Finally getting around the tearing down the generator. All the testing says the windings are shot. Powertech has no parts any longer. Marathon is trying to match this one, however mine is an Isuzu, mat not be the same flywheel pattern as a Kubota. We'll see.
What about getting the part that is haywire rewound.
that may be possible, however some parts are not rebuildable. A new complete replacement placement head from marathon Is 3K. When talking rewinding, starts at around 1400.00 and goes up
From there, then add freight. Got to
Keep in mind this machine is 25 years old. So you get the one part repaired, how long before the next part craps out.
Bruce, have you checked used prices at some of these salvage yards? Of course, it will depend on where they are located, but there are many Foretravels out there sitting in these yards! I know there are not many left still in business, but we had an electric shop in Lebanon, TN that rebuilt just about anything out there. These specialty companies are about gone from the landscape now, but that is another choice if cost is in line with repairs!
I have replaced three generator heads using new ones from Central Georgia Generator. Generator Accessories – Gas Generators | Central Georgia Generators (https://centralgagenerator.com/)
Tom down there is excellent and they are fair and knowledgeable. I have no connections to them other than buying their products.
TOM
I have looked at them their 11K single bearing is 16" long, won't fit in the space. They are very nice folks.
How many hours did that head last Bruce?
2100 hours. Old age got it. Thats how my
Luck works. Same with the engine processor this summer.
Age and wear is something I understand.
Yup, my voltage has dropped as well.
That's a shame. The coach I now have has the pancake style head as well. I'm hoping CGG will have them by the time I need one.
TOM
Bruce, looking at your teardown pix, do you think that amount of corrosion is normal for that age genny? Looks like it might have gotten salted in a previous life??? I've talked to folks with 20,000 hours plus on theirs.
Woody, not since I've owned it(2006), never even been on salty roads. I imagine there are a bunch of these generators operating on boats.
Which windings Bruce?
Stator?
Rotor?
Exciter?
Do they read open or shorted?
Asking because they don't look that bad to me, I've seen a lot worse. I'm not buying the age thing..... unless the voltage regulator went south and caused an overvoltage/overcurrent issue. That would be a valid reason.
Anyway, hoping you can find a cost effective repair. Wishing you luck on this one. ^.^d
Justin all diagnoses leads to a defective exciter rotor/rectifier assembly. Voltage not in the specified range while doing the 12V constant excitation test. At any rate it's a moot point as no parts are available for the unit, per powertech. With that said IF you could find some one to rewind/ repair that piece(s), it is likely going to be half the cost of a whole new head. Additionally to test the unit further one needs a meger, and other equipment. Obviously this will cost additional $$ and time. As you can see I'm fast approaching the cost of a whole part. It has been checked by a Powertech shop, and I have been through the troubleshooting with Jeff at PT.
Bruce,
Look at the two photos, enlarge them, one is yours the other is a pic of mine when I replaced the main bearing.
There is a resistor or diode connected between the "Q" and "R" connections for the rotor leads, I don't remember which and can't find my schematic on the powertech. I see the two yellow crimp on rings on yours but nothing between them. Maybe its there and I just don,t see it (eyes aint what they use to be)
Bruce,did they use a megger to check the windings,if so what was the reading,the windings could possibly need only to be revarnished,we used to use a device that put voltage to the windings to dry them out,if the head will fit in an oven try heating it up for a few hours,won't hurt.Agree about something else may break but you'll have a good engine and head the rest are lower dollar parts.
Justin the resistor is there.
A meger has not been used to check the windings. I haven't given up on the head yet. Trying to find a shop that is close enough that has the ability to continue to check and repair is a challenge. As I said being in Yuma kind of puts you at a disadvantage, not a lot of options. What I have found so far, the cost of reworking the old one is nearly the cost of a new one. Just shipping a 150lb part is costly these days. Already been having troubles with this thing for a year and a half, intermittently producing power, and dropping power out under a full load.
If the exciter rotor is the problem, it's not very heavy and should be much cheaper for a generator repair shop to fix, just windings and diodes. Unfortunately PowerTech said the exciter rotor or exciter stator are no longer available. I forget which.....
You commented "testing says windings are shot"
Did they say which windings?
Justin, I'm doing the testing. The 12v constant excitation voltage indicates a problem with the exciter rotor. No Continuity between T1 andT3 indicates an open in the main stator.
Assuming that yours is connected for 120v and not 120/240, what is the ohm value between T1 and T2? also between T3 and T4?
Reading from T1 to T3 assumes a good connection between T2 and T4..........
Justin .2 ohms on both.
That sounds about right, if there was no continuity between T1 and T3 its sounds like a bad connection between T2 & T4 in the control box. They should be connected together and to the Neutral and ground on a stud in the control box.
Sorry to keep bugging you on this Bruce but I would hate for you to spend a whole bunch of coach bucks on a new generator head if there is no obvious problem with yours.
Keep checking and asking questions.
By the way, what voltage regulator do you have? Model number and photo available?
Those reading are with the main stator on the bench. Basler AVR 63 4v regulator, and it is new. The original issue is very low excite/residual voltage in the line side when running 1V + or-. And low output on the line side 71.5 volts during the 12 volt constant excite test. After talking with Jeff at powertech, that indicates a bad excite rotor.
Finally got the new generator head. It's not a "plug and play" replacement. Having to have a new adaption plate made at the machine shop, as well as drilling and taping some mounting hole to match the old one. This new generator head is a duel voltage 120/240, the old one was 120 only. What's the down side of running this one at 240v line to line, basically the same as the 50 pole you plug into.
Bruce, I don't remember the thread about using 240v but seem to remember that there was a load balancing problem if you used the wires that are on the generator. Maybe you can find it. I personally wired mine to the 120v even though it was 120/240v to keep it the way it was.
Why some generators are wired to produce 240 volts and some are not. (https://www.foreforums.com/index.php?topic=40007.msg395600#msg395600)
ac power question (https://www.foreforums.com/index.php?topic=28989.msg244018#msg244018)
New adaption plates fresh from the machine shop. Generator shipped with 6.5 adaption the flywheel is 7.5. Next up drill and tap main stator case for powertech control box mounting.
We have noted that 50amp 240volt normally will not overload neutral, but not explained why this works.
Picture alternating current having two separate 120 volt 60-cycle/second sine waves. When one wave is peaked above zero volts, the other sine wave is peaked below zero volts. Both waves share a common neutral and if both waves are maximum peaked, neutral will be at zero volts.
You can also manufacture 240VAC from 110VAC using a center tapped transformer, I've done it using two 110VAC lines on different breakers but the same phase, necessity being the mother of invention. And if you're lucky enough to have an alternator that will output 240VAC two phase and your coach isn't already so wired, your transfer switch needs to be double poled and with each phase feeding separate legs in the power distribution box aka the breaker box. Maximum load on the alternator occurs when everything is running, so if wired correctly the load is balanced at maximum alternator output.
ONLY for the very electrically savvy!
Not for 99.9% of coach owners-- do not try this at home, you could let the smoke out!
Brett, I expect people to know their own limits and to hire outside help as necessary. IF someone has a 240VAC 2-phase alternator, I think it's a good idea to have the load split up at the breaker box. I don't see a problem with load balancing if all of the individual loads are split evenly between both legs, with the best case being the use of 240VAC high power appliances.
FWIW, I also think the original poster should realize that re-winding his alternator, by an independent shop or at home really isn't that big a deal. And he should also remember that machinery doesn't care how old it is, but how well it's been maintained. In this case, new bearings, new windings and new exciter brushes equals a new alternator.
I think the potential problem with RV 240-volt generators is most RVers have no idea which outlets and loads are on each leg and do not normally measure AC amps separately for each leg.
RVs are probably not normally OEM wired with balancing outlets in mind, often with most outlets on the same leg along with one roof air. The other leg may mainly carry the other roof air. If not running both roof airs, the gen could find all loads on one leg and zero legs on the other leg. Not sure how this unbalanced situation stresses a 240v gen.
Feels like RVs can't win as either the neutral wires & contactor points could get overheated, or the gen wiring could be stressed. While all electricity is dangerous, 240 volts are more likely to kill than 120 volts.
Do I understand that a 240-volt generator can be 'converted' to 120 volts by jumping the two legs together at the gen's pair of breakers within the gen control box ?
I think the change to 240 from 120 or the other way was done with a wire change in the generator control box. On the regulator? Mine came to me that way I think since new.
I had a 240 v clothes dryer in my coach.
Used it anytime we needed it either in a park on 50 amp service or on the road with the generator running.
Never had a problem. We wouldn't have given that up.
Maybe just lucky but it worked.
Properly wired RVers need not worry about the load balance. I'm plugged into 50A 240VAC and if I needed 240VAC I'd just need to find one outlet on each leg of the incoming.
You can't "convert" an alternator. The alternator needs to be built for 240VAC-2PH. If you're lucky enough that the two breakers add up to 240VAC good for you. But I wouldn't bet on it being true.
Yup, pretty easy. Just need a duplex breaker and verify that the wiring to the new 240 VAC appliance is properly sized.
Got the rotor, main stator , and end bearing support done. Exciter rotor and stator tomorrow. The install instructions say use the 9/16 bolt and washer to pull the roto back on. Problem is the bolt is 8mm not 3/8 and it's not long enough. Hummm. As the debate rages on, I'm leaning towards 240 connection as that is the way the generator was shipped. In our world the Ac is the largest load that will on the generator for any length of time and both units will be running
My head was shipped as 240 volt also but Jeff recommended putting it the way it came from Foretravel. Be careful that something 120v doesn't see 240v or the smoke will escape.
Chuck do you remember how you put the exciter rotor back on ? Hammer and brass drift?
Bruce,
Unless you are planning on installing a 240v dryer in your coach one day, I see no advantage in connecting the leads for 240 volts. I have thought several times about switching mine to the 240v output for the sole reason of having a 240v backup to the house in the event of power failure during hurricane season. (needed for deep well pump, hot water heater, central AC unit, etc.) I have a 25kva 3 phase PTO driven generator that is trailer mounted for use behind a tractor, so I really don't need the Coach generator for that purpose.
There are advantages of the 120v only output, such as better (more stable) voltage control, no danger of loosing a neutral connection between the loads and the source thus causing an unbalanced voltage that is high enough to "smoke" your 120v devices and appliances, or low enough voltage to burn up an AC compressor. The downside? Yes the neutral conductor "could" be overloaded if connected to a 50 amp 120v only shore power, or even the 45 amp output of the generator. I'm not sure just how big of an issue this really is or how often it actually occurs.
Someone mentioned connecting for a 240v 2 phase power, never seen that here in the states, not saying it doesn't exist but in all my years of electrical work, I haven't came across it. Either 3 phase (what our electrical grid is here in the states) or its one leg of that for single phase power. A 240v center tapped transformer (or generator) produces 240v phase to phase (180 degrees out of phase) and 120v to the grounded center tap.
Good luck with whichever way you go, not really a wrong way to do it.......... ^.^d
I believe I used a short piece of pipe with an id larger than the shaft. It was not that tight.
Chuck, you wouldn't have the wiring diagram Jeff told you to use?
I will look in the coach tomorrow, I probably saved it.
Reply #2 use the 120v schematic, the first pdf.
How not to change voltage regulator in genset (https://www.foreforums.com/index.php?topic=32784.msg294847#msg294847)
No need to worry about inadvertent connections. A 240VAC alternator outputs two 120VAC lines than when combined equal 240VAC. Just use the correct outlet and you'll be fine and major loads such as the 120V air conditioners can be split using one line or the other.
There's alot more detail when you have a 3-phase connection such as Delta and Wye configurations, something I don't pretend to understand. I just accept the reality.
FWIW, When I brought Lynn in to work with me at the Tier II auto manufacturer, Lynn kept noticing a different motor on my bench each week and asked why? Well, they were waiting to go out to Wright's electric for re-winding and that's the way it had been done for years. Lynn looked into it and found that the European motors were 240V and were being run on a 208V "lighting circuit" because the owner's never specified the voltage to be supplied when they built the building, so Public Service of New Hampshire supplied a "lighting circuit." Lynn asked Wright's to wind the motors for 208V from then on.
Bruce
I have attached a hand drawn diagram of how your old "beige box" regulator should have been connected if it was connected for 120v output. Also here is the drawing PT sent me to connect the new Basler regulator for 120v
A follow-on to Justin's "Yes the neutral conductor "could" be overloaded. . ." :
RVs have limited capacities for everything and are fully enjoyed by keeping track of limitations.
We mounted our Progressive Industries EMS remote meter in kitchen area. It alternately displayed Leg-1 & Leg-2 amps. Always looked at meter when turning on any high-amp device (toaster, microwave), turning things off, if necessary, before turning things on. We both found a quick look at the meter was part of safe RVing.
Just because a coach has a 10 or 12kw generator, if not 240 volts, does not mean that running everything at the same time is safe. Way too many transfer switches have damaged neutral points & cable. This is a hidden problem and not "taught" when buying a motorhome.
Even with both roof airs running, microwave can be run, just not toaster, curling iron, etc. Knowing limitations is part of owning an RV.
Ok so here are the 2 possible connections 120 or 240 see attached. T2 is obviously the neutral it doesn't change with both connections. Now in the 240 connection T1 and 4 are hot legs, T3 is grounded. In the 120 only connection T4 is now grounded (it was hot in 240) T1and3 are tied together. How is it possible to simply ground a previously hot lead that's a dead short!!!! Unfortunately Marathon is not much help. The generator is a duel voltage and came wired as the 240 connection shows, with a voltage regulator, and the connection block but has to be installed in the original powertech box on top or the generator.
I do have an understanding of single phase and 3 phase electric just not generators. What am I missing here, don't want to let th smoke out
Bruce
That diagram is correct, T1 and T2 are opposite leads of the same winding, T3 and T4 are opposite leads of the other winding. In the 120v connection the windings are in parallel and in the 240v connection the windings are in series.
If you connect T2 & T3 & ground(N), you will have 240v between T1(L1) & T4(L2) = 240 volt
If you connect T2 & T4 & ground(N), you have to connect T1 & T3 together (reason for the factory jumper) to Line 1 = 120 volt
The schematic from PT is correct also that I posted in a earlier reply.
I wish you were closer to N.E. Fla, I would help you with this, PM me or call if you wish. You could give Jeff at PT a call, he could advise you also.
Edit: It is VERY important how the voltage regulator is connected, are you using the same Basler regulator or did you receive a new one with the power head?
Justin, I'm using a new one that came with the power head . It he connections look straight forward. I sent you a pm.
The original PT 10KW has two leads marked E1 and E4, does your new generator have these leads?
No, T1-T4 ftm main winding, regulator connections field +and-, R3and R4. As shown previously a dip sw on he regulator for 120 or 240.
Bruce, this is to satisfy my own curiosity:
When wired for 240VAC what would be the voltage from Line 1 OR Line 2 to Line 0?
I don't understand your question. If you are talking about line 0 being ground it would be 120 on each side. If you are saying accross each other 240
Bruce, that's exactly what I was asking. So the Power Tech generator coaches can be wired just like any American house.
Cool!
Thanks for the information!
when you are plugged into a properly installed 50amp rv plug you are plugged int 240 just like your house. CAUTION NOT ALL POWERTECH GENERATORS CAN BE WIRED 240. Don't attempt ANY modifications to a powertech generator without contacting JEFF JONES at powertech first.
I'm replacing my powertech generator head with a Marathon head. It is the same basic dimensions, it is wired differently it has 8 leads 4 for the regulator, 4 for the voltage connections. He old powertech head has 10 leads all different connections.
Here of the official explanation of how a generator works
Think of T1-T2 an T3-T4 coils as 12V batteries. T1 & T3 are "+" and T2 & T4 are "-".
You can series them for 24V by tying 2-3 and get 12V only by 1-3, 2-4.
If you tie 2-3 for 24V circuit, you can still get 12V from each battery. 1-2 = 12V, 3-4 = 12V and 1-4 = 24V. Look at the +/- locations though.
The ground point is the midpoint for the 120/240 option and the "-" lead as an arbitrary convention for 120V only.
All of that being said, L1 and L2 are 180º out of phase to each other giving 240 when combined and no current on L0. To the best of my knowledge when one load is from L1 and another from L2 those two loads also cancel out any return current on L0. It's only when you run all loads on L1 and L2 that there is return current on L0.
Generator runs, wired 120. All is good glad that job is done. Little over 3 coach bucks.
Sort of..... the neutral carries the unbalanced load (difference) between L1 & L2 on a single phase 120/240 circuit.
Not practical and nearly impossible to balance all of your 120v loads to have zero current on the neutral.
Yeah, that. I went back and fixed the conjunction leaving the assumption to be made that "all loads" equal the same total power on each side of L0.
My point was that in use, wired as a standard US house THAT DESIGN PowerTech alternator only delivers 240VAC when the load is wired in properly and provides two legs of 120 VAC in normal operation and less that total return current in operation thanks to the magic of phase shift technology.
Bruce, thanks for getting this sorted out for everyone that will eventually also follow your path.
Scott
So generator all sorted out, and slid back in. What would be the down side of leaving the bottom out of the generator compartment, it would certainly make things run cooler
Louder?
Road shark hitting something expensive.
Lots of road debris splashing up and all around the generator. Rocks, mud, water, gravel.
Ok then the bottom goes back in.👍
I've got a 1999 U270 with the Powertech Isuzu 8kw generator. The head recently failed, and I was able to get a new head and regulator from Powertech July 31st 2024. So they do still have parts. Also, of important note is that this head was also replaced in 2016 with only 25,000 miles since on the Motorhome, and all within 1200 hrs run time. Another issue was that the head was damaged in shipping as can be seen in the photos. When I called Powertech about the damage, they simply told me that it was my hard luck and refused to do anything about it. I resolved this issue by disputing the charge on my credit card. I still have the broken head which Powertech as of yet has not asked for it's return though they may.
That thing looks like it was dropped. If the rest of the head is OK could the flange be removed at
a machine shop and your old one be welded back on.
rod,
Did you file an insurance claim with the shipper? If not do so ASAP.
Mike