Cangfa ZS1115GN question

[dmarkh]

It currently drives an st10 (direct drive). I need more power. I'm pretty sure it will drive an st15 just fine but would it be suitable for an st20?

Thanks
mark

[dmarkh]

It currently drives an st10 (direct drive). I need more power. I'm pretty sure it will drive an st15 just fine but would it be suitable for an st20?

Thanks
mark

Well, digging a little bit, maybe I can answer this my self. The Label on the engine reads:

1h.rating output   -   16.18kw/2200r/min

Not sure what the 16.18 is but maybe it means 16-18? That's what I'm assuming here. Also not sure why it says 2200r instead of 1800r either. It will run at 1800 rpm. In any case it looks like

16kw equates to 21.75 HP
18kw equates to 24.47 HP

Recommended HP to drive an ST15 is approximately 22 HP
Recommended HP to drive an ST20 is approximately 29 HP

So it looks to me like this engine is a little weak for the ST20 but should be OK for the ST15. If I'm off base here in any way please let me know.

Thanks
Mark

[Thob]

That rating means the engine will produce 16.18 KW at 2200 RPM for 1 hour. (i.e. NOT continous)

That's mechanical power out of the engine; if you connected it with a belt drive so it could run at 2200 RPM and the generator could run at 1800 RPM you would need a very efficient generator to get 15 KW out.  If you take a wild guess at 80% for generator efficiency, then you would get around 13 KW out of the generator.  (I didn't deduct a couple of percent for belt drive ineffeciency).

My best guess is that 1800 RPM the engine will produce around 13 KW mechanical power out; that would give about 10 KW out of a generator.

So I'm thinking it is pretty well matched as it is.

YMMV

[Ronmar]

What Thob said...  That is a 1 hour rating, what you want is the 12 hour rating for sustained output,  which will derate that 16.18KW a bit.  Then you need to derate it for the RPM drop.  HP = torque over time, so fewer torqu pulses in a given time period = less HP. Then there is the generator efficiency.

Sustained generator output requires about 2HP per KW and that engine is a pretty good match for the ST-10, but a full 10KW on the generator will be too much sustained load for it as is.  IMO it won't direct drive a 15, I don't think you would even get that much more if you belt drove it at 2200 engine RPM.

[dmarkh]

What Thob said...  That is a 1 hour rating, what you want is the 12 hour rating for sustained output,  which will derate that 16.18KW a bit.  Then you need to derate it for the RPM drop.  HP = torque over time, so fewer torqu pulses in a given time period = less HP. Then there is the generator efficiency.

Sustained generator output requires about 2HP per KW and that engine is a pretty good match for the ST-10, but a full 10KW on the generator will be too much sustained load for it as is.  IMO it won't direct drive a 15, I don't think you would even get that much more if you belt drove it at 2200 engine RPM.

Thanks Ronmar. Currently, the load the st10 will have "when needed" is around 30 amps with everything running. That is a fridge, a freezor, a couple of led lights, and the AC unit. It's that AC unit that is killing me. I ran the thing for about 8 hrs last a couple of weekends ago and in that time, twice it did not start the AC until a second try a few seconds later. I've gone ahead and installed a hard start kit in the AC but haven't yet tested if it will make much difference. Even if I ran an st15, the normal load "I'm talking power outage after a hurricane", would still only be around that 30 amps. I am just thinking, probably incorrectly that if an st15 was there, my AC start problem would go away. If I ran an st15, I would probably not even change out the 40 amp breaker currently used on the st10.

I know, the AC should be considered a luxury and not really considered for emergency use, but I'm in Florida and if I'm out of power for days or even weeks, in the middle of summer, to me it will be required. Even if I have to relegate time between it and the rest of the other required things.

Thanks
Mark

[playdiesel]

Installing a larger than needed head is good when you have large motor loads like A/C or well pumps IMO. No the engine wont pull the KW on a steady basis but those things require big wattage only to start.  My 1115 is running a belt driven 15KW head and will start the AC while under a full loading from my power hungry wife     The ST15 /20 costs you nothing to run, meaning it is not going to load the engine more than the ST10 doing same work, (slight fan and bearing drag factors ignored). It will of course load it more during start up of your A/C unit.

[dmarkh]

Installing a larger than needed head is good when you have large motor loads like A/C or well pumps IMO. No the engine wont pull the KW on a steady basis but those things require big wattage only to start.  My 1115 is running a belt driven 15KW head and will start the AC while under a full loading from my power hungry wife     The ST15 /20 costs you nothing to run, meaning it is not going to load the engine more than the ST10 doing same work, (slight fan and bearing drag factors ignored). It will of course load it more during start up of your A/C unit.

Thanks for that playdiesel. I was hoping my line of thought might be confirmed upon by someone in the know. Fortunately the ST heads are still easily available. I still need to see if the hard start kit may have eliminated my issue. All the HVAC folk I've talked to seem to think it won't help much as it doesn't actually cut down on the start amps. It just shortens the amount of time that the start amps are needed.

Fortunately ST heads are still easy to find. And what I see has sealed bearings packed with high temperature grease and a western rectifier. My st10 is still running on that "YAK fat".

Mark

[vdubnut62]

I direct drive a ST15 with an S1100 at 1800 rpm. The engine is rated at 16hp @ 2000. Yes, I can overload the engine really quick, (dryer and double oven on top of everything else) but if I use a little common sense everything works out just fine.
Ron.

[playdiesel]

The new and improved western rectifiers in both of my ST heads failed the first time a big load was placed on the head.  I replaced them with a plain ole bridge diode you can buy on Ebay for pennies a piece but they do need to be bolted to a heat sinking material such as a metal junction box. Lots of good ST dope on this site. with a small amount of work they are good heads.

[dmarkh]

The new and improved western rectifiers in both of my ST heads failed the first time a big load was placed on the head.  I replaced them with a plain ole bridge diode you can buy on Ebay for pennies a piece but they do need to be bolted to a heat sinking material such as a metal junction box. Lots of good ST dope on this site. with a small amount of work they are good heads.

I actually went through most all that with the st10. When I inherited the st10 the meter box had basically already fallen apart. The genset had less than 200 hours on it. I replaced the meter box with just a plate, installed an over sized rectifier (70 amp) mounted to the underside of that plate. Directly crimped and soldered the generator wires out to the breaker box. I would be getting rid of the meter box from a new st15/20 also. It's basically useless. Not sure why they even put it on. I would probably just re-use that plate from the st10, wires (#6), and rectifier for an st15/20.

Regards
Mark

[Thob]

Just in case you haven't already added an AVR: (given the other work you've done, you may already have.)

My brain is a little fuzzy right now, but I seem to recall that people have added an AVR to the ST heads and eliminated the use of the harmonic winding to help with starting heavy loads like AC units and wells.  Tom at Central Georgia Generator can fix you up with a good AVR and instructions on how to wire it up.  The AVR helps keep the voltage up during the heavy start current, which makes it easier (and more likely) to start.  Plus an AVR is a lot less money that a new head...

[dmarkh]

Just in case you haven't already added an AVR: (given the other work you've done, you may already have.)

My brain is a little fuzzy right now, but I seem to recall that people have added an AVR to the ST heads and eliminated the use of the harmonic winding to help with starting heavy loads like AC units and wells.  Tom at Central Georgia Generator can fix you up with a good AVR and instructions on how to wire it up.  The AVR helps keep the voltage up during the heavy start current, which makes it easier (and more likely) to start.  Plus an AVR is a lot less money that a new head...

I talked to him a while back about them. But that conversation was strictly concerning the flicker issue. He said it probably wouldn't help with that.  Maybe between the hard start kit and an AVR it would work out.  I'll give him a call and see what he says. Thanks for the advice.

Mark

[buickanddeere]

Go big. A 10Kw generator loaded to 10Kw tends to be loaded 3-4Kw on one 120V line and 6-7Kw on the other 120V. A larger gen eliminates the concern.
Loading the engine to max full injection rack is not s concern. Unless this is a base load generator that generates prime power 24/7.

[dmarkh]

I've concluded that an AVR might help with the AC start problem but a larger gen head with an AVR would take care of the problem for sure and provide other bennies.. So I contacted Central Georgia Generator to get some info. They all come with AVRs now but he has no ST15's. Only ST12 and ST20's. The ST20 is $750. If he had an ST15 it would be $650. He doesn't know when he'll have more ST15's. The ST12 would not be worth the trouble. I'm comfortable over sizing to the ST15 but am sort of afraid of putting a 20 on this engine. I'm wondering, as long as I leave that 40 amp breaker in there I should be OK?

Where else to get an ST15 these days? I thought they were readily available.

Mark

[vdubnut62]

dieselgman might have one out in KS. his website is http://diesel-electric.us/.
Ron.

I looked on said website, only 7.5 and 10kw listed.  Still I suppose one could ask.