Troubleshoot a High Efficiency Furnace

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    LESLIE: Virgil in South Dakota, what can we do for you today? Got a problem with a high efficiency furnace?

    VIRGIL: Hi. I’ve got an old home that I am restoring and renovating and remodeling. It’s over a century old. And part of the process has been installation of a relatively high efficiency furnace.

    TOM: OK.

    VIRGIL: And I just got it started and was away from the home for a while. Came back and everything was froze solid. The exhaust had developed a plug of ice and the furnace would not run.

    TOM: Ooh, that’s not good.

    VIRGIL: No, that’s for sure. Anyway, the contractor that installed it rerouted the pipe so it would go through a heated room instead of up in the attic.

    TOM: Right.

    VIRGIL: And so I have it going above the lay-in ceiling over my bathroom. So I’ve got probably a foot to a foot-and-a-half for the inch-and-a-half exhaust pipe sticking out of the side of the house. And I’m wondering, am I going to have a problem with that? And if so, how can I prevent it from happening again?

    TOM: Yeah. That’s a good question. In this situation, I would turn to the manufacturers, making sure that they’re – that you follow the recommended installation instructions for this type of a system. With a high-efficiency furnace, what happens is you take so much heat out of that exhaust gas that what’s left is mostly water vapor. Eighty percent of it or more is water vapor. And so that’s why you have to be able to have a way to deal with that.

    Now, if that pipe is in a heated area, if it’s insulated, that’s going to stop the ice from forming. But of course, it’s dangerous if it does form because if you can’t exhaust the gas, then that’s going to shut down the furnace, which is a safety switch, basically.

    VIRGIL: Right.

    TOM: So, I – to me, I would make sure first that I’ve – that the contractor has installed that venting consistent with the manufacturer’s recommendations, which I’m sure you can find on their website. There are very detailed instructions on that sort of thing. And secondly, I would just watch it now and see what happens. Time is going to tell.

    VIRGIL: Kind of a vacation home and I’m not there for a good part of the time. So I can’t be out checking it.

    TOM: Right, yeah. Do you have a smart thermostat for that house?

    VIRGIL: No. There’s no internet there.

    TOM: Ugh. That’s too bad. I was going to suggest that this would be a great application for a smart thermostat that can monitor the temperature in the house. This way, you’ll know if it’s working or not.

    VIRGIL: My other choice might be if I put in one of those smart outlets that turns on at 35 and off at 45. And if it turns on at 35, maybe one of the neighbors would see a flashing red light or something.

    TOM: See a light, yeah. Exactly. Yeah.

    Listen, I think that you need to work with the contractor and the manufacturer to figure out why this was – why this is happening. But I do suspect that that venting has to run – be run through a heated area and it’s got to be better insulated. OK?

    VIRGIL: Well, he did have it insulated and it was in the attic, which is totally unheated. So, he did move it down to a heated area. And I can even move the temperature up a little bit by lifting one of the tiles in the lay-in ceiling in the winter.

    TOM: Alright. Well, good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.

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