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Author Topic: 120v rewiring to achieve full wattage  (Read 9456 times)

KellyR

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120v rewiring to achieve full wattage
« on: May 08, 2009, 02:21:43 AM »
I've got my new Mecc Alte 3kW generator head wired for 120/240 and it's running fine.  However, the breakers cut off at 12 amps, which means I'm only pulling about 1300 watts.  I've read on the utterpower page that it's possible to pull the full wattage out of a head by tinkering iwth the wiring. 

Right now, the two black wires (positive) run to the two 12amp breakers.  The white wires (negative) and wired together.  George at utterpower says that by joining together one black and one white and then the  other balck and white, full output can be achieved.  Here's the link to that page:  http://www.utterpower.com/genhead.htm

Has anyone tried this?  If so, what is now negative and what is positive?  Seems to me, it wouldn't matter which was which.  It would be nice to be able to draw the full wattage of the generator.  I only use it to top up the charge on the batteries after a few cloudy days or when the batteries need to be equalized.

Kelly

lowspeedlife

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Re: 120v rewiring to achieve full wattage
« Reply #1 on: May 09, 2009, 12:01:43 AM »
Hi Kelly, the page you linked to on George's site is for the ST style heads, have you tried the Mecc Alte web site to see if this is possible to do with your gen head?  If so when this is done you can chose which wire set you want to be the hot & neutral (with a/c current we refer to them as hot & neutral not positive & negative). I have an s16w , 5kw head, i'll see if i can scan the page you need & post it here.
Scott R.

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KellyR

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Re: 120v rewiring to achieve full wattage
« Reply #2 on: May 09, 2009, 12:28:43 AM »
Hi Scott,

Mecc Alta's site is pretty poor when it comes to diagrams and technical advice.  If I'm reading George's page correctly, he's stating that this cahnge can be made regardless of the type of generator.  I know the page is about the ST and he's showing how to take a center-tapped, three wire generator and turn it to full output, but he does mention at the beginning of the page that getting full output from any type of generator is not rocket science.  It looks like the four wire conversion is fairly straightforward.

lowspeedlife

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Re: 120v rewiring to achieve full wattage
« Reply #3 on: May 09, 2009, 12:29:35 AM »


  Here's the page from my mecc alta owners manual, on the S16W,  5KW single bearing gen head it looks like leads #1 & #3 connect together & leads #2 & #4 connect together tomake it 120volts full output. on the page above it is the lower connection diagram on the far right.
 If you are not running this to an electric panel, you should check the postings on grounding & bonding gen sets, george at utterpower also has a page on his site that explains things well.

   Scott R.
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KellyR

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Re: 120v rewiring to achieve full wattage
« Reply #4 on: May 09, 2009, 12:33:19 AM »
Thanks for the scan.  It looks like you have the same manual I do.  I've got a ground wire coming out of the head.  That and everything else is sent to the AC panel and hardwired in.

Thanks again!

Kelly

mike90045

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Re: 120v rewiring to achieve full wattage
« Reply #5 on: May 09, 2009, 06:08:31 AM »
I've got my new Mecc Alte 3kW generator head wired for 120/240 and it's running fine.  However, the breakers cut off at 12 amps, which means I'm only pulling about 1300 watts.  I've read on the utterpower page that it's possible to pull the full wattage out of a head by tinkering iwth the wiring. 

Kelly

It's also possible, that your charger does not have a good Power Factor rating, and therefor trips the overload.
 This is not easily correctable. Easier to get a charger with good Power Factor.

KellyR

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Re: 120v rewiring to achieve full wattage
« Reply #6 on: May 09, 2009, 09:44:56 PM »
I pulled the generator head yesterday to do the rewiring and realized that nothing is labeled.  There are four wires coming out, two white and two black.  One of each coming from each side.  They then go into a four-way connector, but even though there are two blacks and two whites coming out, they don't correspond to the blacks/whites going in.  Aargh!  Anyone have any idea which wires I should connect together?

Mike, what do you mean by "charger" and "Power Factor?"  The generator is wired into the AC panel of my inverter, which is an Outback VFX .

Kelly

mike90045

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Re: 120v rewiring to achieve full wattage
« Reply #7 on: May 09, 2009, 11:06:53 PM »
power factor
  http://en.wikipedia.org/wiki/Power_Factor
   Apparent power is the product of the current and voltage of the circuit. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power can be greater than the real power.

The outback has a battery charger. It is NOT 1.0 power factor, and so will actually draw more than you think it does. Somewhere in your manual, it will say, or on a label on the inverter, what the power factor is.

Mike

KellyR

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Re: 120v rewiring to achieve full wattage
« Reply #8 on: May 10, 2009, 12:33:45 AM »
I've got the VFX 3524 inverter which, yes, has a charger built in.  I've taken readings in the past and the power factor is pretty darned close to 1.0, maybe 0.98.  It would be pretty silly to junk a $1750 charger inverter because it's 0.02 off, don't you think?

I only have one inverter, which is all I need, but it means that I can't get 240v.  I have to run the genny at 120v.  Since the genny is 3000 watts (a little less actually), I can only draw 1300 watts before tripping the breaker.  Now, if I can wire the generator to achieve full output at 12 amps, that would allow me to draw slightly more than 2500 watts, which would be okay.  That would mean the batteries could be charged or equalized more quickly and I would save fuel.

So, anyone have any ideas about the wiring?

mike90045

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Re: 120v rewiring to achieve full wattage
« Reply #9 on: May 10, 2009, 03:01:59 AM »
Well, if your reading for a high amp battery charger from outback are .98, that's really good.  PF is not your problem.

 So if you look at the outlets on the generator, do you have a pair of 120 and a 240?   That would indicate that the 120 windings are out of phase, and provide 240.  I don't know if you can re-wire things, as it's likely the way the windings are glued in, and not an operator adjustment.   But if someone knows, speak up, I can't help.  You could get around it with a 240-120 autotransformer, but that's another expense and big hunk of iron.

KellyR

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Re: 120v rewiring to achieve full wattage
« Reply #10 on: May 10, 2009, 03:23:06 AM »
The generator came with two 120v outlets, which I took out and now have 120/240 running to a 30amp outlet which is then strung to the hardwire outlet to the inverter.  It would be nice to get 20 amps out of the generator, but that's probably not going to happen.  So, I'm trying to find out if anyone knows how to wire to get the full wattage out of the generator.

By the way, it's a homebuilt genset using the Mecc Alta S15W 3000w direct coupled to a Yanmar type 10hp diesel using jaw couplers.  It works a treat running as it is, but I'd really like to have the extra wattage.  As I said, that would charge the batteries quicker and save fuel.  There's still some work to do on it besides the full power issue though.  I'd like to automate it so that when the battery voltage drops below a certain level, the genny kicks in.  That's easy to program on the Outback, but I just need to find some time to get all the various bits of wiring hooked up between the inverter, the genny and the autostart module I got.  I also need to fiddle with the solenoid for the fuel and tie that into the system.  One of these days.

lowspeedlife

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Re: 120v rewiring to achieve full wattage
« Reply #11 on: May 10, 2009, 04:21:37 AM »
Hi Kelly,
 somewhere on the utterpower site George talks about figuring out the wiring if it is not marked, I saw it this morning & read it, he talks about using a light bulb acros the black & white wires coming out of the gen head to determine which pair (one black & one white) go to each coil inside the head. he talks about connecting the bulb to 1 black & 1 white & "spinning the gen head" to see if the light lights up, by doing this he said you could find the ends of each coil & reconnect for 120 volts. I just spent 45 minutes searching his site & have not been able to locate the info. it's late here on the east coast & I have been to both a wedding & a birthday party today (maybe that's why I can't find it.) I will look again tommorrow morning for you if you are unable to fiind it, but basically you can use a ohm meter & check across the blacks & whites, (separate them first) to locate the ends of each coil, then you should be able to connect them black from the first coil to the white from the 2nd & black from the 2nd coil to the white from the first, now you have two black/white pairs & these will give you 120 volts/full power. as i said I will look again in the morning & post a link for you when i find it.

 Scott R.
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omega 20/2 listeroid

KellyR

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Re: 120v rewiring to achieve full wattage
« Reply #12 on: May 10, 2009, 04:25:19 AM »
I think I remember seeing that page at some point myself.  I'll take another look.  Thanks for the info!