Propane use and smell

[Harth]

Hi, all.
I've got a 2 part question.
2006 38' keystone Montana.
When the temp gets into the 30s at night and 40s during the day, we burn through a 30lb tank in 2 days. Is that normal?
Also, when the tank runs out, there is a strong gas smell inside the trailer. It goes away within a couple hours of swapping the tank. I've heard that empty tanks stink, but why is the smell inside?
None of the appliances have a pilot light.

[flybouy]

The usage is normal if it's cold. As for the smell inside, are you sure your oven pilot light wasn't lite? The furnace, hot water heater, and fridge lp burners should all vent to the outside.

[Roscommon48]

this is why we use the electric fireplace or an electric heater and avoid the furnace. I know that the furnance running all the time would drive me nuts since it turns on so frequently.


have no idea about the smell, I'd be concerned, I've had my propane run out at night but I've never had a 'gas smell.'

[JRTJH]

The "propane smell" (stink is probably a better description) comes from an oily substance called "MERCAPTAN" that is added to propane during the refining/storage process. Mercaptan is an oil that is heavier than propane, can settle out of the liquid propane and remain in the tank. After several tanks of gas have been used, there can be enough mercaptan in the bottom of the tank to "super saturate" those lasts few cubic feet of gas that flows through the regulator. If so, then you'll get a "super strong smell" as the last bit of liquid propane converts to gas and flows through the regulator and into the trailer. Since the mercaptan doesn't burn, but rather "stays around to stink" (as a warning that there's propane around), you'll notice an increased smell of propane as the tank empties and the regulator changes to the full tank.

It's perfectly normal and doesn't present a problem, if the only time you smell it is with an empty tank at regulator changeover....

You can mention it to the dealer when you fill the next tank. If the guy filling the tank is knowledgeable, he can purge the tank to eliminate the excess mercaptan. If, however, you're getting your propane from a hardware store and the part time high school kid is filling the tanks and he only knows how to turn on the valve and weigh the tank, well, he's probably not going to have a clue about what to do to purge your tank.... You'd be better served if you haul it a little further and have them refilled at a "true propane distributor" who knows the correct procedure to purge the tanks.....

[Harth]

Thanks for the replys. I do fill my tanks at the dealership and they Purge them Everytime. What concerns me is shouldn't the odor be contained in the heat exchanger and vented to the outside?
The smell is strong enough to wake us up in the middle of the night before it gets cold inside. This is with the door and windows closed. There's no pilot light on the oven. Never noticed any smell other than when the tank runs empty.

[Badbart56]

Mine do the same thing. I noticed it on the outside of the RV. I checked the tanks and found the one I was running everything on was indeed empty. I don't know where this seepage comes from but it does let me know the tank is empty. Keep us posted on what you find.

[fjr vfr]

Originally Posted by JRTJH

The "propane smell" (stink is probably a better description) comes from an oily substance called "MERCAPTAN" that is added to propane during the refining/storage process. Mercaptan is an oil that is heavier than propane, can settle out of the liquid propane and remain in the tank. After several tanks of gas have been used, there can be enough mercaptan in the bottom of the tank to "super saturate" those lasts few cubic feet of gas that flows through the regulator. If so, then you'll get a "super strong smell" as the last bit of liquid propane converts to gas and flows through the regulator and into the trailer. Since the mercaptan doesn't burn, but rather "stays around to stink" (as a warning that there's propane around), you'll notice an increased smell of propane as the tank empties and the regulator changes to the full tank.

It's perfectly normal and doesn't present a problem, if the only time you smell it is with an empty tank at regulator changeover....

You can mention it to the dealer when you fill the next tank. If the guy filling the tank is knowledgeable, he can purge the tank to eliminate the excess mercaptan. If, however, you're getting your propane from a hardware store and the part time high school kid is filling the tanks and he only knows how to turn on the valve and weigh the tank, well, he's probably not going to have a clue about what to do to purge your tank.... You'd be better served if you haul it a little further and have them refilled at a "true propane distributor" who knows the correct procedure to purge the tanks.....

John, sometimes you sound really smart! Just don't let your head get to big with all this gas talk. It doesn't smell good when it empties out.

Thanks for the explanation.

[Eastham]

If it is really that strong of a propane smell your propane detector should be waking you up.not the smell of propane I would have it checked by a qualified propane dealer befor using it again.Just my opinion I am sure others will chime in.

[LHaven]

Originally Posted by Eastham

If it is really that strong of a propane smell your propane detector should be waking you up.not the smell of propane

Yes, but a propane detector alarms at the presence of actual propane, not at the odorant additive, which is what your nose alarms at. I suspect this is what is happening here.

[flybouy]

Originally Posted by LHaven

Yes, but a propane detector alarms at the presence of actual propane, not at the odorant additive, which is what your nose alarms at. I suspect this is what is happening here.

The additive doesn't "self propel", it needs the lp to carry it.

In my thinking the only way to smell propane inside the camper if not being used by the stovetop or oven is either by an opening into the living space near the fridge, water heater, or furnace from the appliance gas burner, or an open window or vent allowing the exchange of outside air.

The odor would be present if the line pressure was insufficient to maintain the flame of the appliance but still have enough pressure to operate the regulator.

Seems to me the logical resolution would be to use the auto changeover regulator or install one if it's not present so you don't "run out" of gas..

[Eastham]

Originally Posted by LHaven

Yes, but a propane detector alarms at the presence of actual propane, not at the odorant additive, which is what your nose alarms at. I suspect this is what is happening here.

Sorry
I was referring to the original post #1.There was a strong gas smell inside.I also agree with you that the additive wouldn't set off the alarm.its just strange that the smell would be that strong in the rv.

[Badbart56]

Originally Posted by Eastham

Sorry
I was referring to the original post #1.There was a strong gas smell inside.I also agree with you that the additive wouldn't set off the alarm.its just strange that the smell would be that strong in the rv.

I didn't smell it inside my RV, only on the outside. I wondered if when the regulator and lines were no longer pressurized, if there was a venting process when it was equalized with the outside air pressure. I have no idea how these things are put together but it's interesting that more than one of us has experienced it.

[sonofcy]

Originally Posted by Harth

Thanks for the replys. I do fill my tanks at the dealership and they Purge them Everytime. What concerns me is shouldn't the odor be contained in the heat exchanger and vented to the outside?
The smell is strong enough to wake us up in the middle of the night before it gets cold inside. This is with the door and windows closed. There's no pilot light on the oven. Never noticed any smell other than when the tank runs empty.

I have NEVER smelled propane inside other than when lighting the stove. Something is not right with your system and you need to get it checked by a pro ASAP. 20lbs in 2 days is a little high but possible.

[skids]

Natural gas techs seem to do 2 things for testing newly installed line. They pressurize the isolated pipe/line and ensures that it holds pressure for a given amount of time. Also, soap bubble testing of joints is done to ensure there are no leaks.

The nose is very good at detecting ethyl mercaptain, probably something like 5 parts per million for most people. On the other hand, natural gas has a lower flammability limit of 5 percent in air. I suspect propane is similar. So what I am saying is that if you smell the stench gas, it doesn’t necessarily mean the trailer is about to explode. Also, propane is heavier than air and collects along the floor until mixed in air. Opening a window is less effective than opening a door.

Edit: I just checked the lower explosive limit of propane which is 2.1% in air. Also I looked into ethyl mercaptan which is actually a hazardous gas. I would definitely not ignore warnings of the stench gas.

[chuckster57]

RV techs (at least the decent ones) use a manometer and test the entire system for leaks anytime the system is opened up and at the initial PDI. I don’t test after a cylinder exchange.

Proper test is to use a burner on the stove, or the quick connect for an outside appliance, that way the system is “intact”. After bleeding the gauge down to about 5” WC, RVIA standard is zero drop in 3 minutes.

The gauge isn’t cheap, but it will tell you if you have even a slight leak and then you can start eliminating each appliance. BTDT a few times.