Out back FM80 sizing and PV panel config help needed.

bigdogeat

Interesting. I've actually looked into do some experiments with heat exchangers. Thanks for the info and advice. Much appreciated. BTW, the PV system was cranking out some juice today on it maiden voyage with the new configuration. Not sure when it happened but it tripped my 100A breaker that I have between the outback controller and the batteries. I thought the FM80 was limited to 80A output  so I thought it would never trip. I just use it as a disconnect in case I need to work on things etc. Could the breaker be a little off calibration? Or is it something different? The 80A breaker between the panels and the Outback was not tripped.

mike95490

Solar charging is a very demanding, constant load. cheap breakers are often thermal activated, and a long slow cooking can trip them,

Good DC breakers, rated 100% are expensive, but work.

Raj174

Hope you're using a #4 AWG cable for that connection. What is the breaker mfg and model #.

bigdogeat

Got it. And yes, using #4 AWG from the controller to that breaker and 1/0 from that breaker to the batteries. Not sure of the make and model of the breaker. It's probably on the back but I'd have to take it out to look. When my 300A breaker comes in I'll probably just take the 150A that is getting replaced and installing it in place of the 100A breaker.

Raj174

The #4 cable will no longer be protected from meltdown with the 150 amp breaker. It's only rated to 95 amps for THHN. The MNDCE80 made by Midnite Solar is a dependable, quality replacement DC rated breaker, at about 15 bucks.

http://www.midnitesolar.com/productPhoto.php?product_ID=197&productCatName=&productCat_ID=16&sortOrder=13&act=p

Dave Angelini

At some point the person here is going to listen or have a fire! The cable may survive only to burn the structure down if the FM80 has an internal fault. When in doubt read the manual.....

bigdogeat

Thanks for the productive info Raj174.

Dave Angelini, I have read the manual thank you. It says the FM80 is limited to 80 amps output. Is that not correct?

Page 5 "FLEXmax 80:  80 amps maximum continuous output current"
Page 8 "The output current limit of the FLEXmax 80 is 80 amps."
Page 26 "The default charger output current limit setting is:  80 amps for the FM80"

Why would the experts above tell me to wire the panels in a configuration that will produce more than 80 amps if it would just keep tripping the 80 amp breaker?

bigdogeat

Raj174, do you happen to know a surface mount style circuit breaker that would work? 

bigdogeat

Not that it makes it right, but the #4 cable is extremely short. About 9 inches before it hits the breaker. The manual says up to #2 wire from the Outback and I would have loved to use #2 wire, but that is impossible with the lug hole size and the odd angle they make you wire it at. 

Vic

Hi bigdog..,

You are probably using a Thermal type breaker.   This type breaker is generally a marginal "solution" on our battery-based solar systems.

They have a fairly large sensitivity to operating temperature.  There are many of these surface-mount breakers are now coming from China.   You will probably want high quality breakers for the PV in,  CC output,   AND the one between the Inverter ant battery.

Believe that the "fire" reference was for your proposed use of a 150 A breaker on the #4 AWG cable twix the CC and battery.

You have a medium-sized system.   There are reasonable risks of fire,  unless one is careful in what devices are used to protect cables,   especially during Fault conditions.   Breakers (and fuses) are in circuits,  to protect CABLEs,   generally not devices.

Here are a couple of Links to quality DC breakers and enclosures that accept them:
https://www.solar-electric.com/midnite-solar-150-volts-80-amps-dc-panel-mount-circuit-breaker.html

https://www.solar-electric.com/midnite-solar-150-volts-60-amps-dc-panel-mount-circuit-breaker.html

Here is a box that is used to mount these inexpensive breakers:
https://www.solar-electric.com/mnedc-quad.html

For the Inverter breaker,   a bit more info would be required.

FWIW,   Good Luck,    Vic

bigdogeat

Vic said:

Hi bigdog..,

You are probably using a Thermal type breaker.   This type breaker is generally a marginal "solution" on our battery-based solar systems.

They have a fairly large sensitivity to operating temperature.  There are many of these surface-mount breakers are now coming from China.   You will probably want high quality breakers for the PV in,  CC output,   AND the one between the Inverter ant battery.

Believe that the "fire" reference was for your proposed use of a 150 A breaker on the #4 AWG cable twix the CC and battery.

You have a medium-sized system.   There are reasonable risks of fire,  unless one is careful in what devices are used to protect cables,   especially during Fault conditions.   Breakers (and fuses) are in circuits,  to protect CABLEs,   generally not devices.

Here are a couple of Links to quality DC breakers and enclosures that accept them:
https://www.solar-electric.com/midnite-solar-150-volts-80-amps-dc-panel-mount-circuit-breaker.html

https://www.solar-electric.com/midnite-solar-150-volts-60-amps-dc-panel-mount-circuit-breaker.html

Here is a box that is used to mount these inexpensive breakers:
https://www.solar-electric.com/mnedc-quad.html

For the Inverter breaker,   a bit more info would be required.

FWIW,   Good Luck,    Vic

See Dave, now that's how comments are supposed to be. : ) Much appreciated Vic.

I do have breakers for the PV in,  CC output,  AND the one between the Inverter and battery just as you suggested. It is wired just like the schematic in the manual shows. However, you are right, the breakers are probably from China. The system started off as a small experiment just to become familiar with solar power, but has grown as I have had really good results. Probably time to invest in some better breakers. I just wish there were good surface mount units available. They take up way less room in my enclosure. (Which is now getting pretty full with the Outback upgrade and the big inverter upgrade.)

mike95490

bigdogeat said:

Why would the experts above tell me to wire the panels in a configuration that will produce more than 80 amps if it would just keep tripping the 80 amp breaker?

Because that is not what will happen, and the large 100A breaker will not protect the 80A wire from a fire, if the Controller shorts internally and is connected to the battery, the 80A breaker will trip and prevent a fire.

Under a normal happy solar day, the Controller will limit itself to 80A, and not exceed that.   You may occasionally get a nuisance trip, which a 90 A breaker and using #2 wire would prevent.

here is a link to a NEC wire table.  Note that the type of insulation can play a large part in the amps the cable can take.

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

You could use a high rated #4 (95A) wire with a 90A breaker.

MNEDC90 $20.00  http://www.midnitesolar.com/productPhoto.php?product_ID=197&productCatName=Breakers&productCat_ID=16&sortOrder=13&act=p

But don't start a fire.

bigdogeat

Right on. I get it. Point taken. My real point was that my breaker obviously was tripping before its rated load. I appreciate all the feedback.

My particular issues are that a) with upgrades, there isn't much room in the enclosure to mount three breaker boxes and b) that is another several hundred $ in panels and breakers and c:) those panels are only recommended for #4 wire or smaller and all my other wire is already 1/0 so there is even more expense.

I'm obviously at a point where I will have to do some pretty major modification to the system including a new enclosure, new breaker boxes, new breakers, and (perhaps ironically), smaller longer cables.

Vic

mike94--., mentioned,

"   ...  

You could use a high rated #4 (95A) wire with a 90A breaker.

MNEDC90 $20.00  http://www.midnitesolar.com/productPhoto.php?product_ID=197&productCatName=Breakers&productCat_ID=16&sortOrder=13&act=p

   ..."

IMO,   would never suggest using a 90 A breaker on the output of an 80 A rated output of a CC.

At least one reason for this,   is that the breakers that we all use in these circuits,  have a maximum rating of 75C for cables connecting to the breaker terminals.   Even cables with a higher temperature rating (like THHN) would not raise this max temperature,   so we must use the 75C column in the Ampacity Tables.   Just another technicality,  IMO.

The MidNite (and Outback)  DC breakers are rated for continuous currents at/below the Handle Rating of the breaker,   so neither the MNEDC,  not MNEPV breakers need the customary 80% de-rating for continuous currents.

You know all of this,   but  just trying to be clear.   IMO,   FWIW,   Vic,   NOT a real NEC Code whiz ...

bigdogeat

Maybe I could use a DIN rail for the breakers to save some space? Thoughts?

Dave Angelini

Why not just use what the CC manufacture suggested and move on?

Vic

bigdogeat said:

Maybe I could use a DIN rail for the breakers to save some space? Thoughts?

OOOPPPPpsssss,   I let the mouse cursor touch the quote,   and,   of course this means that the ENTIRE reply to the quoted comment looks like a quote  ...    gotta  just LOVE it ...

REPLY FOLLOWS:

YES,   the MNEPV breakers are fine.   They fit into a bit smaller conduit box  --  BabyBox,   and BigBaby box.   Would advise trying to avoid using

the BabyBox,   as there is a limit to the maximum conductor and breaker size for it.   Would suggest not trying to fit more than two DIN breakers into the baby box,   as routing cables in it is quite cramped.

There is a limit in the largest breaker that either of the baby boxes can accept  --  63A.   This may well be due the difficulty in routing larger cables that would customarily be used with higher-rated breakers.

You may not need to have your system inspected,  or comply with Codes.   As you know,   the MNEPV DIN Rail)  breakers are available in 80,  and 100 A  ratings,  but,   both of these breakers are double-wide (they are two breakers in parallel,   with their handles,  tied).

If you could possibly accommodate the MNEDC breakers,   in the MNDC Quad box,  possibly mounted right next to your existing box (by using a close or short conduit nipple),   this might work fine,   and actually be simpler to install,   than a baby box with MNEPV breakers ...

Just more opinions,   again,   Vic

bigdogeat

Did you read the question Dave? Obviously Vic did.

I am trying to learn and I am asking questions. Trying to do it right with the resources I have. I do not recall the CC manufacturer stating a particular breaker in the manual. It just says 80 adc maximum circuit breaker. So I'm trying to figure out which is best for my particular situation.

If you are not going to be helpful, please don't post.

bigdogeat

I guess using 1/0 cables is going to end up biting me in the butt. I was trying to be prepared for the future, but I guess it was overkill.

bigdogeat

Dave Angelini said:

Why not just use what the CC manufacture suggested and move on?

Why don't you tell me exactly what that is and where you found the information please. That would be helpful.

Raj174

You might want to consider getting an Epanel at some point. They make mounting breakers of various types and sizes for specific equipment and their connections easy. They can be expensive, but there are some that can be had for decent price.
I paid about $350.00 for the one I have. It made my install a lot easier and more compact. Photo below: AC bypass breakers top left, 80 amp battery and PV breakers top right and inverter breaker bottom left. 

Photowhit

bigdogeat said:

Why would the experts above tell me to wire the panels in a configuration that will produce more than 80 amps if it would just keep tripping the 80 amp breaker?

First, most of us here are 'handy man' experts. Most of the people corresponding have setup or helped setup a dozen or 2 dozen systems or so.  Dave actually is in the business and makes a living doing this. While he and I don't always agree, I would defer to him generally.  It's good to have him around.

I think all of the configurations suggested, will have much less than 80 amps coming into the charge controller. Typically  you will have higher voltage and less amperage. While the charge controller is only capable of outputting 80 amps and will self limit the output to a safe level for it's circuitry.

bigdogeat said:

My particular issues are that a) with upgrades, there isn't much room in the enclosure to mount three breaker boxes and b) that is another several hundred $ in panels and breakers 

I will soon have 3 charge controllers hooked up to my system, I don't need separate breaker boxes. I use what I think is the smallest E-Panel Midnite makes, it might be the same one that @Raj174 is showing, only his is setup for 240volt and AC breakers. I currently have 2 arrays coming in with a breaker for each before the go out to the charge controller and then back to another breaker, before going to the battery. there is plenty room for the third breakers in coming and out going. I have since added a large 100 amp Din rail breaker for an 1100watt inverter I use for outside things.  As well as the 175 amp breaker for the home inverter.

This box is normally used for AC breakers as well.


Midnite also makes a line of DC breaker boxes, they could handle these as well;


While not cheap, around $200 and they come with the large breaker for your inverter, link to NAWS Power Centers;

https://www.solar-electric.com/catalogsearch/result/?q=midnite+DC+power+center

They also make Combiner boxes for multiple arrays, I redid a commercial combiner box for my 2 arrays, If you need to split them up, it's worth looking for Older Outback combiner boxes (PV12?). I picked one up and hope to swap this one out and use it with the new array which I hope to switch for other uses during the year. perhaps a stand alone Mini-Split assist air conditioner!


Glad to see your trying to figure it out and be safe!

mcgivor

bigdogeat said:

Maybe I could use a DIN rail for the breakers to save some space? Thoughts?

DIN  rail breakers are great for adapting to specific needs, due to unavailability of commercially  manufactured boxes such as the E panel, I had to make my own. The companies I searched had DIN rail breakers up to 63A, over that  they are moulded case, Midnight do have some but since I required 60A, 63A was acceptable in my case that's what I aquired 

littleharbor2

Square D QOU breakers are DIN rail mount and are DC rated 

Dave Angelini

bigdogeat said:

Dave Angelini said:

Why not just use what the CC manufacture suggested and move on?

Why don't you tell me exactly what that is and where you found the information please. That would be helpful.

The Outback FM80 manual 

bigdogeat

Looks very nice. What size inverter breaker do you run?

mcgivor

For the inverter breaker I really wanted to use the Schneider DC distribution panel but it would have been a special order, with shipping it would have been over $500, so improvisation was employed, a regular box with a window cutout and a 225A DC breaker total cost  < $35. There is a 150A fuse at the battery  so the breaker is merely a means of disconnect.

Photowhit

@mcgivor, Where did you find a 225 amp DC breaker for cheap?

If he was asking me, I'm using a 125 amp breaker, per manual...

mcgivor

Photowhit said:

@mcgivor, Where did you find a 225 amp DC breaker for cheap?

If he was asking me, I'm using a 125 amp breaker, per manual...

The breaker was ordered directly from the manufacturer Feeo, they are strictly a solar component company, the products are very well made despite being from China.

bigdogeat

Thanks for all the input everyone. Very helpful. And thanks to the hosts of the forum. I think I'll end up buying the box and breakers from them.