What is a Domestic Hot Water System?
A Domestic Hot Water (DHW) system provides potable hot water to our sinks, showers, and tubs and other places where hot water may be ingested by, or come in direct contact with humans. This is as opposed to non-potable water which is not suitable for drinking and other domestic purposes but may be used for hydronic heating, industrial cleaning and other applications. Most plumbing codes specify that all piping, components, and heat-transfer devices in contact with the potable water shall be intended for use in potable water systems.
Typical commercial DHW systems consist of one or more boilers that provide a reserve of hot water for use. Since demand for hot water is not uniform across the day, DHW control systems are sized to try to balance the costs of heating large tanks of hot water, while still being able to meet the anticipated demand during a peak period (usually when people are getting ready for work in the morning)
Key Parts of a Typical Commercial Domestic Hot Water System
The diagram below shows a typical configuration for a domestic hot water system with a single boiler/storage tank. Many configurations for a DHW system are possible depending on the size, age, demand profile and layout of the buildings involved but they all share a few basic components.
In this system, the hot water tank is providing superheated water at 160F to a 3-way mixing valve that cools it for delivery to the tap at ~110F.
Other Key Design Considerations for a Domestic Hot Water System
The bacterium legionella pneumophila is found in both potable and non-potable water systems. Studies have shown that Legionella does not grow in cold water below 89.6F1 but in water temperatures above 90F especially in stagnant water between 95F (35C) and 122F (50C), legionella bacteria begin to multiply. Legionella can cause legionnaires’ disease or legionellosis, a severe, often lethal, form of pneumonia that occurs primarily when steam or water vapor containing legionella is inhaled. The disease’s name was coined in 1976, when American Legion members who attended a convention in Philadelphia, suffered from an unusual lung infection (pneumonia). Legionella cases have been on the rise for over a decade, with several outbreaks identified in large cities, that have caused severe illness and death. Our society is vulnerable to these waterborne bacteria, and the HVAC/plumbing industry is responsible to do what it can to protect the public.
Studies show that flushing a water system to effectively kill legionella requires water temperature over 160F (71C) throughout the entire piping network for at least 30 minutes; at lower temperatures, some bacteria can remain protected inside the biofilm lining the pipes.
Yet if water at this temperature were to come in contact with your hands, severe scalding would occur in only 2-3 seconds. Key to satisfying both objectives is the use of an ASREE mixing valve which allows systems to maintain high temperatures in the DHW storage tanks, while mixing that water with cold supply to derive just the right temperature.
Heat-Timer® Motorized Tempering Valves Get The Job Done
A valve like the Heat-Timer Electronic Tempering Valve (ETV) is often used as the mixing valve in domestic hot water applications. Whether the system uses boilers and tanks, or generates hot water instantaneously, the function of this valve is absolutely critical in preserving the safety equation. Water must be heated to 160F kill legionella, and a 3-way mixing valve must be used to scalding at the tap. Under control of a programmable console, the motorized valve is automatically adjusted to drive the perfect temperature of water through the system using temperature sensors placed on piping to record the exact temperatures (1 degree accuracy).
Visit our website pages for more information on how domestic how water systems work, or contact a Heat-Timer Representative today
Improvements in the affordability of building management systems, and improvements in digital literacy across the country and across the globe, have increased the prevalence of building automation and energy management systems in almost every walk of life. Consumers are well aware of home automation systems like Amazon Alexa, Google Home, and Apple Homekit, and the commercial world has its own 800lb gorillas.
Historically, full scale building management systems were the province of large budget building operations, costing anywhere from $2.50 to $7.00 per square foot to implement, or close to $250,000 for a 100,000 square foot building. ROI was a challenge for all but the largest buildings and even then, it took 4 or more years to recover costs through energy savings.
It was only a matter of time until these systems came down in cost and complexity to be financially feasible for smaller operators. After all, it is actually smaller buildings which dominate the commercial building landscape. According to U.S. Energy Information Administration statistics from the Commercial Buildings Energy Consumption Survey, 95% of commercial buildings in the U.S. are 50,000 square feet in size or smaller. Furthermore, these small buildings account for 44% of all energy usage across all commercial buildings.
Still, it took what most would consider a disruptive technology to bring a new opportunity into focus.
The Case for More Sophisticated Building Management in Smaller Buildings
In 2008, the “internet of things” (IOT) was born. Though the phrase had been coined a decade earlier, it wasn’t until 2008 that the number of things, or objects connected to the internet actually exceeded the number of people. Standalone smart devices could now connect to central systems or applications without wires. Local devices could incorporate sophisticated sensors and algorithms that fed centralized analysis and control platforms.
Companies like Heat-Timer® were on the edge of developments that made the heating management component of many of these IOT based systems, reach new levels of performance. Development of the IOT made control installation easier, allowed for more flexible space monitoring, and improved on the number of simultaneous monitoring points, for even better analysis and more energy efficient boiler control.
Smaller building owners took notice. With heating costs in many states, making up the primary chunk of building energy expenditures, implementation of a sophisticated system of heating control like the Heat-Timer Platinum Series, that was low cost and easy to install, was a no-brainer.
Heating Control Investments Can Roadmap into a Full Scale BMS Later on.
Any of our Platinum Series Heating Controls can be operated either standalone, or inside a full scale Building management platform. Indeed many operators have referred to our systems as a “poor-man’s” building or energy management system. While it handles primarily the heating and domestic hot water elements of a building, it does so in a way that resembles the user experience of a full blown BMS: remote alarm monitoring on your cellphone, full tweaking and configuration available through our internet portal or free phone app, easily movable wireless remote room sensors that allow operators to solve hard-to-diagnose heating issues, automated reporting, and self-learning features that allow us to get that last 10% of energy savings by learning the heating characteristics of your building.
BACnet for Building Automation Integration
If someday an operator decides to take on the expense of a full blown building management system, our platinum series controls will act as the subcontractor for all heating and domestic hot water management. Our ability to do this is because we’ve embraced the industry standard BACnet protocol for communication between building automation devices. Almost all makers of building automation systems embrace the BACnet protocol and thus manufacturers who embrace the protocol can communicate in a standardized way, over this interface.
All our platinum control alarms, control settings, sensor readings and more, can be transmitted to a building management system which then presents the data through its own human interface.
In this way, operators can leverage the performance of Heat-Timer’s industry leading heating and DHW controls, while incorporating other building automation subsystems into a cohesive BMS.
For more information on the use of Heat-Timer® Controls as an energy management system, or their capabilities when integrated with a 3rd party BMS, please call the factory today.
Original content posted on https://www.heat-timer.com/building-management-systems-heating-controls/
Heat-Timer® corporate office and manufacturing facility is conveniently located in Fairfield, NJ. Here, Heat-Timer® manufactures its electronic controls, sensors, valves and actuator products using specialized computer controlled equipment and automated testing systems.