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Thread: A diesel generator question

  1. #11
    T.M.Haja Sahib Guest
    Quote Originally Posted by iwire View Post
    Has it been checked out by a generator technician?
    Yes.
    He is suggesting to derate the gen set down to load where the engine speed does not drop excessively.

    I think this is not correct.Because the gen set only remained unused for almost two years since purchase.
    Last edited by T.M.Haja Sahib; 04-18-12 at 09:15 AM.

  2. #12
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    Quote Originally Posted by T.M.Haja Sahib View Post
    Thanks for your reply.But that is not the issue here.Resistive load was sized also taking into account the factor 0.8 for gen set KVA.
    If you got rated gen set kVA with a resistive load then you would likely have overloaded the prime mover which would account for the symptoms.
    Last edited by Besoeker; 04-18-12 at 10:14 AM.

  3. #13
    T.M.Haja Sahib Guest
    Quote Originally Posted by Besoeker View Post
    If you got rated gen set kVA with a resistive load then you would likely have overloaded the prime mover which would account for the symptoms.
    Even after taking into account the factor 0.8?

  4. #14
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    Quote Originally Posted by T.M.Haja Sahib View Post
    Even after taking into account the factor 0.8?
    If you got rated gen set kVA with a resistive load then you wouldn't have taken into account the 0.8 cos phi.

  5. #15
    T.M.Haja Sahib Guest
    No.It is not that way.Say there is 30 KVA gen set. Apply 0.8 to it.The gen set should be capable of supplying 30x0.8=24kW i.e 24kW of resistive load.In the present case the gen set is capable of supplying only 20kW of resistive load due to some internal problem in it which I am trying to find out with the help of the members of this forum.

  6. #16
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    Quote Originally Posted by T.M.Haja Sahib View Post
    No.It is not that way.Say there is 30 KVA gen set. Apply 0.8 to it.The gen set should be capable of supplying 30x0.8=24kW i.e 24kW of resistive load.
    If that's what was done, then I agree. I took your comment "gen set KVA" in an earlier post to infer that you meant rated gen set kVA.

    Quote Originally Posted by T.M.Haja Sahib View Post
    In the present case the gen set is capable of supplying only 20kW of resistive load due to some internal problem in it which I am trying to find out with the help of the members of this forum.
    In your original post you mentioned that the speed drops excessively.
    One simple and obvious conclusion is the prime mover is being loaded beyond its capability and that causes it to slow.
    Do you have any nameplate details of ratings etc that you can provide?

  7. #17
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    what do you consider "excessive"?

    It might be within spec if it drops a Hz or 2.

    Is it overheating?

    Is the fuel valve opening all the way?
    Bob

  8. #18
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    Was this generator connected to the exact same load before it went into storage? If so, and it performed as desired, then it's likely that something has become damaged during storage.

    The piston rings in the engine may have got stuck. There may be problems with the fuel system from having fuel sit so long it evaporated. There may be problems with the rubber seals. Sitting for long periods can be fatal for IC machines.

    Just curious, what is the max rated load for the generator and what are you trying to run with it?

    If you want to try to fix this thing, you may need some special equipment.

    You will need to take pressure readings for the fuel system and failing any progress there, compression tests of the cylinders. Did the generator tech that was there take any readings of the sort?
    Cheers and Stay Safe,

    Marky the Sparky

  9. #19
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    One other question

    Is the throttle going into WOT (wide open throttle) as the engine slows down?
    Cheers and Stay Safe,

    Marky the Sparky

  10. #20
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    I've had that problem before with natural gas generators, the pipe fitters installed too small of gas line to the unit. Once it got past a certain load, it would shut down due to fuel starvation. Could be a clogged fuel system, but it looks like the generator tech would have checked that, but then the gas unit I had problems with the generator tech missed that. The customer had us monitor the load because the tech said we had a short circuit in our load wiring. The load was staged with two transfer switches, and as soon as the second transferred, the generator would die. After the test, I went out to look at the generator (100 kva three phase) and saw the 3/4" low pressure line ran to it. They replaced it with the proper size, no more problem.

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