See embedded comments.<br><br><div class="gmail_quote">On Mon, Oct 11, 2010 at 6:25 PM, Chris Toothaker <span dir="ltr"><<a href="mailto:crtooth2000@yahoo.com">crtooth2000@yahoo.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Hello eQuest users;<br>
<br>
I have 3 questions that are all related to each other. I am fairly new to energy<br>
modeling, so please help me resolve these issues that I have been struggling<br>
with for quite some time now:<br>
<br>
Our project is a 17-story residential condo building in Monterrey, Mexico. The<br>
HVAC system for each of the living units consists of a mini-split heat pump<br>
system with 3 zones sharing an exterior condenser.<br>
<br>
<br>
1) I don’t think I am specifying the proper HVAC system type:<br>
<br>
In Wizard mode under the HVAC system definition, if I select the system type to<br>
‘Split System Single-Zone Heat Pump (residential)’, system per zone, and cooling<br>
& heating sources both as ‘DX coils’ with heat pump source ‘Air’ – in DDedit<br>
mode, the HVAC system defaults to a PVVT system. Is this really the same thing?<br>
Similarly, when I model the baseline building as a ‘Packaged Terminal Heat Pump’<br>
in Wizard mode, the HVAC system defaults to a PTAC system in DDedit mode, which<br>
according to ASHRAE 90.1 is a completely different (an incorrect) system type.<br>
When I attempt to change either of these types manually in DDedit mode, none of<br>
the desired systems are available in pull-down options. How then can I<br>
appropriately set the correct HVAC system types?<br></blockquote><div><br><b>These systems are correct. You will notice that they will both default to heat pump rather than dx w/ electric cooling. The PVVT & PTAC just refer to the type of air delivery system not the heat/cool source.</b> <br>
</div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
<br>
2) There is no Space Heating occurring in my simulation:<br>
<br>
Every time I run a simulation, no matter how many options I seem to vary, no<br>
Space Heating occurs for any of the HVAC system zones. I have input the<br>
manufacturers specified heating & cooling capacities for each zone and have even<br>
tried varying the HVAC system types and capacities, but I simply cannot get any<br>
heating to occur. Allowing eQuest to autosize the capacities yields slightly<br>
more success, but if I know the actual capacities, shouldn’t I model them as<br>
such? However, I can get different results if I vary the inputs related to my<br>
last question:<br></blockquote><div><br><b>Check your thermostat schedule, if you have one. If you don't you need one.</b> <br></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
3) Lower input U-values indicate more energy use while higher input U-values<br>
indicate less energy use. This same result consistently keeps happening for<br>
windows, walls, anything. Shouldn’t the exact opposite result occur? In regards<br>
to question 2, if I input a ridiculously high U-value for the exterior walls,<br>
say 13.7 (the R value equivalent of the actual 0.073 U value), I finally get<br>
some Space Heating results...<br></blockquote><div><br><b>It depends on if your building load is internally dominated or skin dominated and if you are in a heating dominated or cooling dominated building. There was a very good discussion about just this subject within the last few weeks. Search the archive.</b><br>
</div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
In DDedit mode, under the ‘Constructions’ component, I have set up inputs for<br>
the building’s U Values using the ‘Layers input’ as the Specification Method;<br>
and for the layers/materials I basically just set up 1 layer that corresponds to<br>
the entire assembly thickness and total U-value. I originally set up the<br>
proposed design with several different layers, but I later changed it so that it<br>
could more closely relate to the baseline input because I was not sure how to<br>
set up the baseline assembly layers only knowing the required minimum R Value as<br>
per ASHRAE 90.1. Honestly I get the same result whether I use the U-value input<br>
or Layers input, but I assumed the Layers Input would be more accurate as it<br>
accounts for wall thickness.<br></blockquote><div><br><b>You shouldn't/can't use layers if you only have the R-value. You should use the U-value input in this case.</b> <br></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<br>
I sincerely thank you in advance for any help that anyone can provide. I am not<br>
an engineer, so I greatly appreciate any advice that I can get. Attached are the<br>
.inp, .pd2, and weather.bin files.<br>
<br>
<br>
Chris Toothaker<br>
Assoc. AIA<br>
<br>
SIMBIOSIS<br>
P.O. Box 132155<br>
Dallas TX 75313<br>
<a href="http://www.simbiosislab.com" target="_blank">www.simbiosislab.com</a><br>
<br>
<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Carol Gardner PE<br>
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