Timothy R - Penn State College of Engineering



Timothy R. Nolan

Mechanical

The Bond Street Wharf

Baltimore, Maryland

Resubmitted, December 13, 2002

Existing Condition Evaluation

Executive Summary:

The Bond Street Wharf has a state of the art mechanical system. It has a raised floor system that only consumes 13 inches of vertical space. The original design for the building was a VAV system. If they used a VAV system it would cause the building to be a skyscraper and would cause all new design criteria. A raised floor system allows the tenant to place partitions where ever they want due to the removable floor panels.

The mechanical condenser water loop and tenant condenser water loop are fairly simple design. When cooling is needed the mechanical loop is turned on. Control valves open and pumps P-1 to P-5 turn on and then the cooling towers turn the fan on low to start cooling. If the temperature of the water is too warm then a sensor tells the cooling tower’s fans to turn on high for more cooling. The tenant loop works similarly but it runs constantly.

Timothy R. Nolan

Mechanical

The Bond Street Wharf

Baltimore, Maryland

Resubmitted, December 13, 2002

Design Objectives:

The design objectives for The Bond Street Wharf were to maintain a large floor to ceiling height, to have large open areas and to keep the total building height under 75ft. The mechanical systems played an important part in these objectives. The designers first looked at using a regular VAV system in the building. This type of system wouldn’t work because of a small floor to ceiling height and a total building height that exceeds 75ft. If a building in Baltimore exceeds 75ft it would be classified a skyscraper and the whole building would have different design criteria. The designer’s second idea was to use a raised floor system. This would cause the total height of the building to be below 75ft and would maximize the floor to ceiling height. The raised floor systems would also allow the building to have large open areas and have the ability for the tenant to place partition walls where ever they want. Tiles in the raised floor can be moved to wherever you would like them.

Energy Source and Rates:

Electric: Baltimore, Gas, & Electric Schedule GL – Primary Service

Demand Charges: Summer Non-Summer

Generation $ 10.16 per kW $ 4.72 per kW

Transmission: $ 1.12 per kW $1.12 per kW

Delivery Service: $ 2.56 per kW $2.56 per kW

Energy Charges (cents per kW) Summer Non-Summer

Generation

Peak 4.111 2.492

Intermediate Peak 2.962 2.159

Off-Peak 1.554 1.577

Delivery Service Charge: 1.184 cents / per kWh

Cost Factors

There were no cost factors in the design of the building’s mechanical system.

Timothy R. Nolan

Mechanical

The Bond Street Wharf

Baltimore, Maryland

Resubmitted, December 13, 2002

Site Factors

A site factor that influenced the design was finding space for the AHUs. There wasn’t enough room on the roof to place the AHUs, so they designed them into the building placing two on each floor except the first floor where there is one. Concurrently the pumps for the cooling towers are placed on the first floor due to the lack of space on the roof.

Outdoor and Indoor Design Conditions:

ASHRAE Design Conditions (.4%) was used in the design of The Bond Street Wharf.

|Cooling (Summer) |Heating (Winter) |

|Indoor |Outdoor |Indoor |Outdoor |

|74-78 F |93 F DB |70-74 F |31 F |

|50-60 % RH |78 F WB |20-30 % RH | |

Design Heating and Cooling Loads:

|Location |Design-Cooling |Design-Heating |

| |(BTU/hr) |(BTU/hr) |

| |493689 |127750 |

|First Floor South | | |

|Second Floor North |598558 |86560 |

|Second Floor South |559822 |86379 |

|Third Floor North |561554 |65612 |

|Third Floor South |555985 |72946 |

|Fourth Floor North |561554 |65612 |

|Fourth Floor South |555985 |72946 |

|Fifth Floor North |561590 |81620 |

|Fifth Floor South |524237 |71314 |

|Sixth Floor North |553513 |120000 |

|Sixth Floor South |535698 |119774 |

| |4944650 |970513 |

| |412 Tons |970 MBH |

Timothy R. Nolan

Mechanical

The Bond Street Wharf

Baltimore, Maryland

Resubmitted, December 13, 2002

System Operations

Mechanical Condenser Water Loop

When Cooling Towers CT-1 and CT-2 are told to turn on then pumps P-1 and P-2 will be turned on. At the same time the pumps turn on the control valves CRV, CSV, CRV-HX-1, CSV-HX-1, CRV-HX-2 and CSV-HX-2 shall open. Simultaneously pumps P-3 and P-5 shall also turn on. Once the pumps are operational and the valves are open than the Flow Meter FM tells the cooling tower’s fans to turn on at low speed. If the condenser water temperature rises then the cooling towers turn the fans to high speed.

The cooling towers have by-pass control valve CRBV to help control the condenser water supply temperature as sensed by temperature transmitter TT.

Tenant Condenser Water Loop

When Cooling Towers CT-3 is on than pumps P-6 and P-7 are on. At the same time the pump are on the control valves CRV, CSV, CRV-HX-3, and CSV-HX-3 shall open. Simultaneously pumps P-8 and P-9 shall also be on. Once the pumps are operational and the valves are open than the Flow Meter FM tells the cooling tower’s fans to turn on at low speed. If the condenser water temperature rises than the cooling towers turn the fans to high speed. This system shall run all the time.

If the water temperature of the distribution loop falls below the set point than the boiler B-1 will turn on to low fire to maintain loop temperature. If the temperature continues to fall than the boiler will turn on to high fire to maintain loop temperature.

The cooling towers have by-pass control valve CRBV to help control the condenser water supply temperature as sensed by temperature transmitter TT.

Timothy R. Nolan

Mechanical

The Bond Street Wharf

Baltimore, Maryland

Resubmitted, December 13, 2002

Critique of System

The Bond Street Wharf’s mechanical system cost was as follows:

• HVAC & Plumbing installation: $3.5 million, $16.06/sqft.

• Raised Floor installation: $650,000, $2.98/sqft.

• Design of Mechanical/Plumbing: $850,000, $3.90/sqft

The mechanical system is easy to maintain. Each AHU has its own room on each floor and there is plenty of clearance around the AHUs to do any type of work. As for the equipment on the roof, there is also enough room to do any type work. The raised floor system can be maintained very easily because your can lift a tile up to see what is wrong, rather than poke through a ceiling tile above. There is no duct work to deal with.

The indoor air quality issues were solved by placing two outdoor AHUs on the roof to get fresh air above the building. The inlets of the Outdoor AHUs face away for any exhaust from the building. The Outdoor air is blown into the rooms of the AHUs below to meet the Outdoor air requirements for the space.

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