[Equest-users] ERV in Ottawa

[Kelsey VanTassel]

I find that ERVs use more energy when the Make-up Air Temp Ctrl is specified as "Float". In other words, there is no temperature control of the air leaving the ERV. For an enthalpy wheel, choose "Modulate HX". This allows the rotational speed of the wheel to vary in order to maintain a particular leaving air temperature.

Kelsey Van Tassel
Mechanical Engineer | kvantassel at sustaineng.com<mailto:kvantassel at sustaineng.com>
608.836.4488 ext. 20 | Fax: 608.836.4477

Sustainable Engineering Group
901 Deming Way, Suite 201
Madison, WI 53717
www.sustaineng.com<http://www.sustaineng.com/>


From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Fleming, Joe
Sent: Thursday, December 09, 2010 2:12 PM
To: Daniel Knapp; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] ERV in Ottawa


I have come across this a lot in eQuest, and the solution for me is usually to only run the ERV in cooling mode, because I am usually in a mostly cooling climate.

I am not sure exactly how eQuest handles the ERV controls under "Operating Mode:", but it does say something in the help file that leads me to believe choosing heat/cool is a bad idea for an operating mode...



"OA-HEAT/COOL           the default for enthalpy ERVs, indicates that the ERV will operate whenever the absolute value of the differential between the outdoor air and the exhaust exceeds the specified differential."



[cid:image001.png at 01CB97AE.8416EDF0]





The difference between OA cooling only or OA heating only and OA heat/cool is the term "absolute value".  If the conditions are such that the absolute value between the exhaust and outdoor airflow is less than 5 degrees the ERV is off.  If it is greater than 5 degrees the ERV comes on.  So the entire period where you are in cooling mode but it is less than 70 degrees outside, (assuming a 75 degree space temp, abs|69-75| = +6, the ERV is adding to your cooling load and is hurting your cause, because we chose OA heat/cool.



If there were a way in eQuest to use an ERV in heat/cool mode but eliminate the absolute value part and make it +5 for cooling and -5 for heating, instead of Del_T > abs|OA-EA| then that would allow the ERV's to operate perfectly and operate in the same fashion as the standard ERV sequence in the field.



Does anyone know if this is correct, or if eQuest treats the control sequence different from what is described above?







Joe Fleming

E.I., LEED AP BD+C, BEMP

Mechanical Engineer I



TLC Engineering for Architecture

Your 2030 Challenge Partner



800 Fairway Drive, Suite 250

Deerfield Beach, FL 33441-1816



phone:Â

954-418-9096

fax:Â

954-418-9296

direct:Â

954-418-4591

website:Â

www.tlc-engineers.com







-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Daniel Knapp
Sent: Thursday, December 09, 2010 12:56 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] ERV in Ottawa



Hello,



I've been trying to understand how ERV works because I am finding the energy savings to be somewhat less than I had expected.  Ottawa has a very cold climate in the winter and a warm, humid climate in the summer and I would expect enthalpy wheels to be a very good energy saving strategy.  Instead, I am finding that in many cases the building uses more energy and in the best case scenario (OA exhaust DH, mixed air reset, modulate HX) on a VAV system saves only 0.15%.  I have built a simple box model with one system in a two-storey office building and tried a number of different control strategies (see attached tables for results).  I have tried a VAV and a SZ system.  The ERV is able to save marginally more energy in the SZ system, but in neither case are the results what I was expecting.



My question is this:  are these results to be taken at face value and believed or is there a better way to model ERVs in a Canadian climate?  It seems very unlikely to me that ERVs cannot be controlled in such a way as to save significant energy in a climate of extremes.  (.inp file attached as well).



With thanks and best wishes,

Dan





-

Daniel Knapp, PhD, LEED® AP O+M

danielk at arborus.ca



Arborus Consulting

Energy Strategies for the Built Environment www.arborus.ca

76 Chamberlain Avenue

Ottawa, ON, K1S 1V9

Phone: (613) 234-7178 ext. 113

Fax: (613) 234-0740




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