I added a gauge to my propane tank. The gauge is color coded - green, yellow, red. During a recent trip, outdoor temps ranged from 80 degrees (day) to 35 degrees (night). Day after day, the gauge was in the green during the day (warm outdoor temps) and dropped to yellow or nearly red every night (colder outdoor temps). So for a week, it looked like I had a nearly full propane tank during every day, but (that same tank) looked nearly empty every night. I never did switch to the 2nd tank. So with this gauge fluctuating so much between day & night, how do I get a true idea of how much propane I really have left?
blijil said
08:11 PM Apr 16, 2007
Gauges generally don't work well. If there is pressure then some liquid is in the tank. If there is no pressure it is empty or pretty cold. The only sure way to know how much is in the tank is weigh it. It should be a little over 4 lbs for every gallon in the tank. The tare weight of the tank is generally printed on the tank itself. For a vertical tank you may be able to detect a frost or water line at the liquid level when the tank is be used because the liquid is cooler than the gas when it is evaporated. There are some little magnetic temperature indicators you can slide around to find the level if you are using gas out of the tank while you are measuring.
After a while we just use the on off type gauge with the experience to record how many days we have been using the tank and under what conditions.
Not really that much help. Am I? Larry
RVDude said
09:25 PM Apr 16, 2007
Was it a pressure gauge?
If so, the pressure of propane in a tank is *dramatically* affected by temperature. This is why tanks are only filled to 80% in order to provide expansion room if it gets warmer. That’s why the OPD devices are now mandatory.
A trick to using a pressure gauge is to note the reading when the tank is filled and make note of the temperature. Then, as you use the fuel, read the gauge at about the same temperature. This will provide a consistent pressure measure. A tank filled at freezing might show only yellow on your pressure gauge but it is full. If you drive that tank south and thus warm it up it will magically show green. Likewise if you then drove it way north to sub-freezing it might only show red or nothing at all. Bit it is still full.
As biljili said, weight is the most accurate (4.2lbs/gal) and volume (of liquid) is the second most accurate method. The frost line trick - or those paste on gauges that measure the liquid level by this temperature frost line difference - notes the level of the liquid in the tank. This is a good way to determine fullness.
-- Edited by RVDude at 22:26, 2007-04-16
Luvglass said
10:36 PM Apr 16, 2007
I also think the weight is the best guage. \
There's a huge difference between the full one and an empty one. We have 2 tanks and it's no problem to get the empty one filled before the second tank has even begun to empty.
On an associated note, propane is really expensive and we've gotten so that we hardly ever use the furnace unless it's down to freezing. We get by with the fireplace and 2 cube heaters, which are free in most full hookup campgrounds.
Fred
Howard said
07:40 AM Apr 17, 2007
We splurged on a couple of propane gauges like the ones you mention. After reading what they do, I determined they would be pretty useless. So they are still in the package as we forgot to return them.
But we do have the little stick on indicators that RVDude mentioned. Here is the link: Accu-Level Propane Tank Gauge. They do a decent job of telling you the liquid level in the tank.
You just stick them on, heat a cup of water in the microwave, and pour the water over the "gauge" strip. The yellow strip turns orange at the level where the liquid is. As the strip cools, it turns back to its original yellow cover and you can use it over and over again.
Don't know how it would work for a built-in motorhome propane tank, but if your tanks are in a place where the water can run out, it's an easy alternative to taking the tanks out and weighing them (which, as said by others, is the best determination). Plus they are cheap at $3 a strip.
Oh, I forgot. They are not long enough for 40 pound tanks. So you might want two per tank. But we still only use one and place it low on the tank since we just need to see when we get below half.
Luvglass said
09:14 AM Apr 17, 2007
This being our first RV, I don't know if it's common or not, but our Carriage Cameo has 2 30# tanks connected to a Marshall #254 Auto Changeover Regulator.
When you connect 2 full tanks to the regulator, you open both valves and position a moveable arm over to point at one of the tanks. A sight window shows a green marker. The system draws from that tank until it's empty and then automatically begins to draw from the other tank. This becomes apparent because the sight window turns red. When you swing the arm over to point to the other full tank the indicator returns to green. You then just simply close the valve on the empty tank, remove it and get it filled. When you reinstall it just open the valve and wait till the indicator goes red again. There's not need to do anything else.
Fred
Cindy T said
08:19 AM Apr 18, 2007
Thanks, everyone for your responses & suggestions! The propane tanks are on the outside of the rig so I think I'll try the "water" method with the stick on indicators. Thanks for being so helpful!
bago40 said
09:09 PM Apr 19, 2007
Thanks guys, My tank is just behind one of the basement doors and that part of the basement has no bottom so the strips and water pouring method will work good. Thanks for being an invaluable source of info. and ideas.
RonC said
02:23 PM May 25, 2016
Fred,
I know this is a very old thread, but we are very new to this RV thing and your explanation of how the automatic LP regulator works was very helpful to me. I ran one of our 30# tanks dry when operating the gen set to run the AC and had the other tank valve closed ... I (wrongly) thought this was the correct procedure to follow. This wasn't good for the AC unit or the gen set. Thanks for sharing your knowledge.
After a while we just use the on off type gauge with the experience to record how many days we have been using the tank and under what conditions.
Not really that much help. Am I?
Larry
If so, the pressure of propane in a tank is *dramatically* affected by temperature. This is why tanks are only filled to 80% in order to provide expansion room if it gets warmer. That’s why the OPD devices are now mandatory.
A trick to using a pressure gauge is to note the reading when the tank is filled and make note of the temperature. Then, as you use the fuel, read the gauge at about the same temperature. This will provide a consistent pressure measure. A tank filled at freezing might show only yellow on your pressure gauge but it is full. If you drive that tank south and thus warm it up it will magically show green. Likewise if you then drove it way north to sub-freezing it might only show red or nothing at all. Bit it is still full.
As biljili said, weight is the most accurate (4.2lbs/gal) and volume (of liquid) is the second most accurate method. The frost line trick - or those paste on gauges that measure the liquid level by this temperature frost line difference - notes the level of the liquid in the tank. This is a good way to determine fullness.
-- Edited by RVDude at 22:26, 2007-04-16
But we do have the little stick on indicators that RVDude mentioned. Here is the link: Accu-Level Propane Tank Gauge. They do a decent job of telling you the liquid level in the tank.
You just stick them on, heat a cup of water in the microwave, and pour the water over the "gauge" strip. The yellow strip turns orange at the level where the liquid is. As the strip cools, it turns back to its original yellow cover and you can use it over and over again.
Don't know how it would work for a built-in motorhome propane tank, but if your tanks are in a place where the water can run out, it's an easy alternative to taking the tanks out and weighing them (which, as said by others, is the best determination). Plus they are cheap at $3 a strip.
Oh, I forgot. They are not long enough for 40 pound tanks. So you might want two per tank. But we still only use one and place it low on the tank since we just need to see when we get below half.
When you connect 2 full tanks to the regulator, you open both valves and position a moveable arm over to point at one of the tanks. A sight window shows a green marker. The system draws from that tank until it's empty and then automatically begins to draw from the other tank. This becomes apparent because the sight window turns red. When you swing the arm over to point to the other full tank the indicator returns to green. You then just simply close the valve on the empty tank, remove it and get it filled. When you reinstall it just open the valve and wait till the indicator goes red again. There's not need to do anything else.
Fred
Fred,
I know this is a very old thread, but we are very new to this RV thing and your explanation of how the automatic LP regulator works was very helpful to me. I ran one of our 30# tanks dry when operating the gen set to run the AC and had the other tank valve closed ... I (wrongly) thought this was the correct procedure to follow. This wasn't good for the AC unit or the gen set. Thanks for sharing your knowledge.