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I recently purchased 2 working 4024 s as back ups . The guy I bought them from also provided me a flat connector that he said connects the 2 of them together . When I showed him my Vantare set up he was surprised they were not connected . So I thought if they were connected we would not need to balance the load cause we would have 8k not 4k @ side . I know they must have thought this out in advance as to why they can not be connected . So can someone explain why they can not be connected ?
If they're stacked then the output is 240VAC. Our Vantare's have no 240V loads so we'd still have to split our loads evenly to each of the two 120VAC legs. This will create unbalanced loads which put a heavy strain on the inverters' transformers. To balance the 120VAC legs across the 240VAC stacked source we need a big center tapped transformer. Trace made one for this purpose. It's the T240 Autotransformer (which can step-up, step-down, or balance the two legs), but this transformer is only rated at 3.9KVA, so we're not gaining any additional current over our unstacked 120VAC legs. The big advantage for us in stacking would be battery charging. Stacking designates one inverter a master and the other a slave. This ensures lock-step bulk, absorption, float transitions, but we'd have to install a large capacity balancing transformer or ensure that our loads are always balanced, which in our application isn't possible.
I knew you would have the answer David , Smile Now another question Mark who I bought them from said they need to be exercised once a year or I may loose the coil or transformer not sure which , your thoughts ?
Hey Al,

He's talking about the battery DC voltage stiffening capacitors. They're aluminum electrolytic and the Trace SW4024 uses 23,400 micro-farad of these things! These types of caps have self-healing properties. They can break down when left on the shelf for prolonged periods of time which results in high leakage current when first turned on. The more they're used the more they heal and return to normal functioning. I never turn my inverters off. These are industrial units built to work for 24x7 for 15 to 20 years.

My power board design removes the caps from the power board and places them on their own capacitor bank PCB - as seen in this post. This way, if the capacitors ever fail it's a very simple swap out to new.
so do I need to exercise them or not ? You see mine work and may not be needed for years .
Sure, it wouldn't hurt to power them up once in a while. They need 24VDC batteries to work but not much in terms of power. Just wire in two 12V home security batteries, or similar, in series. Or, you can forget about them and replace any faulty parts with my new PowerBoards and capacitor bank boards. Smile
so just hook them up and tern it on for 30 min or so every 6 months you say ?
After thinking about this a bit more. I don't think it's worth powering them up. The caps need to be charged and discharged repeatedly to self-heal and the only way to do that is put them under cyclical load. In our buses it happens when the AC's kick on, or the compressor in the fridge turns on, or the water pump powers up. Simply powering them on with no loads isn't going to do the caps any good. Al, I wouldn't worry about it. You can safely store them for 5 years w/o worry. If you do have issues at some point it really is simple to remove your caps and swap them out.
Good to know David , thank you . I will need to remove the # 1 inverter that trips so then 1 will be in use while I drop off the other for repair . wish it was easy to remove as the BB but such is life .
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