Generator head replacement

Topic: Generator head replacement (Read 3399 times) previous topic - next topic

Re: Generator head replacement

Reply #25 – March 06, 2023, 12:25:30 pm

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.

Re: Generator head replacement

Reply #26 – March 06, 2023, 12:34:24 pm

Quote from: craneman – March 06, 2023, 12:25:30 pm

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.

Why some generators are wired to produce 240 volts and some are not.

ac power question

Re: Generator head replacement

Reply #27 – March 06, 2023, 06:00:59 pm

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.

Re: Generator head replacement

Reply #28 – March 06, 2023, 08:40:23 pm

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.

Re: Generator head replacement

Reply #29 – March 07, 2023, 08:46:23 am

Quote from: Barry & Cindy – March 06, 2023, 08:40:23 pm

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.

Re: Generator head replacement

Reply #30 – March 07, 2023, 09:02:07 am

Quote from: Old Toolmaker – March 07, 2023, 08:46:23 am

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!

Re: Generator head replacement

Reply #31 – March 07, 2023, 11:52:04 am

Quote from: wolfe10 – March 07, 2023, 09:02:07 am

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.

Re: Generator head replacement

Reply #32 – March 07, 2023, 03:12:42 pm

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 ?

Re: Generator head replacement

Reply #33 – March 07, 2023, 04:13:53 pm

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.

Re: Generator head replacement

Reply #34 – March 07, 2023, 05:41:50 pm

Quote from: Barry & Cindy – March 07, 2023, 04:13:53 pm

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.

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 ?

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.

Re: Generator head replacement

Reply #35 – March 07, 2023, 05:44:21 pm

Quote from: Old Toolmaker – March 07, 2023, 05:41:50 pm

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.

Yup, pretty easy. Just need a duplex breaker and verify that the wiring to the new 240 VAC appliance is properly sized.

Re: Generator head replacement

Reply #36 – March 07, 2023, 07:15:37 pm

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

Re: Generator head replacement

Reply #37 – March 07, 2023, 07:41:45 pm

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.

Re: Generator head replacement

Reply #38 – March 07, 2023, 08:18:01 pm

Chuck do you remember how you put the exciter rotor back on ? Hammer and brass drift?

Re: Generator head replacement

Reply #39 – March 07, 2023, 08:22:45 pm

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..........

Re: Generator head replacement

Reply #40 – March 07, 2023, 08:31:18 pm

Quote from: bbeane – March 07, 2023, 08:18:01 pm

Chuck do you remember how you put the exciter rotor back on ? Hammer and brass drift?

I believe I used a short piece of pipe with an id larger than the shaft. It was not that tight.

Re: Generator head replacement

Reply #41 – March 07, 2023, 11:04:34 pm

Chuck, you wouldn't have the wiring diagram Jeff told you to use?

Re: Generator head replacement

Reply #42 – March 08, 2023, 12:26:33 am

I will look in the coach tomorrow, I probably saved it.

Re: Generator head replacement

Reply #43 – March 08, 2023, 12:27:10 am

Quote from: craneman – March 08, 2023, 12:26:33 am

I will look in the coach tomorrow, I probably saved it.

thanks Chuck 👍

Re: Generator head replacement

Reply #44 – March 08, 2023, 12:43:19 am

Reply #2 use the 120v schematic, the first pdf.

How not to change voltage regulator in genset

Re: Generator head replacement

Reply #45 – March 08, 2023, 07:09:27 am

Quote from: craneman – March 07, 2023, 07:41:45 pm

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.

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.

Re: Generator head replacement

Reply #46 – March 08, 2023, 09:09:11 am

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

Re: Generator head replacement

Reply #47 – March 08, 2023, 10:58:28 am

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.

Re: Generator head replacement

Reply #48 – March 11, 2023, 12:34:14 am

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

Re: Generator head replacement

Reply #49 – March 11, 2023, 07:38:41 am

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?

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