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

Brandon Nichols BrandonN at Hargis.biz
Tue Feb 27 20:47:47 PST 2007


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

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