• Tag Archives Pressure-Fired
  • RELINING A CHIMNEY – Do Your Homework First!

    Our post is motivated by recent instances of poor chimney relining and their effects on heating system operation. It seems that some installers are gaming or ill-advising consumers with poor installation practices. Again you, the customer should set the requirements, not the provider!

    There is no substitute for consumer education, and let us preface by merely stating: Your chimney must match or exceed the boiler or furnace manufacturer’s specification. Their requirement will always be found in your appliance manufacturer’s Installation Manual. With few exceptions (obsolescence?) these are available on manufacturer websites. Occasionally a tradesman’s account may be necessary or require a direct contact.

    The first question to resolve is that your chimney actually needs relining. This is a question to be resolved with a competent Home Inspector. There may be a further economic value adder to your real estate to consider. Do not assume that updating a heating appliance should necessitate a relining. A newer generation boiler for example will typically exhaust a lower temperature and volume of combustion products.

    Presuming a relining is in order, the diameter (or it’s effective sectional area – length x width) requirement of your appliance must be determined and specified. Your existing flue may in fact be larger than necessary, but again specify your required diameter or cross-sectional area.

    There are two (2) common materials used as chimney liners, stone refractory tile and stainless steel. The former is typically used in new masonry construction, but can be retrofitted into and old chimney where downsizing to accommodate it with filler is available. Corrugated, flexible, round stainless steel liner is currently the most popular and to abuse the terminology a “quick & dirty” fix, albeit somewhat pricey. It is also vulnerable to cost-cutting and shoddy practices.

    Let’s explore recent examples to qualify our observations and statements:

    Case 1: A Public Weatherization Program Installation

    Seven (7) years ago this home was retrofitted with a Weil-McLain WTGO-3 Boiler with a 7″ Exhaust Flue and 8″ Dia. Chimney Requirement. At the same time the chimney was relined with a 6″ Dia. Stainless Steel Liner. The Boiler Flue Piping was then “frenched”, i.e. slit, tapered and forced into the 6″ Liner extension and sheet metal screwed to secure. It must be added that the original chimney was unlined, 12″ square brick construction. The chimney clean-out was removed and the base filled with scrabble and mortared to just below the flue outlet. The larger initial flue cavity permitted the bending of the 6″ Liner to act as the flue outlet as well.  A chimney-top weather cap was installed (reducing draft) to eliminate rain & snow from running down the chimney and then into the Galvanized (rusting) 7″ Exhaust Flue Pipe.

    Upon firing, despite a burner 15 second “pre-purge” cycle, the flue Barometric Damper inverts with a bang, expelling an amount of flue product into the basement area, but quickly recovers to positive draft as the chimney liner warms.  Firing the boiler with the service port open similarly delivers a blast of flue gases. The liner bend is accumulating fly ash, reducing draft as well.

    The Agency stands by its Qualification Test Results. The Statute of Limitations has expired.

    Case 2: Another 6″ Dia. Chimney Relining – Weil-McLain 368 Boiler with 7″ Exhaust Flue

    Here we go again! Same Town, a few streets away. Same installer? Wish we knew …..

    We were solicited for a planned, immediate boiler replacement. Customer lamented that existing boiler was rumbling and pulsating, running erratically since a chimney relining. Can’t imagine why ….

    Installed a Weil-McLain UO-3 with a Pressure-Fired Beckett NX Oil Burner, 6″ Exhaust Flue. “Runs like a top” …..

    Case 3: Our Duplex WGO-6, 400KBTUH Installation – Municipal Facility – Relined Chimney

    Existing 12″ x 12″ Brick Chimney was relined with a 12″ Dia. Stainless Steel Corrugated Liner to suit system requirement. The installer expressed frustration with the “scrape fit” install, then fitting into a 12″ Stainless Tee flue outlet, etc. Has an appropriate Chimney Weather Cap installed and has performed flawlessly for over six years.

    There are more than a few variables to consider in relining a chimney, if necessary. We have purposefully presented a trio of cases that exhibit a worst, a fixable and a proper case to show a progression of conditions to consider for your application.

    We are not Chimney Liner Installers, but we like yourselves have to specify them, live with them, or fix them. Always work from your appliance, current or planned to determine your requirements. You can get a little stretch by pressure-firing, particularly with oil, but doing it right wins every time.

    09/10/2020 P.D.M., Sr.



  • 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.