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Keep in mind, there are a good many manufacturers in China that make ST heads. There is always a possibility that your head has different lead designations! One must also note that the  manufacturer often includes wiring information with lead designations your generator might not have! A good example of this is the 50hz wiring configurations on some generator plates. The leads are often NOT there, because the manufacturer assumes you'll have little use for 50HZ in North America, and has deleted same.  

First, if you have ever lost equipment to mice, you will NEVER forget how much damage their urine, chewing, and bedding can cause over time. I have a tractor ring gear with the teeth corroded away because someone didn't put the cover back on the bottom of the bell housing access hole for greasing the throw out bearing. Mice moved in; damage was extensive, the throw out bearing, clutch, and pressure plate all look pretty sad.

You need to add a screen to the bottom of the fan housing, it will be obvious that mice can enter here. Simply remove one of the side covers for access. I'd use a piece of wire mesh with squares tight enough to keep a mouse out. You can drill some small holes and firmly attach it with flat washers and small machine screws. A five minute job that could save your head!

Many of us that are interested in a generator of this type will be installing it in a shed or some place where we can do some 'noise abatement' for the power source. My approach is to place the generator shed just over the hill where it can't be heard.

Wiring the head for your needs:

Some potential DIYers ask... "How many outlets are built into this generator, and what types are they? If you are asking yourself this question, you may be better off with a consumer type head. These units are heavy, less portable and are not equipped with plug ins. Most DIYers that are attracted to this type of head will buy a $14 circuit box at Home Depot and put two five dollar breakers in it. They will mount a box on the generator frame where they want the plugs and wire from the generator head, to the breakers, to the plugs..." if they want them there". Again, if you are inclined to ask this question, you might be better off with something else.

Many of these heads will be set up stationary, where the generator powers a summer cabin off grid, or the output of the generator passes through  breakers and then onto a transfer switch or "Interlock" assuring that the operator will perform the transfer of power safely.   

Always check the local code for wiring requirements, they may be different. Always include grounding in your wiring scheme. The case of the gen head should be tied to a good ground. If you don't have one, drive a ground rod. It's a good idea to tie this ground to the engine and all the metal within reach of the gen set. If you wire to a service panel, make a connection between the generator head and the panel ground as well.   

Not everyone understands that there are pros and cons to wiring your head for both 115 and 230 volts, the fact is, you can only direct 1/2 of the rated power output to any single 115 volt load when it is set up this way. If you really think about it, this is exactly the same as the power panel in your home, 115volt loads are split,  the electrician made the effort to BALANCE the loads between the two legs coming into your house. Whatever power you can deliver to a 230 volt load, only half of that can be used for any SINGLE 115volt load. 

Wire the head for 115 volts only; UNLESS you have 230 volt loads to support. You can change it later if you find you have the need.


yanwire2.jpg (28008 bytes)

The picture above shows the basic ST setup, verify that your head is not different before you wire anything! the light bulb doesn't do much, people wonder why they bothered with the switch, it can be useful for trouble shooting, and it is what it is. also note that the filament in the light bulb will last longer if you turn if off...

For 230 volt operation, strap U3 and U4 together, take the 230 volt load off U1 and U2, use another wire coming off U3/U4 for the return path some times call the 'neutral' lead.

For 120 volt only operation, Strap U1 and U4. Strap U3 and U2.   Take the load from U1 and U2.

Following are two different presentations of the wiring:

yan115v.jpg (41419 bytes)

Added Note: 6/30/05

People often ASK, when I wire my head for 120 volts only, which terminal is hot, and which is neutral? Well, it really doesn't matter, Pick on to be neutral, and make that lead white, and make the hot black, these are somewhat standard colors. BTW, at this date, it's been a long time since I've seen a K winding like that shown above, you may never see one.


yan230v.jpg (45878 bytes)

Some folks like the above drawing because it more readily explains why only 1/2 of the rated output can be directed to any single 115V load. If you follow the path back into the generator, you see that only one coil is providing the current. The other winding is not able to help out because it is assigned the task of making juice for the other leg, or other phase. Note that B is neutral.


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The above picture shows the ST head wired for 230V/115V to a common service panel. the Neutral and ground bus are often bridged. Make sure you sink a ground rod and attach it to a ground lug on the panel. If you have access to a well casing, or metal water pipe, consider making it part of your ground plane as well. Note the ground lead in the above drawing, this is picked up from the case of the gen head, make sure you get a good solid electrical connection. The power panel is typically fitted with circuit breakers to fit your individual needs. Readers sometimes write and say I need to put a diagram on my pages that shows how to wire to a panel. Here it is, and I changed the color to red so it's easier to find.

Now, take another look at the drawing above! You don't see the Neutral and ground bonded together at the generator do you? There's a reason for this, and unless your generator is the only source of power you have, don't bond the two together at the generator! More about this on the CD.

6/2002 Addendum

I have received several emails asking if one could use the case of the generator as neutral. My answer is NO. If you follow the diagram above you will see that the neutral is wired to the center tap of the windings designated as U4/U3 in this particular head.

If you study the wiring in your house, you'd find that most of them use white for neutral and black for the the so called 'hot' side. If you study a house style electrical outlet, you will see that the white wire should always fit in one side, the hot in the other.

Also note that the home electrical panel is often set up with the neutral and ground connections 'bridged' or tied together. This could cause you to believe that it is OK to use generator case ground for neutral. Ground connections are for carrying fault current, you should never use these connections to carry current for a normal load. Think of them in this way..... 'if they're busy carrying normal loads, they may not have the capacity to protect you when trouble strikes'.

A verbose rant on making connections to your gen head.

As stated in other places on this WEB SITE, we are all about cost effective solutions for DIYers. Sometimes cost effectiveness includes doing it right the first time, or removing the potential problems before they cause you trouble.  During my life, I've witnessed thousands of hours spent on finding troubles with poor electrical connections, in one case, I saw a poorly crimped connection cause intermittent trouble in analog periphery of a computer. This one bad connection cost the company a fortune in trouble shooting to find; not to mention the down time of the equipment.  There are lug terminals that can be installed with an expensive die that makes excellent connections, to place a lug on the end of a wire and crimp it on with pliers or a set of side cutters is asking for trouble. If you are building a generator that could be used for emergency back up, why would you make inferior connections? If you know Murphy, he'll assure the inferior connection fails when you need the genset the most.

The construction of the ST heads looks pretty good in most areas. But like most equipment, I can always find something to complain about. In the case of the ST heads, I think their terminal lugs and the method they used to attach them sucks. The lugs themselves are copper, they are far too soft to maintain a good connection with the wire. The fix is simple? you either replace the Lugs and properly crimp them on, or you solder what is there. It's a quick job, and all the leads I've looked at are plenty long enough to cut off the existing lugs if you wish. Another thing I'd consider, "why not by pass those handy external terminals"? Do it the old tried and true way, make your connections directly to the leads, and take them out of the doghouse via conduit or a proper portable cord through a standard grommet. If these things sound a little too much to deal with, get a friend with electrical knowledge to help you.

You'll note that crimp on connectors are used in all sorts of things, some were put on with the proper tools, some weren't. I know a few folks who have junked their old motor homes simply because they couldn't clear the electrical problems fast enough. Poor grounds, and those poorly crimped lugs can create a nightmare. Many of these motor homes and trailers use the skin as ground. Sometimes you find steel screws, used to attach a wire lug to the alloy skin, dissimilar metal unions assure jobs for countless automotive electricians, I never thought about it, but this whole thing could be part of a left wing secret jobs program :-)

Another example... There's  a company who builds small trailers including small tandems with electric brakes.  A friend bought one of these and several years later, the electric brakes seemed to work on one side only... not the best of things to happen when you're towing something heavy.  When I crawled under the trailer to trace the wiring, I found wire nuts like those used in house wiring. One connection was full of mud, it was wet and green and wide open.  In my opinion, this is a connection that's guaranteed to fail sooner or later in the open environment. For all we know, an assembler thought he had a better and quicker idea, and decided to use this connector on his own, but the fact is, he was creating a condition that could put people and equipment at risk.

To 'sum up' this whole subject,  run proper ground leads, and when in doubt, solder all connections with electrical solder, plumbing solder is different, and will guarantee a problem. Pay attention to these things and you'll eliminate three quarters of electrical problems.

Important:   make sure the generator head gets fresh air . Don't cut off cool air to the head in your attempt to make the power plant quiet!

Look over the Chinese Horizontal/ST setup and note how the alignment is done, consider doing something similar if you are going to belt drive the head.

What about driving the gen head with a coupler versus a belt?

if you have an engine that will be turning 3600 RPM and a head that needs to turn 1800 RPM, you have little choice. But what about the Engine that is rated at 2000 RPM, if you run the head with a belt, you can get a ratio where the head is at 1800 and the engine is at 2000, but there are more losses using a belt versus a coupler. What if you lower the speed of the engine to 1800 RPM,s and couple drive the head? which one would carry more load? I'd bet the direct drive would be nearly the same with less maintenance.

Look under ARTICLES for more information on direct drive couplings. If you have an engine with a very heavy flywheel, a direct drive coupling can be more cost effective and less trouble than a belt system. The more mass you add to the Gen Head side, and the more you decrease the flywheel mass, the more capable the coupler has to be; (read expensive). At this time, I think the L series Love Joys will do the job and reduce the coupler costs on small gen sets. When you go above the 1115, you need to look at more expensive couplings. I swap email with folks who are exploring cost effective solutions for VW diesels, and other small 3 and 4 cylinder engines. If you choose to go belts, you must understand that many of these engines were NOT designed to take a side thrust, so a belt drive system may not hold up without modification. these are things that can easily be overcome, understanding the requirement is key.

I offer aircraft engines versus automotive engines as a thought provoking example. The aircraft engine is designed to handle high side thrusts at the prop end. If you were to machine an adapter for that prop and attach it to an automotive engine, you could be in for some real trouble. There are plenty of examples of automotive engines that are modified for aircraft use, this can be a primer for your understanding.

Whether you decide to drive your gen head with belts, or a direct drive system, there are things to consider, as with most things in life, there are trade offs. No matter what we learn, there's always more to learn, these pages will continue to grow and change.  

Following is recommended wiring for heads that run for long periods of time, swap polarity and re flash the field..

There is more on this on the CD, but this might extend brush and slip ring life in generators that run for hours each day.



George B.