Diversion load settings

[Lowhead]

I looking for help with the settings for my diversion load. Here is my system:

20 Kaneka 60 watt amorphous silicon panels (right now covered in 18 inches of snow)
Outback GVFX3648 grid tied inverter
Outback MX60 charge controller (Both the panels and the hydro are wired into this and it works pretty well thanks to Hydrosun)
Outback Mate
ES&D LH1000 low head turbine (I'm seeing about 450 watts.  It should be more but my wire is skinny and long)
8.5 feet of head
420 feet wire run of 24sq mm conductor solar wire (6 pairs of 4sq mm each)
C40 charge controller set in diversion load control mode
Alternative Energy Engineering HL-75 19amp@56V diversion air heater
8 GC-2 220 amp hour batteries in series


Here is my problem.  I've been running naked without a diversion load (we have a very reliable grid so excess is pushed back) and finally decided it was time to wire it all up the C40 while I was replacing the used old batteries.  My understanding is I should set the diversion to come on at about .2V past the equalization voltage.  My problem is the highest voltage I can set on the C40 is 56 volts and the manual for the Outback Inverter says the minimum EQ voltage is 14Vx4=56.  I don't think I can lower it any further.  What should I do?  Shut off Outback automatic EQ and then just disable the C40 when I run one manually?  Also the C40 manual talks about having a breaker but then the wiring diagram doesn't show one - they show it hooked right to the battery disconnect breaker (mine is 250A). 

My alternative is to use the aux relay on the MX60 to switch a SS relay to run the diversion load ( I think this can be done) and I have the parts but I wanted to have a completely independent system for this critical safety function.  I'm hoping there are some Outback Guru's who have run into this before.  I have to say I like the Outback equipment but absolutely hate the user interface and documentation. 

Thanks
Andy

[dave ames]

Hi Andy,

i'm not seeing how your system could ever "get away" from you, even in the event of grid failure?

have you tried shutting off the GVFX (when batteries are full) to see if it (the MX60) regulates the hydro?

the C40:  that manual jumps around alot the 56v is load control. in diversion mode (wish they would call that "dump mode"). we can go up to 60v..even up to 68v! with the resistor mod they show.

i like the idea of a breaker,  to take that c40 off line to do a manual EQ.

real curious about that control question with the hydro/MX60? ..should PWM only what it needs to stay at the battery set points while the array keeps the voltage at or below the VOC of the array?

cool system!

edit: looking again i can see where we would want to keep that hydro loaded up if the grid fails! your 3 ohm resistance heater should work a charm.

[dave ames]

the ramblings continue,

edit: looking again i can see where we would want to keep that hydro loaded up if the grid fails! your 3 ohm resistance heater should work a charm.

....but our array should keep that hydro loaded day or night, even if the controller (mx60) is in regulation. and the grid is down?  anyone know for sure?  Hydrosun?

still can't see the system in runaway if the grid goes down, with no dump load.

[hydrosun]

The MX-60 will control the amperage going into the batteries of both the solar panels and hydro in this setup. If the grid goes down the voltage of the batteries will rise to the voltage setting of the MX-60. It will start letting the input voltage to rise to limit the amperage going to the batteries. At about 10% above the open circuit voltage of the solar panels they will start acting like giant Zener diodes and shorting to ground. The hydro will put out less than normal output at the elevated voltage and rpm. The solar panels will be putting out zero amps. At long as the output of the hydro is less than the wiring internal of the solar panels can handle they won't be harmed.  So you don't need another dump load to control the voltage with this setup. If you feel the need to add another layer of control or have a use for the power, you could get a C-40 to diversion load. You absolutely want a breaker into the C-40 to provide protection appropriate for the size of wire you use.
I'm glad to see that the MX-60 setup has worked well for your hydro system.
Chris

[dave ames]

hydrosun/Chris,

thanks for that added info. i like what you guys are doing here.. A LOT    with or without the grid tie this is a cool system.

gotta to go find your earlier work!

cheers, dave

[Lowhead]

Thanks guys for the thoughtful responses.  If I understand the thread here, the 56V C40 limit listed in the manual is bogus and can actually go to 68V?  When I got it all wired up and the new batteries installed, I turned the system on, the Inverter immediately went into EQ mode and the C40 started dumping.  I cranked the adjustment knob on the C40 as high as it would go and it wouldn't stop dumping.  The batteries were at 58V.  I shut off the EQ mode and the system stopped dumping when the batteries hit 56V.  What can I do to get the C40 to dump at a higher voltage?  I'm a belt and suspenders kind of guy so I really want to have a UL rated diversion system.  The hydro/PV combined into the MX works well but is a bit of a compromise.  Eventually I'd like to get the hydro running with it own controller - likely the Midnight Classic in order to get my voltage up and reduce my wire losses (long story).  When I talked to Robin at Midnight a year or so ago He told me I would need to get the Clipper unit as well which just isn't cost effective for me.  Since my low head hydro running open circuit only hits 168V I'm not sure why I need the Clipper at all if I just get the 200V Classic. 

If you want to see a bit about my system try Googling "andy's dam".  There's a Youtube video the local newspaper did on my setup.  It's kind of hokey.  You'll notice the C40 isn't wired up to the diversion yet.

Andy

[dave ames]

I'm a belt and suspenders kind of guy so I really want to have a UL rated diversion system. 

i am NOT a code guy but think our (blue book) emergency diversion setup calls for all the possible charging sources times 150% -max pv plus max hydro 1650w? so a dump capable of dumping 2475watts @ 58v..42amps. just over the continuous rating 40a of the c-40, code might want a max of 32amp loading on that controller?

could get close with two of those diversion heater units you have there. 19.3 amps each @ 58v would get us about 38.6amps dump @58 volts or about 2.2kw. WOW doz is alotta clams!

c-40 voltage adjustment: we need to check that the *jumper is on the top pins (charge controll)..find a clean place to move these tiny jumper pins over.. easy to drop it hard to find it! ..especially in tall grass
*page 20 of manual.

that resistor mod page 26 is an extra offset for NiCad batteries. we should not have to go that high..it changes the adjustment from the stock 52v - 60v adjustment to a new range of 60v - 68v for the bulk charge settings.

andy, i'd be nervous leaving the charger function enabled on that inverter/charger in this system.

looking forward to seeing that "hokey" video when i get to a better net connection..my dial-up takes 30 minutes per minute of video to download and run

cheers, dave

[hydrosun]

The reason for the clipper circuit is for protection from spikes in voltage. Starting the hydro or throwing a switch could cause a spike in voltage unless there is something to limit the voltage. That is what  the solar panels acting like a zener diode does.  I'm not sure what is in the Clipper circuit from midnightsolar but it has to be fast enough to catch transients. It probably has lots of capacitors to help slow the voltage rise and then a  fast acting fet to shunt over voltage to ground.  You could rearrange your solar panels to get the higher voltage clamping effect and use the midnight classic.
If your present open circuit voltage is 168 your best running voltage would be 84 volts. So unless you can rewire the hydro to produce a higher voltage you wouldn't gain much with the Midnight Classic.                Because of line losses the MX-60 might be letting the hydro run a bit higher to find the maximum power delivered.
Chris

[Lowhead]

Thanks Chris.  The 84-88 volts is about right where the MX60 is currently running things.  Somewhere I saw a picture of the clipper without the lid on and it looked to me like it was essentially the guts of classic sans display/cover and next to it was a bunch of giant resistors all inside a larger enclosure.  I doubt starting the hydro is going to cause me any spikes.  Its the nature of my low head unit and my "valve" to turn it on that makes it accelerate pretty slowly while it burps out all the air.  It's not like an impulse turbine.  I can see your point with a breaker suddenly switching off though.

Dave, I know my air heater is a bit undersized.  I haven't gotten my solar hot water system up and running yet but the intention is for the SHW tank to be the primary dump load eventually.  As Chris says, my PV system is currently the first line of defense if the grid goes down.  I had the air heater and C40 already so I figured it wouldn't hurt to wire it up now.  When the water heater goes online I was planning on just changing the set-point on the C40 to be a bit higher than the Aux relay on the MX60 which would be driving the SSR feeding the water heater.   The air and hot water dumps would eventually be needed for if I had a separate controller for the hydro.

I'm a bit confused with your telling me to put the C40 jumpers into top row for charge control mode. Are you sure about that?  I have it wired and configured for diversion control mode (which I assume is "dump" mode.  Also why are you nervous about leaving the charger feature enabled on the Outback?  Maybe its because I forgot to mention that I've got the C40 disabled right now?

Andy

[dave ames]

Dave, I know my air heater is a bit undersized.  I haven't gotten my solar hot water system up and running yet but the intention is for the SHW tank to be the primary dump load eventually.

SWEET..some SHW coming on line too... this system keeps looking better and better!

I'm a bit confused with your telling me to put the C40 jumpers into top row for charge control mode. Are you sure about that?  I have it wired and configured for diversion control mode (which I assume is "dump" mode. 

no mistake on those jumper settings. in the top (charge control) slot we will activate the PWM function and enable the proper voltage adjustment range.

with the jumper in the lower position the dump will try to run full on or off.

Also why are you nervous about leaving the charger feature enabled on the Outback?  Maybe its because I forgot to mention that I've got the C40 disabled right now?

hehe, yes i was in full worst case scenario with that one..was thinking the once in the never chance of  "all possible charge sources" we would have to count that charger as well for sizing our redundant emergency dump load...hogwash!

cheers, dave

[Lowhead]

Dope slap!  You are right about the jumper settings.  I made the assumption that the jumper was to switch from charge control to diversion control but now I understand.  Thanks a bunch.  I'm going to peel off the C40 re-scaling labels and move the jumper back and I should be able to set my diversion properly. 

Andy