Harbor Freight Gen Head

[mobile_bob]

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

[DRJensen]

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.

[DRJensen]

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.

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

[mobile_bob]

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

[DRJensen]

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?

[DRJensen]

I found a 60uf cap and now I am in business, thanks for the input.

[buickanddeere]

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..