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  • CONVERTING A STEAM HEATING SYSTEM TO HOT WATER – THE WHYS AND HOWS

    Steam Heating Systems were the Cadillac of heating options for residential applications for about a century. Pricey, tending to be a bit fuel-thirsty (regardless of the fuel used), they were extremely simple, durable and provided a superbly comfortable heated environment. Economics have gradually forced steam heating into the commercial and industrial process realms alone. So where do you go with that residential steam system? It depends upon your goals.

    When do you stay with steam rather than change over to hot water or some other heating form?

    1. If you have a nice, period home that suits your needs excepting to lighten up on your wallet a bit, just upgrade the boiler to a modern, high efficiency unit. Older boilers typically are large, with open heating passages to suit both wood or coal fires that when upgraded to gas or oil result in very poor fuel efficiencies. Presuming the system piping and radiators are serviceable there is little incentive to change over the entire system. (Steam heating distribution is arguably more efficient than hot water. It requires no distribution energy, being naturally convective, as does gravity hot water!)
    2. Similarly, if you like those decorative radiators that warm your hands, food, dry clothes on, etc. and take up less footprint and wall space than hot water baseboard, think again.
    3. If you plan an addition or heated area extension and envision running steam piping everywhere to heat it, there is the little known and utilized steam boiler “bottom water” forced hot water heating option. Circulating the lower water below the steaming chamber (top of the boiler) provides extended heating system flexibility. Furthermore, forced hot water extends capability to attics, garages and additions with baseboard, Unit Heaters (fan forced radiators) and Air Handlers (a ducted FHA Furnace with an internal radiator that heats your hot air vs. using a gas or oil fuel source). You must however convert zero-pressure steam water into approx. 15PSI heating water for circulation to new radiation. A correct plate-to-plate heat exchanger is required and circulation both from the boiler and to radiation added. A separate water supply source and an expansion capability must be provided for the pressurized heating water circuit as well. Note: Remember to size your now “two-state energy” Steam/Hot Water Boiler accordingly.

    There is an interesting “middle ground” where you can convert your existing, newer steam boiler to hot water operation while keeping those aesthetic steam radiators. You must however replace all the old steam system piping in doing so. Steam radiators work well with hot water, but at a moderately reduced heating (temperature) capacity. More importantly is the higher water volume content of steam radiators and how to supply them properly for even distribution.

    Referring to our separate blog on FHW Heating Loops, you cannot pipe cast iron steam radiators in series and get even heating! Even a split loop will not work but for a couple of radiators at best.  The only effective options are the “mono-flow loop system” or the “two-pipe, reverse return piping system” with either branched for both supplies and returns to each radiator. Both will require increased piping and circulator capacity.

    Despite the challenges, converting steam radiation to hot water operation provides some attractive opportunities, heating-wise.

    1. You can maintain your prior heated area aesthetics and functionality with few perceptible changes.
    2. You can now re-pipe and “zone” the prior area with multiple thermostats, even down to individual room level if you desire.
    3. Obviously you can add additional heated areas (zones) as well.

    Fully converting a steam boiler to hot water operation and then replacing or adding all heating distribution components is the last and most complete option. Scenarios:

    1. You have an excellent steam boiler with an economic incentive in mind. If you just wish to swap this unit out for your existing, inefficient or failed FHW Boiler as a one-for-one, be careful. Make certain that the conversion components and labor (as applicable) justify the changeover.
    2. Changing your existing, older steam boiler to FHW in our view is questionable. You are trading off operational efficiency against upgrade costs.
    3. Steam Boilers typically and Weil-McLain Steamers (our expertise) in particular have several advantages over their sister Hot Water Boilers. The front and rear boiler sections are notably heavier and bulkier, containing more cast iron and water and contribute to both durability and theoretically capacity. Can’t speak for other manufacturers, but the Weils are heavier and tougher. Check their Specifications. Also if you are using a DHW Coil (immersion coil in the boiler to generate your domestic hot water), steam boiler coil(s) have nominally higher capacities. Larger (Weil-McLain 6-Section+) boilers sometimes have two coils, or provisions for them for greater DHW capacity delivery. Check.

    A recent phenomenon is the Outside Wood Boiler. You know, that thing that sits beside a house that looks like a Metal Garden Shed with a Smoke Pipe sticking up out of it and a woodpile alongside. They are typically owned by rural folks that have a great wood supply and don’t mind tripping through the snow to keep themselves warm. These boilers are also “zero pressure” systems. They must be adapted to a pressurized FHW System through a Plate-to-Plate Heat Exchanger, utilizing circulators and controls. (You must maintain constant electric service to these systems or it can get exciting and cold, or both.)

    Coupling an Outside Wood Boiler to a Steam System is dubious at best. The only deliverables in this scenario are preheated boiler water that must be then fired and converted into steam by the central boiler, but which can also provide DHW through its internal coil (if equipped) or by an Indirect Water Heater (Insulated DHW Storage Tank) as an option. It just doesn’t make sense except to generate a lot of Domestic Hot Water. Therefore, in order to utilize the Outside Wood Boiler effectively you must do a complete steam boiler conversion (or a hot water boiler substitution) with the appropriate scenarios as previously detailed. There is no “easy road to glory” on this one.

    So procedural, to convert a steam boiler to forced hot water operation you must:

    1. De-plumb all iron and other piping right to the boiler. It must be “bare” as we say.
    2. Remove all of the electric components and associated wiring.
    3. Remove the Boiler Jacket (usually sheet metal) and place aside for reassembly.
    4. First, locate and substitute a 30 PSI (FHW) Pressure Relief Valve for the 15PSI (Steam) Valve. VERY IMPORTANT! Forget, and you’ll get wet — and surprised!
    5. Remove the Water Sight Glass, LWCO (Low Water Cut Off), Pressure Switch, etc. (Clean off the front of the boiler, in other words.) Dope and plug all affected boiler taps.
    6. Check Immersion Coil (DHW) Gasket(s) and Blanker Plates for leaks. Fix them.
    7. The smart guy plugs, fills the boiler and pressurizes it to 30 PSI (until the Relief Valve opens) and then checks for ANY LEAKS! Remember, steam boilers operate at about 0.5 to 5 PSI in use. You may have sectional leaking issues and not see them at that pressure. Sectional leaks between boiler castings are usually catastrophic. Stop and rethink your options. But, assuming it passes …..
    8. Find the manufacturer’s boiler piping diagram and locate the preferred aquastat front tapping and insert an appropriate “Spud Well” to receive the aquastat.
    9. Reassemble the boiler jacket and provide the opening for the Aquastat “Spud Well”.
    10. From the Manufacturer’s Hot Water Boiler Manual, identify the control components and hardware necessary to refit. Present this info to your Qualified Heating Engineer or Technician.

    Pay particular attention that your Master Aquastat selection compliments your application. There are several operational options available and should be qualified prior to final selection. Our preferred is the Hydrolevel “Fuel Smart” 3250-Plus Aquastat with their “Electro-Well” for all conversions.

    You now have a tight boiler ready to reconfigure for your application. Your further risk is minimal, save a hot operation leak(s) that may or may not be seal-able. Now consult and utilize a knowledgeable source.

    Be mindful that in converting any steam system to forced hot water you reduce the capacity of that system by 10% or more, if that is a consideration. Steam operates at a significantly higher system temperature in its vapor state than can be safely achieved with heating water safely below its boiling point.

    It may be implied from the above that we discourage steam to hot water boiler conversions. We have done it very successfully, once with an almost new Weil-McLain Gold Steamer and we’ve never been back, but do your homework!

    The option of acquiring a near-new FHW boiler instead of converting your steamer, particularly with the preponderance of on-going fuel conversions can also make very good sense. Check your local classifieds and internet resources such as Craigslist & Facebook Marketplace. (We have found some great deals there.) Please read our blogs on buying a used boiler, etc. in our www.BoilersOnDemand.com Heating Blog Library beforehand.

    Hope this has helped you assess your particular situation.

    Updated: 04/27/2020 pdm


  • ‘THESE ARE THE TIMES THAT TRY MEN’S SOULS’ — AND HEATING SYSTEMS

    Our apologies to Thomas Paine who coined his famous phrase to inspire the American Revolution, but in a prophetic sense it seemingly applies to all things mechanical. This is particularly evident as we are approaching our seasonal, deepening cold cycle. The car doesn’t start, or does so hesitatingly and emits strange noises upon doing so. You resort to a shovel after the snow blower quits, etc., etc.

    Similarly your heating system is working harder and longer to offset Mother Nature’s Global Cooling Cycle, like it or not. So we must “deal with it” as the expression goes. Approaching this from a positive perspective it is also an opportunity to evaluate your heating system’s performance, both the good and bad.

    Obviously we want to monitor the heating system while it is at a peak demand, placing the most severe duty upon it. Mother Nature is fairly cooperative in this respect, and we like to think particularly so in New England, our venue. Deepest cold is typically about a month (plus or minus) after the Winter Solstice (Dec. 21) when we are not fooled by a “January Thaw”. So ultimately just watch the Weather Report.

    The objective must be to determine if the heating system is capable of heating your structure both adequately and reliably at peak (deepest cold) demand. Ideally this exercise would be unnecessary if the system was designed around a heat loss calculation and the characteristics of each room using a Heat Loss Software Program or Tables while using the Meteorological Data for your area. Unfortunately in particularly older dwellings changes have been made not only to the physical structure, but in central heaters (boilers, furnaces), distribution (piping, ducting) and radiation (radiation, radiators, fan units, registers), windows/doors and insulation that have impacted heating both positively and negatively. This is why it is most effective to determine your situation at peak demand.

    Therefore we will look at the central heater (boiler, furnace) cycling and the resultant effect upon room temperature(s). In between these are the heat delivery characteristics of piping, ducting (or both) to achieving the result(s).

    So, on that deep(est) cold January overnight prepare yourself by setting your thermostats to the normal (day?) temperatures (no setbacks — this is a peak load test) and take note of:

    1. The percentage of time that your burner (oil or gas) is firing.
    2. The percentage of time that the furnace fan or boiler circulator(s) operate.
    3. The actual temperatures of each room vs. the area (zone) thermostat setting.

    Note: If you have a steam system, Item 2 is not applicable. The radiator vents are the only adjustment.

    Firstly, try to balance your room temperatures to settings by adjusting register openings, wall or kick space (toe) heater speeds, steam radiator vent settings over a period of hours preceding peak cold.

    1. Can you bring all rooms up to temperature? Within a zone (thermostat) area or total? Capacity issue — see further.
    2. Can you balance each room? If not note the deficiency by room for future correction.

    Secondly, monitor your distribution components (furnace blower or boiler circulators) that are related to these room temperature observations (excepting steam).

    1. If the furnace blower (FHA System) is running constantly and temperatures are not met it is likely that the blower speed (heat delivery rate) must be increased. If it runs intermittently with significant “rests” between cycles, there is likely a burner, air temperature or other distribution capacity issue. See further.
    2. Similarly, in a boiler (FHW System) observe the circulator operation per zone and overall. If the zone or area circulator runs continuously there are three possibilities:
      • The zone radiation (capacity) or piping is undersized or incorrect.
      • The zone may be air-bound and need “purging”, i.e. water-flushing air removal. Check for incrementally cool or cold registers.
      • The circulator is incorrectly sized (too small).
      • The boiler water temperature is low (unsustainable). A boiler delivery issue. See further.

    Thirdly, observe the burner cycling times at peak demand in light of the prior distribution issues.

    1. If the furnace (FHA) gas burner operates virtually continuously, the unit is at capacity (undersized). Note: On gas units the firing rate is typically fixed or self-regulating.
    2. If the furnace (FHA) oil burner operates less than continuously (particularly less than half), the unit is probably over sized.
    3. If the boiler (FHW) oil burner operates virtually continuously, the unit is either at capacity (undersized) or if not the firing rate should be increased as permissible toward requirement. Note: On most boilers the operating temperature may be increased somewhat to gain some capacity, subject to functional limits. Trained Technician recommended.
    4. If the boiler (FHW) oil burner operates less than continuously (particularly less than half), the unit is probably over sized.

    Summarizing, this is a layman’s exercise to provide working data for a qualified Technician to pursue. There are other diagnostic methods, particularly in temperature measurement of FHW piping distribution to optimize your empirical determinations. A degree of risk is involved and should be deferred to a qualified Technician. You have done most of the leg work, isolated the issues and become an informed client. Let him take it from there.

    Meanwhile, enjoy the rest of our winter.