I am modeling a proposed design for a mixed loop water to air HVAC system. The cooling tower and boilers are connected to the mixed loop by heat exchangers. I’m having trouble controlling the mixed loop temperature and plant operation.
For instance for the cooling tower, the mixed loop is pumping 300 gpm (minimum pump flow from a 1800 gpm variable speed pump) while the cooling tower side of the heat exchanger ramps all the way up to 1800 gpm full capacity (headered pump). The cooling tower
is temperature controlled off the supply branch outlet and the mixed loop is temperature controlled off the mixed loop mixer for cooling and heating heat exchangers. The mixed loop also does not drop to the low temperature set point even though there is heating
call to the boiler.
We also seem to have some issues with zone multipliers. We have plenty of mixed loop pumping capacity, but we have lots of unmet hours with the equipment we were given. When we autosize the zone equipment, we get 2-3 times equipment sizes,
but still at minimum pump flow.
Any insight could be helpful.
Ned Lyon, P.E. (MA, WV)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
|
Engineering of Structures and Building Enclosures
41 Seyon Street, Bldg. 1, Suite 500
Waltham, MA 02453
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
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Posted by: "Edward G. Lyon" <EGLyon@xxxxxxx>
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