[bldg-sim] Heat recovery savings w/eQuest looks low

Mike Tillou miket at etcgrp.com
Fri Oct 14 10:32:38 PDT 2005


Randy,
 
I believe the only way to model air to air heat recovery in eQuest is to use the detailed edit mode.  You are also restricted to certain system types as well.  For example you cannot model heat recovery on heat pump systems.
 
The default values for how the heat recovery operates assume very poor operation, I think this was done to force users to go in and select exactly how the system will operate.  I suggest that you look at the documentation for eQuest / DOE2.2 available on the eQuest website.  Specifically DOE22 Vol 2-Dictonary has all the ERV keywords with a brief description.  The ERV keywords start on page 345.
 
Other than that there isn't much documentation on the algorithms they are using.  It would be nice if more information were available on how the calculation works.  I have figured out the following through trial and error.
 
An ERV summary report is created in the SIM file for each system you model with ERV.  The report appears after the SS-N report, however it does not appear in the report drop-down box in the D2Sim-Viewer.  
 
The additional fan energy used by an ERV is reported as Vent-Fan energy while the power associated with the ERV (motor to turn an enthalpy wheel) is reported as auxiliary energy.  In the ERV report these numbers are combined as total ERV electrical use.   
 
If you look at the SV-A report (detailing air-side systems) the extra static or kW/cfm you specify for an ERV does not get reported.  
 
The ERV fan energy shows up in the Monthly summary of the SS-L report but NOT in the annual breakdown at the bottom of the report.  The ERV fan energy is also included in the SS-M report. 
 
I have also had trouble using the hourly reports to calibrate fans with ERV because of how the different calculations interact.  For example the "Supply Fan kW" and "Return Fan kW" variables do not report any of the ERV fan energy use if you select the ERV Fans as "HVAC supply/Return"  
 
It's frustrating to say the least but I have always had good results once I get the ERV calibrated. 
 
Good luck.
 
Mike
 
 
Michael Tillou, PE
etc Group, Inc.
PO Box 7 Williamstown, MA 01267
Ph. (413) 458-9870   Mbl. (413) 652-1087  
---------------------------------------------------------------------- 
 

________________________________

From: bldg-sim at gard.com on behalf of Randy Wilkinson
Sent: Thu 10/13/2005 5:52 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] Heat recovery savings w/eQuest looks low


Hello bldg-sim readers,

We have been enthusiastically using eQuest 3.55 for energy modeling recently.  However, savings for air-to-air heat recovery predicted seems to always be much lower than expected.  We are comparing savings to a spreadsheet that incorporates a bin method.   The bin method calculates savings that are believable including penalties for additional fan HP, etc.  I have looked in the (hard to use) archives for this list, but can not find anything that helps.  I am curious about the following:

What does it take to model heat recovery using the wizard?

What are the important inputs that effect heat recovery savings?

I have one model that I must use detailed edit mode.  How can I add heat recovery using detailed edit mode?

If you can help me or point me to where these Q's have already been answered, I would be forever grateful.

Randy

-- 
Randall C. Wilkinson , P.E., C.E.M., LEED A.P., Mechanical Engineer 
v:509.747.2179  f:509.747.2186  i:www.lseng.com <http://www.lseng.com> 
L&S  Engineering Associates, Inc.
'High Performance Design'

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