What comes to mind when you hear the term "multimedia?"

Maybe you think of Microsoft, Apple, or other icons of the computer industry that have developed ways for designers to combine text, graphics, photos, sound, and video into very creative presentations.

Or perhaps you think of the incredible sound and video effects in current sci-fi movies like "The Phantom Menace."

But have you ever thought of hydronics as a multimedia technology? One in which piping, wiring, controls, and construction details are all "media" to be manipulated by creative designers to meet the demands arising on custom systems. Think about it. What other field gives you such freedom to approach design challenges in so many ways?

This month, I'll describe four novel approaches to design and installation challenges faced by hydronics professionals who knew how to wield the media at their disposal.

Not Just For The Kitchen

Look over the literature from suppliers of tubing for underfloor heating. In many you'll find an illustration showing foil-faced fiberglass batt insulation suspended with the foil side about 2 inches below the subflooring. These illustrations always make the installation look so simple and tidy. In reality your chances of getting an installation to look just like the illustrations are about the same as getting a Big MacR that looks just as appetizing as the one on the menu board.

Those neatly drawn details don't show how to hold the batt in position now that the stapling tabs are at the top of the batt and essentially inaccessible. They also don't elaborate on the fact that installing batts with the foil side up leaves the raw (unfaced) surfaces exposed to the space below. Oftentimes that space is a basement having at least occasional human occupancy, but no finished ceiling. I don't know about you, but the idea of spending time in a basement with a ceiling made of millions of loosely bonded fiberglass filaments makes me "itchy" for a better approach.

I've been using kraft-faced fiberglass batts (with the kraft paper side down) beneath floor heating systems constructed on wood-framed decks. The paper facing traps most of the tiny fibers that are certain to break loose with repeated vibration of the floor deck. Obviously this precludes the increased downward R-value offered by foil-faced batts - or does it?

Faced with the same situation, Harvey Scelso of Mahd Systems in Atco, N.J., came up with a simple solution. He buys a few rolls of aluminum foil at the local grocery store, cuts them to the proper width, and places cut-to-length sheets on top of the fiberglass batts (shiny side up) as they're installed. The kraft-faced side faces down for stapling to the joists and contains the fiber as described earlier. The 2-inch air space is maintained by offsetting the batt's stapling flange relative to the joist depth. Although Harvey tells me he doesn't need it, a light spritz of spray adhesive might help hold the foil in place on the fiberglass as the batts are lifted in place.

Aluminum foil can be purchased in 12- and 18-inch widths. I priced out some selections at the local grocery store. The cost ranges from about $0.015 - $0.04 per square foot, hardly an add-on that most jobs can't handle.

Good thinking, Harvey. I'll watch for you in the next "101 uses for Reynolds WrapR" commercial.

Crossing Some Wires

The next detail comes from another guy named Harvey. (I guess people with that name are just destined to be creative.) This time it's my local hydronics innovator, Harvey Youker of Undersun Construction in Dolgeville, N.Y.

Harvey installed a multi-load system like the one shown in Figure 1. The system had two zones of baseboard heating, two zones of radiant floor heating and an indirect domestic water heater. The system required a bypass circulator (P4) to run for the two zones of radiant floor heating, but not during domestic water heating or during operation of either zone of baseboard heating. Furthermore, the system was to be set up for priority domestic water heating.

The standard operating logic of a multi-zone relay center is not set up for the logic this system required. External relays that "modify" the built-in logic of the relay center were one option. However, with a little thought Harvey discovered a way to use the extra relays already in the box.

Figure 2 shows how Harvey wired the system using a standard six-zone relay panel. Jumpering the thermostat leads between T4 and T5 energizes the relay operating circulator (P4) whenever the zone two (radiant floor) thermostat calls for heat. Jumpering the line voltage leads (line to line, neutral to neutral) between (P4) and the zone six output terminals allows the low-voltage dry contacts on the injection control to turn on (P4) instead of calling for boiler operation (which is now handled by the XX terminals in the relay center). The built-in priority circuitry of the relay center temporarily shuts down all circulators connected to it (except P1) during domestic water heating. The injection circulator (P5) is allowed to run during the DHW cycle, but without heat input via (P4) all it can do is recirculate system water through the injection risers. This was not a significant problem, since the duration of most DHW calls is only a few minutes. This solution is simple, neat, practical, and less expensive than adding a couple of external relays.

Thermal Priming

Last fall I had a great bunch of guys in an evening hydronics class at Mohawk Valley Community College. One of them was Ken Edwards of Scharf Plumbing and Heating in Utica, N.Y.

One night we were discussing the use of a buffer tank to reduce the short-cycling of low mass boilers connected to distribution systems having lots of small, individually controlled loads.

I had just sketched a schematic showing a primary circuit with the boiler connected as one secondary circuit and the buffer tank as another when Ken's hand popped up. He quickly pointed out that such piping would allow heat stored in the buffer tank to be used to pre-heat the boiler's heat exchanger before lighting the burner. "Thermal priming" of the boiler's heat exchanger could reduce or even eliminate flue gas condensation following what would otherwise have been a cold start.

Although I often advocate the use of buffer tanks and have even piped one into my own system, I had never given Ken's scenario a thought. Would it reduce thermal stresses on a boiler at start-up? Could it reduce the emissions associated with firing into a cold combustion chamber? To say the least, it's an idea worth further study.

A simple implementation of Ken's idea would be to operate the primary circulator along with the secondary circulators of the boiler and buffer tank for a short time prior to lighting the burner. The secondary loads would be off during this period to prevent heat from being drained from the primary loop.

A more refined approach would use a differential temperature control to monitor the temperature of both the boiler and buffer tank and make the decision to preheat the boiler prior to burner operation (assuming the tank is warmer than the boiler), or otherwise proceed directly to burner firing.

Who knows, there's probably an even more elegant scenario just waiting to be programmed into the microprocessor of a future hydronic control.

Building A Better Ladder

One of the harder concepts associated with learning to work with ladder diagrams is that different parts of the same relay usually show up in widely separated areas of the diagram. For example, in Figure 4a the coil of relay (R1) appears in the bottom (low voltage) section of the ladder, while its contacts (R1-1) appear in the upper (line voltage) portion.

Last year Eric Balt, then with tekmar Control Systems, showed me a way to sketch "hybrid" ladder diagrams that help keep different parts of the same relay close together while still preserving the electrical integrity of the diagram. His technique was to show a low voltage ladder within the line voltage ladder as shown in Figure 4b.

Using narrow lines for the low voltage circuit and a consistent color coding for the lines helps make the diagrams easy to follow.

All the ideas discussed came from people with a solid understanding of the basic media used in modern hydronic systems. Innovation comes from professionals who continuously think about what they do and why they do it, rather than simply accept the status quo methods as irreproachable.

Hydronics is rife with opportunities for creative "multi-media" designers and installers. Keep your eyes peeled and your minds open; there are always new approaches waiting to be discovered.