You have undoubtedly noted the creep of computer technology into most everyday home appliances. Everything has digital displays, clocks, menus, etc. that allow varied cycling options. These purportedly provide finite control over the appliance function (and yet another clock to blink 12:00 forever or to be reset after every power failure).
The exception is your heating system. Home appliances are typically “closed-loop” systems, i.e. they execute a task in a contained environment. However, if there is a digital display on a boiler, it is of temperature, operation status and failure modes as applicable. Furthermore these appear predominantly on gas-fired vs. oil-fired boilers. Why? They indicate boiler control system conditions only, not the performance of the total system, and they can’t.
Hydronic (hot water) heating systems are comprised of three elements, a hot water generator (boiler) delivering through a distribution network to radiation (baseboards, radiators, heaters, etc.) that may exhibit infinite characteristics and combinations under varying climatic conditions and demands. Try to specify a boiler for any existing distribution network as a replacement item and you quickly realize that it is virtually impossible to “get it all right”. Reviewing our other blogs you will note the amount of effort given to remedying distribution network issues, particularly on existing installations. Headaches!
Each zone (task) in a hydronic system must be supplied with the correct flow rate (gpm) of heated water for best performance. Currently this can only be done only with a properly selected circulator for each zone. The multi-zoned circulator distribution system is therefore the contemporary, preferred option.
But what can be done with single-circulator, multiple zone valve systems? The short answer is that they by design can do nothing well. Their attraction has been initial cost offset by energy, performance and maintenance costs over system life. In fairness though, on smaller two (2) to three (3) zone systems they can perform respectably, if not perfectly. Hidden is the innate penalty of energy operating costs.
Ironically, the direction to an efficient, reliable and cost-effective hydronic heating can be the single-circulator, multiple zone valve systems we just scorned — but with a very different circulator and very different zone valves!
First and foremost a hydronic (hot water) boiler must be sized (capacity) to match and at worst case nominally exceed the heating demands of the total structure. (Refer to our blogs again.) This value must be determined through measurement and with the use of a Heat Loss Calculator. This value and this value only can determine the properly-sized hydronic boiler for your application. (Note: We specify and use Weil-McLain Ultra Series products exclusively, but we are terribly biased!)
It should be readily apparent that the objective is to supply the ideal amount of heated water to each zone, appliance or storage tank according to its current demand. This can now be accomplished by delivering the varying demand of heated water through an “intelligent” circulation system.
There are two (2) variations of these, employing different principles:
- The Delta-P Method (Δ-P) where P = Pressure: Employs a full-demand capable conventional circulator pump configured within a by-pass loop containing a mechanically variable Pressure By-Pass Valve. Operationally the pump operates continuously and at full capacity providing a preset pressure delivery while returning the excess delivery to the boiler. We recently installed one of these systems. Works well so far, but additional pipe-fitting and valve required with continuous, fully powered circulator operation.
- The Delta-T Method (Δ-T) where T = Temperature: Employs an “Intelligent” Circulator on the output of the boiler that infinitely regulates delivery by maintaining a preset temperature differential between the supply and the return sides of the distribution system. Two (2) Temperature Sensors strapped to the supply and return lines near the boiler control the circulator speed (delivery rate). Taco Delta-T ECM Circulator found at this link: http://www.taco-hvac.com/uploads/FileLibrary/100-68.pdf
Note: We strongly favor the Delta-T Method and thus the impetus for this blog.
The other half of the Intelligent Hydronic Heating System is the Zone Valving that should be mounted beyond the System Circulator, after the air eliminator/air scoop at the end of the supply manifold. We strongly recommend and use only the new Taco Zone Sentry® Zone Valve Series found at this link: http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf. They feature:
- Well ported ball valving to minimize flow resistance.
- Quicker actuation.
- LED status indicator lamp.
- Very low energy consumption.
- Manual over-ride capability.
- High reliability.
- Low cost.
Let’s define the specifics of the common system scenarios:
- New System Installation – Configure exactly per our prior discussion and details.
- Full Existing System Upgrade
- Resize and replace boiler with a correctly sized and configured unit.
- Replace all existing circulators with an intelligent “Delta-T” Technology Circulator.
- Replace any zone valves with the specified “Zone Sentry” Valves.
- Partial Existing Zone Valve System Upgrade
- Resize and replace boiler with a correctly sized and configured unit.
- Replace individual zone circulators and valves as viable.
System Design Notes:
- Intelligent Boiler Systems necessarily use “Cold Start” Hot Water Only Boilers. Immersion-style DHW Coils cannot be accommodated and therefore Indirect Water Heaters are typically used for domestic water generation efficiency.
- System Circulators employed by design in Condensing Gas and Multiple Boiler Systems must be retained! The Intelligent Circulator must be added to the distribution supply line outside of the “Boiler Loop” that maintains through-boiler circulation. READ AND FOLLOW YOUR BOILER MANUAL SPECIFICATIONS!
- Delta-T ECM Circulator selection is crucial not only for thermal flow capacity to match the boiler output, but for head (effective resistance) of the total system. Larger, multi-level systems need particular attention in this regard. Nominally over-sizing a Delta-T ECM Circulator will incur little penalty due to its innate efficiency and flexibility. However, under-sizing it will quickly exhibit a performance penalty.
The Delta-T ECM System by design provides controlled, heated water within a preset, adjustable range to all distribution elements of a hydronic system. Moreover it does this irrespective of the number, size, duration and function of the distribution elements and their infinitely variable demand patterns. In so doing it becomes in effect a “self-balancing” system, eliminating hydronic noise (whistle) from over-driven zones while minimizing heating lag resulting from under-driven (lazy) zones.
Note: The Delta-T ECM Circulator with its built-in controls is about three times that of a conventional one, but you need only one.
The value of a Delta-T ECM System as a diagnostic tool, particularly as a replacement system upgrade should not be under-emphasized. If it doesn’t fix or improve existing distribution issues, it surely will point out any other deficiencies and isolate them for correction. As a radiation assessment tool in particular you can now properly balance rooms using the radiation dampers, and if not identify and supplement radiation as necessary.
To summarize, it’s a terrible system:
- Terribly simple
- Terribly efficient
- Terribly inexpensive
We encourage you to view our Packaged Delta-T ECM Hydronic (FHW) Heating System (Patent Pending) on this site for additional detail.
Ed. Note: Updated 03/27/2017