Yes Frackers, totally doable.
Will be helping a local to do the same thing shortly.
There is no real difference with the boards, just the programming, which can be gotten around easily anyway.. simply bypassing the current tranny with some length of wire will make it whatever wattage you want.... but I advise making your own fan control in this case, as it wont l know that your doing 4000w instead of say 2000w, and won't drive the fan on until it gets to 50C or more. I would be wary of bypassing more than 50% around the tranny.. as the peaks will be well up in the 20kw area on wild occasions... and it will do it too..., but it allows for severe power for long periods... if you cool the fets ( easy to do) and your trannies are big enough to take it for long periods.
My home drive inverter is three torroids from aero sharp 1.5kw grid tie inverters, they are really much larger than that in this use, as using 6 or 7 kw for long periods is very unlikely.
The 8kw power board is electrically the same as the 15000w board, except for the heat sink size, and fet spacing, and a tiny ferrite bead on the leg of the fets.
If you can get hold of dud grid tie units with galvanic isolation ( heavy units, not the light ones) you will have a cheap torroid.. I can buy them over here for $40 a piece, don't know over there, but if they ran aerosharps or inspires over there there should be a few around if you get hold of installers..
So you need the control board and power card... transformers for the size you want, a ferrite filter and a box to put it in... it is that simple.
I use 100amp fused input..... as it won't blow until near 200A, and will protect the input wiring from the bank. I don't use over 5kw for long periods... maybe 10 mins etc, so it is big enough
I use a 6kw rcd on the output, only blown it once when I was over 8kw for a few minutes.... very abnormal, a 200a shunt for the current measurement if you want to see whats going on
Then whatever monitoring stuff you want ( and I know you will have this part computerised )....... an on /off switch, a box and thats about all.
Help is a post away.
Here for less than $600, I have a very solid unit that has now done many mega watt hours without any problem at all.
My fan control has two fans in push pull through the larger heatsink, and don't run most of the time.... when the hot water is on they will breifly turn on and off at varied speed, and keep the sinks down to about 38C, transformer can get up to 45C if it has large loads for long periods ( few hours etc.. eg hot water runs for about 2.5hrs/ day , plus all the house loads) so I can hear it come on if I'm in the shed at this time ( between 10.30am and to about 1pm) It is usually doing the HW, washing machine, fridges freezers and water pumps and telly at the same time.... and a few intermittant 2500w jug events for coffee... it does not care in the least.
I usually have up to 1.5kw of grid tie there as well, and can boost that to 4.5kw if I want too.
I do NOT use it as a charger or automatic UPS, and suggest you do not as well...... as an inverter, it has proven to be rock solid, but read the red writing above for why I dont.
If you want to use quality ( old type) welding transformers, you will probably get pretty reasonable idling results too, but no where near the torroids, but respectable none the less... better quality laminates mean lower magnetising current.
The W7 is a very decent unit... except for the transformers. They are programmed with better time outs for heavy power.. ie pj 8000w will cut out after 12 seconds or so at full power, the W7 will just do it's 6kw honestly continuously... so replace the trannies with better quality steel, and a filter and you will do ok....a few choices...
.................oztules
