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Old 03-19-2013, 10:21 PM   #15
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Originally Posted by Protagonist View Post
Temperature of the liquid propane in the tank and vapor pressure of the gaseous propane in the tank are inversely proportional. As long as the vapor pressure is less than 50 psi, the liquid propane will be below 32°F, and there will be a frost line on the tank if you pour water on the side. At vapor pressures higher than 50 psi, the temperature of the liquid propane will rise above freezing, and there will be no frost line.
A cup of very hot water poured down the side of the tank, then wait 20 seconds or so, run your hand down the tank and you will feel where the warmer Aluminum meets the colder metal. That is the line of the liquid in the tank, and this works fine in any weather, warm or cold.
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Old 03-20-2013, 12:18 AM   #16
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Temperature of the liquid propane in the tank and vapor pressure of the gaseous propane in the tank are inversely proportional. As long as the vapor pressure is less than 50 psi, the liquid propane will be below 32°F, and there will be a frost line on the tank if you pour water on the side. At vapor pressures higher than 50 psi, the temperature of the liquid propane will rise above freezing, and there will be no frost line.
Just like freon. As soon as you start charging an A/C system, the bottle or can starts to get cold and on a humid day, a sweat line will show where the liquid is. Which is why I store partial cans in a freezer and lower the vapor pressure and slows down the leak rate against the rubber seal on the tapper valve.

I suspect on a normal summer day, the only way the propane vapor pressure is below 50 psi is if the propane is being consumed.
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Old 04-07-2013, 07:44 PM   #17
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My LPG tank didn’t read full on my Interstate when I had it filled. But there is some misinformation in this tread. The TouchSensor system doesn’t use the transducers for the LPG tank. They only work on plastic tanks. From the TouchSensor spec sheet: “NOTE: TouchSensor does not supply the LPG sensor. SensaTank RV100 reads the signal supplied from the OEM LPG tank.”
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Old 04-08-2013, 06:27 AM   #18
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From the TouchSensor spec sheet: “NOTE: TouchSensor does not supply the LPG sensor. SensaTank RV100 reads the signal supplied from the OEM LPG tank.”
Good info. Thanks. I would have known that if my Interstate's owner's manual packet had included a Touchsensor spec sheet.

I went to the Touchsensor web page looking for a spec sheet or owner's manual, but none of the models shown on the web page matches the display panel that is mounted in my Interstate. I wonder if mine is an older model that's been phased out?

Oddly enough, mine also seems to be a 120vAC system, too. It doesn't work unless I am plugged into shore power, I'm on generator power, or have the inverter set to Auto/Invert. If I'm just on DC power, the only display that works on the Touchsensor panel is the house battery voltage; the tank level displays and the main battery voltage won't work on 12vDC house power. Weird.

Side note, I sure wish they'd have put a second black/gray tank display panel right next to the macerator pump controls, so I wouldn't have to go back inside just to verify the tank levels before reeling up the discharge hose.
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Old 04-08-2013, 11:58 AM   #19
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Good info. Thanks. I would have known that if my Interstate's owner's manual packet had included a Touchsensor spec sheet.

I went to the Touchsensor web page looking for a spec sheet or owner's manual, but none of the models shown on the web page matches the display panel that is mounted in my Interstate. I wonder if mine is an older model that's been phased out?

Oddly enough, mine also seems to be a 120vAC system, too. It doesn't work unless I am plugged into shore power, I'm on generator power, or have the inverter set to Auto/Invert. If I'm just on DC power, the only display that works on the Touchsensor panel is the house battery voltage; the tank level displays and the main battery voltage won't work on 12vDC house power. Weird.

Side note, I sure wish they'd have put a second black/gray tank display panel right next to the macerator pump controls, so I wouldn't have to go back inside just to verify the tank levels before reeling up the discharge hose.
My LPG monitor seems somewhat erratic but it does occasionally display as full even when I know it is not. FWIW, I see this comment on page H-17 of my Interstate Owners Manual; I haven't tried to make this adjustment:
"The fluid tank monitor system has been calibrated at the TouchSensor factory for the size tanks the Interstate uses and should never need another calibration. On the rear of the monitor panel there is an adjustable potentiometer to manually adjust the monitor panel reading of the LPG tank level, this is set at the Airstream factory for the tank on the Interstate motorhome and needs no further adjustment."

As for your panel being fully functional on AC only, I'm pretty sure mine shows all level indicators regardless of power configuration, as long as the battery disconnect is ON. I can check this the next time I'm where my Interstate is garaged.
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Old 04-09-2013, 06:40 PM   #20
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I also thought my tank monitor panel was also only working on 120V AC, but then I noticed it was erratic on any power source while in Florida last month. Now it doesn’t work at all. Just got back from a trip to Bay City, Michigan and I’ll start trouble shooting what I hope is just a bad switch. My dealer in Colonial in NJ and I’ll give it a shot to fix myself before I trek up to NJ for warranty work. So far I’.ve metered the pins on the connector and it is definitely a 12v DC system.
The Airstream owner’s manuals and other technical data are woefully inadequate compared to the competition. Winnebago has great info on all their models that makes the engineer in me jealous.
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Old 04-10-2013, 05:03 AM   #21
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As for your panel being fully functional on AC only, I'm pretty sure mine shows all level indicators regardless of power configuration, as long as the battery disconnect is ON. I can check this the next time I'm where my Interstate is garaged.
I don't doubt that it's 12vDC. That doesn't change the fact that mine only works when I've got an AC power source hooked up, for whatever reason. If I have my Interstate in the shop for something else, I'll have them look into it, but as long as the panel works under conditions that I can predict (i.e I have a 120vAC power source hooked up), there's no point putting it into the shop just for that.

I'm not enough of an electrician to tackle it myself.
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