ASHRAE Journal - July 2010 - 12

Proper Operation Key To Steam Boilers
“Water & Energy Use in Steam-Heated Buildings” by Ian Shapiro, P.E., in May raised an important question with respect to steam boilers: Why Water & Energy Use in such high water use? Steam-Heated Buildings In a well-designed, balanced and maintained system with A only ONE steam boiler, we will evaporate x gallons of water, condense the same amount and return it to the condensate tank in a conventional two-pipe system at the DT called for by the steam traps. At 5 psig we will see 227°F, and thus expect condensate to be at >180°F or about a 50°F DT. How much water will evaporate at >180°F in a semiclosed tank with a 2 in. vent in a properly operated system? Very little! This shows the importance of steam trap maintenance. In a system with two steam heating boilers (schools, etc.), we see the old coal mentality kick in. With coal one has to keep both boilers at load as it takes about eight hours to get a coal unit up to pressure. In this scenario, we see the operator alternating the boilers at some time interval without good reason. So, what is the answer? It is not switching to a hot water heating system. One cannot beat the 970 Btu/lb at 212°F when it comes to heat transfer. The answer is proper steam boiler operation. In a two-boiler system, shut one boiler off completely, even to the extent of blocking the air vent to minimize Btu loss. One also can do this with a hot water heating system using boilers. A properly designed school boiler system can maintain that building envelope within a cozy temperature range on only one boiler. Yes, around mid-January, one may need two boilers for four to five weeks. This has been done in some school districts with great success. Last, but certainly not least, is the use of a treatment program designed for a steam heating system. We must cease treating steam heating boilers like process units. It is destructive to the boiler and return system, leading to Btu waste and cost to the operator. Frank Rosa, Liverpool, N.Y.
By Ian Shapiro, P .E. n anecdotal report of high energy savings at a multifamily building in Ithaca, N.Y., resulting from the replacement of an old steam boiler with a new hot water (hydronic) boiler, led to a survey of similar completed projects in New York to assess if these high savings have been delivered elsewhere. Four projects were identified in which old steam boilers were replaced with new hydronic boilwith steam, and was almost twice the national average for residential water consumption per person. This difference works out to be 58.2 gallons (220 L) per person per day in water use. The potential waste of water (for example, almost 6,000 gallons [22 712 L] per day in an apartment building with 100 occupants) points to the dramatic energy and water conservation potential in converting steam systems to hydronic heating systems. ers. Savings were significant for all four, averaging 40.5% of total heating use (exceeding predicted average savings). By comparison, three projects were identified where old steam boilers were replaced with new steam boilers. Savings were poor, averaging only 0.6% of total heating use and falling far short of predicted average savings. Overall energy use was compared in a larger sample of buildings and found to be
14 ASHRAE Journal

Gaspers, Germs and Flying
I enjoyed reading “Germs, Flying and the Truth” in the April issue. I seem to spend so much time on airplanes that it’s about time I learned a little more about their HVAC systems. Since I don’t know much about aircraft HVAC systems, I had a question about one statement you made. In the fourth full paragraph on Page 72, you seem to indicate that the induced air from the gaspers (I assume these are the little overhead nozzles that I can never get enough air out of) increases the filtration rate of the cabin air. It seems to me that the amount of primary air would determine how much air passed through the filter, not the amount of air movement induced in the cabin. Perhaps I’m just reading this wrong. Chris P Rousseau, P . .E., Member ASHRAE, Roswell, Ga.

Energy Use

24% higher in buildings heated with steam. An evaluation of water use in steamheated buildings was conducted. Fifty buildings were surveyed for which water use records were available. Water use in steam-heated buildings was found to be 79% higher than in buildings not heated
ashrae.org

Steam heating systems, first developed well over 100 years ago, are still surprisingly widely used in residential, commercial, and industrial buildings. For example, steam systems represent the majority of buildings participating

About the Author

Ian Shapiro, P is president of Taitem Engineer.E., ing in Ithaca, N.Y.

May 2010

The Author Responds
Yes, that is a gasper or personal air outlet. The gasper airflow jet stream has a low pressure turbulent boundary layer, which entrains and mixes surrounding air into the main airflow stream (Venturi/Bernoulli effect). The amount of air entrained is some four or more times (12 cfm or more) the primary (motive) 3 cfm airstream. That entrainment air could include your neighbors’ exhaled breath. Don’t point the gasper nozzle at your face and inhale some of their breath (unless you know they are healthy). Point the gasper nozzle beside you and draw at least one of your neighbors’ breath away from your breathing air towards the floor where it will be exhausted at the grille at the base of the liner wall. This will help, but it is not perfect. We are developing this Venturi entrainment concept to create a modified gasper that will filter any air taken from all your neighbors’ spaces to yours, thereby removing all or at least many of the airborne pathogens that might otherwise enter you breathing zone (whether the gasper is on or not, air is being circulated between passengers by slot diffuser airflows originating near the side wall and aisles, for example), and allow you to point a 10 to 15 cfm filtered airstream into your breathing zone. This modified gasper is illustrated as a portable unit at www.indoorair.ca/veft/index.php and as a built-in unit in Figure 9 at www.indoorair.ca/veft/pdf/personal_ environment_airflow_controller.pdf Thank you for your question. I hope this helps. Douglas S. Walkinshaw, Ph.D., P .Eng., Fellow ASHRAE, Bonita Springs, Fla.

The Author Responds
Thank you for your thoughtful comments. A few people have raised similar questions recently, along the lines of “How about well-designed and well-maintained steam systems?” My concern is that even if better maintenance could reduce losses, entirely eliminating the higher losses (relative to non12 ASHRAE Journal

steam systems) is unlikely, due to several intrinsic aspects of steam systems (higher temperatures, open systems, difficulty in diagnosing steam losses when they happen, etc.). Also,
ashrae.org July 2010

ASHRAE Journal - July 2010

Table of Contents for the Digital Edition of ASHRAE Journal - July 2010