Dear All,
As per the Appendix G requirement, for my project, the Basecase HVAC system
has to be system type- 2 which is Package Terminal Heat Pump, DX Cooling,
Electric Heating. (from Appendix G)
When this is selected from the appropriate menu and the simulations are
done, the output file indicates the system type as PTAC. This usually stands
for Packaged Terminal AC. In principle it can also mean Packaged terminal
Heat Pump as AC is also a Heat Pump.
Can PTAC be taken as to mean Packeged Terminal Heat Pump as well as given in
the output file or is eQUEST performing something starnge ??
Thanks in advance for any clarification
Anura
Anura,
Yes, the PTAC is a PTHP when you select heat source as "Heat Pump". These two units cool the same way, but differ in how heating is done.
HTH,
________________
Demba NDIAYE
i just received a clarification about the f-factor for 4" slab on grade
vs 6" slab on grade for the purposes of leed review. the usgbc response
(through the website/contact section) is:
"Thank you for your technical customer service inquiry regarding LEED-NC
v2009: EAc1. It is assumed that you are following the Performance
option (Option 1) of EAp2 & EAc1, using Appendix G of ASHRAE 90.1.
Yes, the 4" slab (modeled & specified) should meet the requirements for
LEED purposes. Please note that there is no F-factor requirement listed
as part of the Mandatory provisions of Section 5.4; it is only listed
for the Prescriptive approach requirements of section 5.5, which is not
necessary for LEED EAp2/EAc1 compliance.
If you model the slab as a 4" slab with 12" of earth (0.75 soil
conductivity) underneath it in the Proposed Case model, the energy model
should indicate the U-value of this slab. You could simply state in
your submittal (4" slab modeled with 12" of earth with 0.75 Btu/h-ft-?
soil conductivity, U-value calculated within energy model as x.xx).
Please be careful to avoid the common mistakes of modeling the slab
without any earth beneath it, or modeling the Baseline slab "U-value"
using the "F-factor" values from Tables 5.5-1 - 5.5-8. F-factors and
U-values are not interchangeable, of course. Also, if the energy model
cannot reflect an F-factor, please model the Baseline slab-on-grade
floor as a 6 inch concrete slab over earth with a soil conductivity of
0.75 Btu/h-ft-degree F, in accordance with A6.1.
We trust that this will help you with your process and we thank you for
your interest in LEED Rating Systems.
If you have any further questions, please feel free to contact us via
the GBCI contact page: http://www.gbci.org/contactus.
Regards,