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Failed Furnace installer blames propane supply

firesafe Member Posts: 15
Installed a new Bryant gas furnace.  Ran 39 days heat exchangers filled with soot and the air intake from concentric melted a top the burner box. initially the furnace ran on two 100 lb propane cylinders with 11" wc and after nine days they were both empty.  Filled both and 5 days later the heater started to have problems on the cold nights 20* or below not able to maintain temp.  20 days after initial firing of furnace 100 lb propane cylinders replaced with two 300lb cylinders.  Thirtieth day the furnace blew smoke like haze into home and produced a foul odor (burning pvc) again cold night.  Next day refired furnace all seemed well mild day and night temps.  On 39 day odor came back and system malfunction.Had to replace entire furnace.  Installer changed the routing of the exhaust flue and also condensate line leaving furnace.  Also hooked up heat pump at that time and set the cut off at 30* before firing on gas. Concerns what really went wrong with first furnace?Did installer set the switch over to gas too low (jersey shore) to keep the furnace running mostly on the heat pump to avoid it happening again?

Additional information: Bryant BY-355CAV060100 95% modulating natural gas furnace, authorized dealer installer,  concentric for fresh air,  propane conversion, efv gas correctly sized 3/4" gas connector, downflow application, cased up/down flow airconditioning coil, evolution thermastat, condensate to drain.

Bryant will not even look at it for possible equipment failure.  Installer has given statement that the furnace was run on a 30lb cylinder and avised homeowner that this could cause equipment failure. 

Thanks in advance more info please ask


  • icesailor
    icesailor Member Posts: 7,265
    edited February 2012
    30# Cylinders:

    Like I said in an earlier post, it most likely wasn't converted. I've seen it before on more than three occasions. The symptoms are exactly the same. Overheating and sooting up. Once sooted up, the incoming air is insulated from the HX and the HX over heats. And it can't be cleaned. It has to be replaced.

    Just because it ran on a 30# cylinder, doesn't mean it was running properly. Had it been combustion tested, it would have been found out. And if they don't have the printouts, they have no proof it was set up properly. And does the installer even own one or do they just have access to one. Big difference.

    If YOU owned a Digital Analyser like my Fyrite Insight, you could have stuck the probe in either exhaust and intake and got a reading on the combustion. I'll bet the CO was out of sight.

    If you want to generate work, get a DA. You will find more challenging service work than you will ever know about.
  • lchmb
    lchmb Member Posts: 2,997

    When your tanks were replaced did the propane company do a flow and lock up of your regulators or did they re-use the regulator that was present (and were pressures tested on that regulator?) Was a manifold pressure taken to confirm gas pressures? Again, as Ice said, was a analyzer used to confirm the set up? My next concern is, this unit should have over heat sensor's on the air box where the intake was connected...why did they not shut the system down? Did anyone (installer) attempt to find out where it failed? In my area the installer is responsible for final set up. We confirm gas pressures to the unit and they do the final start up...
  • Nat
    Nat Member Posts: 8
    edited February 2012
    Not Uncommon

    This is a common occurance when an "unconverted" furnace gets hooked up to propane. The gas valve will reduce the incoming 10-11 inches to the lower natural gas pressure. If your not totally familiar with what the burners should look like while burning, it can go unnoticed for a while but it will slowly start to soot internally and eventually cause roll-out to trip or CO detectors to go off etc. The size of tank has nothing to do with anything. If the regulator wasn't delivering the 10-12 inches WC, the gas valve on the furnace would have failed as it's not meant to recieve high pressure. I have found my share of these type of situations. Weil McClain Ultras, Buderus G142's and the Lochinvars I have found running on LP Gas without the orifice "coin" installed. Yes, it happens and in these cases will run for a year or more before anyone notices because these type of burners with negative pressure don't soot like a positive pressure furnace or older style boiler. I've been doing this for 25 years. I think the conversion needs to be done by the most knowledgable person about each specific  product, which may not be the person with the license... It ain't the old days anymore. There's alot of new stuff out there and if the installer isn't familiar with the conversion, they need to find someone who does before firing system.     
  • icesailor
    icesailor Member Posts: 7,265
    Low Pressures:

    I guess that's why you need the low pressure gas safety switch on LP and not Nat Gas?

    In that case, the safety should have never beed disabled or removed.

    Thanks Nat.
  • Nat
    Nat Member Posts: 8
    Not Uncommon

    Hey Ice. The "low pressure" switch your reffering to is I believe the little 1/8 thread in thing that comes with LP conversion kit. That part is somewhat unecessary and to my knowledge only comes with Carrier/Bryant kits. I haven't seen that part with Trane or Rudd units over the years. In this case, especially with shotgun style burners, for it to soot up like this , the end of the flame as it entered the heat exchanger, had to be yellow. As I mentioned, to the untrained eye, the flame looks ok but it is going to make soot ever so slowly. An example of this problem is when Carrier/Bryant burners get rusty, the "star tip" at the end of the burner closes with rust causing the flame to start to become yellow and cause sooting to begin. I'll bet your vent smelled a bit and had a slight discoloring on the end of the PVC termination. There should be no odor at all when a high efficiency gas furnace or boiler is operating properly. A plume of water vapor is all there is. sorry about your unfortunate mishap but once your sorted out you should be very happy with your 2-stage furnace and it's savings on your gas consumption...
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    The LP gas low pressure

    shut is required by code and comes also with other furnace conversion kits such as Comfort Maker for one.

    If memory serves me the star piece in the front of Carrier burners needs to be removed when on LP gas I seem to remember seeing that in an I and O manual for Carrier units not sure if Bryant has the same requirement.
  • icesailor
    icesailor Member Posts: 7,265


    Firesafe is the guy with the problems with the gas conversion. I'm just one who suggested that it wasn't converted properly.

    You know me, I'm more of a Soot Sucking guy. Gas is just becoming a bigger part of what I have to do.
  • Nat
    Nat Member Posts: 8

    Hi Tim. The star part of burner I was referring to is the actual slotted star looking part in the end of the "shotgun" burners. When that part gets rusted, it closes up and that's when the soot starts on these warm air furnaces. As far as the "low pressure" adapter that comes with convesion kit, I have only seen it with Carrier/Bryant but you may be right, it may come with some others. My main point on this thread is to explain how sooting can happen whether it be a brand new furnace or an older unit. I think we tend to get ourselves overcomplicating things with all the new stuff out there. Gas still needs to burn blue. If its yellow, it will create soot. Positive pressure furnaces, whether single speed or not, still run on simple gas basics. That's why I feel that this furnace in question wasn't converted properly at the beginning. The size of the tank has nothing to do with it as long as they were using a half pound/low pressure regulator. As far as the shotgun burners go, American Standard/Trane has a stainless steel replacement burner which is a service mans dream. I have asked other manufacturers why they don't offer them.. Maybe they will one day.
  • furnacefigher15
    furnacefigher15 Member Posts: 514

    The burners are called in-shot burners, and the star thing is the turbulator which is responsible for mixing the fuel and air together, and to my knowledge should NOT be removed as part of the conversion from natural gas to propane.

    Also setting the firing rate can not accurately be done by eye. Your eye may get you close, but not close enough.

    I'm guessing the fuel pressure in the manifold was not set properly. I have been finding that just about every gas valve in every new furnace, and those installed as replacement parts are never set to the right pressure. They all say they are pre-set to 3.5'', but I've found most defaulted to about 4'' and one at 4.5''

    The other thing I've noticed it that most techs don't know how to tie in their manometers to the correct pressure reference. It requires the use of the 2nd port on the manometer being tee'd in with the reference tubing that connects to the gas valve. If you only use the one port on the manometer and tie that in to the manifold tap while the reference port is referencing ambient pressure in the mechanical room, the pressure will get set too high every time.

    Also the fuel pressure settings given are only a guide, not set in stone. The pressure may need to be adjusted to meet field conditions (usually lower).

    Soot is generally caused more by over firing, then under firing.

    There is also a good chance that the orifaces on the manifold where not replaced.

    If the natural gas orifaces where left in and not changed for propane, that would likely account for the excessive fuel consumption.


    Being a listed dealer has nothing to do with the knowledge of the company, just there ability to sell a lot of product.
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