Bill,
There should always be at least a slight increase in fan energy when you
add heat recovery to a system, leaving everything else equal (duct size,
cabinet size, airflow rate etc.). By default, eQUEST adds either 1.5" or
1.0" static pressure (depending on the ERV device type you select) to
both the make-up and exhaust air streams. The extra static is added to
the system supply and return fans, unless you create separate
"self-contained" ERV-FANS under the system Outdoor Air -> Heat Recovery
2 tab. If you don't have separate fans in the ERV/HRV, and you know what
the total static pressure of the system is with heat recovery included,
you can enter the system SUPPLY-STATIC under Fans -> Fan Power and
Control, and zero out the ERV-OA-STATIC and ERV-EXH-STATIC.
If the heat recovery system is not designed yet and you are running
what-if scenarios, try different control strategies under system Outdoor
Air -> Heat Recovery 1, ERV-RUN-CTRL and ERV-RECOVER-MODE. Optimizing
the control strategy will help you find the best balance between fan
energy penalty, cooling energy savings/penalty and heating energy
savings.
Regards,
Bill
To piggy back onto this discussion, I've been having trouble with a heat
recovery system that's increasing the cooling energy of my system. I can
understand that under certain control schemes, this might actually be the
case, but even when I set the control method to OA-DT and select that the
ERV will only run during heating operation, the end result is still an
increase in cooling.
Does anyone have any insight into what could be causing this?
Thanks,
*Robby Oylear, LEED**?** AP BD+C*
Bill, I have successfully managed to get rid of the ERV cooling increase
by increasing the OA-DT to about 20 F and using the "only run during
heating mode" function. Why I don't know. My guess is that the smaller
the OA-DT, the more chances the controls have of over shooting their
cooling set points which then adds to the total cooling energy
consumption.
Kathryn Kerns