Axpert invertors

savage said:
Always blows my mind that people are willing to spend 100K+ on PV, Inverter, & Batteries, but skimps out on a R7 fuse for protection and safety... :whistle:
Click to expand...

Chris, can you then advise me. I have a small solar system that only run a couple of 12v down lights in the house. It is a 200W 12v panel, 5 X 7.2AH batteries and a charge regulator. I have put three car fuse holders with these blade fuses in. One between the panel and regulator, one between the battery and regulator and one between the load and regulator.

Will these type of fuses work and are they sufficient or must I rather get other types of fuses that is suitable for solar systems?

Thanks
 
Load and regulator, presuming you are using 220VAC (which I doubt), use circuit breakers...

Otherwise yes, fuses on the batteries and the PV panels are a great idea. Not knowing the ratings of your batteries, PV panel, inverter, or fuses, I can't really help further.
 
savage said:
Load and regulator, presuming you are using 220VAC (which I doubt), use circuit breakers...

Otherwise yes, fuses on the batteries and the PV panels are a great idea. Not knowing the ratings of your batteries, PV panel, inverter, or fuses, I can't really help further.
Click to expand...

No I am not using 220VAC. It is a 12v setup. These are the things installed:
1 X 200W 12v panel;
5 X 7.2AH batteries (I am looking for a 105AH battery);
1 X 40A ECCO charge regulator;
15 X 4W 12v down lights;
3 X 20A car fuses

Thanks anyway.
 
savage said:
Always blows my mind that people are willing to spend 100K+ on PV, Inverter, & Batteries, but skimps out on a R7 fuse for protection and safety... :whistle:
Click to expand...

Hi,

I think Savage is asking a legitimate question. If the short-circuit current is hardly more than the normal operating current, how do you select a fuse that will blow when the wires are short circuited but not blow in normal operation?

You can only get fuses with certain round-number ratings - 5A, 10A etc. If the short-circuit current is 8A then a 10A fuse won't blow in the case of a short. If the normal current is >5A then you can't use a 5A fuse either.

So there is no available fuse that will be effective.

Its not about being cheapskate.

Steve
 
Lets say you have 5 strings
Short current on each string is 8 amps fit a higher fuse on each string
Lets say one of the strings gets shorted at the pannels all the other strings dumps thier current into this shorted pannels 4 x 8 amps = 32 amps
 
Commercially made solar panels over 50 watts have 10 gauge wires capable of handling up to 30 amps of current flow. If you connect these panels in series, there will be no increase in current flow so fusing is not required for this string. This is not the case when you have panels connected in parallel, as when connected in parallel the system current is additive. For instance if you have 4 panels each capable of up to 15 amps, then a short in one panel can draw all 60 amps towards that short-circuited panel. This will cause the wires leading to that panel to far exceed 30 amps causing that wire-pair to potentially catch fire. In the case of panels in parallel, a 30-amp fuse is required for each panel. If your panels are smaller than 50 watts, and use only 12 gauge wires, and 20 amp fuses are required.

As most panels come with 6mm2 (10 gauge) cable, a 30A (Max) fuse isn't a bad thing. I generally install 10A fuses as the panels won't exceed it, and the moment it DOES get exceeded, the panels and cabling to the panels are protected. If I have three strings (8A each), each string will have it's own 10A fuse, and a 30A fuse between the combiner box and the charger / inverter.

If you only have one string, then obviously it's not an issue. If you have multiple panels and multiple strings, you will have an issue. It also becomes an issue in terms of maintenance for example in that with fuses (disconnects), you can easily remove one or more strings from the controller without causing major issues and surges...

EDIT: You also want to use a fast acting, ceramic fuse. Normal glass fuses may break (blow up) which is a nice mess to clean up in a fuse holder. If you have 10 x 40Voc panels in a string, then that's 400VDC, so use a voltage rating a bit higher than 400V.
 
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Hi There
Can anyone on this thread please advise approx cost of the axpert 5000va/4000w model; and a reputable suppliers in Jhb?
 
I'd like to know the Lifespan of the original Axpert inverter as well as the copy ones ? 5 years is my guess ...
 
Why dont you guys buy it via someone who have a rectron account
 
The_Traveller said:
Lifespan ?
Click to expand...

If you properly install and handle the product, my guess would be decades. There is no reason for it to fail after only 5 years of use. The internals are well constructed and obvious components issues (capacitor quality) are addressed as well. My 5kVA unit uses Nichicon electrolytics internally, so no issues there. The fans are of a high quality and run at low spin-rates. Heat flow is well managed and the unit rarely exceeds 40°C operating temperatures at current (winter-time) ambient. All indicators of a product that has been designed to last a long time.

Batteries are a different story - I sprung for the lead-crystals with a design life of 12 years if I manage to maintain DoD (depth-of-discharge) of no more than 50% per cycle.

--deckert
 
Axpert MKS 5kVA inverter installation

Hi,

I installed one of these Axpert MKS 5kVA inverters over 4 days (two weekends). Here's my story.

(Disclaimer: I have an EE background; working on mains electricity can be lethal - get professional advice first. See my list of essential and life-saving equipment at the bottom of my next post)

My main aim was to just survive load-shedding with an option to add PV solar panels at a later date, should I choose to. The 3kVA and 5kVA units just appeared on the Rectron price list, so I ordered a 5kVA. The 3kVA unit runs on 24V and has a max PV capacity of 600W. The 5kVA runs on 48V and has a max PV capacity of 3000W - the 5kVA was a no-brainer choice.

I decided that I wanted the inverter fully integrated into my house wiring, carrying only "low current" devices. All the "high current" stuff, like geyser, oven, aircon and washers (wetter and dryer) would be driven only from the municipal feed. That effectively left the rest of my house to be carried by the 5kVA inverter (note: I have gas stove for cooking).

The first task was to split my DB into high-current and low-current sections. I was lucky that it was almost 80% ready for that - just had to cut my Live busbar and pull through a few wires towards my washer appliances.

DB-busbar-cut.jpg

Here are the two sections along with the earth busbar:

DB-sections.jpg

I used 6mm² fixed-wire cable from Aberdare, rated at 43A (SANS tested and rated), to wire the DBs together as well as for the internal wiring. This is ample to/from the Inverter, which is itself rated at 27A on the 240V side.

Next, I had to add a second DB to house all the safety and change-over switches in order to by-pass the inverter for any reason. My Generator by-pass switch is also housed in this same DB:

2nd-DB.jpg

From left-to-right, the switches are: Inverter isolator, inverter-bypass, generator-change-over, inverter output trip switch. Can you spot a problem? Yes, the isolator on the left should be a beaker (more on this later).

The connection on the inverter itself is pretty straight forward. Bend the cables so minimize stresses and make sure all the strands are bunched in two layers to fit into the screw terminal blocks of the inverter. Any screw terminal connection must be mechanically strong and sound. You don't want bad contacts spoiling your day.

Next, make sure everything is accurately labelled:

2nd-DB-labels.jpg

At this point, the inverter will not fire up yet - it needs to have a floating DC supply before it will switch on. However, this is where I stopped and took a breather. I could flip down the inverter by-pass switch to test what I already had so far and make sure that part worked as expected.

I plugged in my 3-pin outlet tester and verified that my existing and new wiring was working and everything was wired correctly. The 30mA earth-leakage was also tested to be working. This is an essential testing tool; I bought mine from Communica at a sale for R35.

Next was installing the batteries and associated cabling. I used 25mm² flexi cable (basically the same stuff used for welding). The Aberdare spec says this stuff is rated at 104A DC:

25mm2-cable.jpg

I tested the cable over a 3m length with a 30A load. It dropped about 150mV over 3m, which means (using ohm's law) it has a 5mΩ resistance per 3m length. At 100A that would mean that I would drop half a volt over the length of the cable - so the aim was to keep it as short as possible. I ended up using two 1.3m lengths (one for positive, one for negative) towards the batteries.

The connections on the ends need to be really sound - make sure you get a proper ring connector and crimping tool for the job. The Axpert manual is very clear and helpful in specifying exactly the connector types you need. The crimping tool is a different story: it's way expensive. I was fortunate to be able to borrow my company's crimp tool:

crimp-tool.jpg

Don't skimp on this part! The DC currents drawn by this inverter is in the order of 86A - that's a lot of energy (the 3kVA is even higher at 100A). If your DC connections and cabling is not adequate you will have a guaranteed fire hazard!

Continued in next post (due to the silly 6-attachment limit... urgh) ....

--deckert
 
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