MPPT and bus bars in steel cabinet?

[pda1]

I'm inclined to put all of the solar controls into a steel cabinet and run the #2 wires to my multiplus 24 2000 which will be mounted next to the steel cabinet (with a door on it)
Put some fans in there to cool the equipment.

Why? I want to contain a fire in the event something bad happens.

Any opinions?

 

[Ampster]

I want to contain a fire in the event something bad happens.

The typical fire containment consists of depriving a burning object of the oxygen it needs for combustion. However with Lithium batteries with Cobalt in the chemistry, when they overheat, they create their own oxygen so that concept will not work. Your fire suppression strategy should be consistent with the battery chemistry. The best was to contain a Cobalt based Lithium battery fire is to cool it off with lots of water.

It is not an issue with LFP because LFP does not produce oxygen but the electolyte will burn if the cell is punctured. So the strategy for LFP would be different than for a Cobalt based Lithium battery or cells.

 

[pda1]

I'm not concerned, for the moment, about the batteries.

Appearance and fire safety are the major concern.

Most installations I've seen photos of look like wiring rats nests installed on flammable materials. "It wont happen to me" isn't something worth considering.

My controls are installed in a concrete floor and concrete block basement not too near combustibles- except the floor and floor joists in the ceiling.

The idea is just to put the MPPT, bus bars, fuses, disconnects (well, maybe not them) in a steel cabinet then route wires over to the Multiplus. The batteries can sit on the floor.

 

[Ampster]

Most installations I've seen photos of look like wiring rats nests installed on flammable materials.

Yes, wrong size wiring and incorrect over current protection is a risk. Remember, the fuse or breaker should be sized to protect the wire and wire size is important.

 

[pda1]

Well, principally I meant by that comment- "poor craftsmanship"

 

[timselectric]

Wiring,
If done properly, with the correct protective devices in place. Is not a Hazzard during normal operation.
No different than the romex in the walls, floors, and ceilings of your house.
The key is to avoid abnormal operation and the possibility of physical damage.
These are the two things that create a Hazzard.

 

[OffGridForGood]

first line of defence: correct use of equipement, using correctly selected wire, connections, fuses and breakers.
second line of defence: monitoring the sytem to ensure normal operation within expected capacity
third line of defence - build the whole thing 100 feet away from the house in steel building with smoke and heat detectors, exterior siren.
forth line of defence - stand back and let it burn from a safe distance?!

 

[OffGridForGood]

I suppose you could set up an auto shut-down of DC AC everything based on a signal.
Spray liquified CO2 on it after the disconnection process.
I feel the welders & cutting torch set is a far greater risk and it just sits in the corner pretending not to be there. - nothing like a couple bottles of compressed oxygen at 2000psi to get the party started !!

 

[SilverbackMP]

Like my setup? Probably wouldn’t contain a major fire but would slow it down. Might contain a small fire though. Walls (inside to out) of power shed have 5/8 type X drywall, then 3/4 ply, then mineral wool, and then closed cell foam (not really the best for fire), and then strapping and metal.


You can get cabinets with solid doors too.

Also note the shelf reinforcement via all thread in the middle of the shelves. The manufacturer’s assessment of their shelf weight capacity rating seemed to be quite generous.

My buss bar box (MidNite Solar 2000 Amp Battery Combiner Box) is attached via “ass hole” connecters to the main cabinet.



Outside of shed:

I probably would have gone with solid doors if I had it to do over. The holes in these are big enough for mice to come through and I need to add a layer of hardware cloth to the back of the cabinet doors at some point.

Now I just keep a copious supply of the highly effective green rat balls in place (the good kind found at local grain buyers/commercial bins; MFA in my case). I have a rather large supply as part of my preps. It’s one of the things often overlooked. Sanitation and pest control. But I digress.

 

[webbbn]

Wiring,
If done properly, with the correct protective devices in place. Is not a Hazzard during normal operation.
No different than the romex in the walls, floors, and ceilings of your house.
The key is to avoid abnormal operation and the possibility of physical damage.
These are the two things that create a Hazzard.

I think the "if done properly" is the issue. You do see alot of exposed wiring bolted to and exposed to wood, which seems like a bad idea. I don't know of any situation where code allows AC wiring junctions to be exposed to wood structures. 200A+ at 50V DC connections pass much more power than a 120V 15A AC.

 

[timselectric]

I think the "if done properly" is the issue. You do see alot of exposed wiring bolted to and exposed to wood, which seems like a bad idea. I don't know of any situation where code allows AC wiring junctions to be exposed to wood structures. 200A+ at 50V DC connections pass much more power than a 120V 15A AC.

The voltage makes the difference.
The ability for electricity to jump a gap between conductive materials. Is determined by the voltage available.
It's not the wood that is a problem. It's personal safety. (Human exposure)
Above 80v is deadly , for people. It's enough to stop your heart.
Wood is a good insulator (if not soaking wet).

 

[pda1]

first line of defence: correct use of equipement, using correctly selected wire, connections, fuses and breakers.
second line of defence: monitoring the sytem to ensure normal operation within expected capacity
third line of defence - build the whole thing 100 feet away from the house in steel building with smoke and heat detectors, exterior siren.
forth line of defence - stand back and let it burn from a safe distance?!

The 3rd line of defence is exactly what would be best. Confounded LifePo4 batteries and their temperature restrictions! Darn DC needs wires 3 feet thick to do anything!

 

[pda1]

Like my setup? Probably wouldn’t contain a major fire but would slow it down. Might contain a small fire though. Walls (inside to out) of power shed have 5/8 type X drywall, then 3/4 ply, then mineral wool, and then closed cell foam (not really the best for fire), and then strapping and metal.

View attachment 168766
You can get cabinets with solid doors too.

Also note the shelf reinforcement via all thread in the middle of the shelves. The manufacturer’s assessment of their shelf weight capacity rating seemed to be quite generous.

My buss bar box (MidNite Solar 2000 Amp Battery Combiner Box) is attached via “ass hole” connecters to the main cabinet.

View attachment 168768
View attachment 168770
Outside of shed:
View attachment 168771
I probably would have gone with solid doors if I had it to do over. The holes in these are big enough for mice to come through and I need to add a layer of hardware cloth to the back of the cabinet doors at some point.

Now I just keep a copious supply of the highly effective green rat balls in place (the good kind found at local grain buyers/commercial bins; MFA in my case). I have a rather large supply as part of my preps. It’s one of the things often overlooked. Sanitation and pest control. But I digress.

NOW we're getting somewhere! Cost per kW? $50.....but it's fun!

 

[webbbn]

The voltage makes the difference.
The ability for electricity to jump a gap between conductive materials. Is determined by the voltage available.
It's not the wood that is a problem. It's personal safety. (Human exposure)
Above 80v is deadly , for people. It's enough to stop your heart.
Wood is a good insulator (if not soaking wet).

Spark gap distance is determined by voltage, but the distance is so short for either voltage that it's not really significant. What is significant is the amount of power you can deliver with short X/0 wires compared to long 14 awg wires. DC arcs also are much worse than AC arcs due to the sustained breakdown of the insulating air gap.

Obviously most of the rules for AC wiring are to prevent shock, but there's a reason that junction boxes can't be made out of combustible materials, and there are different rules for gaps and such when boxes are installed surrounded by a combustible surface.

We use fuses and breakers, proper fittings, and torque down connections to prevent arcs and overheating due to excess resistance, but there are plenty of examples of catastrophic failures that could start a fire. It can't hurt to add another layer of protection.

 

[SilverbackMP]

Spark gap distance is determined by voltage, but the distance is so short for either voltage that it's not really significant. What is significant is the amount of power you can deliver with short X/0 wires compared to long 14 awg wires. DC arcs also are much worse than AC arcs due to the sustained breakdown of the insulating air gap.

Obviously most of the rules for AC wiring are to prevent shock, but there's a reason that junction boxes can't be made out of combustible materials, and there are different rules for gaps and such when boxes are installed surrounded by a combustible surface.

We use fuses and breakers, proper fittings, and torque down connections to prevent arcs and overheating due to excess resistance, but there are plenty of examples of catastrophic failures that could start a fire. It can't hurt to add another layer of protection.

You realize Tim is an electrician with like 40 years of experience right?

 

[webbbn]

You realize Tim is an electrician with like 40 years of experience right?

Yes, and I'm sure he knows about house fires cause by improper wiring. FWIW, a quick google search indicates there are more deaths due to electrical house fires than due to household electrocutions, but that's beside the point. The point is that keeping high-current electrical connections away from flammable materials improves safety.

 

[timselectric]

There are always more levels of protection, that can be applied. But you have to weigh the likelihood against the cost and effort.
Enough Voltage can create a arc across a gap. And enough amperage can sustain the arc.
Too much amperage on a conductor will create excessive heat.
Both of these conditions can cause a fire.
My point is that a battery built in a wooden box or frame, isn't a problem. As long as it's done properly.
Can you build your system in an underground concrete bunker, and feel safe? Yes
Can I build my system in my bedroom and feel safe? Absolutely.
You don't have to be afraid of electricity, but you do have to respect it.

 

[timselectric]

a quick google search indicates there are more deaths due to electrical house fires than due to household electrocutions,

Yes
And 95% of those fires are due to improper use of extention cords, power strips, and space heaters.
Not the house wiring.

 

[tinyt]

ALso in my to do list

 

[pda1]

ALso in my to do list

That's a nice cabinet. Didn't find the thickness of the steel.

TinyT, you have a nice array!

My wish is to put everything except the Multiplus into a steel cabinet. The MP is best suited for a wall mount separately.

We shall see.