If your stove is still under warranty, then I'm pretty sure that if you use anything but the one that Harman sells, then it will void the warranty.

Call the factory and ask.

Why not a small generator?

Void the warranty? Why. This is a external power source and will not do anything to alter the stove.

It could short out the stove.

I have seen circuit boards fried when a house got hit by lightning. Obviously a warranty will not cover that. The same theory could apply to a back-up that is not within Harman's specs.

As long as the generator your using has a consistant 60 hertz it will not hurt the stove. The sine waves the circuit boards use are very adamit(sp)about its power source. Using something other then this will short your circuit board as Xanndra said.

As for battery back - yes using something other then Harmans back up system will void the warranty due to the fact that it was never tested on the unit. Harman now carries a unit called the 512H that is made specifically for Harman units with auto ignition. The 502H that they used to sell will only work for about 4 hours or so do to the igniter. It was mainly built for stoves without auto ignition.

The Surefire 502H appears to be nothing more than a quality 12vdc-110vac inverter. You can use something similar just as safely as long as it's rated for whatever the stove is rated at (I believe my XXV Anniversary is about 600 watts). Stick with a known power expert (e.g.; Tripp Lite, Xantrex) and get good quality power output. (a.k.a. "expensive"!)

Make sure you cable the low voltage side with an appropriate gauge of wire (the inverter instructions will have a table) and >fuse it at the battery end<. also beware that non-sealed lead-acid batteries marine can generate a flammable gas so they should be stored appropriately. gel cell or agm glass mat are better choice and live inside. these the same kind as used in industrial ups systems. everyone recommends deep-cycle but if your inverter set to charge agms whole lot better. not much more expensive either.>I have two 75aH AGM batteries with 4-gauge wire to a Tripp-Lite APS 750. The batteries are in marine-style boxes, and each is fused at 100a. (the fuses are for a catastrophic short across the 12v, the inverter has its own overload and fuse protection).

I found the components to build a UPS were expensive and the cheapest source ended up being high-quality high-end auto audio system suppliers for the fuses and holders. My power cables were nothing more than battery cables from the auto store, with the post clamps cut off (the AGM batteries have tabs).

I don't know about the Harman unit, but the APS 750 switches to battery in a flash, the stove doesn't even notice. The Tripp Lite also charges the batteries automatically at high current, so they can be ready again in a short time. I have a generator for extended run-time, the Tripp Lite is strictly a UPS arrangement - provide power when a power failure occurs so that the stove doesn't stop and smoke everything up. If Harman had something that could gracefully shut the stove down when AC power is lost, that would be worthwhile.

A small UPS is used for computers all the time and they are full of pc boards. Mine has an annoying alarm that would need to be disabled.