[bldg-sim] equest recovery

[Brian Thornton]

This is a great discussion. There are a lot of control strategies to
mitigate the increased cooling and fan energy impact of energy and heat
recovery units in eQuest. 

However, small (residential) ERVs and HRVs don't have these control
strategies available generally.  The only control option that seems to be
common, is to allow the energy recovery wheel to be turned off for an
economizer temperature range.  ERV/HRV fans still have to run, as there is
no bypass.  Are there small units that do have a full range of control
options?

The eQuest simulation suggests that the units without sophisticated
controlsmay cause a net increase in fan energy, and cooling energy that
offsets or more than offsets the heating energy savings, at least in our
mild Portland climate.  

Do others see similar simulation results for simple ERVs and HRVs, and does
that mean that these type of units may not save much if any energy?  Is that
not true for more extreme weather locations?

Brian

Thornton Energy Consulting
p. 503-231-6600 f. 503-231-3555
thorntonenergy at comcast.net


-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Graham &
Megan
Sent: Thursday, February 02, 2006 12:01 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] equest recovery

Extending on what Brian has said, a few years back I had a good look at the
hourly output to understand what the heat recovery controls were doing.  I
was using dry bulb controls and ran simulations with a number of
diiferential dry bulb cut-out temperatures.  I found that 6-8DegF was about
optimal for the climate / building I was studying.  The moral of the story
was be careful with dry bulb controls as they will often bring in moisture
and increase loads if you are using a small differential DT.  Conversely
setting a low differential enthalpy control will increase sensible cooling
and on coil temperatures under some conditions ...

Periodically there is a thread on this forum about EQuest's ERVs and heat
recovery and non intuitive results.  My experience has been that if you
understand what the various configuration / control inputs mean then you
will get reasonable hourly and thus annual energy results ...

Regards,
Graham
----- Original Message ----- 
From: "Brian Fountain" <bfountain at greensim.com>
To: <bldg-sim at gard.com>
Sent: Friday, February 03, 2006 3:42 AM
Subject: [bldg-sim] equest recovery


> Note that the default "Make-up air temperature control" for energy
> recovery ventilators in eQUEST is to "Float" the supply air
> temperature -- meaning they will continue to recover heat regardless
> of discharge air temperature, increasing the cooling load unless the
> default is changed.   Changing it to "Mixed Air Reset" has a
> considerable effect -- eliminating most of the excess cooling.
>
> I guess it depends on your economizer operation -- whether it is on a
> fixed drybulb or on differential drybulb or enthalpy.
>
> -----Original Message-----
> From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Brian
> Thornton
> Sent: February 2, 2006 11:23 AM
> To: bldg-sim at gard.com
> Subject: [bldg-sim] equest recovery
>
>
>
> One thing I wondered about this was the amount of cooling increase
> showing
> with eQuest modeling of an ERV.  I have not done a real study, but
> tried
> modeling one case without any added fan energy, and running it with
> the
> economizer active with the ERV run control set to WHEN-MIN-OA, which
> turns
> off the heat recovery when the economizer is active (stops the wheel
> for a
> wheel type).  Even with these two strategies, which should eliminate
> the
> bulk of increased cooling, there is still significant increased
> cooling.
>
> Have others tried this, and are there other explanations for the
> cooling
> results?
>
> Brian
>
> Thornton Energy Consulting
> p. 503-231-6600 f. 503-231-3555
> thorntonenergy at comcast.net
>
>
> -----Original Message-----
> From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Andy
> Lau
> Sent: Wednesday, February 01, 2006 12:17 PM
> To: bldg-sim at gard.com
> Cc: bldg-sim at gard.com
> Subject: [bldg-sim] equest recovery
>
> Of course one cannot say conclusively what is happening here, but my
> work with heat recovery systems has shown that they often increase
> cooling energy for two reasons:
>
> 1.  They can eliminate the possibility of operating an air-side
> economizer and getting "free-cooling."
> 2.  The fan power associated with heat recovery can be significant,
> which will also increase cooling load.
>
> I attach a paper that was presented at Simbuild 2004 on this subject
> (not attached to bldg-sim because it exceeds allowable size)
>
> Andy Lau, P.E.
> 7group, www.sevengroup.com
>
> fernando varela wrote:
> > Hello:
> >
> > I'm trying a Packaged VAV system with exhaust recovery, and
> > surprisingly, when I add a recuperator, cooling consumption
> increases,
> > instead of reducing!! Can anybody explain this to me?????
> >
> > Thank you.
> >
> > ======================================================
> > 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
>
>
> ======================================================
> 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