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  • MAXIMIZE HEATING EFFICIENCY WITH A SINGLE ENERGY SOURCE

    Optimization of heating efficiency first requires determining your specific requirements. In general terms there are two or more distinct heating energy uses:

    1. Area Heating – Warming occupied areas fully, or selectively as living habits occupation or use may demand.
    2. Domestic Hot Water  (DHW)– Heated, potable (drinkable) for baths, showers, laundry and personal consumption.
    3. Special Uses – High temperature power washing, sanitizing, etc. (Refer to prior blog.)

    All of these requirements can ideally be met by using a hot water boiler system as a single, central source but the question arises of how to accomplish this efficiently. Specifically, varied heating demands that may range from continuous (?) DHW to very occasional (seasonal?) and selectable area warmth can become a challenge, particularly economically. However occasional demands can “lighten your wallet” to execute and maintain. Let’s address this problem systematically.

    Arguably the most important decision has to be your heating fuel selection. We cannot overemphasize this and the use of a Heating Cost Comparator to define your choice. (See our other blogs.) The standard unit of measure is the “Cost per Million BTU” expressed as a dollar figure. We use the NH-OEP Calculator for our area usage, but similar ones are available online. Use your current or projected new heating appliance efficiencies (AFUE) to get an accurate calculation. New Gas (Natural or LP) AFUE’s are typically 95% for top end (condensing) boilers and 87% for Oil Triple-pass boilers.

    The current and foreseeable heating fuel choices have become quite obvious in the northern climates:

    1. Natural Gas (where available) is the accepted baseline. But BE CAREFUL! Natural Gas is a “distributed fuel” (through a pipeline). Your actual bill will be considerably higher due to service and distribution costs added to your actual therm usage. Get a billing estimate from your gas provider first! (Our local multiplier is up to 2.0 or 100% added for your actual natural gas billing costs.)
    2. Heating Oil is the predominant fuel where natural gas is not available.
    3. Liquid Propane (LP) Gas is another option along with oil where natural gas is not available. LP has been used predominantly for domestic cooking and somewhat for DHW generation. As an area heating and DHW fuel it has traditionally been up to a 100% premium over oil. It is a heating option of choice in our experience.

    Note that solid fuels (wool, coal, peat, waste, etc.) have been purposefully omitted from this discussion. Insurers typically disallow continuous firing fuels using interior combustion equipment. External or “outdoor boilers” are “zero pressure” and require a “plate exchanger” interface with an internal power fired system to assure continuous heating maintenance. Verify these statements and weigh potential penalties for your particular situation.

    Consumers predominantly identify their area heating options as Forced Hot Air (FHA) Furnace or Forced Hot Water (FHW) Boiler Systems. Similarly DHW options as Electric, Gas or Oil stand-alone Water Heaters or from an immersion coil within a boiler. So therefore we usually find the typical FHA System with a stand-alone DHW Heater as a combination. FHW Systems usually provide DHW from an internal Immersion Coil, as previously noted. Currently we are seeing the emergence of the Indirect Hot Water Heater, supplied by a boiler as the efficiency choice.

    But in fact our heating options are more extensive. They include:

    1. Air Handler– A FHA Furnace without a fuel-powered heating source. Instead it has an internal large radiator (heat exchanger) that is externally supplied with energy from a FHW source (boiler).
    2. Unit Heater– A radiator with fan, typically found as an overhead heater in a garage, warehouse, etc. There are also variations of these with provisions for attaching ducting – otherwise similar to an Air Handler.
    3. Plate Heat Exchanger– Basically two (or more) mutually integrated radiators allowing the interchange of heat from varied sources. Source variation attributes may be pressure, temperature, flow rate(s) and composition. Their composition may be aqueous (or not) and adjusted for properties such as freezing and/or boiling resistance.

    Utilizing these latter devices allows us to employ higher efficiency or lower cost hot water generation sources (or both) for all our area and DHW heating requirements. We respectfully suggest that where a single, efficient energy source is desirable or necessary for continuous demand a FHW boiler should be employed. Further, that this source then be applied to all your structure’s heating demands with all the resources detailed within.

    The unmentioned physical fact is that utilizing water as an energy conductor is inherently and significantly more efficient than air. Thus an HVAC System (air heating/cooling) is less efficient than a hot water boiler (heating) coupled with an air handler (cooling) combination. This can be witnessed in their assigned AFUE values.

    So, let us wrap it up by considering some common scenarios for our FHW boiler system source:

    1. A Central HVAC (Heating,Ventilation & Air Conditioning) System Upgrade.

      • Upgrade the existing FHA Furnace with an Air Handler, if desirable, or
      • Install a FHW Heat Exchanger (radiator) into an existing FHA Plenum, plumb and rewire as necessary.
      • Install a “Chiller” in the Hydronic System to provide an A/C source.
    2. Existing or planned FHA System Upgrade – Same as 1. without A/C.
    3. FHA installation into a seasonal, incremental, unheated area or as an expansion.
      • Install an Air Handler or Unit Heater variation to suit.
      • Where freezing protection is desirable, employ a Plate Heat Exchanger with anti-freeze as necessary.
    4. Use a Plate Heat Exchanger to couple “incompatible” secondary heated water sources such as exterior wood & coal boilers, solar & geothermal loops, etc.
    5. In all cases, move to an Indirect Water Heater for efficient DHW generation.

    By the way, these new high efficiency boilers do not necessarily need a chimney. Condensing Gas Boilers typically use PVC pipe for venting and Triple-Pass Oil Boilers with Pressure-fired Burners can use a direct exhausting vent kit.

    Have we run you out of options yet?

    Last Edit: 10/18/2018 pdm


  • THE “POWER VENTER” – “Throwing Good Money After Bad”

    “Throwing Good Money After Bad” is a popular expression that is deservedly applicable to the “Power Venter”, a heating accessory device that enhances a poor chimney’s performance or substitutes for a chimney, depending upon its configuration. Proposed and presented as a “problem solver” it is in our view a “Band Aid Solution”, and deserving of ridicule.

    As a policy we do not install or service Power Vented Systems. One of our collaborators has in fact “cleansed” his entire 1000+ service customer database of all of these devices. “Don’t need the aggravation” is his comment. Recently however we’ve had two incidents that prompted this discourse. One was “doing a favor” for a dear friend with a hardship to discover a Power Vented Weil-McLain Gold Oil Boiler badly in need of maintenance. The second was an invitation to view a customer’s newly pre-built, purchased home only to discover a local plumber’s handiwork, i.e. a non-Energy Star (new?) boiler with the wrong gun affixed — and a Power Venter.

    Situation #1: This is a typical older period local plumber (and not a very good one) budget installation that has survived 15 years of erratic operation. The boiler piping was so improperly installed in fact as to possibly warrant a future addendum to our blog entitled “Plumbing Guys Plumb, Heating Guys Heat”. The Power Vent required mechanical repair and was by current Building Code non-compliant. Primary Power Vents are typically shoved through the box joist of a building near the heating unit as an expedient, in this case without regard for current Code Requirement that the intake and exhaust of a heating appliance MUST be 12 to 18 inches above the anticipated maximum winter snow level. This one certainly wasn’t.

    Situation #2: This is obviously another corner-cutting special, but new and supposedly to Code. Two counts on this one, i.e. a non-Energy Star Compliant Heating System (built from old stock, separate components?) and the same snow level height venting violation as above. Shame on the Local Code Compliance Officer!

    The Power Venter is by definition an energy consuming device, not only in using electricity to drive a blower, but by also forcing ambient heated air out of the structure to induce draft and cool down the exhaust for expulsion. The resultant negative pressure on the building pulls external (cold) air into while driving already heated air out – a “double whammy”. The argument could be made that in a modern, “tight”, energy efficient home the Power Venter air supply should be external for functional operation.

    By specifying modern pressure-fired or “condensing” heating systems the need for the Power Venter is gradually going away, thankfully! There is no longer a need for a chimney, technically speaking, unless it is convenient and likely pre-existing. Replacing it is either low temp plastic piping on “condensing” gas or concentric metal venting on oil appliances for both combustion air intake and exhausting.

    Note: In some existing cases there may be the opportunity to upgrade with a pressure-firing gun to do away with the powered venting device. Consult with your heating engineer or a well qualified technician.

    In summary, comments to the heating system customer.

    1. Older and existing homes with Power Venters:
      • If you’re buying – beware! Your system operating cost will be higher in utilities and maintenance.
      • If you’re upgrading – factor the Power Venter going away and substituting a high efficiency pressure-fired or condensing system. A “win-win,” in both fuel and operational efficiencies.
    2. New homes:
      • If buying, a Power Venter should not be there. If it is, asks the hard questions. Check your Codes.
      • If specifying a new home, use your Power Venter Eraser. You’ll never regret it.