Harbor Freight Generator head 10kw

[Jim_in_Omaha]

Bill,
I went back to a previous posting about your HF generator. You mentioned you ran the A/C and the electric water heater? Any idea of the continuous load you may have had for long durations?

thanks
Jim

 

[Highbeam]

I have seen water heater elements in the 4500 watt range.

Central home A/C units are huge. It would be impressive if you could run both at the same time.

 

[XmasTreeGrower]

Jim

I had the water heater, two refrigerators, a freezer, furnace fan, and the usual rest of the house running.

I think I calculated around 8500 watts with everything going. No A/C though, you need something in the 15K range just to get them started. If you really want A/C, you are probably looking at something in the 20K to 25K range. When you get to this range you are talking full dedicated standby units. Very pricey setups in most cases.

If you are running a well pump, these can be real killers on power demand, as much as 6K alone.

Thanks
Bill

 

[1962]

bill,
that is a nice piece of mind with your set-up. saves on buying a engine to power it too. did you use much fuel on that 96 hour outage?

 

[Jim_in_Omaha]

Bill,
I kind of figured that about the real kick it takes to run A/C. Running an electric water heater is a pretty good demand for power too. Fridges have a high startup wattage.

I picked up a HF head today. I was talking to the manager and he sold me it for $250 and threw in their 2 year replacement warranty. I thought that seems like a pretty fair of a price. Regular price is $299. Now I have to start designing the layout. Direct couple or belt drive. If I belt drive I can slow down the engine some with ratio's.

thx
Jim

 

[Bugsy]

Jim,
For your use there is nothing wrong with a 2-pole alternator. The 2-pole (3600 rpm) unit is there for a reason, and for the most part meets its intended purpose.

Most 2-pole heads are geared for the mating to a gasoline engine, which usually produce their max Hp at 3600 rpm. Can they work on a diesel, of course they can. Would we try and run a diesel at a consistent 3600 - of course not.

For everybody to know, the majority of alternators are produced in China. This can be in component form or complete assembly. Regardless of where you purchased the unit (alternator), it will have some kind of Asian origin.

Back to the 2-pole. The 2 main disadvantages are 1) Noise and 2) Lightweight aluminum

The noise factor comes in the form of having to run an engine at 3600 and the lightweight aluminum can and will take away from the longevity. Of course your unit is not intended to be a "prime" unit - so you should get by fine.

Below are the main reasons people are buying the 4-pole alternators.
1. Many take comfort in the heft, and they are VERY heavy.
2. The ST utilizes brushes, making most maintenance a breeze. It has to be. When you get into a 4-pole cast head, the average person cannot just toss it in the truck.
3. Many people want their genset to be diesel, for many reasons, and the 4-pole fits the bill better.
4. Cost is another factor. Dollar for dollar, a person will get more Kw for the buck via this old and proven technology. (2-pole heads are just not easily available in the higher Kw ranges)
5. After the storms last year, throughout the country, many people who were reluctant to even own a generator now want to own one, but, they only want to make the purchase once.
6. The ST heads are meant to be repairable. This gives many comfort. Especially those that believe in maintaining and repairing what they have vs. purchasing new.

We could list another 30 reasons why, but you have been reading up, so you get the point.

As for the drawbacks to an ST alternator, there is one. It is the fact that they are HUGE. Extremely heavy. Our ST-30 comes close to 700 pounds! Very heavy castings with lots and lots of copper. The ST-12 is not a whole bunch smaller in size or weight.

By now, with all of your research, you should be feeling comfortable with your configuration. When you have completed your backup power plant, you will be overwhelmed with satisfaction!

If we can assist you in any way, please feel free to PM or email. We help many with their self-made configurations and we even encourage it.

 

[crb478]

Even with water heater elements requiring 4500 watts you have to remember that they are resistance heating elements and will therefore take what ever left over current they can get and use it to heat. Your recovery time will not be quick but it will slowly heat the water with the available curent.

 

[XmasTreeGrower]

1962

Regarding the fuel usage, it averaged about 3/4 gallon per hour. Obviously not very thrifty, but good enough to get you through an emergency.

You can get by just running the genny for a couple of hours to get the refrigeration to pull down to proper temps, then shut it down completely for a few hours. If you do it this way, you have to stage bringing back up the major draws items, so they don't all try to start at once.

Jim, when you are planning your set up, the direct coupling will be more efficient, and less headaches in the long run, but I seem to recall those surplus army engines are redlined at less than 3600 rpms. If so, you may be forced to use a belt and pulley set up.

Great project for the summer. Good Luck!

Thanks
Bill

 

[Soundguy]

</font><font color="blue" class="small">( you have to remember that they are resistance heating elements and will therefore take what ever left over current they can get and use it to heat )</font>

I'd like to disagree slightly... at least with your wording.

kiechoffs law will apply here.. .. so will ohms law..

The max max available voltage.. coupled with the impediance of the heating element ( will change with temperature, if you were looking at it with a dc-ohms scale ) will ultimately determine the amperage dray.
For instance.. in round numbers...if the element is designed with an ultimate impediance of about 10.45 ohms.. then the current consumption will be about 22 amps, yeilding around 4800 watts, assum9ing a 220vac source. With the voltage being fixed.. and the elements resistance being fixed.. that doesn't allow for more current consumption, and there fore no wattage increase. now.. if the element has become marginal, or damaged, or is in some way failing so that it's load resistance drops lowert han it's rated impediance/ohmage.. then the voltage being fixed byt he utility, the current consumption will rise, and wattage disipated will rise.

Your statement would seem to indicate that the only limiting factor of the wattage of the heating elements was available power and current... this simply isn't so.. otherwise every hot wate rheater sold would simply take whatever the breaker could supply till there was a failure.

In the end.. the fixed votlage provided by the utility, and the designed impedance by the element manufacturer will determin the current consumption, and the power dissipation.

For what it's worth... I'd rather have resitive loads than inductive loads. inductive loads can use 2x, 3x, and 4x current when starting up.. resistive loads start high as well.. and then settle as temp coeficient takes over... usually much faster than an inductive load... take a light bulb for instance... extremely low off state resistance... more or less a short circuit. warms up pretty fast and settles to a much higher ohm value..

Soundguy

 

[SPIKER]

Soundguy hit it on the head, no pun intended. /forums/images/graemlins/wink.gif ) BUT the one thing he forgot is when you are generating you're OWN power it is limited by the power plant I.E. the engine & the gen head. if the power consumption gets too great (engine slows or gen head hits it's limit) then the voltage starts to lower, this is where OHMS LAW comes in as the voltage drops the current goes UP and that makes the power required iven greater... there for you hit that limit it is a pretty quick STALL or circuit breaker pops quick... it usually happens pretty fast and people don't understand what ACTUALLY happened... anyhow lots of photos please /forums/images/graemlins/smile.gif

It would be better to gear drive it off a gear box using a "LOVEJOY" connection to the gear head rather than a belt drive as I'm not sure how good the head bearings are and IF they could take the load of the belts. (the other option is to belt drive to a small stub shaft which has dual pillow block bearings and a lovejoy/spline connection to the gen head.)

anyhow one last thing, pictures pictures and more pictures /forums/images/graemlins/smile.gif

Mark M

 

[Soundguy]

</font><font color="blue" class="small">( BUT the one thing he forgot is when you are generating you're OWN power it is limited by the power plant I.E. )</font>

Good point. I was using a 'fixed' 220 vac provided by a 'utility' line.. more or less an 'unlimit3d' supply. As we all know.. when you overload a genny head, voltage output drops off... that rearanges the ohms law calcs.. .. usually right before the breaker pops! /forums/images/graemlins/grin.gif

Soundguy

 

[1962]

i considered using a gear box on my home made gen set. the only reason i didn't use it was i didn't feel like pressing the bearings out and replacing them with new ones. i don't remember the ratio, but it has two bull gears in a gear oil bath. maybe in a few years i will change it. as for the love joy lo-195 coupling, i had to upgrade to a hytel type spider insert. it seems like the heat generated from the engine and the gen head got the buna-n spider too hot and it started to fail, and quite possibly the torque load was too much for it.
the shaft alignment is right on, and after a 2 hour test today everything seems ok for now.

 

[Jim_in_Omaha]

I was thinking about your coupler and remembered reading about what the guy at utterpower.com had to say regarding couplers.
http://www.utterpower.com/coupler_.htm

I was wondering if maybe your diesel's high torque pulses were contributing to the destruction of the lovejoy insert after reading that.

Also on his site he talks alot about pulleys. For the bushed pulleys grainger.com has a good selection. Surpluscenter.com has great prices on standard pulleys.

thx
Jim

 

[Jim_in_Omaha]

Heres a response back from the tech support at Harbor Freight regarding this generator. Notice the revisions/errors which explain why the one at the store I saw had a continuous rating of over 9kw.

The one point that I'm wondering about here is they say its 50% efficiency via belt drive and 85% efficiency via gear box (perhaps direct coupling too?). Thats seems like a large difference. Any comments from the engineering experts here at TBN as to just what that means in real world terms would be appreciated.
thx
Jim

----------------------------------------------------
DIMENSIONS 19-3/8"L X 7-3/4"W X 8"H.
WEIGHT 85.6 LBS
THD 3-4%
COPPER WINDINGS
RATED @ 7200 WATTS CONTINUOUS
16 HP ENGINE IS RECOMMENDED. THE ENGINE SHOULD PRODUCE CLOSE TO 20
FT/LBS.
OR MORE AT 3600 RPM. NOTE THAT MOST ENGINES WILL PRODUCE PEAK TORQUE
AT A
LOWER RPM. CAN BE MOUNTED TO A FRAME OR SOLID PLATFORM WITH METAL
BRACKETS.
OR STEEL STRAPS.
TWIST LOCK RECEPTABLE IS RATED 30 AMPS.
13-1/4" X 6-1/4" ON CENTERS
120V: 20 AMPS
240V: 30 AMPS*** CAT/WEB ERROR ADVERTISED AS OK WITH PTO 11/02 ***
IS DESIGNED TO RUN CW (AS YOU FACE THE SHAFT), BUT IT WILL WORK IN
EITHER DIRECTION.
(1) 300-VOLT METER
(1) 150-VOLT METER
THE EFFICIENCY RATING OF THE GENERATOR HEAD: APPROX 50%, WHEN
BELT-DRIVEN WITH
A 20 HP ENGINE. THE EFFICIENCY INCREASES TO ABOUT 85% WHEN GEAR-DRIVEN.
CAPACITOR: 45 MICROFARADS, 450 VAC. THE SHELL IS 4-3/4" LONG X 1-3/4"
DIAMETER
MAX. AMBIENT TEMPERATURE IS 45 DEG C, (113 DEG F)


COMMENTS: CAT/WEB ERROR ADVERTISED AS 1725 RPM 06/02
CAT/WEB ERROR ADVERTISED AS 9500 WATTS CONTINUOUS 07/02
CAT/WEB ERROR ADVERTISED AS REQUIRING A 20 HP ENGINE 08/02

 

[Highbeam]

As far as the efficiency goes, a HP is 745 watts. 16 HP gets you 11931 watts and at 50% efficiency you can only get 6000 watts out of the setup. At 85% you get the full 10,000 watts which oddly lines up with the 10kw model name.

The efficiency will not be 100% but a direct coupling will be more efficient than a gear box.

My best guess is that the efficiency rating is the total loss between the crankshaft of the engine and the available amperage.

The efficiency of converting btus of gasoline into amperage will be way worse but that is not the fault of the generator head.

 

[1962]

well i trashed the hytel spider, after 3 hours of running. i think the torque and the heat from the gen head is too much for it. the last generator i made was a 2 "B" belt set up and it worked great. so now i have to decide wheather to go with a universal type coupling or a stronger chain type coupler. or maybe just start over with a new frame and go with the trusty belts. this engine puts out 31nm @ 2400 rpm's. i dont know how to convert the metric system to foot LBS of torque. but if i do go with the belt set up, i like having the engine run at the slower rpm's than the 3600 direct drive speed.

 

[gbirky]

31nm = 22.9 ft-lb. At 2400 rpm, 31 nm makes about 14hp

22.9*2400/5252 = 14.2 hp

 

[Highbeam]

How about a bigger lovejoy? They make some big ones.

 

[1962]

thanks for the metric conversion greg. yes, they do make some big ones. tomorrow morning i will pick up a #40 chain type coupling from grainger. the bigger lovejoy is a bit more $$ than the chain type, and heat might still be a factor with the plastic type spider. the chain coupling is all steel and should be better for the higher temperatures. if that fails, /forums/images/graemlins/confused.gif it's back to the drawing board and a belt drive.

 

[SPIKER]

as far as the eficiency goes the belt SLIP will lkoose the extra amount. No way around that. the GB is less efficient due to losses in the gear box. the dirrect drive is most efficient.

msark M