# converting furnace from LP to NG



## PrairieBelle22 (Nov 17, 2006)

We just ran a gas line from the NG well on our property to our house and are now ready to change our furnace from LP to NG. I have contacted the local Lennox dealers and they want to charge way more to change the orifices that we are prepared to spend. 

Does anyone know where we can get the information on how to make this change?

Thank you

Belle


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## Jim-mi (May 15, 2002)

For your own long term safety have a pro do it.
It is just a one time deal................


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## farmerj (Aug 20, 2011)

read this information.....

It's a nice explanation that shows the importance and reality of why they get what they get.

It's not just simply changing orifices.
http://www.cozyparts.com/lennox-parts/forum/topic.asp?TOPIC_ID=4256


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## PrairieBelle22 (Nov 17, 2006)

Didn't really get any helpful information but I have to agree with DWP when he said "I will never buy another Lennox product" Our Lennox furnace is very inefficient and local Lennox dealers won't provide service and support.


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## farmerj (Aug 20, 2011)

the point is, to convert a furnace, it's more than just the orifice that needs to be changed out. That was listed on that page. Manufacturers get really edgy about liability and letting that information out for the "general public" to convert a device that has the potential to make a home into a pick-up sticks puzzle.

I can appreciate what it is you are trying to do. Don't blame you.

Sometimes the cheapest route isn't the route you really want to go.


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## watcher (Sep 4, 2006)

Been there done that. . .hire a pro. Furnaces are like cars. Years ago you could do all your own work on them but now there are so many 'safety' devices and circuit boards on them you almost need specialized tools just to 'open the hood'.


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## nosqrls (Jun 9, 2012)

It is not just an orifice change. It is also a pressure change. and air mix adjustment and general check of the furnace.If you have the tools you can do it yourself it is not extremely hard you may have to change regulator entirely depends on furnace. change jets burners and pilot. set regulator pressure burner and pilot I like using air so to not be filling space with gas. Then light furnace and adjust air mixer starting with center burner and working my way out. accurate pressure gauge that reads inches of water is required. ng uses lower pressure than lpg. converted furnace, stove and dryer to lpg.
sometimes you get lucky and get a kit for doing the conversion other tomes you have to piece it together. figure out what jets you need springs and orifice for regulators.
I got lucky the furnace had the sheet inside that said what jets,springs,and orifice to use dryer found kit to convert and stove came with kit maytag inspected the dryer when working on washer and asked who did the conversion. I told him I did he was impressed I figured out You had to flip air mix Plate. I told him when I went to adjust it I noticed one side was stamped NG and other was LPG so assumed I need to flip it and it is not in the directions to flip it.


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## Snowfan (Nov 6, 2011)

nosqrls, you are correct except that, I believe, lpg is at a higher pressure than ng. lpg orifices are smaller because of the pressure difference. You are also right about it being much more than just changing the orifices, let a pro do it.


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## nosqrls (Jun 9, 2012)

Lpg starts at a higher pressure than ng. And you are correct ng is 3 to 6 and lpg id 10 to 13. and the jet size is due to ng does not put out as many btu's as lpg PCM.


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## fishhead (Jul 19, 2006)

Have you looked at the cost of new high efficiency furnace?


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## Steve in PA (Nov 25, 2011)

I recommend having a pro do it since you're asking questions on a message board how to do it.

I have a new high efficiency furnace and the kit to convert from NG to LP is only an orifice. All the metering and combustion monitoring is done by the onboard processor. I installed the furnace myself, but had a pro inspect it before firing it up.


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## mdharris68 (Sep 28, 2006)

There is more to it than changing the orfices. They have the tools to set the gas pressure after the conversion back to NG and the experience to know what to look for to make sure the furnace operates as it was designed to and leave your house with the confidence that the occupants will not be subjected to a gas leak/fire hazard or carbon monoxide poisoning. 

Yes it probably is expensive, but whats it really worth?

I think if you asked around you could find another company other than a Lennox dealer to do the job, especially if you NG parts are still with the furnace. I always left the orfices and regulator springs in the furnace or with the homeowner after the lp kit was installed.


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## ralph perrello (Mar 8, 2013)

this is not a thing amatures should do.

If you mess up gas makes a very large boom and your house is toothpicks.

Hire a pro. I am a retired pro and know what it is about.


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