Micro CoGen.

Replaced the hz pot and it seemed like all was going to be well, but still having some issues.  Had no issues adjusting voltage, stability, and hertz threshold - but now voltage is dropping unacceptably as load is added, like from 240 no-load down into the 220's at less than 1/4 load :-(.

I assume that the original damaged hz pot may have damaged other components, or maybe physical damage just from replacing it.

Anyway, I've got one of the SR7-2G Chinese knockoff regulators on the way to confirm/deny that my mecc alte SR7-2G regulator is good/bad.

I'll post later, comments welcome about dropping voltage as load is added.  Oh, and I think the kubota governor is working fine because frequency remains stable and you can hear the engine handling sudden load well like my air compressor motor.

Thanks!
Jay

Decided to go ahead and remove the hz pot.

It was no joke to get it off the regulator board without damaging anything because the plastic surround on the SR7-2G is filled with resin top and bottom.  I used a dremel, hot #11 knife, and a soldering iron and sucker and with a lot of patience no harm was done.

Turns out the pot is a bourns or similar 3362P-104, 100K ohms, .5 watts.  Have a replacement on order so hopefully by next weekend I can post the results after installing it and attempting to adjust the regulator again.

I tested the pot after I removed it, and it seems that in some spots of the (over) rotation it does give normal readings, but it's totally jumpy or open at most points.  I'm pretty confident that with generator vibration it wasn't holding steady and causing the adjustment problems.

Jay.

Thanks for your replies!

Scratch most of my initial findings after I adjusted the RPMs to get ~62 Hz.

Here's what's going on:

Adjusting the generator's RPM to control Hertz, and adjusting the voltage pot is straight forward.  I have a Sperry meter that does frequency and of course a/c voltage.

I'm pretty sure Thob is right with the Hz pot adjustment.  This pot had sealant on it from the factory but really easy to peel off to reset it.  I have the Mecc Alte SR7-2G manual so I worked through the instructions to reset everything (except the AMP pot which is also sealed) from scratch.  Instructions say voltage and STAB pots fully CCW, and Hz pot fully CW to start.  Crazy thing is that the Hz pot seems like it could be damaged inside because it doesn't hit it's left/right limits solidly like the other two - hope not :-(.  Moving on, I set the voltage to 240 with the gen producing 62 Hz, then the STAB pot gets moved CW until an incandescent lamp begins to fluctuate, then backed off slightly until stable.  For the Hz pot adjustment, the generator is taken to 10% lower than nominal speed (I used 54 Hz based on math since I don't have a tach), and the pot is rotated CCW until voltage drops 5V.  After those settings, RPMs are restored to normal.  After all that, the gen seems pretty normal with no load with only a volt or two of fluctuation and a little instability, about .5 up and down (fast) for Hz.

The new symptom of a problems is that when I add load, the voltage creeps UP.  I started with a 1000W heat gun and voltage increased by about 5V, and it gets worse from there as more test load is added.

My main suspicion is the Hz pot - it just doesn't feel normal and I assume if it's not making solid contact inside it could screw up everything.  Also, not sure if 10% lower than nominal speed translates to what I did by lowering speed from what should be 1800 for 60 Hz to X RPM for 54 Hz.  The math is 1800 - 10% = 1620, and then the ratio of 60/1800 = x/1620 which is 54.  Clever, but maybe non-proportional or something else weird.

Unless anyone has suggestions, I really want to change this pot.  Anyone know it's rating?  It looks like a 3386P but I'm not sure of the resistance and wattage ratings.  I wrote to a Mecc Alte support but got an out of office, lol, and I'm not sure if they'd give that info anyway.  I can likely see the rating on the side of the pot if I take the AVR out of it's housing - or maybe I'll need to remove it from the board if the marking is on the side next to another one :-(.

Hope someone has some theories...

Thanks!
Jay

Hi All,

I have a Kubota D1005-E3BG with a Mecc Alte NPE 32-B/4 10.5kVA generator head with a S.R.7/2 regulator put together by Central Maine Diesel in 2012.

The frequency has always been a little bit high, approx 63.5 since new - maybe since it was set up in Maine and I'm using it in Hawaii - but it never caused any issues so I left it alone. 

I got a new UPS last month and it doesn't like the high frequency (limit is 63) so it beeps constantly on generator power - very annoying. 

I decided to adjust to ~62 no-load Hz which is within tolerance for the UPS and from what I've read it's what many people recommend.

I was easily able to adjust engine speed to get ~62 Hz by by loosening/tightening the two set screws that pinch the throttle lever located on the outside of the governor assembly after loosening the lock nut on each screw.

Of course I had to adjust voltage using the voltage pot on the regulator - pretty easy to set.

Unfortunately voltage now droops by up to 40 volts as load is increased, so of course I stopped testing until I get some advice.  Hz remains steady.  Hopefully someone can explain how I should be adjusting everything as I am obviously doing something wrong.  I see there is also a Stab pot and a Hz pot on the AVR, but it seems like the governor isn't doing it's thing now rather than the need for other regulator adjustments.

Thanks in advance for your help!
Jay L.
Mililani, Hawaii

Thanks for your tips and insight, all good info...

Finally got it all solved with both filters staying completely full.

I was going to put bleeders on top of both filters but it wasn't needed in the end.  What I did was get a small 1-3 psi diesel pump and used it to push fuel through both filters until all the air was out.  I put a tee in the supply line on the other side of the second filter and another tee in the return line near the fuel drum to direct the pumped fuel back to the drum.  Also added a shutoff valve after the supply tee so I could shut off the return line once all the air was removed.  I used the same quick disconnects on the pump as the supply side of the filters so I can plug in the pump when needed, and remove it when done.  Because the quick disconnects are dual shutoff, no (or only a tiny bit) of air gets in the supply line which keeps everything full.  I added a few pictures to make it more clear.  Anyway, I will only have to use the pump when I change the filters once a year, so I think it's a pretty good solution.  The 1-3 psi pump is a bit slow, took like 20 minutes to clear all the air, so maybe I'll get a more powerful pump someday, but it's fine for now.

Thanks again for all your help!
Jay.

Thob,

yes, correct direction - the goldenrod top housings have IN/OUT marked on them :-)

and yes, the drum is vented with 3/4" black pipe - definitely no vacuum happening - you can see the vent pipe in the second picture in the original post - goes through a little notch in the shelf I added afterwards, hehehe.

the drum is actually 1/2 full right now, 15 gallons - I purposely didn't want to fill it the rest of the way until this is sorted out because from every other picture and post I've seen and read, it's typical to mount these filters on the drum edge - in fact, it's a kit from Hardy Diesel and it came with hardware to do so, although I made my own instead.

since i ended up getting the filter closest to the genny completely full, i'm going to wait and see if the level drops over the next couple of weeks - if it does, I'll try putting a 5 gal can above like you suggest - I agree that i should actually see a fuel leak at the filters if it's still sucking air in its current position.

thanks!  i spent a lot of time planning this installation - the whole deal is housed in an Arrow 8' x 3 1/2' metal shed and it all fits great - including space for my air compressor between the drum and the generator, cool stuff!  The generator is anchored to the concrete pad through the exterior 5/8" ply flooring, and it has an automatic 24" intake vent from nooutage.com, an 18" gravity exhaust vent in front of the radiator, and it's grounded/bonded everywhere with #6 thhn and an 8' rod...  I also used a waterproof battery tender through an ELK 912 relay that turns off battery charging while the key is on.  Also put in a new commercial/generator sub panel with mechanically interlocked main/gen breakers, and a powermeter pro outside at the panel so I can manage the load without going in the shed to look at guages on the generator (it actually only has an hour meter, lol), really cool stuff!.  yep, it's ready for the zombie apocalypse! :-)  I'll try to get some more pictures up in another thread when I get some time...

Jay L.

Hi Bob, I hear you new parts with defects, see it all the time in the IT industry!  Luckily this is an awesome little generator and it never got any air near the injector pump or nozzles, so it has always hard-started back up during this troubleshooting...  Never more than 10-15 second and it fires back up.  Since I found others with the same unfilled bowl issues, it could be normal, but it doesn't instill confidence!  At least with the second filter totally full I think it's in better shape, going to watch it until I exercise it again in a couple/few weeks.  Then I'll know one way or the other if I need to do more frustrating troubleshooting...  Thanks!  Jay L in Hawaii :-).

So...  I took everything apart again and just to be sure I redid the teflon tape seal on the close nipple between the filters even though I'm virtually positive that nothing was sucking any air.  I also re-sealed the pickup tube in the 2" bung even though that held air when I pumped it down with a vacuum pump.

I used every method I could think of to refill the filter bowls, but I couldn't get either one to the top even with a fuel pump with its output going back into the drum return line.

I cranked it up and got the filter closest to the generator to fill up completely by working the squeeze bulb and it stays running now.  However, the water block filter closest to the tank will not fill up no matter what I try.  I did a whole bunch of googling and found others with the same issues, and one post said that it filled up over time, not sure how or why.

Attached a new picture so everyone on that's been trying to help can see which end of the setup the generator is on - it's to the left beyond the squeeze bulb.

I'm not sure if the filter will stay full, keeping an eye on it and I'll let you all know.  Anyone have any more ideas?  One thing for sure is that I can't find any air leaks after two days of disassembly and resealing things that were fine all along :-(.

Thanks!
Jay L.

Thanks for all your advice...

Going out to figure it out in a few mins...

Question, if I find and stop any air leak that may be causing the problem, do you think the squeeze bulb has enough suction to completely fill the filters?  Just wondering if it's capable of forcing any air back into the drum?  Not sure how it's really supposed to work - I know it can't really push the fuel forward towards the generator, so I'm hoping it's capable of driving air back to the drum - otherwise it's a REAL pain in the neck to fill the filters completely - assume I have to remove the supply line from the generator and pump it from there, but that means I'll likely get a small amount of air back in the supply line when I go to hook it back up to the fuel filter on the generator - ugh!

Again, appreciate all the advice, hopefully I detect an air leak!

Jay L.

Thanks Ron, I hope I can find it when I dig into it again tomorrow.  One piece I didn't check is just out of the picture - I have quick disconnects before the 2" drum  bung on the supply and return lines so I can easily refuel.  They're those Motion Pro jobbies with buna-n o-rings, supposed to be high quality and seem fine but you never know.  Nothing leaks fuel while running or sitting, so you could be right about an air leak on the close nipple even though it didn't show up when I leak-tested it.  I don't think it's the bowls though, they're new and perfect including their seals...  I'll post again after more checks.

Hi All,

I have a hardy 2-stage filter on a 30 gallon drum for my kubota d1005 generator and after sitting between run-ups, the first filter partially siphons back to the drum.  I have a pump bulb after the filters but it doesn't have enough suction to re-prime the filters - even when I disconnect the supply line from the generator.

Needless to say, if the first filter is full or near-full, the generator runs for about 10 minutes and then quits when it sucks air.  The genny's running suction doesn't fill the filter back up either, even if I pump the bulb.

To make sure it wasn't sucking any air, I did a complete leakdown test all the way to the generator and it holds rock solid, so I have no idea why it's doing this.

It's a REAL pain to re-prime the filters!  I have to take the supply line off the generator and use a pump to get the filters full again.

I thought gravity feed for the whole fuel system would be fine, but maybe I need a lift pump or a check valve or other - any ideas?  And is this a typical problem?

I included a couple of pictures, you can see the second fuel filter seems to stay nearly full, just the first water-block filter is siphoning back to the tank.