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Installation Talk Questions/Concerns and help involving the installation of a Guardian Automatic Generator

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Old September 14th, 2011   #1
rico567
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Default LP vapor or liquid supply?

Do home generators, e.g., Generac, draw LP vapor from the tank or do they draw liquid and use a vaporizer at the engine to cause the LP to change phase for use by the engine?
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Old September 14th, 2011   #2
Ira
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In my case, it's a "standard" LPG setup, so it draws vapor. The gas appliances in my home are supplied by the same line from the tank as my genset.
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Old September 14th, 2011   #3
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I've never heard of any home generator using LP in liquid form. All of them that I've heard about use vapor from the tank like any other conventional LP appliance.
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Old September 14th, 2011   #4
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I encountered a reference by someone who claimed that home generators used liquid LP, but it didn't make sense, particularly with an air-cooled generator. The vaporizers operate by using engine coolant. I believe the person making this assertion had conflated home generators with large equipment using LP. So- I think this question has been resolved to my satisfaction.
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Old September 14th, 2011   #5
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Maybe the misunderstanding was because the Generac's are advertised as (spelled out) Liquid petroleum or Natural gas in the description. How would a device that actually ran on the liquid form receive it? I suspect it would need to be pumped or gravity fed like any other liquid fuel.
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Old September 14th, 2011   #6
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Quote:
Originally Posted by dsc3507 View Post
I suspect it would need to be pumped or gravity fed like any other liquid fuel.
LP in a tank is under fairly high pressure (which varies significantly with the temperature), and this is quite unlike any other "normal" liquid fuel that I'm aware of.
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Old September 14th, 2011   #7
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Quote:
Originally Posted by SkipD View Post
LP in a tank is under fairly high pressure (which varies significantly with the temperature), and this is quite unlike any other "normal" liquid fuel that I'm aware of.
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Originally Posted by dsc3507 View Post
Maybe the misunderstanding was because the Generac's are advertised as (spelled out) Liquid petroleum or Natural gas in the description. How would a device that actually ran on the liquid form receive it? I suspect it would need to be pumped or gravity fed like any other liquid fuel.
I don't know about the pump, but when I went to several sites reading up on this, evidently there's a device called a "vaporizer" (the closest analog would be a carburetor in a gasoline engine) that converts the liquid fuel to vapor, using the heat of the engine's coolant to accomplish this. It seems to be for large engines in mobile equipment, where having a large tank to accomplish the vaporization in the empty space above the fuel would be impractical.
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Old September 14th, 2011   #8
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LP liquid withdrawal just requires a tank outlet with a dip tube to near the bottom. At any temperature above -40 the vapor pressure in the tank will force the liquid out. At the point of use the liquid must be vaporized in a heated vaporizer, which often also contains the necessary regulators. These vaporizers are often heated by the coolant of liquid cooled engines, but vaporizers do exist which are designed to be heated by the cooling air from an air cooled engine. Small engines are usually vapor fed, but liquid can be and is used. Larger engines are usually liquid fed.
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Old September 15th, 2011   #9
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Quote:
Originally Posted by Jack Hottel View Post
LP liquid withdrawal just requires a tank outlet with a dip tube to near the bottom. At any temperature above -40 the vapor pressure in the tank will force the liquid out. At the point of use the liquid must be vaporized in a heated vaporizer, which often also contains the necessary regulators. These vaporizers are often heated by the coolant of liquid cooled engines, but vaporizers do exist which are designed to be heated by the cooling air from an air cooled engine. Small engines are usually vapor fed, but liquid can be and is used. Larger engines are usually liquid fed.
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I have read that some older generators exhaust were pointed on the propane tanks or lines to heat them ( vaporize) as well. Interesting reading for sure!
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Old September 15th, 2011   #10
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That would be true. In colder climates folks installed their propane tanks in front of the radiator end of liquid cooled engines to allow the warmer air to blow on the tank to raise the temperature Liquid propane is a marvel in itself. Would love to discuss further, just don't have the time right now.
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