If one had a large-scale home retrofit program with the goal of saving energy, what would be the pros and cons of a policy to replace all standing pilot light furnaces? Health and safety improvements count, as do energy savings.
1) Turn down the gas pressure, that is a crazy big pilot
2) Replacing this cast iron beauty is a lot more complicated than it sounds. Unless the distribution system is also updated, return water temps will be >120F resulting in your new 90%+ mod con boiler running at 80% efficiency. A boiler like this if running properly will be 75% efficient.
3) The coal soot left in every possible place throughout the distribution system will plug up the low flow heat exchanger of any 90%+ boiler I have seen except the Burnham Revolution. I learned this the hard way!
4) Most people do not have the funds for boiler replacement and serious weatherization upgrades. When forced to choose, I will recommend the weatherization every time.
5) In 50 years when this boiler is still running without issues, how many times will the tech have to come out and service the mod con that is now past it's useful life? If you follow the manufacturer's advice, 16 cleanings at $100 each adds $1600 to the cost of operation.
Most HVAC contractors make their money with changing these old dogs out, but they still have their place. By reducing the load, through air sealing and insulating we reduce the fuel used and if after that the homeowner still wants to buy a Prius or solar panels or a new mod con boiler, then great, but not until the enclosure is tight.
Health and safety improvements count, as do Secure Home Services If one had a large-scale home retrofit program with the goal of saving energy, what would be the pros and cons of a policy to replace all standing pilot light furnaces?
Biggest pro is to keep the clay or brick or high mass chimney warm with the 4-8" flame. We can waste 50-70,000 BTU hr just to keep the flue working.
If firing rate = 100,000 Btu/hr and SSE = 75%, then 75,000 Btu/hr go to the distribution system and 25,000 Btu/hr go through the vent.If the burner on-cycle is 12 minutes (.2 hrs), then during one cycle the vent receives: .2 hr x 25,000 Btu/hr = 5,000 Btu/cycle MASONRY CHIMNEY:A masonry chimney (block or brick + tile liner) requires about 4570 Btu/.ft. to go from 0 deg to 120 deg. So, on a very cold day, about one foot of chimney will be warmed in one burner cycle: 5,000 Btu/cycle @4,570Btu/ft = 1 ft/cycle TYPE B-VENT CHIMNEY:A 6" B-vent chimney requires about 90 Btu/.ft. to go from 0o to 120o. So,5,000 Btu/cycle @ 90Btu/ft = 55 ft/cycle
1) is correct.
2) is not. We install dozens of condensing boilers a year, and I clock them regularly. A sealed combustion/condensing boiler with a vertical/counterflow heat exchanger (think Triangle Tube "Prestige" or Weil McLain "Ultra") runs with an exhaust temp 10 to 20 degrees lower than the supply temp. I routinely test boilers delivering 160 degree supply that have 140 degree exhaust gas and 89% to 93% SSE.
3) "Coal soot" in the distribution fluid is physically impossible. Maybe you are referring to corrosion products and particulates -- a REALLY common problem in old systems originally built for steam, with steel or iron plumbing and radiation. Flush, flush, flush, get the water chemistry right, install a good strainer, and MAINTAIN the system.
4) I sure wish these decisions were always that simple...
5) Wrong again. That 50 year old boiler SHOULD have been serviced every year or two, same as the new one. The only difference is that it will run (poorly to sort-of OK) for years regardless of the neglect. You could have said the same thing about my 1973 AMC Matador, too. But that doesn't mean I want the darn thing back -- no way! The fact that the old cast iron system doesn't shut down due to neglect is a problem, not an advantage.