• Tag Archives High Mass
  • THE DELTA-T ECM CIRCULATOR — The “Automatic Transmission” for Boilers

    After speaking on-site  with a local customer about his system, he inquired as to what else we were doing. A mistake on his part.

    Both of us having differing technical backgrounds I launched into an inspired dissertation of our application of Delta-T ECM Circulation to Residential FHW Heating Systems. Obviously very interested, a running Q & A exchange of increasing technical depth ensued to the point of my noting he was developing that “deer in the headlights” look of incomplete understanding.

    We engineering types have a terrible habit of technically overloading our audiences, not as an “ego-trip”, but to inform as effectively as possible — we think!

    Needing to salvage the situation I paused, desperately searching for that inspired “bolt of lightening” to strike and clarify the atmosphere. By seeming grace, it came immediately! “I’m putting Automatic Transmissions on Boilers.” Yeah”, he responded, “that makes complete sense. Good idea!” Our further conversation became an analogy of FHW Heating Systems to Automobiles, surprisingly clearing our technical disparages. To expound …..

    After all, hot water boilers and automobile engines are both truly “heat engines”. An automobile engine must convert as much fuel combustion energy into mechanical propulsion power as possible via pistons, crankshafts, etc. Less than 60% becomes useful power, the remainder is dissipated as waste heat. The hot water boiler on the other hand necessarily converts its fuel combustion energy directly into useful heat at up to 97% efficiency!

    The automobile uses a transmission to adapt its mechanical power to control vehicle propulsion. A variety of gears, pumps, valves, etc. are used to accomplish this. The hot water boiler conversely needs only to move heated water (via a pump) exactingly to ideally acclimate our heated areas and (optionally) our domestic hot water (DHW).

    The Delta-T ECM (Differential Temperature) Variable Speed Circulator (Pump) is that ideal “boiler transmission” that delivers heated water most efficiently to maintain our comfort. So efficiently does it do so as to reduce system fuel consumption by up to 15% and electrical consumption by up to 85% as documented by Taco, Inc. Published Testing Results.

    No longer is heating system efficiency measured solely (and inaccurately) by the Boiler AFUE (Annual Fuel Utilization Efficiency) Rating, but the aggregate of Boiler, Distribution and Radiation Efficiencies. There are THREE (3) Elements in a hydronic heating system! Just as in Sulky Racing, it’s the combination of the horse, the jockey and the buggy that wins races.

    Even more exciting  is the opportunity provided by the Delta-T ECM Circulator to most efficiently configure a FHW Heating System, which we have done very effectively. Refer to our other, recently published Delta-T Blogs on this site that detail our development, field testing and observations of our systems.

    Our “Packaged Delta-T ECM Hydronic Heating Appliance™” (Patents Pending)exhibits the following attributes in direct comparison to the typical “conventionally installed” system:

    1. Has a higher Combined Boiler AFUE and Delta-T ECM Distribution (System) Efficiency than achievable with any “conventional” system configuration.
    2. Consumes less fuel and electrical power than any equivalently sized system.
    3. Our Integrated Boiler/Indirect Water Heater System occupies 1/3 to 1/2 the floor-space of others.
    4. Our proprietary Fully-Iron & Cast near-boiler piping maximizes durability and distribution performance while using fewer materials.
    5. Further, combining a High-Mass Boiler with an All-Stainless Indirect Water Heater assures a dramatically projected economic life (30 years or more?).
    6. A truly universal, multi-fueled Appliance. Just change the burner —– not the system!
    7. Provides, Simple, Durable, Efficient and Cost-Effective FHW Heating.

    So yes, we do put “Automatic Transmissions” on Boilers!

    Author’s Note: Updated 07/23/2018


  • BEYOND AFUE’S – TOWARD REAL HYDRONIC (FHW) HEATING EFFICIENCY!

    For the past year Mercier Engineering has been immersed in developing and preparing for market it’s Packaged Delta-T Hydronic (FHW) Heating System™, based on our past heating experience projected into the new world of “Delta-T Circulation”. You may have noted our preoccupation with this technology in “The Heating Blog” on our www.boilersondemand.com  website. Time to “put our money where our mouth is”, so to speak. The results of our efforts we deem noteworthy and are initially reflected in this writing.

    As the titling of this blog purposely implies, we must get beyond weighing hydronic heating system efficiencies solely upon the boiler’s Annual Fuel Utilization Efficiency (AFUE) Rating.  It is only one of multiple elements in an operational formulation that is seldom if ever approached, even more poorly understood, and we allege almost universally misapplied. Strong words which must be tempered by the reality that there has been little market incentive to change our approach to serving the residential FHW heating market in particular; but we ultimately must adapt and change it for the consumer’s benefit.

    AFUE is a regulatory, laboratory testing procedure intended to establish an efficiency value for a hydronic (hot water generating) boiler under a defined operating sequence and conditions. It can be presumed that it executes this comparison very effectively, under its terms. However, what it does not measure from our observations is in practice very significant. Specifically these Non-AFUE Test Attributes are:

    1. There are no provisions for qualifying or measuring between-cycle “stand-by” or “idle-time” losses. This is the time between burner firing cycles when the boiler is prone to radiated energy and convective exhaust (flue) losses, presumed to be non-productive.
    2. Similarly, the testing is “steady-state” in execution, providing no qualification or quantification of individual boiler attributes that may contribute to site application efficiency.

    These test attribute observations have been borne out in field applications, where system performances have not correlated well, boiler-to-boiler or system-to-system. To further complicate this is the variability of physicals to each application, however subtle. The forums and blog sites are rife with these seemingly “apples-to-oranges” commentaries. Our developmental efforts may be able to provide some explanations.

    From our observations there are necessarily five (5) elements contributing to total system energy efficiency:

    1. The boiler (heat engine) energy conversion efficiency or AFUE.
    2. The physical attributes of the specific boiler complimentary to system operation.
    3. The energy required to move heated water through the distribution system (radiation).
    4. The effective matching of radiation elements to heating demand.
    5. The control algorithm(s) to match energy creation with varying system demands.

    Our initial efforts have been with oil-fired hydronic systems and is the focus of this document, with gas-fired and solid-fuel applications to follow as resources permit. However, much of this effort is applicable as the basis of other heating systems.

    Varying the output (energy creation rate) of any heating resource is paramount. This has been readily achieved in gas-fired boilers by “modulating” combustion with sophisticated valving and controls. Typically they adjust from 20 to 100% of capacity, from “idle” to “full speed” to use the automotive analogy. However, direct modulation of oil-fired systems is not feasible using current technologies. A fixed (capacity) firing rate via pressurized, nozzle induced fuel atomization is the norm. Therefore, the only option is to adjust the operating temperature of an oil-fired hydronic boiler via controls to compliment heating demand. This is reasonably well-managed with modern “cold-start” aquastats, external temperature sensors, etc.

    The prior unaddressed penalty to particularly residential hydronic systems has been the toll on equipment and electrical energy requirements of circulating heating water with fixed-speed circulators. They are notoriously and arguably universally misapplied and inefficient in practice. Reducing water temperatures merely aggravates the situation by prolonging circulator cycling.

    Fortunately technology has come to the rescue in the form of the “Delta-T” Circulator, now becoming very applicable and affordable to the residential/light commercial markets. The undisputed pioneer and flag-bearer in this market is the Taco Viridian VT2218 found at this link: http://flopro.taco-hvac.com/media/Viridian_VT2218_100-114.pdf  To use the quote “This changes everything” is not an exaggeration! The Viridian is in fact the second generation, replacing the entry product Taco “BumbleBee” found at this link: http://www.taco-hvac.com/uploads/FileLibrary/100-101.pdf We mention the “BumbleBee” only because it has rapidly become a “cult product” in the HVAC Community, somewhat akin to the “Trekkies”. It was our initial “new tool” in developing and thence refining our product(s). Like our brothers, we hate to see it go as we move to the refined and more sophisticated “Viridian”.

    Referring back to our five (5) elements to total system efficiency, Delta-T Circulation is number three (3) on the list but is deservedly and necessarily the foundation of any hydronic system improvement. Taco reports system Delta-T Circulator-only swaps yielding 15% fuel usage reductions. It is the keystone of our Packaged Delta-T Hydronic (FHW) Heating System™, and should be the first improvement to any system! We caution however that this will require substantial near-boiler system re-piping and your installer must be knowledgeable. It is discouraging to note how few of our fellow tradesmen are cognizant of Delta-T or have used it beyond a radiant heat loop. We “Old Dogs must learn new tricks”, and we have!

    The second element of import is the necessity to employ “Cold-Start” Boiler/Aquastat Hydronic Technology, which overlaps Nos. 2 and 5 in our list. We are unabashed in our praise of the Hydrolevel 3250-Plus “Fuel Smart” Aquastat, found at this link: http://www.hydrolevel.com/new/images/literature/sales_sheets/fuel_smart_hydrostat_sales_sheet.pdf   It is now standard equipment on all our Weil-McLain Ultra Oil Boilers, and none too soon! The inter-action of the 3250-Plus with the VT2218 Circulator’s operational software is paramount to total system performance, as we have learned.

    Note: “Cold-Start” Technology applies to “heat-only” boilers. DHW (Domestic Hot Water) must be effected by an external Indirect Water Heater or another dedicated appliance. We combine the Indirect Water Heater in our design for optimized Heat and DHW Generation.

    Element 3: Our development indicates individual boiler attributes are significant. Specifically,

    1. Boiler supply and return tap placements are crucial to system “packaging”, i.e. the ability to compactly (efficiently) structure near-boiler piping. (We can pipe into a space as close as 11″ from the chimney, with all piping and controls behind the boiler, yet readily accessible.)
    2. A very high boiler mass (weight) for its capacity, i.e. for both thermal damping and storage.
    3. Favorable exchanger flue passage routing and exhausting.
    4. Burner type to compliment its attributes.

    The noted attributes lead us to our “Boiler-of-Choice”, the Weil-McLain Ultra Oil Series with the Beckett NX Burner. Refer to this link for detail: http://www.weil-mclain.com/en/assets/pdf/Ultra%20Oil%20Brochure_8%20Pg_web1.pdf   We have had “conventional” system design and installation experience with this boiler for over ten years now, with only one “no heat” service call, a failed aquastat. Weil-McLain has since upgraded it to the Hydrolevel 3250-Plus, thank God!

    The Beckett NX Burner has been likewise flawless in operation. Literally a “plug and play”. Its dual vent typing capability (direct & chimney) has proven beneficial to problematic venting applications, especially when encountering “cold chimneys” in our northern climate. Fully exposed exterior chimneys are sure to give a rough startup without utilizing its pre-purging and pressure firing features.

    The key attribute to system performance outside of Delta-T Distribution has proven to be Thermal Mass (Storage) provided by the sheer robustness (weight) of the Weil-McLain UO Series High-Mass, Triple-Pass Boilers. They are “The Heavyweight Champions” by far and as a result exhibit lower mean boiler operating temperatures and very less frequent burner cycling.

    As a matter of policy we do not cite or criticize our competitors, but we must make a single attribute comparison to emphasize our point. The approximate block weights of the top hydronic (approx. 100KBTUH, 87% AFUE) oil boilers are:

    Manufacturer/ModelApprox. Ship Wt.
    less Tare (lbs.)
    % of HighestComments
    Buderus G115/G21537560%Adjusted for 100KBTUH
    Burnham MPO-IQ11545072%
    Weil-McLain UO-3625100%

    AUTHOR NOTE: Very noteworthy, the Weil-McLain UO is also disproportionately the lowest cost per pound (by nearly half) of the three. Just what is the consumer paying for, we wonder? In our development experience increased boiler mass equates to improved system longevity and hydronic performance!

    Radiation (Element 4) efficiency is the remaining, but least controllable variable in a heating system. It is substantially outside the scope of our system application, yet there are some performance elements we can address.

    Existing hydronic radiation:

    1. Removal of unnecessary valving in zone supplies and returns. All zone supply functions are integrated into our system package.
    2. Zone interconnection and functionality can be optimized by correct pipe sizing and routing. It confounds us as to why some plumbers use virtually no 45° fittings! You can use 3-4 of them vs. a 90° elbow for the same flow resistance, and only 70% of the pipe required for a 90° elbow routing.

    New hydronic radiation:

    The contemporary approach to radiation varies widely, from simple radiation loop(s) for zoned heated areas to individually heated rooms throughout. The more finite the control, the more piping, fittings and control valving, the more hydronic distribution energy is required.

    Ironically, the same Delta-T Circulator Technology we employ to maximize our system performance has preceded us and become the darling in particularly radiant system applications. We have also employed them in these and they perform admirably. They reduce the energy requirements significantly but yet still camouflage that basic issue.

    If your concern is total energy consumption of a system, we would invite you to consider using less sophisticated radiation distribution schemes. A properly designed, installed and balanced series or split piping loop exudes simplicity and will likely be a lower installed cost. The KISS Principle applies — keep it simple ….. (Refer to our Heating Blog Library for additional detail.)

    To Summarize:

    1. Additional Boiler Attributes are important, beyond the AFUE Rating. In particular heat exchanger thermal mass (weight) will lengthen service life while minimizing repair costs. Burner attributes related to exhausting and tuning must also be considered.
    2. Delta-T ECM Hydronic Distribution Technology is key to improving any system’s energy performance, both heating fuel and electrical power consumption.
    3. Inter-related “intelligent” controls determine system operational performance. They are currently the Hydrolevel 3250-Plus Boiler Aquastat and the Taco VT2218 Delta-T Circulator Logic.
    4. Near-boiler plumbing in particular affects system performance. This is optimized in our system piping configuration to include fail-safe “natural gravity convection”.
    5. Interconnections between our system zone access points to existing radiation must be executed with the goal of minimizing flow anomalies.
    6. Existing and/or new radiation installations must likewise be executed by idealizing flow conditions inasmuch as possible.

    References:
    We strongly recommend referring to Taco’s website link http://flopro.taco-hvac.com/deltat_resources.html and refer to the various Delta-T resources therein. There’s a volume of resources here that will properly inform you of this new technology and its place in your Hydronic (FHW) Heating System.

    Author’s Note: Hyperlinks updated 08/27/2019


  • HIGH EFFICIENCY CONDENSING FHW BOILERS – The Dirty Little Secrets

    The popularity and performance of condensing gas technology hydronic (FHW) boilers is both noteworthy and deserved. Kicking up heating gas fuel (Natural & LP) efficiencies from the prior generation average of 80-85% to 90-97% in one technological step is astounding. However like any new technology it has come at a price, both positively and negatively. Problem is the negatives are not discussed with the sales enthusiasm.

    It doesn’t take a very sharp pencil to justify a condensing boiler upgrade from a prior generation unit, and particularly a much older one. That 10% or (much) more is significant itself, but coupled with an indirect water heater operating as a “cold start” system can yield 40% or more in our experience. So where are the issues?

    Hydronic boilers have traditionally been constructed of cast iron or of welded steel plate as a lower cost alternative. The welded-plate alternative has failed historically in both durability and efficiency. We have noted recently a disproportionate number of steel boilers appearing locally in “upscale” newer homes. After all, contractors have to cut costs somewhere!

    In the gas market we are moving to new materials to compliment both the cleaner and more controllable combustion afforded by Natural Gas and LP (Propane). These boilers can “modulate” (adjust) their firing rate up to 80% to accommodate heating demand, much like pressing on the gas pedal of your automobile from an idle to adjust power and speed. This is accomplished using a sophisticated sensor and control system. So now we can utilize materials that are more favorable, specifically aluminum and stainless steel, but for very differing attributes.

    Referring to aThermal Conductivity Chart you can appreciate why copper is so commonly used as a heat-exchanger material in baseboard with thin aluminum fins to compliment. Cast iron is so-so but stainless steel is very poor. So why use these particular materials?

    Cast iron is typically used in larger, heavy sections with a generous amount of water as a “thermal mass” device to manage both combustion and energy distribution. (Refer to our Blog:HIGH-MASS VS. LOW-MASS BOILERS – THE ARGUMENTSfor more detail.)

    Aluminum would also seem to be very desirable in this regard excepting that it is very susceptible to chemical corrosion and must be alloyed and/or chemically surface treated for protection.

    Stainless steel on the other hand is a very poor heat conductor, but with very good corrosion resistance. Designers must therefore carefully define the stainless steel heat-exchanger to attain performance while utilizing a substantially more expensive material. With much poorer thermal conductivity, material thickness and heat transfer surface area become prime design parameters. However, coupling this with the necessity of welding stainless steel components together for structural and process integrity and you have a metallurgical compromise.

    Corrosion is the common denominator in all heat-exchanger materials, caused by oxygen and minerals naturally present in water. As such, appliance manufacturers must deal with their eventual effect in their design executions. It’s not IF, but WHEN chemistry wins. Thus the only way to predictably present a hydronic (or steam) boiler to market is to specify the water quality requirements of the system. Note: All condensing (and other) heating appliance manufacturers detail pH (acidity) and additional water conditions in their product documentation and in their Warranties!

    For the past decade or so, manufacturers have been quietly honoring warranty claims against condensing boilers that are clearly the result of poor water conditions. Cast iron boiler durability on the other hand has always been manageable. We presume that honoring condensing boiler warranties was a calculated marketing effort to promote the new technologies and systems, but no more.

    Weil-McLain (our flagship supplier) is renowned within the heating industry for its warranties (and leniency). We have dozens of stories to reinforce this supposition in fact. “The customer is (virtually) always right.” However, speaking recently with Weil-McLain Field Personnel has prompted this blog both reflecting the industry’s necessary strategy change and the ultimate effects upon the consumer.

    The extent of water quality management and documentation may vary within particular suppliers, but be assured that it is happening! This will be very evident not only in new system documentation but inWarranty Claims on existing condensing boiler systems, the most susceptible and therefore the industry focus.

    Therefore you, the consumer must now “have his ducks in a row” by:

    1. Verifying that the water condition requirements of your boiler are met upon installation and start-up by yourself or your installer.
    2. Documenting your water conditions then and thenceforth.
    3. Qualifying that your serviceman performs the specified pH (Acidity) Test during maintenance cycles.
    4. Keeping these maintenance records on file.

    Note: A similar situation exists in degree within the On-Demand DHW (Potable Drinking) Water Heater market. We in fact are certified and install the premium brand unit. They strongly recommend annual flushing with white vinegar to maintain heat-exchanger integrity. (This requires suitable piping installed on the unit, pump, etc.) Immersion coil heaters within boilers have historically had this issue, but not to the degree of the on-demand units due to their design attributes (less restrictive fluid passages). Their replacement cost is also more reasonable in comparison to an on-demand unit.

    So, hard water can become hard times! Be prepared.

    Continuing with our representatives’ conversations, they further offered an enlightenment that won’t be found in print. Specifically, that the life expectancy of a condensing gas boiler is measurably more limited by water conditions and average life is projected to be substantially less than its less sophisticated predecessors. Their average heat-exchanger replacement life expectancy from a marketing perspective on a condensing boiler, considering the heat-exchanger construction material is:

    1. Aluminum — approximately six years.
    2. Stainless Steel — approximately ten years.
    3. Cast Iron — over twenty years.

    We are in no position to qualify or disqualify these statements, excepting to state that we have had an aluminum heat-exchanger failure at six years. It was replaced at no charge (of course) by Weil-McLain. The water condition at this installation was poor, but had been treated by a salt-based softener. How effectively is the obvious question?

    Note: A heat-exchanger replacement cost can approach half that of the initial boiler.

    No field histories on stainless steel heat-exchangers have been published, so again we must defer to judgment.

    In either case, the substantial differences in both initial condensing gas appliance costs and life expectancy must be considered in making a purchase decision.

    Cast Iron is a different matter altogether. It has been the material-of-choice for hydronic and steam boilers from the onset of the Industrial Age. They live long and harsh lives, particularly as “steamers” where their iron is literally eaten by continual ingestion of fresh water (oxygen and minerals) to create and vent steam as the heating medium. A precipitated “black goop” settles in their bottoms and must be periodically flushed to avoid corrosion and a circulation stoppage. (Note: Steamers typically have heavier castings to suit.)

    There is also a unique hybrid stainless steel/cast iron condensing gas boiler available from Weil-McLain (of course). TheirModel GV90+ Gas Boilerhas a primary cast iron heat-exchanger coupled to an external stainless steel “condensing” exchanger. The combination provides an extremely longer-lived condensing boiler, readily serviceable with modular replacement at a respectable 91-92% AFUE Efficiency. So now there is an alternative with a seemingly longer economic life, but at the penalty of a few points in efficiency less than its more sophisticated cousins. Do the numbers justify the hybrid’s 3-5% lower efficiency and its 20% lower initial cost for a potentially doubled system lifetime?

    Before you “run the numbers”, consider this point. Presuming that the hybrid has a double life over the aluminum or stainless units, you will effectively buy a second unit with no economic incentive at all. At 97% AFUE we have, to quote the old farmer’s saying: “Used everything from the pig except its squeal.” There are only 3 points of efficiency left to play with, most of which is likely technically non-achievable.

    Note: We have not discussed heating oil and other fuel conversions to/from Natural Gas. LP (Propane) in our region remains, and likely always will be a more expensive “fuel of choice”. Refer to our Blog:OIL TO GAS FHW HEATING CONVERSION – ALL OF YOUR OPTIONS for applicable detail. Be mindful also that the past year has become an economic crossover for Heating Oil vs. Natural Gas, particularly when the Crude Oil Per Barrel Cost stays under about $45. We have a recent Blog:OIL & NATURAL GAS AS HEATING FUELS EQUATE @ $45/bblthat can serve to further inform ….. and confuse! Further, Natural Gas is not tracking #2 Heating Oil well, the differential widening substantially. So $45 is probably a low number today …..

    So what conclusions can we offer?

    1. An older Gas Boiler upgrade to a Condensing Gas Boiler is a “no-brainer” economically.
    2. Heat Exchanger Material choice, considering your water condition, is paramount.
    3. There are not two but three condensing gas boiler options available: Aluminum, Stainless Steel and a Cast Iron/Stainless Steel Hybrid.
    4. Condensing Boiler Life is a real factor. Check the Warranties and Conditions!
    5. Factor both efficiency increases and potential system life decreases into your calculations. Initial system cost is also a variable.
    6. Your water condition documentation is paramount.

    Summarizing, the Condensing Gas Boiler is the contemporary appliance-of-choice for cost effective residential heating, where applicable. Hopefully providing you with all of the rules of the game will make you, the consumer, a better player.

    Author’s Note: Recent HVAC Trade Journal Articles are beginning to document premature material and weld failures (leakage) in condensing boilers, some immediately upon or within weeks after installation. Some can be attributed to factory process control by manufacturer, but underlying is that basic metallurgical integrity factor. There is no field repair option yet available.

    Updated 06/29/2017 P.D.M., Sr.


  • HIGH-MASS VS. LOW-MASS BOILERS – The Arguments

    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 of failure 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.

     


  • THE WEIL-MCLAIN ULTRA OIL BOILER — “IT’S A HEMI!” (™ – CHRYSLER)

    While recently taking delivery of a large Weil-McLain Ultra Oil Boiler, our distributor’s driver commented: “I hate to deliver these boilers, they are so (mild expletive) heavy compared to the Buderus and the other ones.” (This large distributor markets several popular product lines.) The driver’s comment became evident when three of us were needed to tip up the crated boiler dolly in the truck, then four to move it into the building. (The driver normally handles it himself in the truck and then another or two assist him to transit into location.)

    This experience prompted us into a little research that confirmed the driver’s observation. Yes, the Ultra Oil “high-mass” is much heavier than its “low-mass” competitors — by 100 to 250 lbs at minimum for the equivalent firing rate (capacity). As Heating Engineers we also appreciate the design integrity of this new, FEA (“Finite Element Analysis”) designed boiler “block”. It is a “beautiful beast” in a very complimentary fashion, both in performance and serviceability.

    As a lifetime “motor head” (car performance enthusiast) the analogy came immediately. “It’s a Hemi!” The original Chrysler Hemi(spherical) Engines of the 1950’s and beyond dominated Drag Racing and other racing forms. Originally designed as an Industrial & Marine Engine, it was big, heavy, durable and ultimately very powerful. A modified 180HP automobile motor readily became a 1500+HP racing motor.

    So what does this have to do with boilers? Boilers are heat engines in the purest sense of the term. They ignite and burn fuels to efficiently generate hot water (or steam) to warm our living environment. In an automobile heat not converted into mechanical power is wasted. The boiler meanwhile is all heat generation and tempered distribution.

    Harnessing heat energy also entails risk. (Boilers are necessarily constructed of “sections” with seals between them. Picture a loaf of bread made up of “slices” with “crusts” at each end.) Controls manage this process but may not ultimately protect the boiler from damage under some circumstances, namely:

    1. Water contains minerals and contaminants that generate an acidic sludge in the bottom of boilers (and piping). (Open your boiler drain valve to confirm, if you dare.) Sludge corrodes, eating cast iron and in particular steel plate boiler weldments, reducing boiler life and heat exchange efficiency. Doesn’t help the seals either.
    2. A damaged combustion chamber may permit direct firing onto heat exchanger surfaces creating “hot spots” that create thermal shocking and failure conditions.
    3. Introducing cold water into a hot boiler thermally shocks it. It can occur even during normal operation when large, cold-water heating zones are suddenly demanded into a hot boiler. The metallurgy of the heat exchanger changes, embrittling it to ultimate failure by cracking, warping the section(s) and causing internal seal failures. These situations can be catastrophic.
    4. Using anti-freeze compounds. Many manufacturers, particularly of older boilers, prohibited their use. Newer seal materials have limited the risk. However, check your Warranties! Even using the recommended anti-freeze increases leakage potential in the system. (Servicemen generally dislike its use.)

    Summarizing: Cast Iron and Water Volume = Increased Boiler Life and Performance (Simple Physics)

    The boiler operates at a lower average temperature and accommodates load and surge conditions more readily with no efficiency penalties.

    May we suggest that a high-mass boiler is also a better value?