B.3.19 Mechanical/Plumbing Requirements

B.3.19.1 Mechanical Equipment

 
Design Conditions:

  • Indoor air: 68 F winter, 78 F summer (where cooling permitted);

  • Outdoor dry bulb: 0 F winter, 90 F summer;

  • Outdoor wet bulb: 58 F summer.

General:

Where possible, designers shall consider tapping into existing underground high-temperature hot water and/or chilled water distribution systems.

Domestic Hot Water Heaters:

Water heaters shall be natural gas fired with electric pilots. Electric heaters shall be used only if natural gas service is not economically available.

Gas water heaters shall be no less than 85% efficient.

"On demand" (instantaneous) water heaters shall be utilized wherever load is limited (1-2 showers, 2-3 sinks, etc.). See below for information on water- conserving plumbing fixtures.

"On demand" booster heaters shall be used wherever point loads requiring higher temperatures exist (commercial dishwashers, etc.).

Hot Water or Stearn Boilers:

  • Boilers shall be natural gas fired with electric pilots. Electric boilers shall not be used.

  • Heating system capacities shall be based on no more than 125% of the calculated demand. No "rule of thumb" estimates for demand may be used.

  • Steam boilers for individual building systems shall operate at 15 psi. Distribution systems within buildings shall operate at 3-5 psi.

  • Boiler systems shall be designed around a "staged" concept: several smaller boilers in place of one large boiler, staged to come on as building load requires.

Air Conditioning:

  • Air conditioning for office space shall be evaporative cooling unless life-cycle cost analysis demonstrates mechanical cooling (MC) to be the preferred option.

  • MC equipment capacity shall be based on 100% of the calculated demand. No "rule of thumb" estimates for demand may be used.

  • MC equipment shall have at least two stages of unloading (100% and 50%), with outside air counted as a third stage. Unloading shall be controlled by HVAC control system, not suction temperature.

  • MC equipment shall use a non-CFC or Halogenated Chloro- Fluorocarbon (HCFC) refrigerant unless such is not economically available, in which case an HCFC refrigerant may be used.

Air Distribution:

Blower motors over 5 HP shall be equipped with variable frequency drives. Reset shall be duct static pressure, outside air temperature, or other as appropriate.

Radiant Heat Systems:

High-bay space (hangers, warehouses, etc.) shall be heated with overhead, natural gas fired or in-floor, hot water tube radiant heaters unless space arrangement prohibits.

Overhead radiant heaters shall be electric ignition, direct fired, with outside exhaust. Preferred for large spaces is combustion tube type with powered direct vent combustion air. Small areas may be heated with single units using conditioned space air for combustion, provided adequate makeup is included.

Radiant floor heat shall be flexible rubberized tubing intended specifically for the application (embedment in concrete, attachment to subfloor, etc.).

Ventilation:

  • Minirnurn outside air per ASHRAE 89-62 shall be provided during all occupied hours.

  • Facilities with large makeup air requirements (i.e., motorpools, locker rooms, kitchens) shall either utilize a heat-transfer technique to recover waste heat from exhaust stream, or shall include a Solar- Wall-type makeup air pre- heater.

Control Systems:

  • Standard control signals shall be 4-20 milliamp at 24 V.

  • Single HVAC units shall have line-voltage electric thermostats with integral programmable night setback function.

  • Air-side economizer control shall be provided on all cooling systems.

  • Morning warm-up or cool-down periods shall use 1 00% re-circulated air.

 
B.3.19.2 Plumbing

 
All plumbing fixtures shall incorporate water-saving features, as follows:

  • Toilets: Flushometer valves, 1.6 GPF.

  • Urinals: Flushometer valves, 1.0 GPF

  • Lavatories: Flow-limiting aerator faucets, maximum 1.5 GPM.

  • Sinks (kitchen, laundry or janitor): Flow-limiting faucets, max. 2.5 GPM.

  • Showers: Flow-limiting, vandal proof aerator heads, max. 2.5 GPM.

 

 

  
 

B.3 PROJECT DESIGN