12VDC inverter system

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

A couple of points that immediately come to mind.

1. In the UK batteries for such a system need to be replaced at 5 yearly intervals which stops the running costs being minimal.
2. you can't use "mains rating" for cables carrying 12v. You need to work out the voltage drop over the length which, for a 12v system probably shouldn't be more than 1v.

Does anyone have any ideas for inverter systems equipment they might be able to share with me? Thanks, Lenny.

If I can recap the situation: Old buildings need emergency lighting. what is the best way to go?

First check local fire codes. When using a central unit during a fire, the wires may melt killing the entire functionality of the system. You might as well bite the bullet and put in locally powered emergency lighting. i.e each fixture has it own battery.

By the time the wires in the walls melt, there's no-one left alive in the building anyway. Unless of course the emergency lighting system set off the fire...

Bill

What if a fire in one room melts the wires and trips the circuit for the rest of the lighting? It's not hard to imagine a situation where that could happen.

As someone else said, check local codes on the matter.

Check the electrical codes too. I have this nagging feeling that automotive batteries are explicitly prohibited for this application here. Also, a cobbled together system will not have a 'UL' or 'CSA' or any other mark and I don't know what AHJs or insurers will think of that.

I saw a thing very similar to what is described by the OP, in a dank crawlspace under a ~15 storey apartment building one time. This equipment looked like more of a hazard than some darkness. A string of car batteries can pack a whollop. A DC whollop. Plus they can offgas hydrogen and are full of acid and lead.

I am sure that there are commercial emergency lighting systems available, some that are inverter based ...

try these

If you are going to do some work make sure the electrical inspector is OK with whatever you propose. And/or hire an engineering company to give it a review for code compliance or practicality.

I'd also point out there are some non-electric possibilities too (I know, sacrilege in a EE group :)

Non-toxic, non-electric, glow-in-the-dark exit signs and route markers (as well has stairway markers) are available. About the only maintenance they need is to be sure *not* to paint over them.

daestrom