Kubota D850 generator swap

[john11139]

I puurchased a Coleman light plant with a Kubota D850 engine and a Leroy Somer gen head.  It is rated at 6kw. continous.  I was going to use it to replace my 6.K gas gen set.  My house hold load is some where around 3000 to 3500 wat.  Lights, Fans, frezer. ref.  Without intermitt a 3/4 well pump (220)  Got it hooked up and everything works great except it really (almost puts lights out) drops the voltage for a few seconds when the well pump kicks on.  With my gas gen it dropped some but not this much. (I think governor kicked in)  I  have a chance to purchase a 8.5 Kw Leroy Somer gen head. I know that you usually figure 2 hp per kw.  But if I dont put any more of a continous load than on the 6.kw, would this engine handle the 8.5 and would this help in starting my well pump?  I have heard that for the most efficent use of your engine 80% load is what you should have on it. I notice when I was testing the gen that after putting 3 1500watt heaters that it started pulling it down and the 4 one voltage started dropping.  I would say that about 4500 watt is the max productive point.

[mobile_bob]

i am not familiar with your genset, however diesel engines in general
all will do what you describe if ...

1. the fuel filters are starting to clog, restriction of proper fuel flow will reduce power under load, so if you haven't changed filters, i would start there.

2. air filter is the same, as it clogs up badly, it will start to cause issues with power, easy enough to check out, remove the filter and try your load test again.

3. there maybe some issue with the governor, is it mechanical (which i would suspect) or is it electronic?  there might be some binding issues with the linkage if mechanical, so check all that out very well, under load make sure the linkage is pulling the fuel rack wide open... if you can move it further toward full fuel position when it is running a full load then there is your problem.

does the engine start putting out darker smoke at 4500 watts of load?  smoke is an indicator that the engine is either starved of air or there are other issues limiting the engine's ability to pull a heavier load.

how old is this thing?  how many hours does it appear to have on it?  is it a home built rig or a manufactured unit?  does the genhead get hot under a sustained load of 4500 watts?  its possible there might be an issue with the genhead, but i doubt it.

have you checked the output voltages under load? both legs appear pretty even?

i would have to look up the engine model to see what hp rating it is, i am thinking however it ought to do better than 4500watts electrical output.

just thinking out loud here
bob g

i see this is a  coleman product,  is it a belt driven unit?  what is the condition of the belt? is it good and is it properly tensioned and not showing signs of slippage?
is it direct driven via some sort of coupling, in which case the engine would have to turn 1800rpm to make 60hz, this of course will reduce the available hp potential of the engine from about 15hp to something like maybe 11hp which tells me the unit out to support about 6watts electrical load at unity power factor. so in testing i would expect the unit to do very close to that level of power with resistive heaters used as a load bank. however you might have an issue driving the well pump if it has poor power factor and you have a substantial amount of other stuff running at the same time.  the surge of the well pump at startup might exceed the capability of the genset too, so the genset might be doing all it is supposed to do and you need a larger unit.

[Thob]

In addition to what Bob said -

Do you have a kill-a-watt meter?  Or another meter that measures frequency?  You should check frequency and voltage under load.  If the frequency is dropping, then the RPM of the engine is slowing down, which may cause the voltage to drop.  If the frequency is staying good, then RPM drop is not your problem, voltage regulation is.  Some of the generator heads used in lights plants have little voltage regulation, or voltage regulators that work poorly with low power factor loads (like a well pump).   Light plants are typically designed to run a few halogen bulbs which don't care about frequency or voltage very much.  You might just need to switch to an AVR, if that's possible on your generator head.

[john11139]

The engine has been serviced, air, fuel filter ok, engine runs ok, no smoking, question is will it run the 8.5 kw gen head.  I know this is a non current engine.  I did see where they used this same engine on a Lincon welder with a 10 kw gen head.  My worry isntt getting the full 8.5 kw out of it, just lets say 3.5 kw load on it, will it take on a monentary surge better than gthe 6.kw, when the well pump kicks on.

[mobile_bob]

i would expect that the larger head would provide a bit more surge capacity, however
it will only be able to do so if the engine has the balls to drive it reliably

what i am saying is this, if the engine has a fault, such as a sticky governor it may not respond
quickly to a heavy motor starting load, and droop badly.

if the power factor of the load is poor, perhaps the larger head is better able to handle that load
and it would then start it without brownout conditions?

i say give it a try, if you have the larger head, why not?

on the other hand if you have to go out and buy another head, i would want to dig a bit deeper for the cause first.

does the engine rpm droop badly while starting the well pump? if so you don't have enough hp as it is, however if the rpm doesn't droop badly perhaps there is an issue with the genheads ability to service that load, either by design or fault, the result is the same. the fix however might be anything from easy to expensive?  hard to say from here.

seems like we are missing something here, i would expect a diesel powered 6kva generator to do anything a 6.5 gas generator can do. and the leroy summer heads are at least as good if not much better than the typical gas drive genheads are, so it leads me back logically to a problem with the engine, not responding well under that load demand.

can you get enough resistive space heaters to load test the generator to its full 6kva output? might be interesting to see if it can deliver a full 6kwatts into a near unity power factor load
which resistive heater are very close to.  if it can power them to full output reliably without excessive droop then we know the head it doing all it should, and we then would know the engine can make the required power, leaving us in the direction of governor response and/or low power factor issue with the combined loads.

process of elimination, if we can get their a step at a time, then it will be easier to make a decision or recommendation as to whether or not buying the larger head is the way to go.

last thing anyone wants to suggest is buying the larger head, you then swapping it out, and finding you still have the problem because we overlooked a 10 cent easily fixed problem.

proper diagnosis is key here, unless you got lots of money, don't mind spending it, or time is a huge factor for you.

i can't tell you how many times i have seen mechanics throw parts at a problem, racking up maybe a thousand dollars in parts, hundreds in labor all because of something so basic overlooked.

worst was a truck that had been sitting for a while, it wouldn't move out of its own way, 3 mechanics, a set of injectors, a new turbo, pump removed and sent out for service, and 2 weeks in the shop  only to find out in the end birds had built a huge tightly packed nest in the airfilter intake stack effectively cutting off the engine's air supply... removed the nest and the truck ran liek a top... hard to explain that one to a customer!

could you imagine replacing the engine and having the same problem?  there was talk of doing just that! at the time a 10k dollar proposition, all for a bird nest!

sometimes it really is the most simple explanation to a problem.

bob g

[john11139]

This is a light plant and that might be part of the problem.  I have been told that the governor does not work like on most gen sets.  Most 6kw light plants have 4 1000wt bulbs and that leaves 2kw reserve.  I understand they just set the speed at 60hz with what ever load they have on them.  I have a volt meter and hz meter, I went down to my bulding awhile ago and fired the gen up and here are my readings.  At start up I have it set at about 132v and 61.3hz add one 1500 watt heater and reading is 127v. 60.3hz, 2 heaters 119v and 59.3hz (this is about what my house hold load is) 3 heaters 114v at 58.9hz, 4 heaters 104v and 57.7hz.  Gen does not get hot.  I can slightly incerase engine speed with 4 heaters on (6kw) and the hz and voltage comes right about where iit is supposed to be.  I dont see any way to adjust the sensitive to governor setting so it will pick up speed slightly when applying load.  Its just the surge of my well pump that I am worried about.  When I get time I will hook my meter up and see what the figure is when the well pump kicks on.  I imagine it is dropping to around 100v. but comes right back up.

[Henry W]

Bring the rpm's up so you get 63 Hz, than give it a try.

The generator head might not have enough surge to handle your well pump.

6-Kw is not much to start the average submersable well pump. My well pump manufacture recomended that a generator needs to have at least 9000 watts surge for my well pump.

Henry

[Thob]

According my calculations, your voltage dropped 21% and your RPM dropped 6%.  I'd say you have a voltage regulation problem.  I would suggest checking to see if you can get an AVR that will fit that generator head.

[Henry W]

Is this generator head capacitor regulated? If it is I wonder if the capacitor is going bad. Another thing you might be able to do is contact Leroy Somer and explane to them your problem. They might be able to help trouble shoot the problem. Thy might also have a trouble shooting guide for the model you have that they can send you.

Henry

[john11139]

Bring the rpm's up so you get 63 Hz, than give it a try.

The generator head might not have enough surge to handle your well pump.

6-Kw is not much to start the average submersable well pump. My well pump manufacture recomended that a generator needs to have at least 9000 watts surge for my well pump.

Henry   

I think you may have the right answer.  This gen does not have a AVR, only a capacator and I replaced it with no improvement.  My old gen I think had a 7kw surge and a 6kw run.  The well pump started fairley good with it, still dimed the lights some but I figured with thia Leroy Somer gen head which is about three times as large would do the same thing, but must not have quite enough surge.  Thats why I was thinking of getting the 8.5 kw gen head and put it on.  I really dont neeed any larger capacity at run,, as I am only pilling around 3.5 kw with every thing I run except the well pump.  I just dont know if the D850 engine will handle the additional surge.  The 8.5 kw is the same size physically, must be differnt windinings in the fields or rotor.























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[Chris]

Here is my 2 cents worth on this.
Many years ago when I was working with a general contractor we had the guy across the street build us a 4 kw diesel generator. The generator guy was my best friend at the time. He used a Izuzu 10 hp @ 1800 engine or there abouts and attached a Fedelity pancake generator to it. Load tested it with 55 gallon water barrell with a bunch of water heater elements installed. He could wire it up so that he could check 120 volt 240 volt and combinations of loads. The generator worked great and started blowing black smoke at about 6 KW.

Off to the jobsite. It bogged down with two skil saws running. Back to the work shop. The generator checked out fine. Checked the ski saws. Could not find a problem there. After two or three goes with this he changed out the gen head for believe it or not with a Leroy Summor (sp) unit and all was fine. For some reason that Fedelity unit could not handle inductive loads and all the loads were inductive. So it was a power factor issue. In one of my Lister manuals, long lost, they talked about adding capaciitors across motor loads to correct the power factor.

[RJ]

This may seem like a silly question but how old is your well pump?  If it's old, 10-15 years and up it might be a good time to think about a new pump instead of a new gen head. I installed a grundfos sq pump when I built my home, it's a soft start pump. I have a generator setup close to yours, when I was building my house before the grid was connected I put about 200 hours on my setup. It was a D905 direct drive to an ST-12. With the soft start pump the generator hardly noticed it at all, and my pump is a 1 hp pump at 220 ft down. It's good for about 17 gal/min at that depth.

[XYZER]

I start our 3/4 hp 220v submersible with a 6/1 and a st5 with no problem. I have pumped water for days with a 1-1/2 hp 220v centrifugal with the same generator. Does your pump have the starter capacitors above ground in the pump house? I know the make 220v submersibles with the capacitors in the pump and they tend to draw on start..... just about any size air compressor will behave about like you describe your pump. They are real hard to start. Just thinkin............ 

[john11139]

My pump is a 3/4 hp about 6yrs old. (well  depth is about 70ft with 55' 0f water) It is a submersible with capacator in the pump if it has one.  Read some where that starting elec motors that sometimes you can move up one size on your gen to aid in starting.   Remember my gen is handeling the total house load fine and once the pump kicks on, it is fine.  Going to talk to someone who sells Marathon gen heads and get his thought.  Engine does not seem to labor when running all the loads I put on it.  Just a blip, causing lights to dim for just a second.  If it doesnt hurt any thing might not bother with it.  Just worried at the right conditions existed that it might nause one of my freezers not to kick on if this all happened at the same time.

[XYZER]

When I need to go on backup power all normal living bets are off. I only have around 3000watts continious with maybe a 4000watt surge. I rethink the whole program and do not allow anything to just come on and overload. I will run the pump when the tank looses preassure and the 2nd flush is used. I can add a few light loads while it is pumping. If all of your needs are drawing current and the pump kicks on and it dim your lights I would expect that. If i loose power the refer and freezer would get there quality time for several hours every day but not all at once. I have a 11,000watt welder to run the house like nothing happened even at that I might still have to loadshare.