Condensing Oil-Fired Boilers

Customers who invest in condensing oil-fired appliances pay an initial premium for the equipment, but can reap savings year after year through reduced consumption of fuel oil. That is a selling point that fuel oil dealers can play up in the marketing of such equipment, manufacturers said.

Beyond that, fuel oil dealers should be aware of the different factors associated with installing condensing furnaces and condensing boilers, advised Bill Spencer, formerly of Kerr Energy Systems, now of Devonport Engineering, Fall River, Nova Scotia.

Installing a condensing oil-fired furnace is ‘no more difficult than installing a conventional furnace,” said Spencer, who gave a presentation on condensing oil-fired furnaces at this year’s Canadian Oil Heat Association annual conference. ‘You do have to provide things like a condensate pump that oil guys aren’t normally used to, but that’s just basic plumbing.”

Spencer contrasted condensing oil-fired furnaces favorably to traditional oil-fired furnaces. ‘Especially when you get up into the Energy Star range – the high efficiency ones – there’s a great danger that [a conventional furnace] can condense in the vent, in the chimney somewhere, which is a bad thing,” Spencer said, because the sulfuric acid that naturally occurs in the condensate could cause damage.

When installers replace an old furnace with a conventional one that has an annual fuel utilization efficiency (AFUE) rating of 85 percent, for example, ‘They have to be very conscious of what the old vent is like and probably put in a liner,” among other steps, Spencer said, ‘and even then you can still have a condensation problem in the vent.

‘With condensing appliances,” Spencer pointed out, ‘you know it’s happening in the appliance. It’s designed for that and the vent is designed to withstand it too and it’s fairly easy because the temperatures are very low so you can use plastic.” The return temperature of warm air in the duct work is usually 65- 70 degrees Fahrenheit, Spencer said, ‘So there’s no problem condensing there.”

Wringing the same level of efficiency from condensing oil-fired boilers can be a bit more complicated, Spencer said, noting that condensation will not occur unless the water temperature can be reduced to approximately 112 degrees Fahrenheit. Spencer said that reducing the temperature ‘is difficult in systems where the return water temperature is high.

‘It’s great technology, except that the performance of it is really a function of the heat distribution system that you’re putting it in,” he said. ‘The end user might spend several thousand dollars for a condensing boiler and never reap the benefits of that in a poorly designed system,” Spencer cautioned.

For example, in Nova Scotia, where Spencer lives, most of the older homes have radiant baseboard heating, designed for 180 degrees Fahrenheit in and 160 degrees Fahrenheit out. ‘Returning at 160 degrees you can’t condense,” Spencer noted. The technology ‘works great for in-floor heating where typically supply temperatures are somewhere around 100 degrees and coming back below that,” he observed.

Kenneth Webster of Viessmann Manufacturing Co. Inc., Waterloo, Ontario, agreed. ‘Choosing the right temperature application is very important,” he said. ‘You need low-temperature heating systems to begin with. There wouldn’t really be any financial benefit to consumers to spend the money if they’re heating high-temperature baseboards instead of radiant floor heating or lower-temperature wall panels.”


Viessmann Manufacturing has been manufacturing condensing oil-fired boilers in Europe for years, Webster said, and is weighing a decision whether to begin marketing such an appliance in North America next year.


PB Heating, Valley, Pa., makes and markets a condensing oil-fired boiler called the Peerless Pinnacle.

With an AFUE rating of 92 percent, the boiler qualifies for a federal tax credit of 30 percent, up to $1,500, for purchase and installation, Mike Kaufmann, business manager for PB Heating, said. (The tax credit is due to expire at the end of this year.)

Added appeal for customers is that the residential boiler offers savings on fuel oil consumption year after year and operates very quietly or, as Kaufmann said, ‘People don’t believe it when they don’t hear it.”

Fuel oil dealers and their technicians find that installation is straightforward, Kaufmann said. The boiler is equipped with the Beckett AFG burner, familiar to fuel oil dealers and their technicians, he added.  ‘They don’t have to stock the van with anything special or out of the ordinary,” he said.

Two firing rates are available ‘ .5 GPH and .6 GPH ‘ with input ranges from 70,000 BTU/Hr. to 84,000 BTU/Hr. respectively. Both ratings qualify for the Energy Star rating. The unit is shipped with a nozzle installed for the higher input, Kaufmann said. The nozzle for the lower input is included separately so that it can be substituted by the installer if needed, based on the size of the house.

The boiler can be vented through a sidewall or vertically, up a chimney, without the need for an additional blower unit for exhaust, Kaufmann noted. Concentric piping is necessary for correct venting. The outer pipe, which is metal, is used for intake of fresh air, and the inner pipe, which is polypropylene, is for exhaust.

In the sealed combustion, fully condensing unit, the heat exchanger is made of 904L stainless steel, a grade that combines molybdenum and copper with iron. That grade of steel is used because it is designed for resistance to acids, including the sulfuric acid in the condensate.

The unit features a slim design and occupies a small footprint, but requires at least a six-foot high ceiling in the basement. ‘That’s very important,” Kaufmann said of the clearance, because access to the burner and internal components is at the top of the boiler, which stands approximately four-and-a-half feet high.

Control features include multiple temperature set points for heating and domestic hot water, and outdoor reset capability. Test and diagnostic functions are displayed on an LCD screen.

The challenge of condensing with oil-fired appliances generally ‘is really a materials problem because of the sulfur in the oil,” said Spencer of Devonport Engineering. While manufacturers know that the steel in the heat exchanger must be a high-quality grade to resist corrosion, they continue to seek less expensive yet equally durable alternative materials.

European manufacturers use EN 1.4539 grade steel, Spencer noted, but he said, ‘If you price that in North America [the cost is] incredible.” Spencer said two pounds of it currently costs about $700. ‘It’s very, very expensive.”

U.S. manufacturers often use AL29-4C grade steel to cope with the sulfuric acid, though that too is expensive, Spencer noted.

Adams Manufacturing Co., Cleveland, Ohio, which makes four configurations of condensing oil-fired furnaces, uses AL29-4C grade steel, Jeff Dubasak, sales manager, said. The four configurations of furnaces that Adams makes are upflow, downflow, horizontal and lowboy. ‘Each has a different input rate and fan size,” Dubasak said. In general terms, Dubasak said, a condensing oil-fired furnace costs about twice as much as a conventional oil-fired furnace, but typically provides the customer savings in fuel consumption over a 20-year period because it is more fuel efficient.

There are plastic heat exchangers, but Spencer said incoming temperatures were ‘too high” for thermoplastics. Looking ahead to possible innovations, Spencer said that coating technologies held out some promise.

‘There are all kinds of coating technologies out there,” he said. ‘I think in the future when those technologies advance, someone’s going to come out with a carbon steel heat exchanger that has some kind of coating on it,” Spencer predicted, ‘and that’s going to reduce the cost significantly.”

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