HF has a 10kw/7.2kw gen head on sale right now, does anyone have any experience with these? Are they any good or comparable to an ST head? I am under the impression that an ST head is for continuous use for years and these HF and other heads you see might be for backup only and will play out if used for extended periods. Northern tool has one also and it looks better just from the pictures but it is right at $900 for it as the HF one is $299.99!!!
That's a 2 pole 3600 rpm head. I have not heard good things about them.
:o,,, thats what I was a fraid of. Golden rules is you normally get what you pay for. Thanks for the reply.
I have one and works good.It came with the rear plastic cover broken from shipping so I called them and they are sending that and the capacitor out no charge.
I will let you know if they come.
As far as working,I have used it approx. 2 -3 hrs. and so far so good.It's connected to my Xantrex 6048 inverter and the inverter syncs up fine with it.
The previous head I had was a Mc-allte 5000 watt and had issues with low voltage until I replaced the capacitor,then it was ok.But the inverter would spit it off when a heavy load first came online.
I paid $500 for the McAlte so could almost buy 2 of the HF heads.
If you do get the HF head,check the wire connections under the end cover.Mine had a plastic 4 wire connector with 1 wire not pushed in completely.Come to think of it,the Mc-alte head had a loose wire in it too.Gotta double check everything.
They are not as bad as some people think. If members or others want to make them more reliable. Replace the capacitor with a higher quality one and have an extra set of diodes on hand. I had one and I looked at it close enough to see that quality was pretty good. the windings and bearings looked good. For the price they can be picked up just buy 1 or 2 spares and members or others will be set.
What kills generator head is dis-reguarding the power factor that the generator head is rated for. The Harbor Freight generator head is rated for 10kw surge and 7.2kw continuous for so many hours. I don't know how many. Mc-Allte rates their lighter 2 pole units the same way. So if members or others want the Harbor Freight Gen Head units to last on a power factor of .8 than limit the Harbor Freight Gen Head to 5000 watts and it should do fine. Motor starting is another factor that is over-looked. Look at the LRA Label (Locked Rotor Amps) LRA is the max amps a locked compressor or motor will draw. it is best to keep below the LRA Rating. So when members or others figure out max load, RLA has to be included when sizing a Generator Head. This is the reason I am going with a 27.5 - 33Kw generator head on my next build.
The Harbor Freight Gen Head should last fine and be more efficent if they are limited to 4000 - 5000 watts anyways. Members and others could double the life (and longer) of many generator heads if they follow what I written.
Hope this helps.
Henry
It is my understanding that the inverter/chargers have a terrible PF. I've read several reports of the HF heads dieing after a few hours of battery charging. Also reports of bearing issues. I am a HF fan and buy lots of toolz from them. My philosophy is if I use a cheap tool enough to break it or wear it out the purchase of a good one is then justified.
This is why I de-rate generator heads. $500 and $700 brushless Mc-allte generator heads will have the same issues as the cheap Harbor Freight generator heads. They are pretty much designed the same. About bearings. It is not hard to replace the bearings in the Harbor Freight head. Plus higher quality bearings are inexpensive. I know an OEM for Mc-allte, and on projects in the works I will use them because of my cost. But for do it your selfers that want to save dollars the Harbor Freight unit can be updated with better bearings and capacitor and an extra set of spare diodes for around $100.00. That is still much cheaper than a Do it your selfer purchasing a Mc-allte 6.8kw head. As I said before the copper windings on the stators and rotors looked good on the Harbor Freight units. So, it is possible to save at least a couple hundred dollars after the upgrades on a Harbor Freight unit, and have a unit perform just as good or better than a comparable priced Mc-allte unit that is rated at lower watts.
De-rate a Harbor Freight unit and do some proper power management and they will most likely last last as long or better than some 3000 to 5000 watt high dollared units.
Henry
Now if your thinking of making a 10kw generator than I would look at an ST head. But I would still would de-rate any ST. For 10Kw output I would look at a 15Kw.
I have a Nice ST-10. It is an earlier unit that can be set up for 50 or 60 Hz. it weighs over 320 lbs. It looks like it is built better than the ST-12 I had.
The ST-10 will be de-rated to around 7Kw. I don't expect any problems with it, but you never know. The bearings should be replaced with higher quality bearings down the road.
Henry
Good points, Henry. The ST heads often need new diodes, doghouse replacement, and new bearings within the first hundred hours, and they need an AVR, in my opinion.
If I was starting over I'd give the HF 10KW unit a serious look, for my 2.5 KW application.
QuoteIt is my understanding that the inverter/chargers have a terrible PF.
And some have .9 PF on the charger. My Xantrex XW does.
Quote from: mike90045 on April 04, 2013, 12:03:54 AM
QuoteIt is my understanding that the inverter/chargers have a terrible PF.
And some have .9 PF on the charger. My Xantrex XW does.
Yea, that XW is one of the best.
Power Factor can be corrected if you know if its a leading or lagging power factor. Utility companies use capacitor banks most of the time to correct power factor since most loads are inductive.
Ok my ST head would not develop voltage any more, I purchased the Harbor Freight gen head with the 20% coupon online and it was shipped to the house for 275.00. The fan melted the first run so I took that off and also replaced the flimsy plug/gauge panel with a 12x12 carlon pvc box and mount two 4 inch fans forcing air thru the gen head, so far so good. The only concern is that it will not maintain 120 VAC or 240 VAC when loaded @ 3000 watts. It drops to around 110 or 220, I don't think it will hold if I loaded it more. It has a plastic capacitor 45uF 450volt, would a higher quality and/or different value make a difference in output voltage. So far this is the only issue I have with it. It is much quieter and has less vibration than the ST head. It runs hotter than the ST but that is to be expected with it's compact design. I hope someone can advise me on the capacitor as I really don't understand how this brushless unit works ???. I had a 5500 watt portable unit once that would maintain 240 vac with our electric water heater appling the load. Thanks for looking and have a good day.
I replaced mine with a 40 uf and it maintains voltage better.
Surplus center is where I got mine.
Keep in mind the cap is located such that the cooling fan pulls air across it to keep it cool.
I replaced the plastic end cover on the head with a metal breaker box and left enough space along side for the cap to get all the airflow that the cooling fan draws in.
As previously stated. Just because the nameplate states 10Kw doesn't mean that 10Kw continuous load is a good idea. I would not continuously loading a discount or consumer grade generator beyond 7.5kw .
the harbor freight heads are rated at 10kw at unity pf intermittent
and either 7.2 or 7.5 kw at unity pf continuous duty, that assumes probably
a 70degree F ambient temperature probably.
iirc the voltage can be as high as 126vac no load to as low as 108vac and still be within NEC specifications or 256 and 216vac on the 220/240 side
you could replace the cap with a known value quality unit and see how things improve
if that does not help then increase the capacitance value as stated, but work to keep the unloaded voltage around 126vac or so to be safe.
all this of course assuming that the rpm/frequency is not dropping under load and that is what is causing the abnormal voltage droop.
be sure to double check for stable frequency before you do anything would be my recommendation.
bob g
I verify the freq and voltage with a digital fluke meter and at 60hz no load I get @ 116 volts per leg. I bought an american made motor run cap yesterday at my local HVAC shop and nothing improved. I will head back over there today and get a 40uf cap and give it a try. Also at 62hz I get @ 124 volts per leg no load but when loaded with about 3kw it droops to 110 volts per leg and even lower when more load it placed on the genset. Thank you guys for the input it is much appreciated.
Ok the 40uf cap went the wrong way with the voltage so tomorrow I will get a 50uf. I guess I read your post wrong Bob, my bad.
Quote from: mobile_bob on April 13, 2015, 10:48:16 PM
if that does not help then increase the capacitance value as stated, but work to keep the unloaded voltage around 126vac or so to be safe.
bob g
been very busy here, so i may be foggy and missed a lot of the conversation here,
as earlier stated that genhead if working properly should carry ~7kw load at unity power factor
that being basically a resistive load, if on the other hand you are trying to power a reactive load that has a rather poor powerfactor the head will have to be derated.
i can't imagine that 3kwatt of load would cause the voltage to droop so far unless the rpm and frequency is also drooping? and if that is not the case then there is probably something wrong with the head?
if you have 3kwatts of resistive load, which is near as you can get to unity pf, and the engine rpm is not drooping much below 60hz (and at 3kw load i would expect right on 60hz or very nearly so) then there is some sort of issue we are missing.
it is possible that the head has a tapped stator? in that some of the other parts of the globe run on 100vac or somesuch, maybe the head is connected wrong internally?
even that doesn't make sense to me? because you are getting ~126vac at no load 62hz? hmmmm
however those places that use 100vac nominal are also 50 hz i think, maybe spun up to 60hz those heads would put out ~126 or so?
we are missing something here, or so it would seem to me.
i know these hf heads are not first world built to the most stringent standards, but most i have heard about have done a pretty good job of delivering over 110vac at near full load and ~58hz
fwiw, just rambling
bob g
The largest load on the unit is my pool pump. I supplement my electric usage with a generator transfer panel. I swap my 120 vac load in the house and shop. I also run a 500 watt attic fan to remove the heat from the attic which reduces my AC load. So the pool pump, attic fan and lighting, TV's, pc's and ceiling fans are the load and it is about 2800 watts or 111 volts x 11.7 amps on one leg and 112 volts x 11.3 amps on the other. Do the math and that is 1299 watts on one and 1266 on the other plus 1/2 an amp for cooling fans on the genset. So that's less than I said at 2600 +/- watts. My Fluke 287 on the terminals of the disconnect indicates 60hz and the corresponding voltage per leg. It doesn't really decay much as the genset temp goes up like the ST head did. Just my luck I guess. I will put the water heater on it tomorrow by itself with is 4500 watts of resistive load and report back. Increasing the capacitance value would mean going from 45uf to 50uf or the other way around, 45uf to 40uf????
I found a 60uf cap and now I am in business, thanks for the input.
Even with a nameplate of 7.2Kw continuous. I would not recommend operating that generator head at 7.2 Kw continuous. De-rating current back to 80-85% of rated is a desirable safety factor..