hp needed for genny?

[frankc]

Paul C. THANK YOU. That is easily the best (most complete) article I've read to date.

JB. Looks like your fine tuning your setup just great. I'd be curious to know how your monitoring your current draw when applying load. One of the reasons I did most of my testing at lower draws was because the Kill-A-Watt meter can only handle 15a/120V loads thru it. I guess I could spring for a clamp-on meter that measures AMP draw thru a line and handles much higher draws, but the ones I've seen that can do this for 220V are quite expensive. Does anyone have any recommendations for an affordable (ie. $50 or under) meter that has the ability to measure draw up to say 30A @ 220V????
JB, I like your 3ph cart better every time I see it. It really is a pain in the Azz to get the PTO shaft real straight with the wheeled cart, your setup although not as mobile, looks like it would take up less storage space and certainly be easier to line everything up. Although, I bet getting that PTO shaft hooked up with your I-match setup is quite interesting to watch. I'd probably be mumbling some illiterate phrases while doing that!
Frank

 

[RonMar]

That is a great article Paul.

JB4310
That "Trick" you described about setting it near the high side of acceptable under no load is exactly how I setup my genset and a good way to configure a mechanically governed generator. 62HZ and 125VAC no load yields me 60/120 at half load and 58/115 at my full rated(sustainable) load. The freq/volt relationship only applies to non AVR gensets as an AVR will control the voltage and break up this relationship. But the RPM/frequency will still droop as the load increases.

Because of this relationship, I can easilly monitor generator load by taking the Killawatt meter inside and plugging it into any outlet and watcing the frequency. Since it is such a small generator, we have to guage our useage, so when cooking, the Killawatt gets plugged into the outlet by the kitchen sink and it is quite easy to monitor what effect our appliance useage is having on the generator load. IMO, no one who is making, or contemplating making their own power should be without a Killawatt. It is the handiest little device I have found for monitoring/controlling a genset.

Another issue with using a tractor as a power source is the range of authority the manufacturer gave the governor. Ideally a generator governor should have full throttle authority, but some manufacturers may have limited this authority to help the operator know when the load on the machine changes and forcing the operator to make a throttle change to maintain RPM. This is similar to most automotive cruise controls which do not have full throttle authority. They will start to loose speed on really steep hills as they can't apply enough throttle to maintain speed. You as the operator do have full throttle authority and can step on the gas and use all the avaialable HP to maintain speed up the steep hill. the trick JB mentioned will help to compensate for this, but the larger the generator is in relation to the tractor, the greater this problem may be. Some tractors may have more throttle authority than others but this is where a large tractor would operate a smaller genset in a more stable fashion as the governors available HP control is greater than the generators potential HP demand. Unfortunatly this is not as efficient.

FrankC
Here is a link to a few just search "clamp on amp meters" or "amp clamp meters"
Clamp meter | clamp on amp meter
You can get the full meter type, or a probe that plugs into a digital volt/ohm meter and displays amps measured in the form of millivolts on the DVM. I have both types, and the amp-clamp probe is a little smaller and easier to get into panel wireing, but ties up the volt meter when I need to take voltage readings at thesame time. I need another standalone metr now anyway as the meter movement on my older one broke a few weeks ago.

Did I understand that you were running your generator without it's frame being attached to your tractor 3PH? I would not reccomend this as a sudden high load such as a shorted circuit or a failed bearing or gearbox could cause a sudden mechanical load on the generator and cause its platform to shift or tip and do real bad things mechanically to that spinning driveshaft. Lotta available torque in a PTO shaft(they occasionally pretzel humans and rip arms and legs off) I don't think I would feel comfortable running a PTO generator not physically attached to the tractor or securely bolted to concrete...

 

[frankc]

Thanks for the links Ron, and the concerns. But I must have written something illogical in one of my posts to give you that impression. I ALWAYS keep the trailer connected to my tractor via the draw hitch. The tiger-power trailers are very well made, tires are full size 14" load-rated for towing on steel wagon wheels. The hubs and bearings and axle are tagged for 3500lb capacity!! BUT,
its still just a wagon pin setup, so its not like there is a ball mount to hold the trailer tight. I like JB's skid, more compact, height and side/side alignment should be easier to adjust and since it's attached to the 3ph, can't really shift that much under load.

Frank

 

[JB4310]

Paul, Thanks for tha informative link.

Frank,
I'm simply using the ratings on the equipment to calculate draw, I know I'm not going over on any thing except maybe the compressor, 15 amps X 3 at start is over the rating but should be within the surge, took the cover off today and see it will be easy to wire it for 240 volt, I think that would make it easier to start and maybe save me some money when normally operated??? The 5kw heater is 240V so that's balanced between the 2 hot legs.
The meter in the link is what I want, and will mount it to my homes panel board between main panel and a new 50 amp outlet, it''s for permanent install but I guess you could use it as a tester, or as Ron explained in another forum you could split the cable and measure the individual hots with a regular current tester, I have a multi meter that I can barely figure out and don't own a current tester now but maybe I'll start looking for a cheap one.

Reliance Controls 50-Amp Indoor Wattage Meter MB125 @ Electric Generators Direct.com - Your Online Portable Power and Home Standby Generator Superstore

As far as the 3 pt carrier goes, mine is not as heavy as yours but I think it's more mobile when on the tractor and when off can be stored up on a rack when not used, this is the first pto operated piece of equipment I've ever owned so I don't have anything to compare to but it could not be easier, just hook up to 3 pt and connect shaft, the shaft takes all of maybe 10 seconds it is short and not heavy, with the imatch you don't even have to get off the seat to pick it up and move it.

Ron,
I guess I'm learning something, I'm kinda thinking maybe I should have gotten the 15 kw but we so rarely loose power I think the 10 should be fine, might be nice to have a little more for the duty factor, I would probably still go with the non avr though but not sure, the fluorescent flicker a little, should that be expected?? would avr solve this? I want a killawatt meter, what's the best source? couldn't find one in any store. I got a plug in Hz/volt meter from the gen company for no charge and I have the old analog Hz meter that works fine out of the generator, the company is sending me a box and an ac cord for that, so I'll be able to monitor from a couple of strategic locations in the house which I think is a necessity, alot of that storey that Paul linked to was about the problems caused by the fact that many of those older setups had no meters what so ever, there were alot of older looking equipment there, some of them were huge.

This is a pic of their plug in meter, which is the same as the internal unit, only 1 light to indicate 120 volts, it's pretty nice and simple.

 

[Mickey_Fx]

Don't know how you feel about harbor freight but they have 2 models of low cost clamp-on multimeters. The highest priced one is $20 and has ranges that more than cover the needs here. They also sale kill-a-watt meters. Thank the price on these are about $30 and seems to be close to what I've seen listed from several locations.

 

[RFB]

Just a quick than you to you guys for all of the information and experience. It's a gold mine.

 

[RonMar]

JB4310
As mickey mentioned, Harbor freight sells them in their stores, but I don't think they list them on their website. A good thing is that the killawatt allows you to do long term power studies on appliances such as how much power is this freezer using per month, and look for hidden loads(freezer is off but still pulls 6Watts). It also gives you power factor information for the inductive loads. A bad motor run cap can skew the power factor when running and appear to use more power than it actually is which costs you money. There is a newer model out that has an internal battery backup. The old model looses it's recorded info if you have a power fail or unplug it before you read all the info.

As for loads, get everything you can onto 240VAC. If your generator is 10KW capacity TOTAL, that means 5KW per 120V leg. Based on the physical size of your generator, I would guess it does not have much more surge capacity beyond 10KW(smaller windings, less copper?). The surge load of a large 120V compressor starting is probably pulling that 120V leg way down into the dirt(browning it out). As the voltage drops, the motor has to pull more current to compensate for it and the generator can't provide enough to overcome the air pressure load. A 240V config would pull half the current for the same KW.

I have a similar problem when running a microwave on my available 3KW. It is a constant 1.3KW and is my largest 120V "necessary" appliance, which really knocks the voltage down on that leg(UPS on the entertainment system starts to beep). I bought a 3KW 240-120V transformer and I am making up a special circuit to power the reefer/microwave and get their load spread across the 240 to help balance things out on the generator. You can do a lot with very little, It is all about energy management

Frank
No, I didn't get the impression that your generator was on a trailer attached to your tractor. Now that I understand how it is configured, Your setup sounds fine. If it was setting unattached, I was envisioning it doing a "stoppie" if somehow the gearbox or rotor locked.

 

[JB4310]

Thanks Mickey, I ordered the killawatt meter today from harbor freight, CT is one of only 5 states that they don't have a store, so I really didn't know much about them, though I have heard the name before, cost $40.00 with the shipping.

Ron, thanks for the explanation on the governors authority thing, that helps me understand it better.

We had a good discussion here, but I think that's the problem with having a separate category for generators, I know alot of people have gennys here but once glory of learning all about your new equipment wears out, there's not much to talk about until a new guy comes along and needs to learn, like I did.
But like I think it was Frank that suggested a broader category that I believe should include alternate energy supply, inverters as well as generators, would be an interesting and active topic.
I was thinking today that after food-clothing and shelter, electricity has now, in the last 150 years or so become the next basic necessity, and we really take it for granted that it's always gonna be there, I know I take it for granted, on the rare occurrences we loose power (just had one 2 weeks ago for about 4 hours) I go from room to room turning on the switches and can't wrap my head around the fact the power is not there as usual.
I grew up in an unpampered environment, so I can handle a little hardship but you should see my 3 kids, who have a pretty good lifestyle, when the power goes out, they sit around like Zombies, thinking they're gonna die.
I have not had the guts to power up the house yet, have to get a few things in order first, I'll pipe back up when I do, as I'm sure I'll have some questions/comments.

 

[Soundguy]

Someone is advertising a 20kw PTO generator for about $1300 in the local paper. Seems like a decent price, but how much tractor does a generator that size need? It's way more generator than I need for backup, but more power is often nice.

as a 'soft' number.. figure 2 pto hp per kw.

technically it is less.. but once you figure in variables.. the 2hp per kw number is 'safer'.

never hurts to have too much hp.. or too much generation capacity.

IE.. a 20kw gen on a 10kw capable machine just means you won't ever thermally overload the head.

having 50 hp available on a 7kw genny just means you won't ever bog the tractor down with the genny at max load.

I got a 12.5kw genny from northern tool

i paid about 1k$ for it and am happy.

soundguy

 

[John_Mc]

How lucky was that that I bought this thing 4-5 weeks before actually needing it for 4 straight days???? ... What's really weird is I happened to pickup a used Jinma Chipper 3 days before the storm hit, and I used that chipper for 3 straight days cleaning up from the storm. Sometimes I scare myself!!!!!!!!!!!!

Just don't go out and buy a defibrilator