Natural Gas to LP gas conversion .. orifices

NorthWestLowerMichigan

Hello,

My 95% efficient furnace was installed by a licensed contractor in November 2012.  This furnace is a 90,000 BTU with 6 in-line burners.  Upon the furnace installation ..the installer converted this furnace from NG to LP.  But, he installed size 54 orifices even though the owners manual specified size 1.15 orifices. 

The furnace failed in December 2013 due to the secondary HX completely plugged with soot.

The furnace has had a new HX put in.  When the new HX was put in and the furnace turned back on, it started short-cycling immediately ..approximately 6 minutes burners on then approximately 2 minutes burners off ..all the while the blower motor was on.  Note: It had been short-cycling like this since I can remember.  I originally assumed it was the new 2-stage blower kicking in.  (I am not an expert in furnace operation!)

Eventually I asked for the improper gas orifices to be replaced with the correct size orifices, and the furnace seems to be working properly.

The original installer told me that the old HX might not be covered by warranty, and that he would not accept responsibility for the cost.  He said that improper size gas orifices will never cause soot. 

It seems to me after a bit of internet research that he may be wrong.  It seems an improper (oversized) gas orifice will cause incomplete combustion, and that the 2 products of incomplete combustion are soot and CO.

(Also, as a side note, ..during the time this furnace had operated on the oversize gas orifices, my propane usage increased by nearly 30% even though last winter was relatively milder than most in my area.)

I would like to ask the furnace installer to assume the cost for fixing the furnace, but again, he says his improper size gas orifices would never cause soot.  He says it might have been my outside regulators at the tank and at the house are probably faulty.  If I could get the manufacturer to honor the warranty on the HX, then I would only have the costs for labor to fix the furnace.  Unfortunately, hHe also says it is not his responsibility to pay for labor to fix the furnace even if it were possible that the wrong gas orifices were part of the problem (which he insists was not the cause).

Is my furnace installer correct that the oversize gas orifices will not cause any soot and that he has no responsibility at all?  Also, is there any possibility that the oversize gas orifices might have resulted in increased propane usage.

NorthWestLowerMichigan

No responses yet?

No replies?  Did I explain my situation wrong ..or did I word my questions wrong?



Just want to know 2 things about NG to LP conversion in a 90,000BTU furnace:

Can improper & oversized gas orifices can cause excessive soot?

Can improper & oversized gas orifices can cause wasted propane.



I seek this information to pass along to the original installer to see if he can work with me on the cost to fix my furnace.

NorthWestLowerMichigan

No responses yet?

Edited out .. Duplicate post.

Jamie Hall

Yes and yes

I am no gas expert, but I do know that anytime you change an orifice size -- or a nozzle for oil -- you have to adjust the air as well.  And that goes double for changing from natural gas to LP; they have very different air requirements.  Assuming that the rest of the system is correctly set up for LP (keep in mind that there may be other components which should have been changed, in addition to the orifice) you have to set up the system with the proper test equipment.  No shortcuts.

icesailor

Expert Gas Conversions:

Jamie & Poster:

I'm not a gas expert but I've converted a few appliances.

I posted something along this on another forum on The Wall that may cover this.

All the appliances (gas furnaces) that I have converted, that CAN be converted, have a conversion kit supplied by the manufacturer to be used by the "qualified" person doing the conversion. They will always (in my experience) state what size orifice to use and supply them. I don't know what a #54 or a 1.5 equals but if the installation and/or conversion kit say to use a #54, you damn well better be using a #54 orifice. Or call the manufacturer and find out what's up.

As far as the burner tube, what almost all furnaces use now is what someone calls a "Shotgun Burner". In that the actual burner tube is set, and there is a cast iron piece that the gas is shot through and air mixes with the gas in the burner tube. If you have high moisture levels in the intake air, the cast iron rusts and expands. Shutting down the air and changing the air/fuel ratio. causing it to make smoke and soot. I haven't seem many adjustments in a lot of them like in old, but the same burner tubes are used for both NG and LPG. Just the orifices are different. And matched to the burner. That is why I think that most of the LP ratings are lower for the same NG appliance. So, if you put the wrong orifice in for the application, there is no way to make it right. You also need to combustion test it. I'll bet that the installation manual on a furnace that is 95%+ requires combustion analysis.

If the guy doesn't know that the wrong orifice will make soot, he probably thinks that only high air fuel ratios are the only settings that make CO. That a lean burn can make CO too.

He probably doesn't own a digital analyzer or know how to use one.

The other question I would be asking here is was it really soot-ed up? or was the system condensing and the HX, especially the secondary HX was plugged up with rust, then soot-ed up. Either way, it was a bad installation, made worse by someone that didn't know what he was doing.

Also, was it "regurgitating"? Was the intake being contaminated by the exhaust? I'd like to see photos of the vent terminations. Are there bushes planted in front of it to hide the terminations? I saw 2 furnaces go like this from planting decorative grass along side the length of the house.

Someone screwed up. I'm glad it isn't me.

Tim McElwain

I do not know what keeps happening

I had a nice long posting to answer your questions but the site kept dumping me off. You can e-mail me at gastc@cox.net or call me at 401-437-0557 and I will answer all your questions.

Tim McElwain

Let metry this again

·                                 Natural Gas to LP gas conversion .. orifices

Hello,

My 95% efficient furnace was installed by a licensed contractor in November 2012.  This furnace is a 90,000 BTU with 6 in-line burners.  Upon the furnace installation ..the installer converted this furnace from NG to LP.  But, he installed size 54 orifices even though the owners manual specified size 1.15 orifices. 



 

A 90,000 BTU furnace with 6 burners is 15,000 BTU per burner. The correct orifice size for LP at 10” W.C. is a # 57 drill. A lot of poorly trained folks have been told that you can always be safe with LP using a 54 drill and for natural gas a 42. Well that is not always the case you have to calculate each installation. Your furnace with a #54 drill size was firing at 25,000 per burner which is 150,000 BTU’s way over gassed. If he had ordered a conversion kit from the furnace manufacturer he would have received the correct orifices.

 





The furnace failed in December 2013 due to the secondary HX completely plugged with soot. The furnace has had a new HX put in.  When the new HX was put in and the furnace turned back on, it started short-cycling immediately ..approximately 6 minutes burners on then approximately 2 minutes burners off ..all the while the blower motor was on.  Note: It had been short-cycling like this since I can remember.  I originally assumed it was the new 2-stage blower kicking in.  (I am not an expert in furnace operation!)

 



Because it was overfired it was cycling off on high limit. This also can damage the heat exchanger due to thermal stress.







Eventually I asked for the improper gas orifices to be replaced with the correct size orifices, and the furnace seems to be working properly.

The original installer told me that the old HX might not be covered by warranty, and that he would not accept responsibility for the cost.  He said that improper size gas orifices will never cause soot. 

 

The oversized orifices will definitely cause soot (Carbon Monoxide), you are fortunate no one was killed.







It seems to me after a bit of internet research that he may be wrong.  It seems an improper (oversized) gas orifice will cause incomplete combustion, and that the 2 products of incomplete combustion are soot and CO.

(Also, as a side note, ..during the time this furnace had operated on the oversize gas orifices, my propane usage increased by nearly 30% even though last winter was relatively milder than most in my area.)

 

You will definitely use a lot more fuel when you oversize as drastically as this was done.







I would like to ask the furnace installer to assume the cost for fixing the furnace, but again, he says his improper size gas orifices would never cause soot. 

 

Again he is definitely wrong as too much fuel into a combustion chamber will always cause soot.

 





He says it might have been my outside regulators at the tank and at the house are probably faulty. 

 





If that were the case why didn’t he have the LP provider look into that?

 



 If I could get the manufacturer to honor the warranty on the HX, then I would only have the costs for labor to fix the furnace.  Unfortunately, hHe also says it is not his responsibility to pay for labor to fix the furnace even if it were possible that the wrong gas orifices were part of the problem (which he insists was not the cause).

Is my furnace installer correct that the oversize gas orifices will not cause any soot and that he has no responsibility at all?  Also, is there any possibility that the oversize gas orifices might have resulted in increased propane usage.

 





I think it is time for the lawyers to get involved as you have definitely been wronged if all that you are posting here is a fact. I would also contact the manufacturer of the equipment.

NorthWestLowerMichigan

Thank you very much..

First I would like to thank everyone who responded.  I am not a furnace guy ..so all of your comments are highly appreciated.  I am learning as I go. 

The furnace came with size 50 orifices for Natural Gas.  When converting to LP Gas, the installer put in size 54 orifices ..which are .0550" diameter.  The owners manual AND the installation manual specifically call for a size 1.15 orifice ..which are .0453" in diameter.  He kept telling me over the phone that he knows for a fact that all recent 80% efficient furnaces call for a size 54 orifice.  Unfortunately, he must have merely ''assumed'' that the 95% efficient furnaces are the same.  They are NOT!   So, it just goes to show that he did not consult the installation manual ..and his mistake damaged my furnace.

I have talked with the furnace manufacturer several times via telephone.  They are very reluctant to provide any information at all, except to say "You need to contact your local service agent".  Unfortunately, this installer is the ONLY local service agent within reasonable driving distance from my home.  

I recently talked to my propane supplier too.  He has agreed to come over to my home sometime this week to check my outside regulators.  However, he explained to me over the phone that even if there were/are any problems with the 2 outdoor regulators (on tank and on house), there is nothing that could go wrong with them that would cause excessive soot.  In other words, the regulators could NOT be the cause of the soot.

Yes, the HXE was totally plugged with soot.  In fact, I now have physical possession of the sooted up HXE.  The secondary is so plugged up with soot that most of those little curly stainless air-circulator stems will not even pull out of the exchanger.  I have since learned that the moisture extracted out of the heat within the secondary HXE is what usually causes the excess soot to adhere and accumulate there.

I think it may be possible that the furnace supplier sold the furnace installer the wrong size orifices.  Mistakes do happen in the warehouses when putting together a shipment.  And it is also possible that the the furnace installer may have even ordered the wrong size orifices from the supplier.  All I know is that the orifices he installed into my furnace were incorrect ..and all evidence I see points to that mistake as being the sole cause of the failed HXE due to it being plugged with soot.  However, whether the supplier provided the wrong orifices or whether the installer asked for them is besides the point.  The point is that the installer has absolute responsibility to ensure that the right orifices are installed.  It could have been worse than a failed HXE, ..his mistake could have caused a house fire or worse!

Now all I wish is that the installer would be kind enough to cover the expenses that I have incurred due to his error.  Is that too much to ask?



And finally, Thank You again to all who responded.  I appreciate you taking the time out of your life to help me with my little problem.  Bless you!

Ironman

Not Just Orifices

There's more to converting a gas appliance than just changing orifices. It also involves replacing the regulator spring in the gas valve and setting the manifold pressure with an accurate manometer. The pressure MUST be set to the manufacturer's specs and the installer must assure that the inlet pressure remains at a constant minimum level with ALL appliances on the line firing. Then the fuel to air ration needs to be adjusted and the only accurate way to do this is with a digital combustion analyzer - something your guy has probably never even seen.



Had all these steps been followed, you would not have had any shooting.

Derheatmeister

City Sewer ?

How high was this Install?...Sea level or 12 000 feet ?

Was this a replacement, and if so what happened to the prior furnace?

Did your Installer check the temp difference between the supply and return air duct and adjust the fan speed to have a proper delta T ( if applicable)?

Is the combustion air near the exhaust ?

Are you on a City sewer or your own septic tank/Leach field ?

Do you have Cast iron Drains in the Lower level?

NorthWestLowerMichigan

I do not know the pressure specs..

I am not a furnace guy.  I'm just a homeowner who hired a licensed mechanical contractor to install the furnace that I purchased from him.  The 'technical' information about the air pressure, the temperature rise, the combustion analysis, and any other totally technical stuff was not provided to me by the installer.  The only info I have from him besides the owners and installation manuals is the receipt showing that I paid for the furnace and for the installation of the furnace.

This is one of the problems with licensed mechanics making a mistake when they install equipment into a private home ..they typically do not provide all that technical stuff.  Thus, the average homeowner usually has no idea why something went wrong when their relatively new equipment breaks down ..and the result of that is the homeowner pays additional service fees and replacement fees for something that was never installed correctly to begin with. 

I consider myself fortunate that I contracted a different furnace company to troubleshoot and repair my furnace after it failed.  If it had been the original installer, ..I seriously believe he would have 'hidden' his mistake and fabricated a different excuse for the failure.

A brand new furnace should not totally fail after only 1 heating season unless it was a manufacturers defect or an installation mistake.  In my situation, the installer made a potentially dangerous (possibly fatal) mistake and I am not at all happy that he is still in 'denial' mode.

NorthWestLowerMichigan

Only 650 feet above sea level

By the way ..my location (my home) is approximately 650 feet above sea level.  The orifice specification does not change until 2000 feet above sea level. 

Derheatmeister

just was trying to help...

I understand that your original installer Screwed you over....Time to call the BBB

I questioned you certain things just tiring to help.. I understand that you are a home owner and do not understand some of the requirements or the technical side of things...

Guess it does not matter if you have a septic tank /leach field or older cast iron drains that will need to be replaced in a couple years....Sorry for trying to help..

SWEI

Listen carefully

Richard is telling you things you (or your attorney) need to understand before you release the installer of any liability.

icesailor

Attornies:

Like, copy and print out this entire string and discussion and take it to YOUR attorney. So he understands the situation.

You've been wronged.

NorthWestLowerMichigan

It is a furnace for heating my home .. LP Gas .. High efficiency ..

Hello Derheatmeister,

I apologize to you if it sounded like I was disrespecting you.  I was trying to be polite ..but to the point.  My problem does not involve a septic tank, nor a leach field, nor any cast iron drains.  My problem has to do with a basic name-brand 90,000 BTU 95% high efficiency home furnace that was supposed to be properly converted to feed from Natural to LP gas.  The dealer and installer failed to install correctly and it caused the heat exchanger to fail due to being plugged with soot.

You might have been thinking about something else.

NorthWestLowerMichigan

I understand .. just not able to afford attorney

I fully understand that some of the technical terms may be important.  But most likely an attorney would not understand that kind of technical stuff either.  Some of that technical stuff requires advance training that a majority of lawyers would not have experience with.  Moreover, I do not have enough money to pay for an attorney anyway.

I may have to seek remedy via small claims.  Unfortunately, the technical stuff may work in the defendant's favor in small claims even though the defendant is in the wrong.

Oh well.

Derheatmeister

Condensate Neutralizer

What i was trying to get to is that a High efficient Furnace will produce Condensate (Looks like Water) the PH on this condensate is low/Aggressive which will harm your Nitrobacters in a septic tank ....After it kills this Nitrobacters it can clog up your leach field which will have to be replaced and is very expensive $$$$$...

If by any chance you are not on your own septic and have cast iron drains you may have to replace the Drains because the Condensate will corrode them to Swiss cheese...

A regular Condensate Neutralizer will help prevent these issues...I hope this helps you from having more problems "down the line"..Richard.

icesailor

Affording:

you can't afford to NOT hire an attorney. You've been Jose'd once, why go for twice?

Attorney's are smarter than you think and have resources to ask other experienced "brothers".

I hate Attorneys too. But I don't go to a Proctologist if I have a toothache. If the pain became unbearable where I sit, I'd be making an appointment with a Proctologist.

KC_Jones

Attorney

Just a homeowner here.  I had to consult an attorney a number of years ago about something.  I found out in my state (PA) that there is a service (through the state) that will put you into contact with an attorney and for a very small fee (and I mean small fee) will get you a 30 minute consultation with an attorney who is an expert in whatever field you need help with.  I do not know if all states offer this, but it can't hurt to look.  They basically pick the attorney for you based on your needs, state approved.  I was able to find out I didn't need an attorney.  I mention this because in your situation you could find out the more affordable route, take them to court or just pay outright.  I am sure the attorney could help with this.  My personal opinion is go after the contractor because of the principals involved here...your families lives.