Hot Water Freeze Protection Using Ra Operation; Smoke Purge Operation - York eco2 050 Installation Operation & Maintenance

Sequence of Operation
• If the OAT is above the speciÞ ed "Cmfrt Vent High
SAT" setpoint, the action will be Reverse Acting. In
this case, the economizer control can in crease the
SAT temperature just by opening the economizer
damp er and using more outdoor air. However, if
the econ o miz er controller can not prevent the SAT
from increasing above the top control band limit by
closing the economizer damper to its programmed
minimum position, one or more compressors will be
turned ON as required. Sim i lar ly, if the economizer
controller can not prevent the SAT from dropping
below the bottom control band limit by opening the
economizer damper to its programmed "Cmfrt Vent
Low SAT setpoint" setpoint, one or more heating
stag es will be turned ON as required.
• If the OAT is within the SAT control band, (i.e. be-
tween the programmed "Cmfrt Vent High SAT" set-
point and "Cmfrt Vent Low SAT setpoint" setpoint),
the economizer damp er will be overridden to fully
open po si tion subject to OA ß ow requirements if
in stalled and enabled. In this case, no other control
action needs to be taken to maintain the SAT within
the speciÞ ed con trol band
Staging Control During Comfort Ventilation
The economizer control alone may not be able to
main tain the SAT within the speciÞ ed control band.
A sep a rate staging control algorithm supplements the
econ o miz er control and stages heating or mechanical
cool ing as necessary.
The cooling and heating operation will be as follows:
• If the SAT increases above the "Comfort Vent High
SAT" setpoint for more than 5 minutes:
◦ If heating is ON, destage a heating stage - At 5
minute intervals, repeat this test until all heat ing
stages are OFF.
◦ If heating is OFF, stage a compressor ON - At 5
minute intervals, repeat this test until SAT is below
the "Comfort Vent High SAT" setpoint .
• If the SAT decreases below the "Comfort Vent Low
SAT" setpoint for more than 5 minutes:
◦ If cooling is ON, destage a compressor - At 5
minute intervals, repeat this test until all cool ing
stages are OFF.
◦ If cooling is OFF, stage a heating stage ON - At
5 minute intervals, repeat this test until SAT is
above the "Comfort Vent Low SAT" setpoint.
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As the heating stages, or compressors are staged up, or
destaged, the economizer controls continue using the
economizer damper to "trim" the effect of the staging
and to maintain the SAT as near the middle of the SAT
control band as possible.
If the unit is using hydronic heat, the control will mod-
u late the water valve to maintain SAT at the pro grammed
"Comfort Vent Low SAT "setpoint. At this setpoint, the
hy dron ic heat control does not conß ict with the econ-
o miz er control, and will prevent SAT from dropping
out side of the speciÞ ed control band when the econo-
mizer can no longer maintain the SAT at its middle-of-
the-band setpoint.
HOT WATER FREEZE PROTECTION USING
RETURN AIR OP ER A TION
When programmed for Hot Water or Steam, Return Air
mon i tor ing will be used for freeze protection. If the RA
tem per a ture is less than 40°F and the Supply Fan is OFF,
the Heating Valve output will open to 100%.
When the Supply Fan is ON, or the RA temperature
is greater than 50°F, the Heating Valve output returns
to normal operation. No fault is generated by this
operation.

SMOKE PURGE OPERATION

The Smoke Purge Operation will have Þ ve selectable
options.
Setting #1, Shutdown
If the smoke purge setting is set to 1 and the Smoke
Purge input is activated, the unit will do the follow-
ing:
• Disable the Exhaust Fan, if activated.
• Disable the Supply Fan, if activated.
• Close the Outside Air damper(s).
• Open the Return Air damper.
Maintain this operation until the Smoke Purge input is
deactivated, then return to normal operation.
Setting #2, Pressurization
If the smoke purge setting is set to 2 and the Smoke
Purge input is activated, the unit will do the follow-
ing:
FORM 100.50-NOM1 (604)
YORK INTERNATIONAL