• Tag Archives hydronic distribution
  • HYDRONIC (FHW) HEATING OPTIMIZED – “Going Back To Nature?”

    A primary tenet of Industrial Engineering is: To properly justify a process change you first optimize the existing process, then define the proposed process and make your CBA’s (Cost-Benefit-Analyses) for both. From weighing these you will then derive your best course of action. Speaking from painful experience as a Manufacturing Process Engineer, you will make this mistake only once. Somewhere in a dark corner of a semiconductor facility (or hopefully a scrap pile) lies my personal ill-advised, sophisticated process equipment humiliation!

    The makings of similar embarrassments are appearing within the hydronics heating industry. Hydronic component suppliers can be placed into three primary groups: boiler, distribution and radiation providers. They correspond to the three basic elements of the hydronic heating process. Component suppliers define the scope and applications of their products within a heating system, but that’s all. History and physics now become excellent teachers.

     A century ago there were two competing water-based energy heating methods, Gravity Hot Water and Steam. Both were based upon the natural (gravitational) convection attribute of water in the liquid or the vapor state, respectively. Energy distribution from a boiler to radiation required no external energy, only variation of the fuel supply ….. more heat, more fuel. Powered burners and thermostats were added for control. Pumps (circulators) doomed gravity water by adding zone management while reducing costs. Thus the modern hydronic heating system evolved.

    I’ve had the benefit of “playing with pipes”, beginning as a teenager within our family heating business for over 65 years while pursuing a paralleled hi-tech engineering career. (You can’t raise ten kids even on an engineering day job.) So while doing hydronic work “on the side”, so to speak, hydronic evolution followed me. My “engineering hat” always questioned why natural convection shouldn’t be an asset rather than a flow-checked nuisance. The old “gravities” were so simple!

    Post-engineering “non-retirement” provided time to aggressively play with hydronics. My “motor head” also makes me analogize heating systems with automobiles, i.e. the boiler being a pure “heat engine” with air, fuel and ignition for example. So when the delta-t circulator came along, there’s the “automatic transmission”. Now what can we do with the drive-line (distribution)? Can we re-evolve the Model T Ford car as a hydronic “Model Delta-T Appliance” by incorporating natural gravity convection into delta-t distribution? Well, we can and we have …..

    The old Gravity Heating System featured a large boiler, proportioned larger piping and radiation, typically all cast iron and pipe. They were skillfully defined and installed, used no distribution energy and lasted almost indefinitely, a tough act to follow. Its modern contemporary uses a much smaller (albeit more efficient) boiler, features multiple, circulated zones with smaller piping and radiation. Arguably it trades off fuel efficiency and comfort convenience for some increased distribution energy and “sophistication”.

    The sophistication referred is almost entirely within the distribution element of hydronic heating systematization.This is the consequence of a component-driven marketplace, as prior mentioned. The contemporary build-in-place method of system installations relegates hydronic interconnection of boiler to radiation in particular as “The Plumber’s Playground” wherein there are few rules and little consequence. Every system differs in a similar application, and therefore all perform differently in practice.

    If the objective is to provide overall hydronic system energy efficiency including electrical power consumption, freelancing must be both qualified and quantified in practice. Redefining near-boiler piping to optimize natural (gravity) convection with the boiler and integrating a delta-t circulator to refine hydronic delivery dramatically reduces distribution material and energy usage. Our now-patented “appliance” exhibits a typical 8 to 13 Watts total distribution energy usage while heating, over 90% reduction depending upon the contemporary configuration. Coupled with a high-mass, cast-iron boiler to enhance gravity operation, it also exhibits a thirty-plus year economic and operating life, twice or more that of low-mass, condensing units.

    Further gravity convection enhancement is available within the appliance-to-zone interconnects. The “level & square, pipes everywhere” approach does not fly in a gravity world. Minimized, pitched piping to simple series and split perimeter radiation loops are ideal. Full port valving if necessary and fewest 90° fittings further contribute to minimizing head pressures and thus distribution energy consumption. It won’t win a beauty contest, but it will win the race.

    Our 2,700 sq. ft. personally built (1970) raised ranch home has been our gravity test stand. An indoor wood boiler was convection-coupled to the cast-iron, flow-checked supply and circulator returned 3-zone “oiler” back in 1975. Multi-mode, multi-fuel operation also permitted completely unpowered, manually adjusted flow check wood gravity convection heating. As an example some years ago up here in “Frostbite Falls, NH” we were powerless from a severe ice storm for 10 days. A mere inconvenience for us ….. just feed it wood and adjust the valves.

    We currently have a series of up to six-year installed appliance “Beta Sites” that have now aggregated over twenty-five years service with no system-related calls! Two oil-contamination incidents did occur and last year a power line short-circuit blew out every control on a system. Our appliance is comprised of all standard, domestic trade components, so it was restored within the day.

    Our “appliance economics” haven’t been mentioned but are profound. Very significant complexity, material/labor content reduction and extended operating life vs. traditional architecture eclipse contemporary materials and methods. This observation was similarly but subtly affirmed in the 2019 Annual Boiler Report by several contributors opining that in effect it’s still hard to beat the economics of a well designed and installed cast iron boiler system. Their commentary and our natural (gravity) convection appliance development experience confirm that the existing, i.e. the “pre-condensing” process has yet to be optimized, to our potential peril. But try to find trade journalism and process development efforts to the contrary!

    So, is history due to repeat? That is, will a hydronic “Model Delta-T” displace this industry’s “Carriage Makers”, or will there be yet another technical “skeleton” in my closet?

  • WHAT IS A GRAVITY HEATING SYSTEM? – Gravity Convection Heating Revisited

    The three (3) basic elements of hydronic heating are heat generation (boiler), distribution of energy (pumps) and conversion to area warmth (radiation). Of these hydronic distribution is typically the least understood, generally misapplied and desperately needs revisiting!

    What is a Gravity Heating System? A century ago all water-based hydronic heating (hot water and steam) employed the natural gravity attributes of heated water and water vapor (steam) to distribute energy. NO DISTRIBUTION ENERGY WAS REQUIRED! These were effectively single-zone systems that could only be modulated by varying the energy input of the boiler and the radiation outputs using register dampers or steam radiator vents, respectively. Natural (gravity) convection of heated water underlies all hydronic distribution, yet is never considered in contemporary practice. So, check-valving is installed to negate its less desired effects.

    The introduction of electric circulation pumps in the 1920’s enabled forced hot water heating (FHW) and changed hydronics forever. Gone was the large, pitched piping and radiators, replaced with zoned heating and finned radiation. The heating market never looked back, and justifiably so. Underlying this however remained the natural gravity convection effect that had to be controlled using check-valving as noted within the system.

    Early electric circulation pumps (circulators) were large, power consumptive and constructed of discrete components, i.e. motor to coupling to pump. We “old-timers” have vivid memories of failed couplings of varied types, seized and leaking pumps and smoked motors. The advent of wet-rotor circulators was like manna from heaven, reducing circulator issues with greater longevity and reduced power consumption benefits.

    Now the evolution and introduction of particularly Delta-T (differential temperature sensing) ECM Circulators projects hydronic distribution management to an entirely new level. The inherent integral instrumentation features and operational data display of delta-t circulators provide us with finite attribute identification and application control.

    The focus of our work has been to optimize the innate, but hidden contribution of natural gravity convection as both a distribution energy saver and a selective fail-mode feature in hydronic heating. As such the Delta-T ECM Circulator has been the crucial tool in the development of our “Neo-Gravity Delta-T ECM Hydronic (FHW) Heating Appliance™” (U.S. Patent 10,690,356, Canada to follow). We claim optimization of natural gravity convection within our boiler, near-boiler distribution piping with distribution energy requirements using a single, dedicated Delta-T ECM Appliance Circulator. Citing an automotive analogy, we refer to it as “putting an Automatic Transmission on a Boiler™”. This intelligent, variable speed circulator is effectively a hydronic CVT (Continuously Variable-Speed Transmission) in practice.

    Let’s go back again to that old gravity hot water heating system of a century ago. By comparison, contemporary hydronic heating systems have smaller piping with multiple zones for heating flexibility. The old “gravities” employed high-mass cast-iron boilers with larger piping to modulate heating supply, otherwise control was particularly difficult when using solid fuel firing such as with wood or coal. With generous distribution piping sizes and radiation elements gravity convection worked fairly well, and again with NO distribution power requirements!

    Properly piping a contemporary FHW system using a dedicated “Delta-T Mode” system circulator with complimentary low-energy ball-type zone valves vs. flow-checks yields great results! Transpose this configuration onto the old gravity system layout and you functionally emulate its performance as depicted in the following figures.

    The advantage is in applying natural gravity circulation to the contemporary upgrade. We have seemingly lost all trade skills in managing or enhancing gravity convection. No consideration is ever given to pitching, compacting and minimizing distribution piping in particular. Additional gains are available in radiation layout by using properly sized and configured perimeter series and/or split radiation loops. The 45° elbow fitting as an example saves 30% of piping and reduces head pressure significantly over a 90° elbow run. All this increased pipe volume and head pressure reduces the natural gravitational convection effect, not to mention increasing materials, labor and lifetime operating costs of the system.

    Our Delta-T Mode Circulator measures this head effect well via its wattage indicator. All of our single, dedicated system circulator Beta Site installs to date exhibit an 8 to 13 watt distribution power consumption with typical 4 GPM flow upon a 20° delta-t (adjustable) differential attainment. Compare this to 80 watts typical for each 16 gpm fixed-speed circulator or even 20 to 25 watts each for the new delta-p installs. With delta-t stabilization you can then witness circulation wattage steadily decay to half or less as natural convection contributes. We refer to this as “paddling your canoe with the current”.

    A secondary effect of gravity convection seems to be radiation heating profile modification, smoothing demand amplitude variation and increasing comfort. Some of the extended fuel savings we observe and the delta-t manufacturer claims seem to be due largely to this radiation profiling effect. Another contributor is the lowered system operating temperature effect of using a very high mass cast-iron boiler vs. contemporary low-mass units. Burner operation cycles are also significantly less frequent than the system it replaces, increasing component lives.

    A personal cast-iron boiler observation: This author has never replaced a “cold shot” cracked or magnetite impaired cast-iron boiler in over sixty-five years of hydronic and steam installations! Perhaps a discussion for another day, but have we also “thrown the baby (cast-iron boiler) out with the bath water” to cite the old adage? Commentary in the recent 2019 Annual Boiler Report would seem to support our contention. Read our “reading between the lines” blog on this report.

    Finally, the combination of higher boiler thermal mass with enhanced gravity convection extends selective fail-mode heating continuity substantially. Recently and four years prior our Beta Site #3 experienced a fail-safe circulator interruption. The latter an over-current condition from a voltage surge “fail-safed” its operation. In both instances the condition was not discovered for an estimated 2 to 3 days, despite significant heating demand. Neither living area heating nor indirect DHW generation were affected. Second level heating reduction was eventually noted, as it was prior. The customer called and we reset the power switch over the phone to resolve. It is also noteworthy that we have had no system related service calls in over twenty-five aggregated operating years on our multiple Appliance Beta Sites!

    In closing, the contemporary excesses and misapplication of hydronic distribution are troubling to this author. If tradesmen are promoting their prolific  system distribution piping efforts as efficiency measures they are most sorely misdirected and possibly even deceitful. Witnessing customers proudly showcasing excessively installed systems or trade supplier contests for the “prettiest system” installation pics are also particularly disconcerting. Trade practices and hence consumer perceptions need challenging. Are we selling parts and labor ….. or performance?

    Perhaps it is time for an engineered “appliance” approach (as ours) to rein in “The Plumber’s Playground©”.

    Updated 07/12/2020 P.D.M., Sr.


    It ultimately comes down to economics, as do most things. The current trend is to market low-mass (light-weight) boilers against traditional heavy, high-mass cast-iron boilers. However, there are non-publicized risks involved that must be assessed and quantified.

    New gas-fired appliances in particular have a technological efficiency milepost that must be considered. Specifically, the traditional tube/ribbon gas burner “dry base” boilers vs. the new condensing technology based low-mass boilers. They have a significant energy efficiency increase of 10+% in AFUE Efficiency Rating. Along with this however is a marked increase in appliance costs and operational risks — both quite important, yet never publicized!

    Stainless steel heat exchanger condensing gas units are the most popular and have been doing reasonably well service-wise. Cast aluminum heat exchanger units on the other hand where supply water pH (acidity) has not been addressed at installation or in operation have had issues, to which we can personally attest. Given this reservation they have also performed reasonably well. Being quite sophisticated control-wise, one has to admire the engineered system integrity of condensing gas systems. They certainly do flag service and maintenance issues with their sophisticated sensor complements!

    However, a disturbing pattern is emerging and the alarms are sounding in the trade journals and forums. Premature welded stainless heat exchanger leakage failures are being reported, some even “out-of-the-box” or within weeks of installation. An installed system operating life of 15 years or less is being reported in trade journal articles. The British Market Experience is much deeper and lengthier than ours and their forums are full of user complaints of premature failures and high maintenance costs. Reported system economic lives are commonly less than 10 and up to 15 years on “upscale” products. Cast-iron boilers have been effectively regulated out of the EU market. Do we have a similar lesson coming?

    The common cause for all condensing boilers should be water condition issues, but it’s also become manufacturing process integrity in some cases. Regardless, manufacturers are countering with stringent water condition qualification requirements within their typically 10-Year Pro-Rated Warranties. Not only do water conditions have to be measured and recorded at installation, but subsequent annual service procedures must re-qualify and record these values. Violate your water control guidelines and void your warranties!

    Oil-fired appliances on the other hand are a different animal, with combustion energy containment and management paramount in their design. Heating oil has over 60% more energy content per gallon than gases and can’t be technologically “modulated” (vary the firing rate) as with a gas appliance. Adjusting the output of an oil boiler is done by managing system temperature and/or by utilizing multiple boilers (MBS Systems) in larger installations. Therefore the oil boiler must be designed to perform at its maximum firing rate and within its design parameters. This is typically accomplished by using a cast-iron heat exchanger, and has been the norm for the past two hundred years!

    Let us first disqualify any “dry base” welded-steel-fabrication (oil or gas) boilers from this discussion. Their poorer field performance history in both thermal efficiency and longevity are well documented and recognized. They are sold on price alone. If you have one, you won’t have it for long — unless you were born under a lucky star! (They now barely meet D.O.E. Energy Star Ratings as well, and we hope for not much longer.) Particularly disturbing to us is the poor field history of a nameless, highly publicized “high efficiency” gas-or-oil welded plate construction boiler. Their factory service record as emoted both directly by us, our trade service collaborators and their customers is damnable! Independent servicemen hate to touch them. Parts are product-specific, pricey and their eventual structural fate is predictable. We regard them as a “black eye” upon our industry. Beware of the sales pitch and do your homework! Always get customer referrals at a minimum (including for ourselves)!

    The “wet base” full-combustion-containment cast-iron oil boiler is the industry standard, with a solid performance history. They do however differ by both manufacturer and specific model design attributes that may affect life performance. If your oil boiler does not last at a very minimum 30 years or more, something is very wrong. We have replaced 100+ year old cast iron boilers with still beautiful castings, but you just couldn’t afford to feed them! You are more likely to see a cast-iron boiler section seal corrosion failure in particularly older units or hard-freeze icing fracture neglect than a “worn-out” boiler. Either situation is economically catastrophic though, requiring unit replacement.

    The high-mass vs. low-mass oil boiler argument ultimately comes down to design parameters, material selection, application integrity and its performance under field conditions. The design safety factor of any cast iron boiler can be readily extended by simply providing more iron and more water capacity. “The more it weighs, the longer it stays” – our poor poetry. Works every time, but potentially adds cost to the boiler — as it should.

    We must now extend the preceding arguments to contemporary oil & gas appliance issues. There are three emerging problems well documented in Heating Trade Publications that must be addressed:

    1. “COLD-SHOTTING”. A trade term that describes the condition where cold water is introduced into a hot boiler and thermally “shocks” the heat exchanger metallurgy. Single or cumulative events can result in catastrophic metal fracturing, seal and/or weld joinery failures. The “solution” is the additional piping and installation of a Boiler Return Water Temperature Control Valve to any condensing or low-mass boiler system. This is not an issue with a high-mass cast-iron boiler, nor has it ever been. Please note that Delta-T ECM Hydronic Distribution Technology properly applied will also negate this issue altogether.
    2. MAGNETITE ALLEVIATION. Magnetite is a magnetic, accumulating ferrous (iron) oxide (rust) present in boiler and supply water and attaches itself to internal boiler components, reducing in particular circulation efficiency. It has virtually never been an issue in a cast-iron (a naturally magnetite scavenging material) boiler, but here it is with very low iron content condensing systems. It can only be addressed with an integral, full-time Magnetite Filtration System – a significant initial cost and recurring maintenance additive.
    3. HYDRONIC DISTRIBUTION. Contemporary practices of near-boiler and distribution (to radiation) piping are excessive, unwarranted and inefficient. (We refer to this as “The Plumber’s Playground”.) The seemingly excessive piping and controls witnessed in new installations are so, REDUCING system efficiency while increasing distribution power demands. Low-mass and condensing boiler systems are disproportionately affected. Again, correct application of Delta-T ECM Hydronic Distribution Technology is a must for overall system performance.

    If you’ve read from our “Heating Blog Library” on this site, you would certainly qualify us as “High-Mass Boiler” advocates. We have additionally optimized our system design and performance by fully incorporating “Delta-T ECM Hydronic Distribution Technology”. It smooths hydronic system thermal demands while significantly reducing operating costs. We slogan this as: “Putting an ‘Automatic Transmission’ on a Boiler”™ — to use an automotive analogy. In fairness this technology would certainly be very beneficial when applied to any low-mass boiler! In fact we consider it a prerequisite in any low-mass boiler installation. Please reference our new Packaged ΔT ECM Hydronic (FHW) Heating Appliance™ (Patents Pending – USA & Canada) on this site, interchangeably fired by OIL or GAS.

    Considering the aforementioned, we much prefer high-mass boilers with their “thermal damping” and reduced cycling characteristics. More iron mass and greater water content equals less burner cycling and ultimately longer component life. We have noted in fact (although we don’t necessarily advocate it) that ultimately a boiler maintenance cycle is now more dictated by the quality and amount of fuel oil passed through our Weil-McLain Ultra Series Triple-Pass Boilers than calendar cycles. Their heat exchanger passages are very open compared to prior generation two-pass units. Combined with the combustion quality of the Beckett NX Burner you generate very little ash accumulation. The same cannot be said of a nameless foreign boiler that seems to have high ash generation and more frequent maintenance calls. (We refuse to service them, by the way — hire the mechanic with that “Mercedes”.)

    TRY THIS: Divide the Cost of a Boiler by its Shipping Weight to determine its approximate the Cost per Pound. The Weil-McLain UO is 1/2 to 2/3rds the Cost-Per-Pound of ANY equivalent U.S. or Foreign Boiler! Just what are you buying – durability or ….. ???

    Summarizing, weigh the operating characteristics of your particular hydronic system application before you select any boiler. In particular look at an intelligent hydronic distribution option such as the Taco® Delta-T ECM Distribution System. Just “plugging and playing” a low-mass boiler into your system may not play too long, nor too well.

    Additionally, a very timely read is our commentary on the just published 2019 Annual Boiler Report. “Reading between the lines” we extract the admonition by several manufacturers that despite their pursuit of highly engineered condensing product offerings, a well configured cast-iron boiler system is still economically favorable. It appears, as we advocate, that a proven high-mass, triple-pass cast-iron boiler system fully integrating Delta-T ECM Distribution Technology prevails. The resultant is “SIMPLE, DURABLE, EFFICIENT HYDRONIC (FHW) HEATING ….. PERIOD!  Judge for yourself …..

    (Please refer to our other blogs and appropriate external sources for detail related to this discussion.)

    Updated: 04/03/2020 PDM, Sr.