Humidifier corrodes furnace heat exchanger?

If the humidifier is an atomizing type and the water sprays on the HX, it will rust the HX out fast.

If it's a vapor type humidifier, like an AprilAir, it won't cause faster rusting.

Most of us do give honest answers. Even Davey (HVAC Fella) gives honest answers, but they are honest to him only. The answers are honest, but not correct.

I agree.

This is not MY Howie in NY is it?

I'm not sure how big an issue this is, if at all. However, if you're worried about it, I think there is a solution. The most common humdidifiers are bypass models. They short circuit some hot air thru the humidifier where it picks up moisture and then send it across to the intake plenum, where it goes back through the furnace. If corrosion were to be a problem, that would seem to be the source of the problem, because now you have hot moist air going over the hot heat exchanger.

There are humidifiers that are not bypass, cost a little more, but have a built in fan. These only circulate air from the hot plenum throught the humidifier and then back into the hot plenum. With the furnace blower running, this air then just goes up and out, never going through the heat exchanger. They also have the advantage of not reducing the furnace blower capacity by short circuiting air. I have an Aprilaire and it has been superb, I highly recommend it.

nope, this is Howie from Regina, Saskatchewan, Canada...

I haven't heard of a Aprilaire type... what about the drum type? I'm not that familiar with humidifier types, I've seen the old style plate types, as well as the drum style. I think I've seen the type where the air is drawn into the unit through flexible vinyl tubing.

I don't care for the drum types. To prevent water from getting yucky, you have to flush if daily(at least). The flush valve adds to the cost and that makes the prices higher than the panel style humidifiers.

Aprilaire is what most of your better contractors will sell...

We install several dozen a year...