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HVAC Salt Test


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I've heard of this, but don't recommend it. You supposedly spray a saline solution into the heat exchanger chambers, then hold a lighter above a register. The saline soultion, if it's mixing with conditioned air, causes the color of the lighter's flame to change . . . to pink, if I remember correctly. The apparent problem is that the saline solution can damage electronic ignitors and get an inspector in heaps of trouble.

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Well it is a little more complex than that. In the old days you would use a propane torch with a copper plate in the flame that would siphon off air from the exterior of exchanger. Then spray a salt solution into flame of each exchanger. As the siphoned air passed into the environment of the copper plate and propane flame, the flame would turn bright red, indicating a crack or hole. Left a nasty residue, damged ignitors, looked like crap, etc.. No longer used by professionals and hopefully inspectors.

This falls into the realm of "things we used to do". I could write a book about how much this industry has changed in the past 20+ years.

One of my old time favorites was the penny kids balloon with a few drops of water in it, tied at the top and used to test microwaves. We only saw 2 or 3 per year. Throw the balloon in oven, turn dial to 30seconds and hit start. Balloon would expand if particles were present, or break. Nobody knew any better!

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Originally posted by homnspector

what do you guys think of the "smell" test. Peppermint or insence in the burn chamber can be smelled at the registers? I have tried it but never gotten any odor so don't really know if it works.

Extremely unreliable. Remember that, during its normal operation, the pressure inside the heat exchanger is lower than the pressure outside.

Do a careful visual examination and recommend that people install carbon monoxide alarms in the house.

If you really want to offer a heat exchanger test, use the AGA method. Shut down the furnace, use a special manifold device to inject a non-explosive mix of propane into the heat exchanger and sniff the outside of the heat exchanger with a calibrate-able combustible gas detector. It's a bit of an ordeal, but it really works. If you're interested, I can give you more details.

Whatever you do, don't resort to street magician tricks.

- Jim Katen, Oregon

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