Propane Generator Question

Discussion in 'General Survival and Preparedness' started by T. Riley, Jun 6, 2018.

  1. T. Riley

    T. Riley Monkey+++ Site Supporter++

    I have a 10kw propane generator fed by two 500 gallon above ground tanks. The tank feed lines are tied together with a tee. I usually use one tank at a time, switching over and calling the supply company when one gets low. I decided to use both tanks at the same time reasoning I would have to have the company out half as often. The takes have about 275 and 400 gallons respectively. After I opened both values feeding the single line to the house and generator, the generator refused to run. It would crank and shut down after about 10 seconds. This happened over and over. The hot water heater and stove worked fine. The generator is designed to shut down if the oil pressure is too low but that is the only shut down safety precaution I am aware of and not other in documented. I then thought it might have something to do with using dual tanks. I shut down the fuller of the two and sure enough the generator starts up and runs just fine.

    My question is: Why? What is going on when the two tanks are being used that lowers the gas pressure so low it will not allow the generator to run?
  2. DarkLight

    DarkLight Live Long and Prosper - On Hiatus Site Supporter

    Is there a regulator after the T? If it's just a T, the delta in the internal pressure between the tanks may be causing back and forth between the tanks rather than sufficient pressure through the T to run the generator. Different temps on the tanks, even just a couple of degrees can cause massive pressure differences between the two.

    The other thing that comes to mind is that maybe it's too high rather than too low. Two regulators pushing 20 psi each isn't going to be 40 psi, but may push things up enough to be outside the safety specs for the generator
    Last edited: Jun 6, 2018
  3. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    If there is not a regulator and both tanks are connected you may be getting Liquid to the engine. Because the dual tank allows enough time to allow the gas to reliquefy.
    A check at a engine fitting will tell the tale.

    Edit> or maybe not
    Last edited: Jun 6, 2018
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  4. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    The correct way to feed a Genset from Two Propane Tanks is to have a Two Tank Feed Regulator that has a Switch Over Valve, built into the Regulator... I have such a Regulator on my Propane 50,000BTU Heater, for 'winter Heat in the Store, here...
  5. Ura-Ki

    Ura-Ki Grudge Monkey

    Or, The tanks try to "equalize" the pressure differences between the two with out a regulator, starving the engine of fuel! That's my guess! If it runs on ether tank, but not both, that's the most likely situation.
  6. ghrit

    ghrit Bad company Administrator Founding Member

    Should not be possible. Both tanks should have check valves to prevent backfilling thru the take off pipe/tube. In any case, the feed line to the gennie should have two regulators OR a two stage regulator. The usual case in these parts is one more or less at the tank to control pressure in the house piping (here, it's about 12 IWC) and another at the using appliance which can vary depending on the burner design (or carburetor requirements.)
    The very best way is the auto changeover valve BT mentions. Some of those will have a visible indicator that will tell you when it shifts. With different size tanks, the operator has to know how long each will run before shifting.
    Last edited: Jun 6, 2018
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  7. T. Riley

    T. Riley Monkey+++ Site Supporter++

    Thank you for the input. Each take has a regulator before the tee and the genset has a regulator as well. I would think if I wanted to run both tanks then the best thing to do would be to fill them both and then run them both from that point. I have decided there is not much advantage to be had running both at once and a gas leak might drain both of them when I am not there..
  8. Cruisin Sloth

    Cruisin Sloth Special & Slow

    BT nailed it !!
    And that setup of a fight pair of regulators is the problem (think 2 wives & which one to sleep with makes the witch of NUN 4 U )
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  9. Asia-Off-Grid

    Asia-Off-Grid RIP 11-8-2018

    I realize the case I am about to mention is using much smaller tanks. But, I am certain the same principle still applies.

    Many years ago, I had a 31' tag along travel trailer. In a tray mounted on the trailer tongue, there were 2 - 40# LPG tanks, with a similar regulator between them, as earlier mentioned by Bruce.

    I opened both tank valves, and turned the switching valve knob atop the regulator to either of the tanks. When that tank emptied, a little red flag popped up, serving as notification. Internally, the regulator had automatically switched, opening the flow from the full tank. I switched the valve knob to point to the full tank and the flag dropped. Afterward, I could remove the empty and have it refilled.
    Last edited: Jun 8, 2018
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  10. T. Riley

    T. Riley Monkey+++ Site Supporter++

    The only two gas home appliances I own are a stove and on demand water heater. I do recall the stove burners would sputter, for a lack of a better term, when both valves were open and the oven was hard to light. Both due to a low or inconsistent gas pressure, I assume. Lesson learned.
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  11. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Whats is happening is like i posted UP ^^^ THERE (((fight pair of regulators)))

    To do this !!!! NO OTHER WAY , AND DO IT RIGHT THE FIRST TIME !!!!!
    Feed only one regulator ( HERE IS THE THING )!! Genset full load needs (say [Make up numbers ]) 5000 btu , BBQ is 4000 BTU and the DHW heater is 8K BTU , So total is 17, but a 20K BTU regulator will do all 3 JUST fine .
    The propane is say 125 PSIG and the reg can pass gas like me @ 20K BTU at a pressure of less than one pound , one half a pound or point six of a water column . this is the fight after . Use one reg & supply the reg with 2 bottles PLUS ++++ as many as you want .
    SO join under tank pressure only (say 125 PSIG) and then feed only one regulator (THAT CAN PASS ENOUGH GAS TO FED ALL UNITS AS ADDED) [ IM GOOD FOR YVR]

    reg for 2 tanks & 15K btu :
    Automatic lpg Changeover Regulator | eBay


    Top part of reg decides on the tank main pressure !!

    OK everyone ?
  12. Asia-Off-Grid

    Asia-Off-Grid RIP 11-8-2018

    I find that hard to believe. Two regulators, possibly three. But, not just one. :D :D
  13. VancleVector

    VancleVector On Hiatus Banned

    I have a 6k propane diesel generator, lasts about 4 hours on a 20lb tank, but since propane is for ever I plan on getting a large tank installed and feeding my dryer, generator and stove from the one tank.

    I'm happy with mine. how ever it's important to remember that power from propane will cost you double the cost of power from diesel fuel as propane has a lot less "energy" when compared to diesel.
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  14. Asia-Off-Grid

    Asia-Off-Grid RIP 11-8-2018

    First, welcome to the Survival Monkey Forums. Find a branch and feel free to hang 'round the monkey tree.

    LPG is great. I wish we had large bulk tanks, here in Cambodia. Thus far, I have been unable to find any. (Of course, I can't say that I have searched really hard, thus far.)

    I was going to go with a 15 kva (~12 kW) Denyo diesel, early last year. I wasn't sure where I would even set it at the time, as we were still in the air concerning where we would construct what buildings, on the property here. So, we just went with Honda Inverter EU-20i generators. Now that we have more of a plan going on, I am pretty sure where a site sized generator would go. It may not be until other structures on the site are built. But, eventually, I will buy one. Currently, a 15kva will cost $3,500 US. I like the features Denyo offers. Not to mention, just about every commercial building in this country uses that very brand.
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  15. T. Riley

    T. Riley Monkey+++ Site Supporter++

    I went with propane because of the unlimited storage life. When full, my two tanks will run my genset 17 days, 24/7. I would likely only run it only 8-12. In hurricane country that might not be long enough. The oil has to be changed every 100 hours (4 days) so I keep spare oil and filters around. My only regret is that I did not install one 1000 gallon underground tank.
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  16. Asia-Off-Grid

    Asia-Off-Grid RIP 11-8-2018

    Live and learn, don't we? That's why we don't make fast, definite decisions regarding the farm, any longer. (Yep. We made a similar decision in the past.)

    We think things over, consider future changes, and talk about it a bit more. It's a heck of a lot easier make a proper plan in advance, than it is to break up a lot of concrete and start over.
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  17. ghrit

    ghrit Bad company Administrator Founding Member

    As a general rule the per BTU dollar cost of propane is lower than diesel. However, there is a very wide variation depending on location, taxation, transportation, yadda yadda --. There is a very real advantage to diesel in that the storage volume is smaller for the same energy content, but with that comes more stringent storage requirements.
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