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Old 21-04-2013, 07:02   #1
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Diversion Load

Hello,

Setting up a new power system on a 60 foot Teak vessel I just bought (Full restore project).

I have the solar, wind, inverter, and other hardware piled up ready to install, but have been thinking about the "diversion load" now that I have the vessel in the marina in a birth connected to shore power.

I was thinking... rather then just diverting the excess power from the wind and solar to a 6 gallon water heater I converted into a DC by removing the AC heating element and installing a 24v 1,800w element. I could install a switch to connect to a choice of 1) the water heater while out at sea, or 2) a small grid tied inverter when on shore power when no one is on board.

I have attached an image to better explain my thinking.

The details are:
All DC banks are 24v
All AC is 230V 50Hz
1,200W of solar connected to a MorningStar TS-60 MPPT
2 - 400W wind turbines (AC out from turbine to a 24v DC rectifier)
A TS-60 PWM controller as the diversion controller
MorningStar Networking Hub w/remote Monitor
A Victron MultiPlus 24/3000 Charger/Inverter
An Onan 7.5Kw Diesel Generator
Converted a 6 Gallon AC water heater to 24vDC 1,800W heating element
A 1,000W pure sine wave inverter (18vDC to 30vDC input)

I do believe that the 24v 1,000w Grid tie inverter is enough for a maximum diversion load. I read in the TS-60 PWM manual that I should not put on a "Load" to big or the diversion controller will switch off, same is too small.

Am I correct by doing the math of 1,000w divided by 24v =41.67 amps I can divert with the Grid Tied inverter ?

I am asking because the inverter changes DC to AC so not sure that math works... The watts are rated for AC (would I divide 1,000 by 230 ? If so I need more then 1 HaHa), so here I am asking the question. Better to ask around before I dive in !!!

I know I am not saving the world with the little amounts of diversion power this system would make, but since I have a complete system... why not do it right, and should I want to add an additional 1,200W of solar to another controller at a later date !!! It is flexible and safe !!!

... As they say... Measure twice and cut once HaHaHa

Thanks,

Alan
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Old 21-04-2013, 08:23   #2
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Re: Diversion Load

The solar panels do not need to be diverted. If you have a separate controller for the solar panels, it will just cut off (open circuit) the solar panels when the batteries get full and there is not enough DC load.

Wind generators do need to stay loaded to keep them from overspeeding. But you can stop them and tie the blades if all of your diversion loads are full.

And is your power at the marina individually metered? That is the only circumstance that would be worthwhile financially to send excess solar panel to the grid.

Now if you are just trying to do something good for mankind, that is another story.

David
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Old 21-04-2013, 09:03   #3
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Hello,

Each birth has its own electrical meter, and free water.

This is the first time I have had more then one small wind turbine on a vessel.

In a perfect world, they could pump out 35amps I would need to divert. The 1,000w grid tied inverter should be ok by my calculations...

Have you viewed my basic plan ?

Alan
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Old 21-04-2013, 11:30   #4
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Re: Diversion Load

Alan:

A couple of observations:

Your house battery bank according to your diagram is 200 amphours at 24 V, not 800 amp hours.

I don't see why you need two Tristar controller/diversion controllers. I haven't used one myself but from what I understand they divert excess current (once the battery voltage gets up to fully charged state) to an external load. So you could do away with the bottom controller and wire the diversion load to the upper controller. But.....

In any case, the solar controller/diverter is taking all sources of excess current from solar and wind generator, and diverting it. That is much more source current and wattage than either of your diversion loads can handle.

Like I said in my first post, I would not use a diversion load. Tie down the wind generators when their current becomes excessive.

If you must use a diversion load, isolate the wind generator from the solar panel with a diode. Put a 40 amp (minimum) diode on the pos line from the wind generators to the battery. Then put the lower diversion controller on the wind generator side of the diode. This will limit the source current being diverted to the wind generator only.

But this is a complex DC system and I am sure that I am missing or mis interpreting something. I would get an electrician who really knows this stuff to help you design this system.

David
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Old 21-04-2013, 13:10   #5
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Re: Diversion Load

That Grid Tied Inverter might bite you in the butt if the dock meter is an electronic one instead of a bidirectional mechanical.
You would wind up PAYING for the power you are SENDING to the grid because electronic ones only measure current through the meter, not which DIRECTION it's flowing.
They assume it's being consumed by you.
That's why my home has two meters, one for solar production and one for use.
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Old 21-04-2013, 18:50   #6
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Re: Diversion Load

Hello,

The meters at the marina do spin backwards. I am good in that department. It does with my inverter on the boat I live on.

The picture was made for reference to show I am using two 12v deep cycle batteries to make each 24v series connection, with 4 of those in parallel. I have a total of 800Ah in the house bank.

The MorningStar MPPT controller is for charging, and the PWM controller has the DIP switch set to divert. The PWM controller has many functions, but it can only do what you set it to do. This one is set to "Diversion" to watch that the bank does not over-charge as I have the wind turbines connected directly to the batteries.

I am not on the boat enough to go out and tie blades down. Technology is much more fun HaHaHa

Here is a picture of what MorningStar has recommended for systems with multiple controllers I have based my plan on, and purchased the hardware for.

The only thing I am not clear on is... if the 1,000W grid tie Inverter is the right sized load.

I have contacted MorningStar by email, but that takes nearly a week for a reply (speaking from experience).

I have the Victron Blue Power Panel to monitor the bank as well, and to relay to the generator, and auto start if the bank falls low.

Thanks,

Alan
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Old 22-04-2013, 10:15   #7
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Hello,

For anyone interested. I found the answer to my question.

The maximum grid tied inverter I should use as a dump load, must be rated at no more then 1,800 watts and no less then 1,500w.

Thus my 1,000w is a bit too small !

Have a great day everyone !!!

Alan
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Old 22-04-2013, 14:41   #8
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Re: Diversion Load

Alan:

I don't know where you got your answer but it sounds silly. Why would it matter how big the inverter is that supplies the diversion load? What matters is the wattage of the load connected to the inverter. Here is a quote from the Mornistar Operation Manual:

6.4 Selecting the Diversion Load
It is critical that the diversion load be sized correctly. If the load is too small, it
cannot divert enough power from the source (wind, hydro, etc). The battery
will continue charging and could be overcharged.
If the diversion load is too large, it will draw more current than the rating of
the TriStar. The controller’s overload protection may disconnect the diversion
load, and this will result in all of the source current going to the battery.

An inverter connected to the grid has practicaly infinite load capacity. Yes it is limited by its wattage rating, but most inverters will self destruct when the output is connected to the grid because the grid can absorb anything that is directed to it.

The only way to use an inverter as a diverter load is to connect it to a fixed AC wattage load, like a water heater element which you already have with your 24 V element.

And you still haven't considered my earlier comment that your diversion load is not enough to handle the full wattage output of your sources- solar and wind as noted in the first sentence the Morningstar quote above.

And like I said in my previous post, if you don't understand the foregoing, get an electrician who does.

David
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Old 22-04-2013, 18:26   #9
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Good morning,

I went to the service department of the shop that sold me the victron MultiPlus, grid tie inverter, and 24v water heater element. The service tech told me... I quote...

All the circuits have protection and limits, lets compare these Alan...

A 24v 1800w water heater element is set to pull no more then 30 DC volts, thus a max amp draw of 60 amps.

The 24vdc 1,500w (max 1,800w) to 230v AC pure sign wave grid tied inverter is regulated to draw max 30v DC (there is the +/- of that). On the DC side of the inverter it should not pull more then 50 DC amps (max 60 amps at 1,800w). The 230v AC side of the inverter will put out 6.5 amps (7.8 amps max). The math matched (in my calculations and like the manual shows).

As the Morningstar manual says, the diversion load should not be to large, or the diversion controller will shut down. I don't want that. I am trying to keep the max amp draw of 60 amps, as it is a 60 amp controller.

This is a learning curve for me, and lovin' every minute of it.

I am still waiting for what Morningstar will tell me !

I bought the Morningstar from the Alt Energy store online in the USA, and had it shipped here. They had no knowledge to pass on about my question. The service tech here said valid technical replies...in my opinion. Your thoughts ?

Alan
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Old 22-04-2013, 18:33   #10
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Hello,

I forgot.. The solar array is connected to the TS-60 MPPT. That controller will not allow the batteries to over charge and will shut down when the bank is full.

We are only diverting with the TS-60 PWM controller as the diversion load controller, the overflow of the 2 wind turbines that are directly connected to the battery bank. Not the solar.

The switch to select a choice of grid tie inverter is when I am connected to shore power, and then switched to the 24v water heater element when on the hook.

Alan
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Old 23-04-2013, 07:56   #11
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Re: Diversion Load

Alan:

Both the source current from the wind generators and the solar panels will be available to be diverted because both are connected to the battery.

Let me modify my earlier comment about connecting an inverter to the grid. Marine inverters cannot be connected to the grid. You need a grid tie inverter made for this purpose. But grid tie inverters cannot usually be used as a source of AC power when not connected to the grid.

David
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Old 23-04-2013, 09:16   #12
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Hello,

Yes... Although Victron has a Phoenix grid tied inverter, the grid tied inverter is a domestic unit that will only be on when connected to shore power. It will be switched to divert to the water heater element while at sea.

Have a great day !!!

Alan
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Old 30-04-2013, 22:35   #13
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Re: Diversion Load

Hello,

After receiving the reply from MorningStar. Using the TS-60 PWM as a dump load controller is very sensitive. The unit can not be put in a "real world" situation where it would use its full capacity.

I have found an online supplier in the USA (Missouri Wind & Solar) that has a 440 amp dump load controller that is a work horse to put any load you give it, any place you want it. They have also provided the wind break switch with 24v rectifier.

My plans and hardware are nearly complete, and the current hardware is nearly 80% completely installed.

Here is the diagram of my system.

Alan
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Old 06-08-2013, 01:07   #14
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Re: Diversion Load

Alan,

Thank you for your continuous updates on this project. I have been reading for a few days and some of the information more pertaining to my situation can be found on this thread.

I am trying to install a 1600w Wind turbine, but am having a hard time convincing myself just to have a "dump load" built with a bunch of resistors. I am looking into have a water heater as you have in the same concept of having a switch installed.

In theory I would have a switch to turn on the inverter to run the hotwater heater when the wind is not high enough or the powers are drained further than the controller wants to dump the load, but at the same time it would automatically turn on the inverter in order to run the hot water heater when the wind was at higher speeds.

I was only unsure of the concept of dc to ac, and sine to modified sin inverters.

I hope all has worked out with your project, and thanks again.

-B
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Old 06-08-2013, 01:37   #15
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Hello,

A commercially purchased "smart" dump load controller is connected directly to your battery bank, and the device that is connected to the dump load controller should be a resistive DC load. I use a DC water heater element. That is most efficient and smooth for that type of controller.

I use the Morningstar PWM TS-60 for dumping up to 50 DC amps. I have this on a 24v house bank. The TS-60 will start dumping when the battery bank is at 30v

I also have a dump load controller I made that is connected to the house battery bank that is connected to a 2,000w grid tied inverter. That way I can feed the extra to the grid when I am connected to shore power. I set the controller to begin the dump at 29.9v.

As you can see... I have 2 dump load controllers, and use the voltage levels be the switch.... As long as I am on shore power I will be dumping to grid when the bank hits 29.9v... If the grid is not there, then the voltage will increase .1 volts (30v), thus the Morningstar will connect and them the extra will go to the DC water heater element.

When you buy a dump load controller such as the Morningstar as I have... You really need to follow the guidelines for their "touchy" circuits. You cannot connect a Morningstar to a grid tie inverter or any kind of inverter. I had to make my own controller circuit and use a 0-440 DC Amp relay that is very basic and heavy duty.

Morningstar is focused on restive loads.

Alan
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