• Tag Archives Indirect Heater
  • “PROGRAM” YOUR INDIRECT WATER HEATER (IWH) FOR SYSTEM EFFICIENCY

    An Indirect Water Heater (IWH) driven by an efficient hydronic boiler is the acknowledged cost-effective method for domestic hot water (DHW) generation. However, installing an IWH as a stand-alone (dumb) heating accessory can limit its potential and in fact reduce your overall annual heating system efficiency (AFUE) in practice. Let’s examine the elements comprising a complete hydronic system and their effects.

    The Indirect Water Heater (IWH) has experienced a renaissance with the availability and effectiveness of modern materials and manufacturing. Specifically Stainless Steel, Super-Insulation and Automated Manufacture provide a superb product-performance package, eclipsing its predecessors and current competition. Even so they are not “cheap” in a monetary sense, yet provide an outstanding service life while maintaining efficiency!

    Referring to our website www.BoilersOnDemand.com you will note that we integrate an IWH into our “Packaged Delta-T Hydronic FHW Heating Appliance” as standard equipment for overall performance. The HTP Superstor Ultra has been our exclusive IWH offering for over twenty years with stellar performance! There are many IWH Products available, even within HTP, but the SSU Series still exceeds.

    Referring to our “Packaged Delta-T Hydronic FHW Heating Appliance” image provided you will note four (4) basic system components:

    1. A “High-Mass” Weil-McLain Ultra Series UO Boiler.
    2. A “Green” Taco Delta-T ECM Circulator immediately above the boiler.
    3. Several Taco “Zone Sentry” Valves near circulator (for IWH) and @ top, center for heating zones.
    4. A HTP “Superstor” IWH, close-coupled to the right.

    As a standard feature on all systems utilizing an IWH as pictured, we provide a SPST (ON/OFF) Switch mounted on and in series with the IHW Aquastat. This allows selective engagement during system set-up, quick start-up, operation and diagnostics. It is visibly evident between the boiler and the IWH, placed for convenience.

    Our “System User’s Guide” refers to the IWH Selector Switch as a means of customer-inhibited operation with a two-fold purpose:

    1. Cycling only preparatory to demand DHW usage such as a dishwasher or shower(s), then “tailing” hot water via additional tasks to efficiently utilize remaining storage.
    2. Turn off DHW during protracted absences such as vacations, etc. while preserving primary area heating without risk or penalty.

    In either sequence boiler temperature is significantly reduced, ultimately approaching area ambient, reducing fuel consumption in the process.

    Using our SPST (ON/OFF) Switch as a junction box we also offer to our clients extension via another switch in series to a more convenient operating location. This is particularly helpful when considering site physicals and customer physical impairments or limitations.

    Carrying this to the next logical level is using at minimum a 1-Day or preferably a 7-Day Programmer, as may be applicable to your lifestyle. Keep in mind though that an IWH Zone uses a “dry” switch, i.e. no power applied, or you will “fry” something (your system aquastat!). Program your IWH Service to compliment your usage pattern for energy savings.

    Then you can proceed into the “wireless”, intelligent world via Wi-Fi Thermostats, Home Automation and the like. Like our “techie” customer on a work assignment in Hawaii who called us to advise he had a heating problem in his seasonal home up here in New Hampshire, the world is changing and beneficial technology is available to us all.

    By becoming “smart”, we can save ourselves a bit of trouble and a little money in the process.

    Author’s Note: Updated 01/10/2018


  • DOMESTIC HOT WATER (DHW) GENERATION – YOUR OPTIONS

    We just returned from a hardship “no heat” service call. These folks are obviously up against it economically, as are many these days. However they recently substituted an electric water heater for their boiler immersion coil to generate domestic hot water and hopefully reduce their summer fuel bill. Now they are concerned about the increase in their electric bill as a consequence.

    This brings up the timely subject of options available in DHW generation. Please refer to content in our other blogs, specifically related to energy source selection, tempering tanks and using a Heating Cost Calculator. For the latter we use the NH OEP Heating Cost Calculator at http://www.nhclimateaudit.org/calculators.php. There should be equivalent calculation tools available for your region.

    Heating Cost Calculators don’t lie. They provide a unit energy cost per Million BTU’s for each fuel. You should apply an appropriate AFUE (Energy Efficiency Rating) for your or the best competing appliance by fuel type to get an accurate comparison.

    By calculation DHW heating fuels from lowest to highest costs are: (NH Region)

    1. Natural Gas – Rate factored by 1.5 to 2 for actual billing. (Divide total fuel billing by actual fuel charge for factoring.)
    2. Fuel Oil
    3. Propane
    4. Electricity – Must be also factored for actual billing. Ours is 1.85. (Varies significantly by Provider & Region)

    Note: 1&4 are “distributed fuels”, necessarily incurring varied pipeline and distribution service costs.

    Natural Gas has been historically the most efficient fuel for both heating and DHW generation vs. fuel oil until recently. A very rough crossover is a $45/bbl Crude Oil Price. Local fuel market variations and appliance installation costs must be considered. Propane, a manufactured fuel, is by comparison a significantly higher cost product. This is unfortunate in that they utilize the same appliances (with minor modification) with similar efficiencies. Propane fuel cost is a killer!

    Fuel Oil and Gas Heating Appliances provide the same function, however differing significantly in configuration to accommodate their particular combustion characteristics.

    Electricity despite its extremely high energy efficiency is offset dramatically by unit cost. Electric Water Heaters are enticingly priced, too. Too bad.

    We are considering only the intermittent combustion fuels (oil and gases) in our analysis. The continuous combustion fuels such as wood, coal, etc. suffer by nature to being very inefficient DHW generators. This is not to allow that these fuels fired in boilers can provide seasonal DHW to Indirect Storage Heaters or coupled to a central boiler with an immersion coil. Although increasing in rural popularity, they don’t represent a significant market segment to date, nor likely will they ever.

    Gas and Oil Combustion Appliances are limited to Boilers and Water Heaters. Their configuration options are similar with the exception of the Gas “Demand” Water Heater and are as follows:

    1. A “stand-alone” (dedicated) Oil or Gas Water Heater. These are a virtual necessity when the central heating appliance is Forced Hot Air (FHA). The stand-alone Oil-fired Hot Water Heater has suffered from poorer fuel efficiency by design and has been limited to high demand users such as restaurants, etc.
    2. The Gas “Demand” Water Heater – A unique, hang-on-the-wall device, it stores no heated water but fires only when DHW flow demand is detected. It is very sensitive to water conditions, including acidity, contamination and lower delivery temperatures.
    3. A Central Heating Boiler with an Immersion Coil therein to create DHW.
    4. A Central Heating-only Boiler coupled to an Indirect Water Heater (Super-insulated DHW Storage Tank). Provides higher efficiency in both heating and DHW generation. Significantly increasing in popularity.

    The Gas-fired “On-Demand” Water Heater has a distinct DHW market application, subject to several limitations:

    1. They are “pricey” relative to other options.
    2. Initial DHW delivery is mildly delayed during warm up.
    3. Long cycle demand capacity reduces with supply water temperature decrease (colder water from source).
    4. Annual chemical treatment to control sedimentation is required to maintain performance.

    Note: Both the Gas “On-Demand” Water Heater and Boiler Immersion Coil Systems mentioned can benefit from a “Tempering Tank” placed in line with their water supplies. (Reference our prior blog on these.) It’s a non-insulated accumulation tank that allows water to acclimate to ambient (room) temperature before entering the DHW heating device. Increases heater performance significantly by temperature and delivery maintenance over total cycle demands.

    Otherwise, Indirect Storage Heaters are the path to efficient DHW generation and storage – regardless! They compliment lifestyle variations and usage patterns when coupled to an efficient heating-water-only generating device, commonly referred to as a “Cold Start” Boiler. It fires ONLY when area heating or DHW recovery is demanded. Otherwise they revert toward ambient temperature, saving significant “standby losses” when not in use. There are several options to “getting there from here”, depending upon your situation.

    1. Purchase a High-efficiency “Heat-only” Boiler and Indirect Water Heater as a package and be done with it.
    2. You can convert your existing Immersion Coil System Boiler to a “Cold Start” Type by:
      • Changing your Master Aquastat Control to a “Cold Start” Unit
      • Adding an Indirect Water Heater with its own circulator or valved zone.
    3. Couple an Insulated DHW Storage Tank to your current Boiler Immersion Coil with a POTABLE WATER CIRCULATOR ONLY (Stainless or Bronze) and Temp Aquastat Zone in the loop. Substitute a “Cold Start” Master Aquastat to convert your boiler to a “Heat-only” as in Option 2.
    4. Do Item 3, but convert a good 80 Gal. Electric Hot Water Heater into a Storage Tank. Strip its wiring and utilize the upper, internal Thermostat Switch as a DHW temp control. Note: This last option is the “Cheap Trick”. It costs significantly less to install, despite the pricey circulator requirement. DHW piping is typically run in parallel with the immersion coil with a flow check function.

    Whenever employing ANY Storage Tank for DHW, place a Thermal Expansion Tank in-line on the cold water supply line! Heating cold water expands it, creating pressures well above the supply pressure and potentially bursting the system. This is particularly evident in municipal or well supplies where there’s a check valve in the cold water service. Cheap insurance!

    So, using the appropriate fuel costs from a Heating Cost Calculator and reviewing your current or planned appliances, plan your Heating and DHW Systems together for best efficiency.

    Last Edit: 06/24/2017 pdm


  • A GUIDELINE TO ECONOMICAL HEATING SYSTEM UPGRADES

    Reviewing all of our installations in recent years, every customer has reported fuel usage reduction of 40% and more. Impressive — and yet humbling. More importantly is how we have achieved these and sharing our experiences with others.

    Predicting the economics of an energy efficiency product, whether you’re proposing insulation, window or heating upgrades is a difficult and potentially an “egg-in-your-face” task. It would seem that claims range from the modest to the scientifically unachievable, qualified only by the sales skill of the presenter. Ultimately, putting it down on paper is the only real documentation. Admittedly we are conservative as well, opting on the side of caution, but predictable. In reality all of the energy product upgrades in combination must be considered.

    It has also become apparent that we personally are in a niche market by default. The predominant activity of “swapping boilers” by dealers and service tradesmen eludes us. We seem to get the “tough ones”, and love it! This also provides us with a developed and unique skill-set to apply. Watching the online forums and fielding direct questioning reinforces this contention. Also consider that our commitment is to efficient, high-end hydronic (hot water) oil, propane and natural gas heating systems by Weil-McLain ONLY, and more specifically their Ultra Series. Reading our prior blogs on this website will clarify and further detail our activity.

    ALWAYS CONSIDER YOUR HEATING REQUIREMENTS AS PART OF A SYSTEM. By a system we mean all of your energy requirements, typically heating (and cooling), domestic hot water, pool heating, spas, etc. Firstly,

    1. You must define where you are now, heating-wise
    2. Where do you intend to go, then
    3. How are you to get there?

    In simplistic terms, your heated space is a “box” to be maintained at a comfortable temperature regardless of external influence. The influences to the “box”, in general order of importance are:

    1. Infiltration: Air leakage is the most significant robber, moving both warmed and exterior air into and out of the structure. Seal these as much as possible. The technical measure is ACH (Air Changes per Hour) and is difficult to field measure, requiring substantial equipment. An ACH of 1 is considered good, 2 or more poor and below 1/2 or so requiring air exchange. Things can get too tight — and unhealthy!
    2. Cap Insulation: Heat rises and consequently the ceiling level temperatures and hence losses are significant.
    3. Windows & Doors: Energy efficiency of these has improved significantly in the last 25 years or so and can substantially improve things. Note that Infiltration (No. 1) is a significant consideration of these as well.
    4. Sidewall Insulation: The remainder of the vertical heated exterior wall structure.
    5. Sills and Floors: Tightened structure to the ground (and below) level, including basement windows & doors.

    To determine where you are (or plan to go) requires measuring the “box”, hence using a Heating Loss Calculator.  (Refer to our prior blog on its use.) In so doing you can “play the numbers” by changing values therein to determine effect(s) and hence a strategy. This is the standard tool of Heating Professionals and some free software is available on-line. Don’t let it scare you. If you can use a measuring tape, fill out a form or translate a recipe you’ve got it made. If you’re still bashful let that geek kid loose at it.

    The Heating Calculator not only tells you where you are but where you are going, as prior mentioned. Remaining then is how do we get there?

    AGAIN OUR TENET: ALWAYS CONSIDER YOUR HEATING REQUIREMENTS AS PART OF A SYSTEM. You have many tools to work with, not just replacing a boiler or a furnace to satisfy all of your energy requirements. Again consider ALL available tools to meet your heat energy requirements and maximize efficiency. Generally, they are:

    1. Furnace — A fuel fired appliance that heats and circulates warmed air to maintain comfort.
    2. Space or Unit Heater — A self-contained gas or oil-fired heated air appliance dedicated to a room area.
    3. Air Handler — A furnace that utilizes an internal heater (electric, hot water or steam) supplied by an external energy source (wired or piped to it).
    4. Boiler — A fuel fired appliance that heats and circulates heated water (or steam) through radiation to maintain comfort.
    5. Heat Exchanger — A device to transfer heat from a differing medium to another without mixing and therefore isolating them. (Useful for special environment applications and situations that we will detail.)
    6. Tankless Heater — A coil immersed internally into a boiler to also provide domestic hot water service.
    7. Indirect Heater — A detached water storage tank heated by a boiler to provide domestic hot water service.
    8. Demand (Instantaneous) Heater — A gas-fired appliance that heats domestic water on demand (no storage).
    9. (Common) Water Heater —- A fuel fired (electric, gas or oil) appliance that heats domestic hot water directly.

    As you review your requirements in lieu of these tools, you will note that there are two (2) distinct scenarios:

    1. Separate appliances for heating and hot water. (A furnace or space heaters with separate demand or common water heaters in combination to suit your local and peculiar fuel economics.)
    2. A combination system utilizing a single fuel source boiler providing all demands.

    First, determine fuel selection. Referring to our other blogs you will note that we are in the higher heating demand New England, and are further restricted by available fuel options and economics. Briefly, in cost order:

    1. Electric rates are very high and not considered for efficient area or domestic hot water heating.
    2. Propane (LP) is generally available but of significantly higher cost as a heating fuel. It is considered a fuel-of-choice, typically providing cooking and/or hot water requirements.
    3. Natural gas has limited availability but is currently the lowest cost heating fuel option. Where available, its choice is obvious with a single caution: Get an actual billing estimate! As a distributed fuel (like electricity) its total delivered cost will be higher than the mere cost of the “fuel”.
    4. Fuel oil is predominant and is a low cost option, competing with natural gas only. Note: Heat pumps, photovoltaic, geothermal, wind and solar are very economically protracted options and not considered currently competitive.

    Scenario 1 (FHA Furnace & Separate Water Heater) can be well executed particularly where natural gas is available and used in “Demand Appliances” i.e. Condensing Gas Furnaces @ 95% and “On-Demand” Water Heaters @ 83%. Propane (LP) efficiencies are of course similar, but at a significant fuel cost premium.

    Scenario 2 (Single-source FHW Boiler) offers the most viable option both economically and physically and is the basis for our system configurations. Selecting the most cost-effective fuel, an efficient appliance to convert, the best medium to distribute and the appropriate devices to transfer energy equate to a “win-win” solution. Using water as the heating medium is ideal for efficient and flexible distribution. Specifically:

    1. A Condensing Gas Boiler @ 93+% or a Triple-Pass Oil Boiler @ 87% providing the heated water.
    2. An Indirect Water Heater providing Domestic Hot Water efficiently and on-demand.
    3. Conventional Radiation to warm full usage areas.
    4. An Air Handler to adapt existing FHA (Forced Hot Air) ducting and distribution without alteration, or to heat an occasional usage area where cold and/or freezing is not detrimental in the off-use cycle.
    5. A “Plate” Heat Exchanger to adapt heated water to physical conditions:
      • Freezing applications such as deep cold areas, selective seasonal shutdowns, snow removal and some pool applications by using glycerol (anti-freeze) as a medium without passing it through the boiler.
      • Adapting zero-pressure sources (steam and exterior wood boilers) to deliver to pressurized systems.
      • Couple a cold-environment source such as an external Solid Fuel Boiler (Wood/Coal/Corn/Peat, etc.) to hydronic (hot water) distribution.

    Existing Systems vary widely in configuration and so must be approached individually. However there are a few distinct patterns and approaches:

    1. The existing Scenario 1 above, i.e. a Forced Hot Air System and Conventional Water Heater. Consider a High-Efficiency Boiler, an Air Handler and Indirect Water Heater combination. This is typically a one-step option — all or nothing vs. individual unit upgrades.
    2. Let’s call this Scenario 2A. An older, inefficient boiler system in poor condition and in need of replacement. Upgrade in entirety when the existing boiler (the high-ticket item) is in jeopardy and fuel efficiency is poor.
    3. Scenario 2B is an existing stand-alone boiler in fair shape with either an internal Tankless Heater or a detached Conventional Water Heater. This common combination offers a step approach to higher efficiency. Consider replacing your Domestic Hot Water Source (Internal Coil or separate Heater) with an Indirect Water Heater and converting your boiler to a “Cold-Start”, On-Demand System. This requires additional plumbing and wiring but you now have attained most efficiency gains minus the boiler efficiency gain itself. Stand-by heat losses are now minimized. You’ll love the savings.

    A story to make our point. We replaced an old, terribly over-sized boiler recently with raves from the customer — with one exception. An adult daughter had moved into an open room next to the “Old Dragon” in the basement. Now she is cold. The next step is to finish off the basement and provide heat only where it is needed (and more efficiently).

    This analogy brings us to our last point. As you make energy improvements to a structure you do two (2) things:

    1. You improve its energy efficiency, the desired result. But,
    2. You also effectively increasingly oversize your boiler for your heating application, an undesirable result. Considering that the Old Dragon was likely over-sized by practice initially, you are now incurring very substantial “stand-by losses”. These energy losses up the chimney, into the surrounding area and poorer energy conversion become substantial indeed, inviting the greater improvement opportunity. Change the boiler.

    We trust this is of some help to you in assessing your energy needs and determining a course of action.

    Last Edit: 10/12/2012 pdm