David Grassl, P.E.

Professional Engineer

Wisconsin

M.S.

Environmental Engineering

MSOE

2004

B.S.

Architectural Engineering - Building Environmental Systems

MSOE

2004

Faculty Coach-Third Place

ASCE Pre-Construction Competition
2019 Open Division

Faculty Coach-Second Place

ASCE Virtual Design & Construction Competition, 2018 Open Division

Top Projects of 2013

Northwestern Mutual Van Buren Office

Maximizing Hydronic System Design – The Fundamentals; Parts 1, 2, & 3

Webinar: April - June, 2017  Cleaver Brooks

Don’t Blow Your Money on a Steam Trap

Grassl, David L.

2014-01-16

According to the U.S. Dept. of Energy (DOE), approximately 20% of steam leaving a boiler plant could be lost due to leaking steam traps in steam systems without a preventative maintenance program. This represents a considerable amount of wasted dollars in energy production. A relatively simple maintenance program can help reduce losses by approximately half, while more sophisticated programs can virtually eliminate steam trap losses for improved building performance and reliability.

Unfortunately, loss of steam through a steam trap is virtually invisible as steam is lost into the condensate system—unless a program is in place to quickly and accurately identify these leaks. This bypassed steam provides no useful heating value to the system and effectively reduces the overall capacity of the system or requires additional capacity to make up for the system losses to meet the demand of the building.

This article will provide a holistic approach to steam and condensate systems by discussing the various types of steam traps, recommended locations for them, basic trap sizing, general steam and condensate design guidelines, and the various methods for testing steam traps to reduce wasted energy and dollars.

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Optimizing Hot Water Systems with Condensing Boilers

Grassl, David L.

2013-12-16

Hydronic hot water heating systems circulate hot water throughout a building to heat its air and come in varying shapes, sizes, and configurations. Boiler selection

and traditional hot water systems have been designed to maintain high hot water temperatures, but changes in boiler technology allow efficiency gains to be achieved by using lower water temperatures and condensing boilers.

Traditional boiler system designs consist of some way to heat water from ambient conditions to a temperature suitable for conditioning a building’s air. In these older, conventional systems, the standard design was to maintain hot water supply temperatures upwards of 180 to 200 F with hot water return always above 140 F to prevent condensing in the heat exchangers. Similarly, conventional, noncondensing boilers were designed so that variable flow through the heat exchanger was unacceptable. Consequently, primary-secondary pumping configurations were used to maintain the desired flow through the boiler heat exchanger while varying the flow in the secondary loop based on the building’s demand.

Today, boiler system design has completely shifted. Hot water supply temperatures are decreasing, and condensing boilers are great choices for systems that use lower hot water temperatures as efficiency is increased. Condensing boiler systems are good for systems that include in-floor radiant heating systems, water source heat pumps, and standard hot water systems specifically designed with lower hot water supply temperatures.

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Selecting Chillers and Chilled Water Systems

Grassl, David L.

2013-09-16

Chilled water systems are cooling systems that circulate chilled water throughout a building for cooling and dehumidifying a building’s air. They come in all shapes, sizes, and configurations. Chilled water systems are closed-loop systems, meaning that the system water is continually recirculated and not exposed to atmospheric pressure, similar to domestic water systems. While selecting the type of chiller to use is generally dictated by capacity, there are still many philosophies on the best way to control, operate, and calculate system operational costs.

The first step in chiller selection is understanding the options available. A building’s block load will determine the overall capacity, whereas part load will determine the number and quantity of chillers required, with multiple chillers providing the ability to stage chillers in response to load. A block load will take into account building diversity and load changes based on exposure, internal and external loads, and building schedules because all portions of the building will not be peaking simultaneously. The function of a space may also dictate sizing and plant reliability. Essential services, such as data centers or hospitals, require reliability and redundancy with the use of a backup chiller or chillers for N+1 or 2N redundancy based on an owner’s requirements. Furthermore, the hourly building profile run time may require equal or unequally sized chillers.

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