Generator suggestions

Discussion in 'Off Grid Living' started by Minuteman, Sep 24, 2015.


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  1. Minuteman

    Minuteman Chaplain Moderator Founding Member

    Where I live the power grid is iffy at best, especially in the heat of summer. I am installing a whole house generator system and am trying to decide how much I need. I had a guy from a company come out and survey my house and needs and recommended a 25KW Genset. That seems a little overkill to me. I was thinking more along the lines of 12-18KW. It's not the cost, just getting what I need. I have been reading and researching online and it seems that the 20+ are much quieter units than the lower KW's. That is a factor, plus the run time on a tank of fuel. All the units on the island are diesel and I have had some guys tell me that their 8-11 KW units keep them up at night. I need an automatic start and will run one AC/heat unit, water heater, lights and pumps(our water system runs from a cistern with 12v pumps).
    With me gone so much I need a system that my wife doesn't have to mess with. Start when the power goes out and stops when it comes back on. The 25KW the guy recommended burns about 5 litre an hour at 75% load. With an 85 litre tank that should give a good run time on a tank of fuel. The longest the power has been out since we lived here has been 8 hours.
    So any suggestions or recommendations?
     
    Last edited: Sep 24, 2015
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  2. Dunerunner

    Dunerunner Monkey

    You will need a unit that can handle the starting current of your A/C when you have the rest of the house load online, like a refrigerator, stove or oven, freezer, lights, maybe a well pump too. 25KW sounds just about right and you don't want to be running your gen set at or near full load capacity anyway. JMO
     
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  3. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Hey Mm, What is the HVAC Power Requirement, and the Water Heater Power requirement? The Total of those two, will be easily 80% of your load. Then when you are running and the Water Heater Cycles ON, you could dump the HVAC for an Hour or two, except in the Middle of the Day. By doing this, you could easily reduce your required Generation Capacity by 50%. Also understand that there is a Giant difference be Liquid Cooled GenSets, and Air Cooled GenSets, in the Noise Area.... a Liquid Cooled Genset is much quieter than an Air Cooled Genset. Look for a "Medical Grade" Muffler System, that dumps the exhaust, at least 12 Ft above the Ground. Also look for a maximum of 1800 Rpms, and preferably 1200, or even 900 Rpms if you can find one.
     
  4. Minuteman

    Minuteman Chaplain Moderator Founding Member

    The 25kw is water cooled and that's what I read were the quieter ones. The RPM is 1500. The AC units are the biggest draw, the water is heated by a propane, on demand unit so not much draw there. I was reading all the calculations and charts and had my head spinning. I think the 25 may be the way to go. It just seemed a bit overkill. I had a 5 KW back up before that ran the basics, kept the lights on and the freezer cold. The guy has a used one, less than 500 hours on it for $6k installed. 3 year guarantee 24/7 service and complete service every 6 months.
    This will give me a pretty good set up. Redundancy on all my systems. I have 3 hot water sources, solar, propane and electric. 3 heat sources, wood, propane and electric. I hve 1500 gallons of potable water storage with two 12v pumps. One supplies water pressure directly to the house, the other keeps a 300 gallon tank on the roof full that has solar heating and supplies hydrostatic pressure. With the generator I will have a backup power source.
     
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  5. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    @BTPost
    Mm is in 50 cycle land these days. I'd stick with 1500 rpm machines for this case, 750 revs is a rare bird in less than industrial sizes.

    @Minuteman
    If you know the size of the loads, we can point you in the right direction readily. You can get the wattage off the nameplates of all the devices. It is critical to know which ones have motors (A/C, reefer, washer, dryer and fans if more than bathroom exhausts) as versus those that are purely resistance (as lights and the water heater most likely is. Kitchen stove, IIRC is propane?) 20 Kw does sound a bit heavy.

    Very general rules of thumb, diesels are happiest at 80% to 90% of max rated steady load, but doesn't leave much for surges. If the A/C is running when another load kicks on, there should be no problems. Gas engines are happiest at 50% load and have a lot of surge capacity IF they are heavy enough in the flywheel department to compensate for the lower torque they normally can produce. (That last is partially due to the lower speed recommendations.)
     
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  6. Dunerunner

    Dunerunner Monkey

    Sounds like you are set and if you don't want to shed load when running the Gen Set, I think the 25 would work. Take into consideration spares. Spares for the Gen Set as well as the engine, unless you intend to pay a service company to fix it for you. Insure that spares will be available for your equipment by purchasing a well distributed brand.

    Gen Sets running at higher RPM's assume load with less sag than slower turning units and they will hold frequency better while loads come on and drop off line. That is important if you are running any electronics...Stable frequency and voltage with a pure sinewave output.
     
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  7. Minuteman

    Minuteman Chaplain Moderator Founding Member

    I'll have to get the step ladder out of the shed tomorrow and climb up and look at the AC units to see what the nameplate says. These are all wall mounted in each room. Not like an American central air unit. Everything is 220volt also. It's good though as you can cool just the room you are in. We run the living room during the day then turn it off and turn the one in the bedroom on at night. We run just ceiling fans most of the year. It's only AC hot for about two months. We use the units some in the winter on heat mode to conserve propane so I don't have to make so many trips to change out bottles.
     
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  8. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    OK, split systems like I had in Singapore, compressor/condensor outside, evap coils and circ fan inside. That will allow you to reduce the size of the gennie if you can be disciplined enough to run just one or two of however many there are, and I know you would do that. Particularly useful to know if they are all the same size or if different.

    Even so, if there's an operational error, the gennie will let you know by tripping off and (should) require a manual breaker reset, even if the engine doesn't shut down. 220 is good. Also very good to know what the heating coils need for figuring gennie size.
     
  9. Minuteman

    Minuteman Chaplain Moderator Founding Member

    I'll look tomorrow. It's nearly midnight here and I'm not traipsing around in the yard and the shed in the dark. Still snake season here. Nasty little vipers they have on this island, killed 4 last year.
     
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  10. Dunerunner

    Dunerunner Monkey

    My bet, since they are 220V is that they are 24,000BTU units, or 2 refrigeration ton capacities.
     
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  11. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    That is important. However, if you suffer regular power losses and have to wait out a gennie start anyway, a UPS beats that problem totally. Recommended.
     
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  12. Dunerunner

    Dunerunner Monkey

    Correct, sensitive electronics should be connected to an UPS on a permanent basis. [winkthumb]
     
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  13. Minuteman

    Minuteman Chaplain Moderator Founding Member

    OK, the main AC unit is in the living room. That is the one we would run during a power outage, the ones in the bedrooms are smaller units.You probably won't know the model, it is made in Turkey, Arcilik. 220-240V - 50 Hz. "P Design C Capacity 3500W". Max power input 1600W. Max Current 8.0A. Don't know what all that means but that is what is on the nameplate. Luckily it was in English!
    Like I said that would be the main energy draw. We wouldn't run the washer and dryer or dishwasher. Just lights and water pumps. Course if the 25 KW could handle it all it would be better to just have the wife continue on with whatever she was doing and not worry about going around and turning things off.
     
  14. Dunerunner

    Dunerunner Monkey

    Your 25KW Genset would deal with that load handily. Depending upon the load the other machinery would represent, I would think that it could handle the entire home.

    Washer - 700 Watts
    Dryer, electric - 4000 Watts
    Microwave - 1500 Watts
    A/C Unit - 2000 Watts
    Dishwasher - 1500 watts
    Lighting - 400 Watts
    TV - 250 Watts

    Total - 10,350 Watts

    Your Genset is rated at 25KW, 90% load would be 22.5KW or 22,500 Watts.

    With the above loads all online, you would be running about 41% of your Genset capacity. Easily enough for another A/C unit and a couple of freezers.
     
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  15. Minuteman

    Minuteman Chaplain Moderator Founding Member

    Thanks DR. Yeah I was sure the 25KW would handle everything I wanted to run I was just wondering if it wasn't overkill. You have to be careful here as soon as they see you are an expat the price doubles and they will try to sell you all kinds of stuff you don't really need. But I think I would rather have it and not need it than need it and not have it. Also I think the bigger unit will last longer if I have to run it continuously. They had one of the two power plants damaged in an explosion year before last and now are supplying all the power for the Island off just the one. One reason we have so many blackouts. If something was to happen to that plant the entire island would be without power for no telling how long.
    From what I have seen online the price isn't bad either, compared to US anyways. A 25KW unit installed was averaged around $9500 from what I seen. 6K for a slightly used one doesn't sound too bad.
     
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  16. john316

    john316 Monkey+

    don't forget storage of fuel...........do you have a truck or car to use the fuel and keep it fresh?
     
  17. Minuteman

    Minuteman Chaplain Moderator Founding Member

    Actually I am getting ready to buy a vehicle soon and am thinking of getting a diesel. So that would give me another source of fuel. Storage would be limited to a few 5 gal cans.
     
  18. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    No question about it, DR is right. The 25Kw unit will run your house, top to bottom and all the time. It is somewhat of an overkill if you do the least amount of load management when commercial power is out. Using DR's estimated loads in post #15, a 10Kw machine would work with a very small bit of load management and be a tad more fuel efficient. Methinks it might be worth a bit of thinking in that direction if expense is a real concern. All that aside, it looks like the prices are very good, especially if they include foundations and the electrical work you'll need.
     
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  19. techsar

    techsar Monkey+++

    As has been mentioned, the 25kw unit should easily handle your loads with headroom to spare...and yes, you might be able to downsize to a 10 or 12kw unit, but the ones I've seen around here in the 10/12 range are air cooled and higher reving models. Not to mention that the price quoted is going to be hard to beat.
    Sounds like the big question is whether quiet is worth a bit more fuel?
     
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  20. Minuteman

    Minuteman Chaplain Moderator Founding Member

    12 kw is minimum for automatic start function and 20 kw for water cooled, ergo quieter running. I'm leaning toward the 25. Have a guy coming out to give me an estimate on a solid foundation for it. That's not included in price. Going to be nice to have back up power. The temporary outages are a nuisance but like I said I am concerned about a long period if something were to happen to the only power plant we have. They had a building boom for the last several years and it has really put a strain on the power grid. Thanks all for the info. I'll let you know what I decide on.
     
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