06-06
and the minimum hot water temperature shall not be less than
140oF. The modulating steam valves installed on the convertors
shall operate in response to a change in the leaving temperature
as shown in VA Standard Detail No.15900-3.
2. Pump Control: The pump(s) shall be allowed to ride on the pump
curve during part load conditions. Care shall be taken to ensure
that at least 15% water flow remains in circulation and water
flows up to the end of each water branch (or a riser). With two
pumps of 50% in operation, staging of the pumps shall be based on
the actual flow and/or outdoor temperature.
4.3 MISCELLANEOUS HEATING APPLICATIONS
Where the outdoor winter design temperature is 40oF and below, a
thermostatically controlled, forced air, heating terminal device(s)
shall be provided for the building entrances, vestibules, attic
spaces, and exterior stairs. In addition, the vestibules shall be
pressurized by supplying conditioned air at the rate of 2.0 CFM per
square foot and allowing it to exfiltrate outside by not providing
any ducted exhaust or return air connections.
4.4 PREHEAT COILS (FREEZE PROTECTION)
For situations, where the preheat coils located in the air handling
unit casings could be subjected to below freezing temperature, either
the steam preheat coils with integral face bypass dampers or a
separate heating system with hot glycol water heating coils shall be
used.
4.5 EMERGENCY ELECTRICAL POWER
The following components of the heating system shall be on emergency
electrical power:
A. All hot water heating pumps.
B. All steam condensate return pumps.
C. All automatic temperature controls, local and central (ECC) control
panels, air compressors and dryers.
D. All hot water boilers if used in place of steam to hot water
convertors.
5. COOLING SYSTEMS
5.1 GENERAL
The mechanical cooling for the spaces shall be provided by chilled
water systems, or direct expansion systems, or modular heat pumps
(with closed loop air to water heat source). Based on the life cycle
cost analysis, the most cost effective system shall be selected.
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