12
Meridian
Systems
Zoning Design Guide
036-21478-001 Rev. A (0802)
Design Considerations
Increase your static pressure setpoint. This will help
reduce the amount of air being bypassed. Be aware of
increased noise levels and the cost of operation if you
use excessive static pressures. This will not work if you
are using pressure independent zone controllers, since
they will maintain a constant flow of air to the zones
regardless of duct static pressure. This technique will
likely cause over cooling of the spaces due to increased
airflow at minimum positions.
Warning:
If the fan system has the capability of producing static
pressures which could damage ductwork you must pro-
vide a manual reset, high pressure limit switch (Dwyer
1900-5-MR or equal) to cut off the fan system in the
event of high duct static. Do not use your Meridian
Zoning system as a safety device!
Heating - Partial Load Conditions
Heating difficulties are less common than cooling dif-
ficulties. They are similar in nature, however, and the
cures are generally the same. Again, a number of things
can be done to reduce the effects of this problem.
Increase heating minimum airflow. Increase your heat-
ing minimum airflow or damper position settings to
allow more air during heating operation. Be careful to
avoid minimum settings that are so high they may cause
over heating of the spaces.
Increase the static pressure. Set the static pressure
setpoint to be as high as practical. Increasing static pres-
sure does not help if you are using pressure indepen-
dent control operation.
Avoid oversizing the unit. Do your all load calculations
carefully. Since the zoning system directs the heating
or cooling to the zones which require it, you may find
that you can use a smaller unit in many cases.
Bypass the air into the ceiling plenum. If you have a
system without ducted return, bypass the air into the
ceiling plenum instead of into the return air intake. This
method works best with plenum returns. Do not use
this method with ducted returns
Use auxiliary heat . Use an auxiliary heat source in
either your VAV boxes or use baseboard heaters.
Meridian
has a number of auxiliary heat control op-
tions which provide solutions to most problems. Refer
to the Auxiliary Heat Control Options topic near the
end of this section.
Override Conditions
After-hours overrides can produce aggravated partial
load conditions in both the heating and cooling modes.
A single zone being overridden for after-hours use most
commonly causes the problem. This causes the rooftop
equipment to operate for only one zone. The Meridian
system offers an improved solution to this common
problem by allowing a single override to trigger a group
of zones via a “global” override. This allows the sys-
tem to operate with sufficient load to reduce cycling
caused by light load conditions.
Building Pressurization
If you are using an economizer, building pressurization
must be addressed. Failure to properly handle building
pressurization may result in doors remaining open when
the economizer is operating. Pressurization problems
can render economizer operation useless. The follow-
ing suggestions will help to avoid potential problems.
Use powered exhaust. A power exhaust fan(s) must be
used when the system utilizes ducted returns. The re-
turn duct pressure drop will cause most barometric re-
lief dampers to function poorly or not at all. Meridian
has the ability to control a powered exhaust whenever
the economizer is operating.
Use a separate building pressure control. Use a con-
trol that operates a relief fan or dampers to relieve build-
ing pressure
Summary of Contents for Meridian
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