Replacing 15kw diesel Gen with Propane - Recommendation & Important Considerations?

muirhousemuirhouse Solar Expert Posts: 82 ✭✭
My over 10 year old china diesel genset is knocking horridly and on its way out. Looking for a propane replacement that requires no babysitting. Can you please recommend? And are there any expensive diesel to propane replacement issues? Current generator is in its own shed, large underground propane tank about 20 feet away and basement of house with inverters and batteries about 20 feet away from that. The 15kw was oversized to charge my 16 surrete/48 volt system alternating with 8 panel with PV, so looking for propane 8KW, I think. Any discussions around this would be much appreciated!
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Comments

  • mike95490mike95490 Solar Expert Posts: 8,417 ✭✭✭✭✭
    Wait before you dump it. When was the last time you de-carboned the head ? Or tried a water sprayer and spritzing a mist of water into the intake manifold (remove the air cleaner first) ?

    I was having a heavy knock in my lister, and did not have the time to open it up and so I used a hand held spritz bottle and while running at hot temp, sprayed some water in. As it flashes to steam it cleans carbon out.

    For converting diesel to propane, you cant. You have to keep some diesel as pilot ignition, and can not go too far past 70% propane. To convert a diesel engine to propane, you have to install a spark plug, adjust timing and reduce combustion ratio to at least 11:1 or lower.
    here's a LONG thread about the issues of converting diesel to 100% propane
    http://listerengine.com/smf/index.php?topic=7344.0
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    Thank you Mike95 for the carbon cleaning suggestion, I will try this, it does sound like a thrown rod however, but keeps on running. I don't want to convert to propane, just replace the diesel generator with a propane generator, and am unsure about what propane generator to get and what changes/additions I might have make in the infrastructure, wiring, etc.
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    I have a CumminsOnan 20 kw propane, water cooled, 1800 rpm unit.

    A little larger than what you are looking for but a good choice for larger off grid applications. Not sure if they make the lower rpm propane models below 20 kw but try their website.

    In my opinion, CumminsOnan manufacture well engineered and reliable gensets.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    Thank You Mangas, I am in NH and have a PV setup which has cut the runtime of the generator in half. So really, the generator is now backup to the PV, used to charge the batteries in bad weather.  20 KW seems like overkill for this, am I wrong? But I am really having trouble getting the right recommendation for a new generator, as it must be correct size for my series stacked Xantrex inverters to handle. I am being recommended an 8.5kw Kohler air cooled. One supplier says this is too small, another installer says it is just fine, not sure who to believe. I know the water cooled and 1800 rpm is way to go but too expensive for me right now. So with my two Xantrex 4kw inverters and my PV doing lots of work on sunny days, can I manage with the 8.5kw?  Thanks guys ~ Jan
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    muirhouse said:
    But I am really having trouble getting the right recommendation for a new generator, as it must be correct size for my series stacked Xantrex inverters to handle. I am being recommended an 8.5kw Kohler air cooled. One supplier says this is too small, another installer says it is just fine, not sure who to believe.
    Who to believe depends on data you haven't provided to us.  

    What is the ah capacity of your battery bank?  If I know the ah capacity I can calculate how many generator watts it will take to charge the batteries at a reasonable rate.   What other loads will the generator handle while it is charging the batteries?  Those loads, plus the charging load will be the generator capacity that you need.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    VTMaps: 16 Rolls Surette 6 V 350 amp hour batteries. My useage is small. 240 well pump, radiant floor heat, w/d, refrigerator, 1 computer, radios, sometimes TV flat screen, lights, normal household: toaster, microwave, hairdryer.
  • inMichiganinMichigan Registered Users Posts: 50 ✭✭
    42 SP-335's (14.1kw) ->   4 FLEXmax 80's /  100 AH CALB /  FLEXnet DC  /  MATE3  -> 2 Radian GS8048A and watched over by Vantage Pro 2+ PWS
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    muirhouse said:
    VTMaps: 16 Rolls Surette 6 V 350 amp hour batteries. My usage is small. 240 well pump, radiant floor heat, w/d, refrigerator, 1 computer, radios, sometimes TV flat screen, lights, normal household: toaster, microwave, hairdryer.
    So that's a 48 volt, 700 ah battery bank.  Charging at 10% of the ah rating is 70 amps.  If your absorb voltage is 60 volts and 70 amps are going into the battery, that's 4200 watts.   There are some losses in the inverter/charger, so add another 10-15%... so that means the generator must put out almost 5000 watts to achieve a 10% charge rate. 

    If you are also running loads while charging, you may want a larger generator than 5000 watts. 

    I believe that your inverters can limit their charging to prevent overloading a generator... i.e. if you have a 5000 watt generator and are charging the battery, and then you switch on the 1500 watt central vac, the inverter will drop the battery charging down to 3500 watts so as to not draw more than 5000 watts from the generator.

    By the way, I based the generator size on giving the batteries a 10% charge rate.  You don't need that high a rate... it's just a rule of thumb.   It is especially useful for solar charging because using higher current (like a 10% charge rate) allows the battery to be charged in less time (and in the winter there is not much time).

    If you are using a generator to charge the batteries, you don't have to worry about the sun setting, so you can charge at a slower rate (and the batteries are probably better off being charged at a somewhat lower rate).  

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭

    Based on your battery bank description, I'd research 10 - 15 KW units.  Personally, I like to have lots of KW headroom when my batteries are being charged by the genset simultaneous with running the house, wells etc.   

    In addition to Cummins Onan, Kholer makes a very good genset.

    Most 1,800 rpm, water cooled propane units are 15 KW or more. My opinion is higher rpm, air cooled units will probably be your best bet.  I prefer propane fueled gensets.  If you search the forum, you can get a good feel about the back and forth between gas, diesel and propane generators.  Everyone has their own opinion based on their set up and fuel availability.

    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    One issue--How cold does it get in your area... You may need to pre-heat the motor on cold winter days. And if you have smaller propane tanks, they may run cold and you lose your propane pressure. Unless you get a liquid propane fueled genset (need vaporizer at engine to turn fuel into liquid).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    Hi BB - I am in NH, and babying the 15kw diesel all winter is why I am switching to propane. My propane tank is 500 gallons, is buried underground. The genset I am set to get is a used 2007 Kohler 8.5/12 RES, LP vapor, natural gas rated.
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    And wondering about issues re the change from 1800 rpm (my old diesel) to the 3600 rpm Kohler propane. Looks like the two wire start is the only electronics that has to be done (no transfer switch, off grid). So the rest of this is going to be negotiated via settings on the SW 4048. I think I should call Xantrex perhaps.
  • AnawaAnawa Solar Expert Posts: 211 ✭✭✭
    Muirhouse: I installed the same Kohler 8.5 (propane) and due to the current weather conditions in my area, I've been using it every day for the last 2 weeks. My battery bank is 804ah at 48 volts. The charging amps start out at 80+ at 58 volts, but drops fairly quickly. At this rate, I do not think the gen efficiency is nothing to rave about.

    The only downside I've discovered is it uses a fair amount of fuel, so take that into consideration when sizing your tank.

    Paul
    In Georgia
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Here is a nice PDF from Generac on sizing for propane:

    http://www.probuilder.com/showvillage/2013/products/pdf/Generac_SizingGuide.pdf

    Down to Zero F, it appears that a 500 gallon tank is OK for 15 kWatt load.

    Of course, if you run your tank towards empty before refilling it--Then there is less heat transfer from the outside to vaporize the fuel--And you could still lose propane pressure (cold weather, tank less than 1/2 full, heavy load on genset).

    As always, get confirmation from your local propane supplier about tank/genset sizing for your area/installation (above/under ground, etc.).

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • notesnotes Solar Expert Posts: 47 ✭✭
    Try this place. Great service and a 3 year warranty. http://www.genconnexdirect.net/
    Moderators, if I am not supposed add a link please delete post. Sorry in advance.
  • BB.BB. Super Moderators, Administrators Posts: 29,634 admin
    Not a problem. On topic links are fine. Always nice to hear good things about a supplier.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    edited November 2015 #18
    muirhouse said:
    And wondering about issues re the change from 1800 rpm (my old diesel) to the 3600 rpm Kohler propane. ...
    The conventional wisdom is that 3600 RPM generators, regardless of the fuel, are not really well suited to prime mover use with several hundreds of hours per year. The higher engine speed just produces too much wear, even when under low load. There are, of course, always exceptions and there are ways of improving the like of 3600 RMP engines by careful (and more expensive) design.

    From http://www.generatorjoe.net/html/stepxstepgenerator.html :
     To produce 60 Hz electricity, most engines operate at 1800 or 3600 RPM. Each has its advantages and drawbacks. 1800 RPM, four pole sets are the most common and least expensive in large generators. They offer the best balance of noise, efficiency, cost and engine life. 3600 RPM, two pole sets are smaller and lightweight, best suited for portable, light-duty applications. 3600 RPM sets are considered "Standby Generators" and can never be considered for prime power use.

    In simple terms it’s like operating your car at 90 mph, versus 45mph – at 45mph your car will last longer, is quieter, less maintenance and longer life.  Most 3600 rpm units are twin cylinder air cooled lawn mower engines, while the water cooled 1800 rpm units are comparable to those found in forklift and tractor engines. The bottom line is the 1800 rpm water cooled units will last longer, offer less maintenance problems and be more fuel efficient. In addition, 1800 RPM generators are designed to be rebuilt, 3600 RPM units are designed to replaced and are much lower in cost (most of the time). Some 3600 RPM stationary units and most RV and commercial power units can be rebuilt at least one or more times but this process is not inexpensive.






    SMA SB 3000, old BP panels.
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    The concern is what size generator to get, given the confusing input from suppliers making site visits - One supplier says that my two Xantrex inverters each pull 18 amps, and an 8.5 kw generator is too small, only puts out 30 amps. I am confused by the 18 amps, don't know where he is getting that as it says max charge amps is 30 amps right on the Inverter. Please help me get this straight.
    Here are the specs on my Xantrex units, stacked, 240 volt system, batteries are 16 Rolls Surrette 350 ah, wired series/parallel.

    Generator Model Numbers SW4048 and 4048 Plus
    Inverter 4000 Watts each Stacked.

    Top Inverter S/N 445428  4048  7/2002

    Inverter System -
    Nominal Battery Bank Voltage 48 Volts
    Nominal DC Operating Voltage  59 Volts
    Range of Operating Voltage 44-64
    Max op DC current 100 Amps
    Nominal AC output 120 0 ~
    Nominal frequency 60 H
    Max continuous output current 33 amps
    Max output overcurrent protection 35 amps AC
    Max output fault AC current 78 amps AC rms 

    Battery Charging System -
    Nominal AC input voltage 120 Volts
    Operating Frequency 60 hz
    Max continuous battery charger AC current 30 Amps AC
    Max continuous battery charger DC current 60 amps DC
    Max continuous battery charger input VA 3600VA
    Max AC Transfer switch Input current 60 amps AC
    --------

    ***Also, when I have had down time for repairs to the old china diesel, I have in the past plugged in to an AC outlet, a gas driven Honda generator I think it was 6.5kw.  That was backfeeding I know, but Was that going straight to the batteries, bypassing the inverters?


  • MarkCMarkC Solar Expert Posts: 182 ✭✭✭
    edited November 2015 #20
    I've always gravitated toward this supplier - have NO EXPERIENCE - simply the combination of supplier choices of build parts and price for 240 volt split phase designs in the sizes appropriate for relatively small KWH usage designs (small compared to "whole house" generators).  
    http://www.centralmainediesel.com/order/Honda-5kw-Propane-Generator.asp?page=H04585

    Did I miss something about your number of PV panels?  Seems you might have inverter/battery capacity for almost double your PV panel count - further possible reduction in generator demands?  Would you consider a MPPT CC to further unload the generator - more effective battery charging via solar?  I use the SPS of the SMA Sunny Boy as emergency off-grid charging for a 48 volt system, but realize it is not that effective.


    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    I only have room on the roof for 8 panels, and MPPT CC SPS SMA, whoa, need translating.
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    Here's another question. I will be decoupling the old two wire start from the diesel wiring, can I just hook the new generator's two wire start right into that same wire set? the change from 1800 rpm to 3600rpm won't be an issue?
  • MarkCMarkC Solar Expert Posts: 182 ✭✭✭
    muirhouse said:
    I only have room on the roof for 8 panels, and MPPT CC SPS SMA, whoa, need translating.
    Maximizing the PV panels to match the battery charging requirements (say 70 amps minimum @ 50 volts - likely 4000+ panel nameplate watts), combined with an efficient solar charge controller (MPPT type) could more adequately "fill" the batteries via solar power daily - and depending on patterns of energy usage, could reduce generator usage substantially - may allow you to go to a much less expensive generator system that "fits" the needs.   Just a thought!

    On the other hand I use what is called a "secure power supply" (SPS) that comes with the SMA SunnyBoy on-grid inverter to charge the 48 volt battery system with the OEM golf cart battery charger (110 volt AC powered by the SPS).  The SPS only works when the grid is down. Not the most efficient by any means, but it is only for emergency - not really "off-grid".  

    3850 watts - 14 - 275SW SolarWorld Panels, 4000 TL-US SMA Sunny Boy Grid tied inverter.  2760 Watts - 8 - 345XL Solar World Panels, 3000 TL-US SMA Sunny Boy GT inverter.   3000 watts SMA/SPS power.  PV "switchable" to MidNite Classic 250ks based charging of Golf cart + spare battery array of 8 - 155 AH 12V Trojans with an  APC SMT3000 - 48 volt DC=>120 Volt AC inverter for emergency off-grid.   Also, "PriUPS" backup generator with APC SURT6000/SURT003  => 192 volt DC/240 volt split phase AC inverter.  
  • arbyarby Solar Expert Posts: 103 ✭✭
    <<Max continuous battery charger AC current 30 Amps AC
    Max continuous battery charger DC current 60 amps DC
    Max continuous battery charger input VA 3600VA>>

     I have one SW 5548, so I don't have this question, but will each inverter put 60 amps into the bank , boosting the charge rate to a theoretical 120 amps?
     It appears that one inverter will only accept 30 amps AC, or 3600 watts.  If both inverters were putting out full charge , that would require a maximum input of 7200 watts by my thinking.
     To get 7200 watts continuous I would guess that you would need probably something like a 10,000 watt genny.
     Propane seems to give trouble starting in very cold temperatures.
     That's how I would read those ratings, but I'm a neophyte in these things.
    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
  • VicVic Solar Expert Posts: 2,970 ✭✭✭✭
    arby said:
    <<Max continuous battery charger AC current 30 Amps AC
    Max continuous battery charger DC current 60 amps DC
    Max continuous battery charger input VA 3600VA>>

     I have one SW 5548, so I don't have this question, but will each inverter put 60 amps into the bank , boosting the charge rate to a theoretical 120 amps?
     It appears that one inverter will only accept 30 amps AC, or 3600 watts.  If both inverters were putting out full charge , that would require a maximum input of 7200 watts by my thinking.
     To get 7200 watts continuous I would guess that you would need probably something like a 10,000 watt genny.
     Propane seems to give trouble starting in very cold temperatures.
     That's how I would read those ratings, but I'm a neophyte in these things.
    <<

    arby,  you are basically correct,  in all regards.   But  I have been told that a pair of venerable SW inverters will NOT stack well,  as one of muirhouse's inverters appears to be an SW,  Stacked with an SW Plus ...  I have never tried stacking a combo like this.

    Regarding just how much genset that one needs,  if does depend upon the amount of battery charge current needed,  plus the amount of AC loads on the inverters,  as the genset needs to supply these ...   AND,  there are latitude and high temperature deratings,  as well as a 10 - 15% derating from Standby rated power to Prime power,  and so on.

    OOOPPPppssss  looks like I have erred again,  as this all looks like it is a Quote,  with no added Comment!    Gotta love it!   FWIW,  Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    HI Vic, That's OK, thanks for weighing in. I hear alot about inadvisability of stacking my 4048s - they have been stacked for a over ten years now without a problem. - Arby: that's the question I was not understanding. If I was running my system all these years with the 15kw diesel was putting out 60amps, and an 8.5 propane would put out 30amps, there's a big gap in my understanding of electricity that needs filling.  Yes I can adjust settings on the Inverters, but 30 amps is a big differential.
  • arbyarby Solar Expert Posts: 103 ✭✭
    You will just have to adjust the input amps down until it no longer pops the genny's breaker. You will probably still get the at least the 70 amp input to the bank with the 8500.
    3310 watts panels, Classic 200 controller, 8 Surette S530's, Xantrex 5548 inverter, Honda EX5500 backup Genny.
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    Right, so simple!  Thank you alot for confirming.

  • AnawaAnawa Solar Expert Posts: 211 ✭✭✭
    Muir: my 8.5w Kohler (propane) will easily output a max of 90+ amps through my 2 stacked Outback 3648's (off-grid) and when the SG is low at 1.24. 

    Paul
    in Georgia
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • AnawaAnawa Solar Expert Posts: 211 ✭✭✭
    Muir: if you decide to go with the Kohler, don't forget to run a 110v AC circuit to the unit that is used to power the built-in charger for the starting battery. 
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • muirhousemuirhouse Solar Expert Posts: 82 ✭✭
    The SG? and your 3648's are 36 amps?
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