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mattkoch
Posts: 1
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 Posted: Thu Jun 05, 2008 3:10 am Post subject: ... various semi-newbie questions ... |
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Hi All,
Andy Tindale suggested I post the below messages here in this forum. My apologies for the length. I'd appreciate any support y'all can provide.
I am currently moving on from editing the geometry to actually running design and simulation analyses. In this context, I have - surprise! - more questions:
1) Say I have a "box" with a pitched roof. Say box is an occupied zone and roof is an unoccupied semi-external zone. Furthermore, I check heating and cooling for box, but not for roof in the various HVAC tabs. When I do heating or cooling design, is only the heat loss/gain in box considered, or is heat/loss in roof also included? I know roof takes in a lot of heat in the summer, for example, and it gets very hot, so it must load box heavily, in addition to any load that comes in trough the walls and windows of box.
2) In 1) I do one cooling design with an uninsulated roof, then another with an insulated roof, but the total cooling loads/system sizes come out the same! How can that be? I would think when the roof is insulated, less heat can get through to the box, thus reducing the HVAC load?
3) The ventilation setup is a tad complicated. If I only want to consider mechanical ventilation and intrusion through cracks, but also want to account for air movement through the house, but not for ventilation through windows and such, what do I best check or not check off where?
4) I do not really understand the explanations in the manual about "exclude all zone natural/mechanical ventilation" in the heating/cooling design tabs. It seems to me a HVAC system designed without accounting for its own flow rate is pointless?
5) For design vs. simulation, I assume the HVAC system arrived at in heating/cooling design is then used in simulation? In my case, I get to 35 kBTU/h from cooling design, but then in summer week simulation, I get as much as 60 kBTU/h total cooling?
6 ) My ground floor has an area with floor tiles, and another area with hardwood floor. However, they are part of the same block/zone. How can I split up the floor area to have these two different covers?
Thanks and Regards,
Matt Koch, Ph.D., P.E.
Science & Technology Consultants (SciTeX) |
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Laurent_Support
Posts: 275
Location: Vincennes |
| Posted: Mon Jun 09, 2008 9:55 am Post subject: |
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Hello Matt,
| Quote: | | 1) Say I have a "box" with a pitched roof. Say box is an occupied zone and roof is an unoccupied semi-external zone. Furthermore, I check heating and cooling for box, but not for roof in the various HVAC tabs. When I do heating or cooling design, is only the heat loss/gain in box considered, or is heat/loss in roof also included? I know roof takes in a lot of heat in the summer, for example, and it gets very hot, so it must load box heavily, in addition to any load that comes in trough the walls and windows of box. |
All the building is simulate so roof space will impact your box zone. You could check the thermal balance to know how energy is flowing from a zone to another (through internal floor in you case).
| Quote: | | 2) In 1) I do one cooling design with an uninsulated roof, then another with an insulated roof, but the total cooling loads/system sizes come out the same! How can that be? I would think when the roof is insulated, less heat can get through to the box, thus reducing the HVAC load? |
I think you do not set the right surfaces, to be sure in the Navigation tree go down to the surface level and verify in the Construction what king of construction is actually used.
| Quote: | | 3) The ventilation setup is a tad complicated. If I only want to consider mechanical ventilation and intrusion through cracks, but also want to account for air movement through the house, but not for ventilation through windows and such, what do I best check or not check off where? |
If you mean you want calculated natural ventilation through cracks but not for doors and windows. You should parameter windows/door operation to Off every time (Openings tab).
| Quote: | 4) I do not really understand the explanations in the manual about "exclude all zone natural/mechanical ventilation" in the heating/cooling design tabs. It seems to me a HVAC system designed without accounting for its own flow rate is pointless?
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This is only a facility you may not need it but some one on other project could. It avoids to change all your schedules if you want to compare thermal efficiency with/without air flow.
| Quote: | | 5) For design vs. simulation, I assume the HVAC system arrived at in heating/cooling design is then used in simulation? In my case, I get to 35 kBTU/h from cooling design, but then in summer week simulation, I get as much as 60 kBTU/h total cooling? |
Take care, there is many design options (ASHRAE, Unitary, fan coil, air temperature or operative, solar distribution) you will find in the Simulation dialog but not have set identically. Also, the design day is not exactly you should have in Simulation because simulation uses the hourly weather data.
| Quote: | | 6 ) My ground floor has an area with floor tiles, and another area with hardwood floor. However, they are part of the same block/zone. How can I split up the floor area to have these two different covers? |
Draw a subsurface on the floor to enter two constructions, one for the tiles (for instance as Ground floor construction) and one for the wood (as Subsurface construction).
Hope it will help you!
_________________
Laurent |
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