Load Shedding Transfer Switch

SolarLurkerSolarLurker New UserPosts: 118Solar Expert ✭✭✭
recent snow storms in the area have got me thinking that I really need a backup generator sooner than latter.

It appears that to get a low rpm, liquid cooled, propane generator I have to go at least 15,000 watts. I would like to keep this generator operating as efficiently as possible. Is anyone aware of a transfer switch or device that can intelligently manage loads to keep the generator running as efficiently as possible.

I see that APC makes a device for honda portables, however I am looking for something that would work with a standby generator.


  • icarusicarus Super Moderator Posts: 5,070Super Moderators
    Re: Load Shedding Transfer Switch

    First question is do you have a need for a 15 kw generator? To load that efficiently would require a load ~12kw. Do you really have that much consistent load.

    If this is only for an emergency/standby perhaps consider something that isn't low rpm/water cooled/lp fueled. The size/style of the genny should IMHO take into account it's normal expected use as well as any potential abnormal use. Some times that might mean two gennies. For example, I run the Eu1000 for almost all chores. If I need small tools going, (grinders/drills etc) I'll fire up the two of them. Big worm drive skill saw, or portable table saw, I'll use the 2900 Mitsu.

    When all else fails, the 5 kw lister is still hanging around!
  • SolarLurkerSolarLurker New User Posts: 118Solar Expert ✭✭✭
    Re: Load Shedding Transfer Switch

    What I found digging around it that a decent low rpm generator used as much fuel at 25 to 50 load as 7 to 10 k standby unit. I intend to eventually add battery backup to my solar, and will need to both run the house and charge batteries.

    I want to build in a little excess as I have plans to build green houses.
  • cajun666cajun666 New User Posts: 27Solar Expert
    Re: Load Shedding Transfer Switch

    at dad camp we have a 20 kw gen set

    in winter it never get more than 30% load

    in summer it porblem run at 60% load

    dad have have that gen set for 20 yrs

    it porblerm was made in the 70

    we have ant had any problem cause to this gen bye not haveing it loade to 80% of rate out put
  • BB.BB. Just some guy Posts: 23,746Super Moderators admin
    Re: Load Shedding Transfer Switch

    Was the generator diesel or other fuel (gas, propane, etc.)?

    In general, there are two reasons for minimum loads... First is fuel efficiency. Take a look at the fuel flow at 100%, 50%, 25% loads... Most times, the 50% and 25% load fuel flow is about the same (if even given in the specifications).

    The second really applies only to diesels---And that is diesels tend to carbon/coke up the heads and glaze the cylinder walls when loaded to less than 50% loads (and really, that number is 60% or even higher). To that end, people put dump loads on the generators to achieve loading.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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