12VDC inverter system

Jun 04, 2008 8 Replies

We have a customer who owns a series of 24 and 30 unit apartment buildings. Presently on each floor as per local requirements there are several self contained emergency lighting units. Some of these are equipped with a small 6V battery and just two low voltage lamps that aim in different directions down the hallway, while other larger units having larger batteries sometimes might have as many as six 12volt lamps wired remotely. These all are equipped with sealed lead acid rechargeable batteries which need to be replaced every few years. Two of his buildings are exceptions though and don=92t have this type of lighting. In these buildings, the hallway lighting circuit is wired through an inverter system. This system, which was built by a company in Massachusetts many years ago is installed in the boiler/electrical room, and consists of two 12VDC to 120VAC 450W solid state inverters operating in parallel and two group 24 size wet cell automotive batteries. There is a built in charger and a huge contactor which drops out upon loss of AC and applies 12VDC to the inverters. Loss of AC will cause the load to toggle over to the inverter outputs and the hallway lighting circuit remains powered. Maintenance on these two buildings is minimal and his ultimate cost savings projection becomes significant when multiplying installing this type of system into the



100=92s of buildings which he presently owns. He has asked me to look into finding this type of equipment for him to retrofit his other buildings. The typical load is about 400W CFL and will probably never exceed 550W. I don=92t know how picky these particular 13W CFL units are to anything other than sine wave AC. I know sine wave or even modified sine wave will probably increase cost somewhat. Does anyone have any ideas for inverter systems equipment they might be able to share with me? Thanks, Lenny.

How bout salvaging some old computer UPS from the local dump or advertize to relieve folks of their defunct units for recycling

al

Whatever he gets will need to be inspected and approved. The regs in most municipalities are much more stringent in commercial buildings. I don't think he's going to convince Codes that a solution based on salvaged, repurposed pc hardware is going to do the trick.....

jak

CFL's _Shouldn't_ be picky about power. They are usually always rectified to DC inside.Sine,Square,sawtooth even-it doesn't matter to the rectifier.

news:alt.engineering.electrical would be a better place to ask.

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I'm not too convinced by that argument. The inverter squeezed into the base of these lamps, is by necessity very small, which only allows for a filter cap of around 10uF. It is often this cap that fails in these lamps, so clearly, it is stressed already, by the heat, and the job it's trying to do filtering the raw DC from the reccy. I reckon that if you start hitting it with a real bad shaped waveform, it might be just a bit too much for it. Bear in mind also that these things are inherently electrically noisy, and only just about squeeze by the RF emission regs - at least here in the UK - with a sine wave going in. With a rough wave being supplied, they might just kick up enough radiation, to cause a problem.

Arfa

A lot of these low wattage CFLs where the ballast is part of the fixture still use magnetic choke ballasts. In my experience they do still work on inverters, but they tend to buzz and are more reluctant to start.

You might find it helpful to look about RV supply places. There are a number of (often somewhat spendy, unfortunately) inverter/charger units available that do it all automatically and have decent sine wave outputs. Basically, they just hook up to the AC input, battery, and output, and will charge the battery as needed when AC is around and automatically switch over to inverter mode when AC is removed--essentially a UPS circuit, really. I'd trust them to work reliably in an emergency more than I'd trust a cheap no-name inverter.

Andrew Erickson "He is no fool who gives what he cannot keep to gain that which he cannot lose." -- Jim Elliot

There are going to building codes issues that will mandate some sort of purpose-built commercial solution to your problem. IME, you won't be able to home-brew something of this sort. The potential liabilities if someone is hurt in an emergency situation are too great...even if it can't be directly attributed to the performance of the system.

I'd just google 'emergency lighting' or 'backup lighting'; see which companies supply such things and bite the bullet. In fact, having just done so ("emergency lighting"), I got 1,940,000 hits. I'll bet there's an answer there somewhere. For instance, is one of the top results. Clicking that site, then category 'inverters' shows about

40 different products.

jak

jak

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