Warm Air Furnace Burner Conversion

camiarrobino

Hello -

Wondering if anyone has any direct experience with, or opinions on, installing a natural gas or propane burner on an oil burning warm air furnace.

I've had 2 younger, well functioning cast iron oil boilers converted to burn natural gas before, as in both situations I would have had to put in a new oil tank if I stuck with oil. Still own both of those properties, not giving me any issues. Granted, not exactly sure on the efficiency of the combustion as I don't pay the gas bills there (tenant-paid)

Is it something that can be done in essentially the same fashion to a warm air furnace, and if so, is it advisable?

Apologies if this thread is in wrong location

Ironman

There are conversion burners available, but it’s probably more practical, and more economical in the long run to replace the furnace with a gas one.

bburd

How old is the oil furnace, and what make and model?

mattmia2

The cast iron of a boiler is a lot more forgiving of seeing a different flame pattern than the sheet metal of a furnace. You could find yourself with a cracked heat exchanger or it could be fine. Replacement is less of a gamble.

SuperTech

bburd said:

How old is the oil furnace, and what make and model?

I think this is the most important question.  If the furnace is a newer Thermopride, then yeah why not convert it? If its anything else, Carrier, Lennox, Nordyne then I wouldn't do it. 

STEVEusaPA

Ironman said:

There are conversion burners available, but it’s probably more practical, and more economical in the long run to replace the furnace with a gas one.

This is the only answer.

camiarrobino

Thanks for all the input. It's an 86% efficient Williamson low-boy, believe the model is CLB-105, either 2012 or 2013 can't remember. I understand if I convert it, the combustion efficiency of the new burner, even if a more economical / cleaner burning fuel, will drop. This is fine as it's still more economical in my area (boston suburbs) to get heat from nat gas compared to oil ($1.33 for 1 therm of nat gas = 100,000 BTU vs. $3.80 for 1 gallon of oil = 138,000 BTU, do the math). My concern as mattmia mentions is the furnace having a much shorter lifespan because the heat exchanger is not as durable as a cast iron boiler. Maybe I'll just leave it alone as oil (do have a newer oil tank so no concern there) and just run it into the ground.....have been told oil furnaces will go much longer than natural gas, all else equal, due to much beefier components (not sure how true). had gas brought into the house in the spring and using it for cooking & tankless WH at the moment so whenever it's time for a new furnace, will be going with gas (if I still own the place)

EdTheHeaterMan

way back in the day when I was a lot smarter that my parents and my mentors in the trade, (About 17 years old) I "Helped" an old neighbor at the summer home in Sea Isle City, NJ by installing a $10.00 part that would save him lots of $$$ on his oil bill. It was a conversion head made by the Delavan folks that attached to the end of a 1725 oil burner. The idea was to convert the existing oil burner to a "Flame Retention" burner with out buying the complete burner. I used it before on a boiler in Philadelphia and it saved the customer about 20+% on the oil usage.

The following summer, when I returned to Sea Isle City, I asked my neighbor how much oil he used, He said the old furnace heat exchanger cracked and he needed top get a new furnace in the middle of last winter. WOW, I found out the hard way that changing flame patterns and flame temperatures in older furnaces is not a good idea. My service manager told me that furnace heat exchangers have something he called MEMORY. Since the day it was new, the flame would heat up the metal and cause it to expand, when the flame went out the metal would contract. Over the years the metal got used to that same rate of expansion and contraction and the heat exchanger would last for years and years.

When I changed to burner head to make the flame more efficient, that changed the flame pattern and flame temperature. The metal memory was not used to this change, and the metal failed and cracked in short order. No good deed goes unpunished! Ever since I learned that lesson the hard way, I would not recommend swapping burners from oil to gas or gas to oil or (Back in the day) standard burner to high temperature flame retention burner. Furnace heat exchangers don't have water on the other side to keep the metal temperature from overheating.

@Ironman & @STEVEusaPA has the correct answer. Get a new furnace, then sell the 10 year old furnace on Facebook Marketplace or eBay. Or just keep the oil furnace for 10 more years.

HVACNUT

I've never done a gas power burner conversion on a furnace. If the burner manufacturer has retrofit specs for one, I guess, but replacing with a gas furnace actually seems easier than a conversion burner, repipe the flue, and spill switch. 

clammy

Completely agree w iron man I ve seen it done on a thermopride and it was a total fiasco and worked terribly but the plumber who 1 st installed the oversized oil furnace then suggested a gas conversion gun to settle issue w the oil burner short cycling which it did not . We were called in to take a look found the guy replaced every part in creation on the unit when the issue really was a giant 7.5 ton straight ac coil completely packed and a filter in the return on the unit beyond packed. Aside from all the issues and cleaning the coil changing the filter it still short cycled . For all the money they spent it would have been 1/2 the price to install a gas furnace . Years later we ripped it all out installed a trane roof top all new spiral duct work and registers and a few mini splits .
I would vote bite the bullet get the tank and oil furnace to the curb and install a properly sized gas furnace w a good filter housing possibly add a ac coil assuming your ducts and registers and return duct work are properly sized to handle it .
Peace and good luck clammy

Steamhead

HVACNUT said:

I've never done a gas power burner conversion on a furnace. If the burner manufacturer has retrofit specs for one, I guess, but replacing with a gas furnace actually seems easier than a conversion burner, repipe the flue, and spill switch. 

To your point, Carlin does have specs for some furnasties:

https://carlincombustion.com/wp-content/uploads/OEM-Guide-2023-010623.pdf

Steamhead

EdTheHeaterMan said:

way back in the day when I was a lot smarter that my parents and my mentors in the trade, (About 17 years old) I "Helped" an old neighbor at the summer home in Sea Isle City, NJ by installing a $10.00 part that would save him lots of $$$ on his oil bill. It was a conversion head made by the Delavan folks that attached to the end of a 1725 oil burner. The idea was to convert the existing oil burner to a "Flame Retention" burner with out buying the complete burner. I used it before on a boiler in Philadelphia and it saved the customer about 20+% on the oil usage.

The following summer, when I returned to Sea Isle City, I asked my neighbor how much oil he used, He said the old furnace heat exchanger cracked and he needed top get a new furnace in the middle of last winter. WOW, I found out the hard way that changing flame patterns and flame temperatures in older furnaces is not a good idea. My service manager told me that furnace heat exchangers have something he called MEMORY. Since the day it was new, the flame would heat up the metal and cause it to expand, when the flame went out the metal would contract. Over the years the metal got used to that same rate of expansion and contraction and the heat exchanger would last for years and years.

When I changed to burner head to make the flame more efficient, that changed the flame pattern and flame temperature. The metal memory was not used to this change, and the metal failed and cracked in short order. No good deed goes unpunished! Ever since I learned that lesson the hard way, I would not recommend swapping burners from oil to gas or gas to oil or (Back in the day) standard burner to high temperature flame retention burner. Furnace heat exchangers don't have water on the other side to keep the metal temperature from overheating.

@Ironman & @STEVEusaPA has the correct answer. Get a new furnace, then sell the 10 year old furnace on Facebook Marketplace or eBay. Or just keep the oil furnace for 10 more years.

You're thinking of the Delavan "FlameCone". I actually have a couple of these sitting around.