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  #1  
Old 11-18-2009
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Propane system mystery

Hi all,
I have a propane system mystery, and I am hoping that there is a propane guru out there that can help solve it. We have propane range and heater on our boat, and once lit both function well. Our mystery is: when we have not used the range for a week or longer, it takes a long time to light. I turn on the solenoid valve, turn on the range burner valve and hold a lit match to it, but it may take 30 or 40 seconds (and several matches) to light. "Something" is coming out of the burner all this time, I can hear it and it will even blow the match out if I am not careful, but it is apparently non-flammable and has no odor of propane. After this 30 or 40 seconds, the burner lights, and all is well. If we are using the boat for the weekend once we go through this initial light up ritual, the burners light quickly for the rest of the weekend. Once we leave the boat for a week or two, the slow light up happens again. The propane heater always lights off with no problem, so it makes me think it may be something wrong with the range (all 3 stove burners do it, as does the oven burner). I have leak checked the system with soap bubbles several times, and with the pressure gage at the tank and have found no evidence of a leak. We also have a Trident propane leak detection system aboard that has not indicated propane leakage. I even replaced the propane regulator, thinking it may be the culprit. We have owned the boat for over six years and this mystery has been more of an annoyance than a problem, but I would really like to find out what is causing it. So, has anyone out there had and solved a similar mystery?

Dave
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Old 11-18-2009
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Dave
If your system is installed properly there are no connections outside of the propane locker except the two at the appliances themselves, with two separate lines from locker to heater and stove. What you are describing sounds like the line to the stove is draining itself of propane when you leave it for a while, like a week or two. The line to the heater is not affected. I would concentrate on the line to the stove, starting in the propane locker, but after the solenoid. I think the leak, and there must be one, is in this line and since your sniffer doesn't detect anything is amiss I would expect to find it in the propane locker. If this doesn't turn up anything I would continue to follow the line to the stove, paying particular attention to where it goes through bulkheads. Hope this helps.
Brian
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Old 11-18-2009
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Brian has the right line to follow... See if you can find some 'Snoop' brand leak detector (soap solution in a bottle, but much better than Ivory). A local welding supply store is probably the best bet. This stuff will bubble with the smallest of leaks. Another test is to disconnect and plug one line, charge up the connected line, and turn off the propane cylinder. Watch the guage for the next 24-48 hours, if it slowly bleeds down, you've found the offender. If it is the stove, and you find no leaks in the connections, it's probably one of the burner control valves.
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Old 11-18-2009
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Two things come to mind. Fitst is that your lines are getting air into the system after the gas is turned off and the slow start is due to waiting for the air to purge out of the system. It' a simple test. After turning all appliances off, shut the valfve at the tank and monitor the pressure gage. If pressure falls off ther's a leak, otherwise pressure should hold. The second thought is that you're shutting off the gas before securing the appliances. Newer gas bottle valves have a feature where if they sense a gas line rupture they shut down thire delivery rate. If you close the tank valve before shutting down the appliances they think htis has happened and the way to reset thei is to shut off all appliances and repopen the tank valve.
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Old 11-19-2009
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Quote:
Originally Posted by DMD View Post
The propane heater always lights off with no problem, so it makes me think it may be something wrong with the range (all 3 stove burners do it, as does the oven burner).
Just to let you know that I have the same mystery and the same setup as you with the exception that the heater exhibits the same delay as the stove if not used for several months. In fact the line to the heater is a longer run than the line to the stove and it takes longer to pruge the air out of the system. Also we had a propane heater installed in our home and sure enough it exhibits the same purging problem. There has to be a leak in the system, but I'm unable to locate it and neither is the surveyor who recently did the boat.
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Old 11-19-2009
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Quote:
Originally Posted by DMD View Post
Hi all,
I have a propane system mystery, and I am hoping that there is a propane guru out there that can help solve it. We have propane range and heater on our boat, and once lit both function well. Our mystery is: when we have not used the range for a week or longer, it takes a long time to light. I turn on the solenoid valve, turn on the range burner valve and hold a lit match to it, but it may take 30 or 40 seconds (and several matches) to light. "Something" is coming out of the burner all this time, I can hear it and it will even blow the match out if I am not careful, but it is apparently non-flammable and has no odor of propane. After this 30 or 40 seconds, the burner lights, and all is well. If we are using the boat for the weekend once we go through this initial light up ritual, the burners light quickly for the rest of the weekend. Once we leave the boat for a week or two, the slow light up happens again. The propane heater always lights off with no problem, so it makes me think it may be something wrong with the range (all 3 stove burners do it, as does the oven burner). I have leak checked the system with soap bubbles several times, and with the pressure gage at the tank and have found no evidence of a leak. We also have a Trident propane leak detection system aboard that has not indicated propane leakage. I even replaced the propane regulator, thinking it may be the culprit. We have owned the boat for over six years and this mystery has been more of an annoyance than a problem, but I would really like to find out what is causing it. So, has anyone out there had and solved a similar mystery?

Dave
Assuming you have properly pressure tested your propane system, what you describe does not sound very mysterious or worrisome to me.

A propane line will often lose much of its content over a period of a few weeks. If there is no detectable leak in the system, that loss is from hose "permeability".

ABYC mandates the UL standard for LP hose permeability for marine installations of propane appliances. Those standards allow for a certain degree of hose permeability. The amount of gas lost through permeability poses no risk during normal operation, but will eventually drain a run of propane hose of some or all of it's contents over a period of time. This is yet another reason (the foremost being true leaks) why it is important to always turn off your propane system either via a remote solenoid valve or at the manual tank valve.

The loss of propane to hose permeability increases at higher temperatures. You'll probably notice it more in summer than in the early or late ends of the season. Also, it's more noticeable on longer propane appliance lines for the simple reason that it takes longer for new gas from the tank to refill the line and reach your appliance when the valve is opened again.

One other suggestion: If you suspect a leak in your propane system, you start by pressure testing it. There is no need to leak check "with soap bubbles" or other fluid unless you've already determined that a leak exists via the pressure test.

To pressure test, you open the tank valve and pressurize the entire propane system (all appliance should be off). Then you close the tank valve (leaving the remote solenoid open or "on"). Record the psi reading on the pressure gauge. Wait 15-20 minutes. The pressure reading should remain constant or not drop more than a few psi. If the pressure holds fine, you do not have a leak, and there is no need to test connections with bubbles.

Note: The pressure test is conducted in a 15-20 minute time period. Not overnight. Not over 3-4 hours. Most systems will lose or gain pressure due to permeability and environmental changes (ambient temp swings) over longer periods. It's conceivable that you could have a slow leak, but not detect it, if temperature increases substantially over a period of time and causes the pressure to increase. Likewise, a big temp drop can cause pressure to decrease, giving the false impression of a leak.
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Old 11-19-2009
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If you are not turning the appliances off with a manual valve (they should be right before the appliance) the pilot and automatic valve on the appliance may "bleed" the remainder of gas from the lines when you leave. Even manual valves can bleed at the packing, the only way to find a line or system 100% leak proof is without valves and appliances attached to the line/s The same is true in piping systems that must be pressure tested by local authorities in buildings. all lines must be capped without valves of any kind.
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Old 11-19-2009
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There shouldn't be a manual valve installed just before the appliance. This would add a connection between the propane locker and appliance which ABYC says shouldn't exist. How old is the line to the stove? Is it older than the line to the heater? Maybe the line to the stove should be replaced simply because of age.
Brian
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Old 11-19-2009
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Brian that's scary! But I suppose in a emergency they would just kill the solenoid. Still, the appliances will bleed out the residual gas over time. it'w why the lines always are required to be capped for testing.
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Old 11-19-2009
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Scary? I don't think so. It would seem to me that flexible lines will probably become more permeable over time. In a lot of boats the stove line is original or at least older than the heater line which is often added later in the boat's life. This could explain the problem. Nothing lasts forever.
Brian
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