Have you ever felt that there are too many pipes, circulators, controllers, and other gadgets in your circulatory system? Why do many well-organized two-dimensional schematics-systems that look beautiful on paper-often turn into a pile of intricate hardware during installation?

Over the years, many of us have seen the "winning" cycle system in trade journals and other publications. Most of these systems are unique installations. With proper design, documentation and regular maintenance, they can serve the owners well. Remove any of these necessities, and you will have a series of very expensive hardware that no one seems to understand or willing to provide services for. 

The latter case is a serious problem. The last thing our industry needs is to make ordinary consumers think that circulating heating must be very complicated to be correct, or that the circulating system beyond the boiler, circulator and a series of finned tube bottom plates cannot be easily maintained by one person. Quite competent HVAC technicians.

The following are suggestions for simplifying residential circulation heating systems. The goal is to reduce design details and hardware. In many cases, the system can provide efficient operation and superior comfort without providing these details.

A common situation when planning a radiant panel heating system is that multiple water supply temperatures are required. An example is a system for heating basement slabs and wood frame floor areas of houses. The latter type of floor heating is usually achieved using a tube sheet system installed above or below the subfloor. 

A common method is to provide separate hybrid components for each type of radiator structure. Some designers specify separate hybrid components for each area of ​​different types of floor coverings, such as tiles and upholstered carpets. Sometimes, even if the water temperature requirements of the supplied panels are the same, separate mixing components will be specified on a floor level basis.

I have designed a residential system with three different hybrid components, and I have seen systems with at least five independent hybrid components. Can these systems work? Yes. Is this complexity necessary? unnecessary.

The following procedures can be used during the design process to help determine whether multiple water temperatures are required:

For example, suppose you are planning a pipe for a bare concrete slab and you need a heat output of 20 Btu/h/ft2 under the design load conditions. Under these conditions, the space should be maintained at 70° F. Figure 1 shows that if a 12-inch pipe pitch is used, the average loop water temperature needs to be approximately 27° F higher than room temperature (for example, 27 70 = 97° F). 

Assume that the same building has a gypsum sheet in which pipes for heating the upper layer are embedded, and under the design load, these circuits require an average water temperature of 115° F. 

Increasing the pipe spacing of the concrete slab section of the system to 18 inches will increase the average water temperature to approximately 104°F. Assuming that the circuit temperature drops by 20° F under design load conditions, the supply temperature of these circuits will be approximately 97 20/2=107° F and 104 20/2=114° F, respectively. These supply temperatures are within 10° F of each other, so they are likely to be supplied by the same system. In this case, the control can be set to produce an intermediate temperature (approximately 110° F) between these two values. 

In this case, people may also argue that it is better to reduce the pipe spacing on the higher temperature loop, thereby reducing the average system water temperature to increase the efficiency of the heat source. This is an effective proposal for systems that use mod/con boilers, geothermal heat pumps or solar collectors as heat sources. Comparing the life cycle cost of changes in heat source efficiency with the higher installation costs of more pipes can provide a reliable answer to this. However, when a conventional boiler is used, the boiler efficiency will change very little, and the cost savings are mainly due to not installing multiple mixing components.

If the change in pipe spacing is not enough, discuss the possibility of different floor finishes with the customer before giving up using a single supply temperature.

I found that in some cases it is possible to combine board-level systems with thin boards or even under-floor pipe and board systems. Eliminating the need for multiple hybrid components in these situations can reduce installation costs by hundreds of dollars.

When a single water supply temperature is possible, consider using a zoned manifold with zone valves or a separate circuit with valve actuators. Another possibility is to mix in a non-electric thermostatic valve for zone control. This method lays the foundation for a simple conveying system using a single variable speed pressure regulating circulator. Figure 2 shows an example of this "home run" power distribution system provided by a mod/con boiler.

The ability to divide the system into multiple independent control zones is one of the most frequently cited benefits of cyclic heating. There are several technologies that can be used to provide multiple zones in almost all modern hydraulic systems. In most cases, the cost of zoning is much lower compared to the same number of areas in a forced ventilation system. 

However, just because you can set each room in a building as a separate heating zone does not mean you should. 

This is especially true when installing wired zone control. When all transformers, valve actuators, relay centers, and thermostats are connected, you may have installed a few miles of thermostat cable, as shown in Figure 3. This tedious work can easily add thousands of dollars in installation costs. Even if money is not an issue, all these thermostats may only be used to balance the heat flow in the building, rather than continuously adjust the temperature.

The important thing is not to get confused by "over-partitioning". When selecting areas, look for open areas in the building. As far as heating is concerned, these areas are "communicating" and rarely need to be located in different areas. Also look for areas that receive a lot of solar thermal gain, and place them in different areas from non-solar gain areas. 

If you really like the idea of ​​room-by-zone control, please take a closer look at non-electric thermostatic valves. They can be used for skirting boards and panel radiator systems, as well as wall-mounted cabinets for radiant panel systems built on site. No wires and full modulation control. 

Primary/secondary pipeline engineering. For several years, we have designed systems around this pipeline method. However, there are simpler and cheaper ways to realize the benefits provided by P/S pipelines. 

Figure 4 compares the two methods of achieving the hydraulic separation of all circulators and the same water supply temperature for each load.

The system shown in Figure 4A uses a parallel main circuit to connect the boiler to each load. A dedicated primary circulator is required to move the flow through the primary loop.

Figure 4B shows a system that uses a hydraulic separator instead of the main circuit. This eliminates the need for a primary circulator. It also eliminates the need for dedicated air and dirt separators, as these functions are handled by the internal coalescing media in the hydraulic separator.

Have you ever been in a machine room where six or more transformers are installed on a 4x4 J-box and are buzzing 24/7? Figure 5 (page 70) shows an example of this situation. There is a transformer in each red cloud. 

Put your hand on any active transformer and it will feel very warm. This is because regardless of whether there is an active load on its secondary winding, it sits there and converts electrical energy into heat through the primary winding. The installation cost of multiple transformers is definitely higher than the transformer itself. Each requires a J-box and related wiring. Multiple transformers can also cause problems if they are connected in parallel without the proper "phase".

Consider using a single larger transformer, such as a transformer rated at 100 VA, instead of several smaller transformers. When the part of the system that is not serviced by the transformer, use a control device that turns off the transformer. The energy saved by reducing the control transformer may not be great, but everything helps.

I have a saying about antifreeze: "The only benefit of antifreeze is that it does not freeze." Antifreeze based on glycol reduces the heat capacity of the fluid relative to water. For the same heat transfer, this requires an increase in flow rate. The higher viscosity of glycol-based antifreeze also significantly increases the head loss. At 120° F, a 50% propylene glycol solution will increase the head loss (at the same flow rate) by approximately 24%. When the flow was increased to compensate for the reduced heat capacity, the head loss increased by 47%! This means more pumping power and higher operating costs. 

As many of you have discovered, glycol-based antifreeze also has a tendency to seep through threaded joints and produce surface oxidation. In this case, the water will not leak or evaporate quickly without scaling. . Last but not least, filling the system with a 50% glycol solution can easily add hundreds of dollars to the installation cost.

So, where should antifreeze be used? Snow melting systems and closed-loop solar collectors obviously need the protection it provides. In the northern climate, we also specify ethylene glycol in the heating circuit of residential garages and several consecutive uninhabited households in winter. 

We used to specify antifreeze for floor heating systems in large ground facilities such as highway garages. However, many of these buildings now have emergency generators that can continue to operate during prolonged power outages. Due to the constant circulation of "mixing" heat in the large concrete slab, even if the boiler is not running, it may take several days of cold days to make the water in the slab circuit risk freezing. In view of these favorable possibilities, we are now avoiding the use of antifreeze in such facilities.

Writing about removing hardware from the system is always a bit unstable. This hardware generates revenue for its manufacturers, all the way to the professionals who install it. 

My suggestion is to reduce costs without compromising quality, and to eliminate the stigma that the circulation system seems to have developed in the eyes of many architects, builders, energy planners, and consumers. We want to build market share instead of the number of parts. When our customers need Piper Cub, why build 777 Dreamliner?

John Siegenthaler, PE, is the consulting engineer and person in charge of the appropriate design of the Dutch patent in New York. His latest textbook "Renewable Energy Heating" will be published from Cengage Publishing in January 2016. It shows how to use modern hydropower technology to create a system provided by solar heat sources, heat pumps, and biomass heat sources. For more information, please visit www.hydronicpros.com.

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