[BLDG-SIM] eQuest 100% OSA & Heat Recovery with System Type PZRH & SZRH Only?

[Steven Gates]

Our research at the time we implemented the eQUEST/DOE-2 algorithm (approx
10 years ago) showed that 1" was typical.  However, that static did not
include any pressure drop for filters upstream of both the exhaust and the
OA inlets.  

Some manufacturers of heat-wheel ERVs state the wheels are "self cleaning",
as the airflow reverses as the wheel rotates through each air stream.  I
haven't seen one of these operating after 5 years without filters, so I
don't know whether this is a valid claim or not.

My understanding is that all other types need a filter on each airstream or
they will plug up over time.  The typical 30% filter has a pressure drop of
about 0.5".  So the total pressure drop is on the order of 1.5"  Hence the
DOE-2 default.

The energy savings of an ERV is highly dependent on how it is controlled.
If it simply runs all hours of fan operation (the eQUEST default), it will
almost certainly use more energy than it saves.  

Why such a poor default operating mode in eQUEST?  Our logic at the time was
that, if the designer does not think about and specify the required control
sequence, then the unit would be installed in the cheapest way possible,
which is to simply interlock operation with the HVAC fans.  I have observed
ERVs that run in exactly this manner...  

Steve Gates

-----Original Message-----
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Brandon
Nichols
Sent: Tuesday, February 27, 2007 8:48 PM
To: BLDG-SIM at gard.com
Cc: Sudhir Avasare; Shawn Gavras; Eric Nordlund
Subject: [BLDG-SIM] eQuest 100% OSA & Heat Recovery with System Type PZRH &
SZRH Only?

Hello All,

First some generally useful information to model heat recovery
parametrically.  The following parametric components were used to obtain
about $5,000 savings on a $90,000 per year utility bill in the Pacific
Northwest on a 'PSZ' system.  Most of them don't make much difference, the
keys are the static pressure drops across the recovery coils, specified to
be 0.5" in the HVAC design.  If the pressure drops are left at the eQuest
defaults of 1.5", the system does not exhibit any net savings... all of the
conserved natural gas is burned up in fan energy. 

RECOVER-EXHAUST  = YES
ERV-RECOVER-TYPE = SENSIBLE-HX
ERV-RUN-CTRL     = OA-EXHAUST-DT
ERV-RECOVER-MODE = OA-HEAT/COOL
ERV-TEMP-CTRL    = FLOAT
ERV-CAP-CTRL     = MODULATE-HX
ERV-MOTOR-CLASS  = PREMIUM
ERV-OA-STATIC    = 0.5
ERV-EXH-STATIC   = 0.5
ERV-FROST-CTRL   = USE-CAP-CTRL


So does this essentially answer my own question, just set the statics right
and any system can be modeled with heat recovery?  I think the answer is
'no', because believe me I tried... there seems to me some deeper issues
heat recovery-wise with some of the systems in eQuest/DOE2, not issues with
the software necessarily, just issues I don't yet fully understand... hence
any insights still appreciated.
  

BTW, all references in previous message to 'PZRH' system should've been
'PSZ'


Thanks
Brando



-----Original Message-----
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Brandon
Nichols
Sent: Tuesday, February 27, 2007 6:43 PM
To: BLDG-SIM at gard.com
Cc: Sudhir Avasare; Shawn Gavras; Eric Nordlund
Subject: [BLDG-SIM] eQuest 100% OSA & Heat Recovery with System Type PZRH &
SZRH Only?

Hello All,

In simulating a 100% outside air heat recovery system with multistage DX
cooling and supply air reset capability (40,000 CFM x2 units, in my mind a
couple of big PVVTs), it was most time-consuming to learn by trial-and-error
that heat recovery does not seem to work as expected for certain types of
systems.  For the PVVT, PVAV, and VAV system types the baseline system would
always outperform the heat recovery system, despite numerous iterations of
parameter tweaking, and even if 'extreme measures' such as high internal
heat loads were applied to force a large delta-T.

However when I at last selected a packaged or single zone reheat (PZRH or
SZRH, after getting a clue from the BLDG-SIM archives)... Voilà!,
reasonable results are instantly obtained.

My question is... do we need to stick to a list of simple systems when
simulating heat recovery, regardless of whether its a 100% outside air
system?  If so, does anyone have a list? So far, my list consists of just
PZRH and SZRH, which seems a bit limiting.

Any empirical or quantitative insight into the mysterious inner workings of
eQuest that would account for these observations much appreciated...


Regards

Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS
600 Stewart St
Suite 1000
Seattle, WA 98101
d | 206.436.0400 c | 206.228.8707
o | 206.448.3376 f | 206.448.4450
www.hargis.biz

==================
You received this e-mail because you are subscribed to the BLDG-SIM at GARD.COM
mailing list.  To unsubscribe from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE at GARD.COM



==================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM


===========================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM