question with more confidence it would be best to see your file. That way the ventilation schedules and any ventilation settings at the system level can be reviewed.

tj.olson gravatar image tj.olson  ( 2020-02-18 08:46:44 -0600 )edit

answered 2020-02-13 07:53:49 -0600

updated 2020-02-13 07:55:20 -0600

Since OA is controlled based on HVAC operation, it might be that the OA differs because the air loop operation is different (e.g., building loads are different). You should also include information about the type of HVAC system to better understand possible reasons for the difference you see.

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Hi. Thank you for answering. The project is about residential building and proposed model has VRF system for residenatial area. In baseline model, obviously having PTHP. The loads for both model are different based on different construction set. I believe HVAC system operates based on the setpoints in the model and ventilation schedule. But still do not get why different amount of outdoor air hourly.

KLim gravatar image KLim  ( 2020-02-13 10:17:19 -0600 )edit

Does baseline PTHP use constant fan mode or cycling fan mode?

rraustad gravatar image rraustad  ( 2020-02-13 10:57:52 -0600 )edit

Hi. It was constant fan mode as given in Trane Trace followed by ASHRAE 90.1

KLim gravatar image KLim  ( 2020-02-13 11:09:20 -0600 )edit

Can you compare the hourly supply air flow?

rraustad gravatar image rraustad  ( 2020-02-13 11:17:44 -0600 )edit

The main cooling and heating coils for both model, main heating coil airflows are same for both model but having huge difference in cooling

KLim gravatar image KLim  ( 2020-02-13 11:28:19 -0600 )edit

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Asked: 2020-02-12 15:51:15 -0600

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Last updated: Feb 13 '20