RV propane problems: When the furnace fails and the stove still works

One system, one pressure

Everything downstream of the regulator runs at a single pressure, and the makers state it the same way. Marshall Excelsior, who make regulators, describe the job as compensating "for variation in tank pressure from as low as 6 psig to 240 psig and still delivers a steady flow of LP-Gas at 11" w. c. to running appliances." Suburban, who make the appliances, describe the same figure arriving at the same place: "the second stage takes it down to around 11 inches water column, which is the right flow for your RV's appliances."

Their own regulators are set and adjusted around that number. Marshall Excelsior lists an outlet set point of 11" WC with an adjustable range of 9 to 13, and states their first stage is factory set at 10 PSIG.

What matters more for diagnosis is the figure on the other side. The remedy instructions for the Winntec regulator recall, written by the RV makers and filed with the safety regulator, state the acceptance criterion plainly: "Ensure system operating pressure is at 11" (+-0.5") water column with 50% load, and lockout pressure does not exceed 14" water column." A regulator that cannot hold 11 under load, or that locks up above 14, is out of specification whether or not any appliance has complained yet.

Read that slowly, because it explains the fault this page is about. 11" WC is measured with appliances running, not sitting idle. A system can look fine at rest and fall short the moment something large asks for gas.

Why the furnace is the appliance that complains first

Appliances are not equal consumers, and the makers' own demand figures show the spread. The table the regulators' handbook reproduces from NFPA 54 gives a warm air furnace at 100,000 BTU/hr, a freestanding range at 65,000, and a refrigerator at 3,000. A furnace asks for roughly thirty times what a refrigerator does.

Suburban states the consequence from the appliance side: conditions that affect furnace performance include "low gas pressure caused by a number of factors, including a malfunctioning regulator or low gas levels in the tank."

What the makers do not say, and this page will not claim: no manufacturer document found for this page states in as many words that a marginal regulator starves the largest appliance while a small one keeps working. That explanation is common on forums and it is consistent with the demand figures above, but it is an inference, not a manufacturer's statement. Treat it as the reason to test, not as a diagnosis. The test below settles it either way.

Testing it, in the order the makers specify

The drop-pressure test

This is the makers' own procedure, taken from the regulator replacement instructions filed with the recall. It tests the system for leaks rather than the regulator for accuracy, and it is the first thing to run because a leak and a failing regulator produce the same symptom.

Insert a manometer into the system, turn both LP tanks on, then turn both off, and bleed the system down to 8 inches of water column. The system must then hold 8" WC for a minimum of three minutes. If it does not hold, you have a leak, and the regulator is not your problem yet.

Operating pressure under load

With the system holding, the acceptance figure is 11" WC within half an inch, measured at 50 percent load, with lockout not exceeding 14" WC. A manometer is the instrument; a cheap gauge that reads only static pressure will not show you the problem, because the problem appears when gas is flowing.

Leak detection by the maker's method

Dometic's own procedure is a soapy solution applied to every connection, where "the appearance of bubbles indicates a leak and should be repaired immediately." Their manual adds one line that needs no elaboration: "Never use an open flame to check for gas leaks."

Marshall Excelsior document an instrumented low-pressure drop test as the formal method, using a manometer or a low-pressure test gauge, which is the same test as above performed properly rather than by eye.

The regulator itself

How long it lasts

Two makers publish a life figure and they do not agree, which is worth knowing before shopping. Marshall Excelsior state that their domestic regulators "feature a 25 year recommended replacement life." Suburban advise the shorter and safer interval: "your RV propane regulator should last a while, but it won't last forever. It's a good idea to replace them every ten years."

Those are recommendations, not warranties, and Marshall Excelsior are explicit that wear is expected: their products are "mechanical devices made of materials such as rubber and metal, and are subject to wear, the effects of contaminants, corrosion, and aging, and these devices will eventually become inoperative."

How old is yours

You do not have to guess. Marshall Excelsior document the marking convention on their regulators: "the Part Number, orifice size, spring range and date code" are on the spring case. Find the date code and you know the age without trusting anyone's records.

How they fail

The makers document two mechanisms worth knowing, and one of them is a fire risk rather than an inconvenience.

Vent obstruction causes overpressure. Marshall Excelsior: obstructions of the regulator vent "caused by snow, sleet, freezing rain, ice, mud, or other debris, can prevent the regulator from operating properly. This can result in high pressure gas at the appliances resulting in explosion or fire." Forest River's owner manual turns that into an installation rule in capitals: "LP GAS REGULATORS MUST ALWAYS BE INSTALLED WITH THE DIAPHRAGM VENT FACING DOWNWARD… TO MINIMIZE VENT BLOCKAGE WHICH COULD RESULT IN EXCESSIVE GAS PRESSURE CAUSING FIRE OR EXPLOSION." If your regulator is mounted with the vent facing up, or the vent is packed with mud or ice, fix that before anything else on this page.

Seal migration, and plasticiser from the hoses. The recall report describes both: "the second stage valve seat in the regulator has an inadequate mechanical lock, resulting in seal migration. Once out of position, the valve seal will not properly regulate propane flow and pressure to the recreational vehicle appliances." The same report names a second mechanism: "the rubber hoses (pigtails) that connect the onboard propane cylinders to the regulator release a plasticizer which is a liquid that collects in the body of the regulator."

Regulator makers design against contamination. Marshall Excelsior advertise fluorocarbon seats "for maximum protection against contamination" and a stainless steel inlet filter screen "to reduce debris from passing through", which tells you contamination is a known failure route rather than a theoretical one.

The Winntec recall, and a distinction most sources get wrong

This is the largest propane-hardware event of recent years and it ran across at least six RV makers: Jayco 21V-425, Keystone 21V-427, Grand Design 21V-393, Triple E 21V-400, Holiday House RV 22V-067, and Rich Specialty Trailers 22V-336, plus an equipment recall by the importer. The defect is the seal migration described above, made worse by plasticiser from the pigtails.

The part to get right, because secondary coverage conflates it: there was no recall of Fairview regulators. Fairview was named as an approved replacement in the Winntec remedy. A separate recall did involve Fairview-brand hoses, leaking at the swivel joint. A regulator recall and a hose recall are different things, and reading them as one leads people to replace the wrong part.

The remedy instructions themselves are a useful model for anyone working on the system, and they read in the order you would actually do it: close the bottles, unscrew the pigtails, remove the regulator, fit the new one, reconnect the pigtails, check every fitting with an approved leak-detection method, run the drop-pressure test, and confirm 11" WC at half load with lockout under 14".

Pigtails: the hose between the tank and the regulator

The citable rule from the maker is not a year figure. Marshall Excelsior "recommends every new installation or replacement regulator have a new pigtail installed." If you are changing the regulator, change the pigtails with it, which also removes the plasticiser source that the recall blamed for contaminating the new one.

Their pigtails are rated to 250 psig and tested to UL 569, and MB Sturgis publish a pigtail rated at 450,000 BTU/hr with a note on why capacity matters: a higher flow rate results in "a decreased potential for the system to go into bypass mode therefore shutting down the gas supply."

Carbon monoxide and gas alarms

Your detector has a service life, and the maker publishes it. The Safe-T-Alert combination alarm manual states it is "recommended that this alarm is replaced after five years of service", and that it "has an End of Life (EOL) signal that will sound after 5 years of use." A detector that has quietly stopped detecting is worse than none, because the habit of trusting it survives the device.

The same manual lists the ordinary household gases that cause false alarms, "Acetone, Alcohol, Butane, and Gasoline", and notes that it "has a recheck cycle before alarming" to prevent brief puffs from triggering it. So a detector going off while you are cleaning with solvent, or fuelling a generator nearby, is behaving as documented. It also warns that it "will only indicate the presence of gas at the sensor", meaning a clear reading near the alarm does not clear the coach.

Propane at altitude

Dometic publish the clearest statement from any maker, and it is a low threshold: "All gas appliances experience lowered efficiency (or rating) at high altitude… Reduced cooling performance and burner outage may occur at altitudes higher than 5500 feet above sea level (while operating on LP gas). Always operate refrigerator on electric power at altitudes higher than 5500 feet."

Their European-series manual gives an even lower figure for ignition faults, around 3,280 feet, and adds a phrase worth reading twice: "(No malfunction!)". A gas appliance that will not light at altitude may be working exactly as designed.

What is not published: the widely repeated derate figure of four percent per thousand feet, and the idea that a smaller orifice is the fix, come from forums and retailers rather than from the appliance makers. Dometic's own remedy is to run on electric power. Do not let anyone re-orifice your furnace on the strength of a forum post.

What the makers say you must never do

Forest River's owner manual carries the clearest list of prohibitions: "DO NOT attempt to adjust or repair the regulator. Adjustments and repairs require specialized training and tools… DO NOT MODIFY YOUR LP SYSTEM. DO NOT REMOVE COMPONENTS OR REPLACE WITH COMPONENTS THAT ARE NOT OF EQUAL VALUE."

Suburban say simply: "NEVER OPERATE FURNACE IF YOU SMELL PROPANE GAS." If you do, their instruction is to turn the gas off at the source immediately, extinguish any flames, and contact a dealer or qualified service person.

And on the risk that makes all of this worth taking seriously, Suburban state that if the appliance is not maintained in the condition it shipped in, or is not used solely for its intended purpose, "the risk of a fire and/or the production of carbon monoxide increases which can cause personal injury, property damage, or death."

What this costs

A regulator and a pair of pigtails is a modest part cost, and a manometer is a cheap instrument that will outlast the RV. Against that, the alternative path, replacing a furnace because it will not light, is an appliance cost plus installation, on a fault that a pressure test would have identified in minutes.

The order to spend in: a manometer first, because it is the only thing that tells you whether you have a problem. Then pigtails if you are changing the regulator. Then the regulator, matching the flow rating to your appliances. Nothing else until pressure has been ruled out.

Sources

• Marshall Excelsior, LP Gas Service Reference Guide, for the 11" WC system pressure, the appliance demand table reproduced from NFPA 54, the documented overpressure from a blocked regulator vent, and the instrumented leak-test method.
• Marshall Excelsior, Excela-Flo regulator brochure, for the 11" WC outlet set point and 9 to 13 adjustable range, the 25 year recommended replacement life, the fluorocarbon seats and stainless inlet filter screen, and the first-stage 10 PSIG setting.
• Suburban, LP Gas and Safety, for the 11 inch water column figure stated from the appliance side, and the ten year regulator replacement advice.
• Suburban, gas furnace operation guide, for the instruction never to operate the furnace if you smell propane, and the carbon monoxide warning.
• Jayco Part 573 safety recall report 21V-425, for the seal migration and plasticiser descriptions, and the operating and lockout pressure criteria.
• Winntec model 6020 regulator remedy instructions, recall 22V-067, for the drop-pressure test, the 11" WC at 50 percent load acceptance figure, the 14" WC lockout limit, and the replacement procedure.
• Dometic Americana refrigerator operating instructions, for the soapy-solution leak test, the prohibition on using an open flame, and the 5,500 foot altitude guidance.
• Dometic RML 8555 operating instructions, for the lower altitude threshold at which gas ignition faults begin, described by the maker as no malfunction.
• Safe-T-Alert combination carbon monoxide and gas alarm manual, for the five year replacement interval, the end of life signal, the documented false-alarm gases, and the limit that the alarm only senses gas at the sensor.
• Forest River travel trailer and fifth wheel owner's manual, for the prohibition on adjusting the regulator or modifying the system, and the requirement that the diaphragm vent face downward.
• Marshall Excelsior pigtail product documentation, for the recommendation that a new pigtail accompany every regulator change, and the UL 569 listing.
• MB Sturgis RV Type 1 pigtail, for the flow rating and the note that insufficient capacity can put the system into bypass and shut off supply.