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Jason,<br>
<br>
Couple of things (not having looked at the file yet)...<br>
<br>
Firstly, on the 2nd tab of the heat recovery are static pressure
values for added static (supply and exhaust) across your heat
recovery heat exchanger -- these are added to the total fan static
pressure. Further, they are NOT reported in the SV-A report, but
are on the ERV report and are included under ventilation fan energy
in the BEPS etc. <br>
<br>
Secondly, OA-FROM-SYSTEM does not do what the name suggests. There
is no actual air transfer. What DOE2 really does right now is set
the OA temperature for the borrowing system equal to the return air
temperature of the lending system. That much is fine. The issue
comes in when you do heat recovery -- it is recovering heat based on
the dummy zone which has none of your internal heat gains. So, the
return air temperature you are recovering from is not correct. The
exhaust air from the borrowing system does NOT go back to the
lending system (in fact there is no air transfer as already
mentioned). So, to model heat recovery correctly, you need to watch
the dummy system exhaust air stream properties. Being from Canada,
I am much more interested in heat recovery than cooling. As such, I
am pretty happy to ignore the cooling impact but that may not be the
case for you. To model heating heat recovery correctly you have 2
options. One is to put a dummy internal heat gain in the dummy zone
and tweak it until the exhaust air properties meet your
requirements. I am lazier than that. What I do is use the frost
control of the heat recovery unit tab, using the EA preheat to fix
the exhaust air stream at a set value. It should likely be 75F but
I tend to use 72F to be conservative on the heat recovery. So, I am
preheating the exhaust air to 72F. I use an electric coil to do
this (again, still in the 2nd tab of the heat recovery coil) -- and
I put this electric heat on a separate meter with no cost. I also
verify that the heating on this meter is some reasonable fraction of
my lighting and equipment energy as that is what it is mimicking. <br>
<br>
I cannot wait until eQUEST does DOAS for real but for now it is
important to understand what it is doing and workaround accordingly.<br>
<br>
Regards,<br>
<br>
Brian<br>
<br>
On 3/28/2012 6:31 AM, Jason Quinn wrote:
<blockquote
cite="mid:CAHA4r_=d-N8oh=BMqwed_7jbjwFepszYOUDd-fzxN1-xog=KoQ@mail.gmail.com"
type="cite">
<pre wrap="">So this is pretty odd I'm running a simple SD wizard generated office
building and adding the DOAS to it in DD edit mode. The DOAS works as
expected (Thanks to Brian Fountain) slightly lowering the space
heating & increasing vent. Fans. over a case without the DOAS. Now
when I add a heat exchanger to the DOAS (PVVT) it causes the fan usage
to go nuts increasing Vent. Fans from 0.2E6 kWh to 6.5E6 kWh while the
space heating drops from a resonable (I think) 3.7E9BTU to 0.4E9BTU.
If someone could point me in the right direction to sort out why the
heat exchanger is causing such a huge increase I'd really appreciate
it.
I have played with the DOAS fan schedules and can effect the increase
downwards but not enough to make this reasonable. I've attached the
DOAS with Heat exchanger .pd2 & .inp file. To see the results without
the heat exchanger just turn it off. I'll attach my weather file as
well so that it's easier to look at my file.
Thank you for the help.
Jason
</pre>
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