Running short of AC, tripping generator fuse

[windtrader]

So, is there a way to balance the circuits in the main panel to eliminate an overload condition?

I've had a few incidents where the generator (Generac 8kv: 120V x 33A x 2) is tripping the breaker on the generator. I'm not a qualified electrician but studied the diagram showing the routes to the main AC panel from the shore and generator power sources.  https://www.dropbox.com/s/542kh1wa4nb137m/IMG_20171003_120239.jpg?dl=0

The main panel is fed two 110v AC lines, 33 amps (generator) or 50/30 amps (shore) each side. If so, this means it only takes 120v x 33 amps to trip the generator when pulling more than 4,000 watts. Image shows the main panel fuses to the devices/boxes.  https://www.dropbox.com/s/3ycjwlavxin03yv/IMG_20171003_113335.jpg?dl=0

More detail showing the panel wiring. https://www.dropbox.com/s/ijegyh3yv3t4jts/IMG_20171003_113159.jpg?dl=0

When the breaker triggers it is usually when the inverter is charging the battery in full bulk charge (24v x 35a = 840 watts). The electric water heater is on and pulls 1500 watts. Then the front AC gets started and pulls at least 2000 watts to start. All this overloads the generator.

From the diagram it seems the inverter ties in before the main panel on the black/white wire. But just the electric water heater and AC is going to max one line 120v x 35a.

What can be done to increase the overall capacity? There is some way to configure the generator to output 240x66a. From what I gather most RV generators are set to do 120x2 so are not truly 240 power sources. LIke I said I'm no electrician but I know some of you are!

BTW - The inverter itself can handle much larger peak loads. It's the generator that is triggering. Maybe there are more elaborate methods using more inverters and the generator and having all three coordinate and distribute the load better. Or something that will pull from the inverter briefly if the generator is maxed out. Anyway I got what I got. Probably them premium Prevost have that set up, right Jon? lol

Thanks Don

[gumpy]

Which AC is being started when it trips?

I assume you mean electric hot water heater, rather than heater, as it doesn't make sense to have the heater plugged in and the AC running at the same time.

Your inverter is attached to black.

Your front AC is attached to red. Your rear AC is attached to black. Potential to overload with inverter charging and rear AC start.

Your electric water heater (52) is attached to red.   

So if your electric water heater and front AC are both on, you have a potential problem there. Either use the rear AC or shut off the water heater until it's cooler outside. That's not very convenient when you're running the generator to charge batteries as you want to heat the water at the same time.

You can swap the positions of the double breakers 52/53 and 71/72. This would put your water heater on black along with the inverter and would leave the front AC on Red. Be aware you could overload it then if you turn on the microwave, which is on black.

[Oonrahnjay]

      It also appears that your A/C startup current is adding to the big loads.  A lot of people have reduced those big starting current spikes by adding a "soft start" kit to their A/C circuit.  These kits have a big capacitor - it "fills" with power slowly and then - at startup - releases the stored power to kick the compressor off without drawing significant power in a big spike from the ordinary power wiring.
     Just google "soft start kit - air conditioner" for a lot more detailed info.  If a part of your problem is that spike overloading your system, this might help.
     HTH,  BH  NC

[belfert]

My Powertech generator can do either 120 volt or 240 volt.  Powertech recommends 120 volt for 12 KW and under unless there is a 240 volt load.  Powertech also recommended tying the two 120 volt outputs together so going over 33 amps on one leg would not cause the breaker to trip.  I have a 50 amp breaker in my main load center that will trip if load on one leg goes over 50 amps.

[TomC]

I have my bus wired straight 120vac. My 10kw Powertech generator is also wired straight 120vac-which means having to run 2 sets of 3 wires to the breaker box. I also only use one leg of the 50amp land line when parked. But 6,000 watts when sitting is more than enough since your A/C load is less. I can run all 3 roof airs, or 2 roof airs with power to spare on the land line. It eliminates a whole bunch of problems trying to "balance" the loads between legs. Good Luck, TomC

[windtrader]

Which AC is being started when it trips?

I assume you mean electric hot water heater, rather than heater, as it doesn't make sense to have the heater plugged in and the AC running at the same time.

Gumpy, the front AC is the one starting during the overloads. And yes, I mean electric water heater.

So, it seems there is just a bit of compromise on what I can run all at once during those unusual conditions. I'll take a look at your suggestions about swapping a few circuits.

I'm hoping that once I get solar on top to keep the battery banks fully charged, this situation will less somewhat but the bulk charging is not all that much. Maybe a on demand water heater is the answer. LOL.

Thanks Don

[windtrader]

     It also appears that your A/C startup current is adding to the big loads.  A lot of people have reduced those big starting current spikes by adding a "soft start" kit to their A/C circuit.  These kits have a big capacitor - it "fills" with power slowly and then - at startup - releases the stored power to kick the compressor off without drawing significant power in a big spike from the ordinary power wiring.
     Just google "soft start kit - air conditioner" for a lot more detailed info.  If a part of your problem is that spike overloading your system, this might help.
     HTH,  BH  NC

Bruce, Thanks for the great suggestion, a large capacitor would sort this out. It is the initial AC startup load that shuts things off. There is a current limiter on the charge function of the inverter. I just did not want to limit the current during AC startup thinking that might damage the AC unit if it does not get the power it needs to properly start up.
Thanks Don

[windtrader]

My Powertech generator can do either 120 volt or 240 volt.  Powertech recommends 120 volt for 12 KW and under unless there is a 240 volt load.  Powertech also recommended tying the two 120 volt outputs together so going over 33 amps on one leg would not cause the breaker to trip.  I have a 50 amp breaker in my main load center that will trip if load on one leg goes over 50 amps.

The Generac has the same option to output 120v x 33a x 2 or 240v x 66a x 1. Seems like switching that would require a number of changes since the inverter is 120v. Like I said I'm not an electrician but thanks for the idea. Don

[buswarrior]

Wired as you are, you have two 4000 watt circuits available, which, as you are discovering, is limiting.

If the generator internals were wired for straight 120, then you would have the whole 8000 watts available, a more flexible situation.

What do you have onboard that needs 240 volts?

Happy coaching!
Buswarrior

[windtrader]

Hi BW,

The documents indicate the opposite. Output from the generator is one line out at 240 x 66amps or two lines out at 120 x 33amps. The circuit breaker on the generator is a double one; 35 amps each. I'll check the docs again tomorrow to see if there is some way to have a single 120 line at 66 amps.

Even if it did, it seems the main panel would need to be different to put all lines off a single panel unless there are 110 panels that connect all breakers to the same single input. Again, I'm no electrician so fumbling in the dark on this.

[niles500]

Evidently the laws of physics do not apply to your Generac, try 66 amps at 120 volts

[Oonrahnjay]

      For a demonstration of the effectiveness of a "soft start" kit, have a look at https://www.youtube.com/watch?v=6kawAXMbOz0 .  This is a test on a 15 year-old 3 ton household air conditioner system but results should be similar on an RV unit.  The "inrush" amperage becomes only about 20% of the average running amps versus approx 4 times. 
      I'm posting this one because the guy seems very knowledgeable and has the equipment that best demonstrates the exact load differences that the soft-start unit gives. 

      Does anyone know anything about a delay for the blower and evaporator fans?   It seems to me that current A/C designs are set up so that when you (or the thermostat) hits "Start", the fans come on and draw current; then, when the controller confirms that the fans are running, it switches on the compressor.  In this way, at start-up you have the amp draw of fans, compressor running amps, and in-rush all combined.  Would it make sense to have a delay on the fans so that the unit starts only on compressor amperage plus in-rush?  This should be a considerably lower amperage than with the fan amp draw added.  The controller must start the fans within a few seconds but in-rush only last milli-seconds.  This would be especially good if the in-rush were managed well with a soft-start kit.
      Sure, it would be somewhat complicated and it would add some cost, but what's the cost of upsizing a generator, burning extra gennie fuel, etc. if you could make your A/C loads start and run reliably and safely on less current??

[buswarrior]

If you have no 240 needs, get that generator wired for straight 120, an electrician can readily combine the panel, and all your problems go away.

Electrician has to understand the wire size implications, and set you up so that you can still use your shore hook-up for maximum power and minimum trouble.

You don't need to jump thru any hoops, with an 8k generator, the coach should perform like home.

Happy coaching!
Buswarrior

[eagle19952]

You don't need to jump thru any hoops, with an 8k generator, the coach should perform like home.

not with two old AC units
a hot water heater
a 35 amp charger..
one circuit of 8000 is no better than two 4000 watt circuits that are balanced.
ok....maybe a little, but not enough
especially if you want tv lights microwave and wall warts/ computers and refrigeration.
no matter how u slice it the load exceeds 80%.

[Bus Lurker]

Don,

Please post when you start the solar project.  It will be very interesting to see how the panels are mounted on the roof and how the wire(s) are routed to the basement.  It would be great if you could supply a trickle/float charge to the house and chassis batteries from the solar panels.

Mike