how to use Trace700 modeling mix-use building & 90.1-2007

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I am modeling a mixed use commercial retail, offices (3 floors) and residential tower (20+ floors) to meet and exceed 90.1-2007. Climate zone 5.  Retail and offices are heating and cooling  using water souce heat pump with condensing boiler. Heat rejection is through parkade exhaust fan system (in lieu of cooling tower). Residential tower is heating only hot water baseboard heating using condensing boiler. According to 90.1-2007, the residential units to be modeled with cooling as packaged AC unit. In Trace700,  I set up the systems accordingly, and the cooling plant for WSHP and PTAC. Heating plant with boiler.

1) how can I separate the commercial portion and the residential portion? my first run seems the program using the WSHP for heating the whole building.

2) how to model the energy saving of heat rejection to the parkade exhaust fan in lieu of cooling tower?

Thanks.

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Hey Helen-

 

1) It seems like you got a good jump on this with your systems. So the separation occurs when you assign the residential rooms/zones to the PTAC systems, and then assign the non-res rooms to the WSHP systems.

Continue this by making multiple plants (in BOTH heating and cooling!!!!) and assign those systems to the corresponding plants. Then, everything will be separated as you intend. You need to assign the residential system to a 2nd boiler plant (and not share 1 boiler plant for residential and non-res). Otherwise, all heating will be sent to the WSHP's (because the backup boiler is "linked" to the heat pumps)

 

2)  I am  not sure how the parkade system works, but you will want to model heat rejection savings by creating a custom heat rejection piece of equipment in the library (you can define the kw/ton and give it the appropriate curve, depending on the fan operation, ie CV or VAV and then selecting that as your heat rejection in the cooling equipment tab of create plants.)

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Thank you very much, Joe. I have separate the boilers for residential and commercial. Should I assign the capacity of the each plants as per design for the proposed case as per design, and leave the capacity blank for the baseline of ASHRAE to let the program calculate for it?

Now I am strugling with the fans. I have been thinking is again of the design.  The design is during cooling season,  the condensing water is pumped into a coil at a AHU located in the parkade, and AHU is exhaust parkade air. There is a spray water to pre-cool the parkade air before the the WSHP heat rejection coil.  The parkade exhaust fan will run on both HP calling and the CO sensors. In winter time, the WSHP loop is by-passed the AHU and tie to the boiler loop.  I don't  think this AHU fuctions better than the cooling tower in kw/ton point of view. The energy saving is basically less running time for the general parking exhaust fan. 

I agree what you said is the way to go, I need a custom heat rejection equipment. I will try it. Now I should also add all the parking exhaust fans to the modeling. Should I create a room, called parkade, with no heating and no cooling, just add exhaust fan systems? Or the parkade exhaust fans should be added in the plant--Misc equipment?

Thanks

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Hi Helen: How is the ventilation (ASHRAE 62.1-2007 5cfm/person & 0.06cfm/sf) provided to the residential spaces, assuming apartments and not Hotel/Dorm? Just wondering why there's heating only to the residential loads. Also, is there kitchen or laundry exhaust, again, how is treatment of outside air (for make-up air) provided? But then also, look at 90.1-2007 and conditioned space is defined as any space requiring cooling above 5BTuh/sf.

Be Sustainable -- Never let today use up tomorrow!.

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Hi Bob, the ventilation air in supplied to corridor in each floor by a make up air unit (MUA) sitting on roof. The MUA has hot water heating coil only, fed from the condensing boiler. Currently I use the 5cfm/person and 0.06 cfm/sf.  Yes, there is bathroom, kitchen range hood and laundry dryer exhaust individually in each suite.

The residential tower (apartment) has no cooling. But according to 90.1-2007, table 11.3.1-item 10 d, when there is no cooling, cooling system to be modeled and an air cooled single zone identical to propose and budget building, one unit per thermal block. Did I interpret it correctly?

The purpose of the modeling is to determine if 90.1-2007 can be met and exceed, and how many energy points can be obtained for LEED. It is expected for 2-3 points, which means to be 14-16% better than baseline building.

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Helen: I hate to ask the obvious, but how do you cool the ventilation air being delivered to the apartments or is raw outdoor air being provided to each apartment? Zone-5 is the same Climate Zone as Buffalo, NY which can still get up to 82°Fdb ambient conditions, not sure where your project is located.

Be Sustainable -- Never let today use up tomorrow!.

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