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iwannadiy 01-21-2013 05:21 PM

HighEfficiency Furnace Shuts off before reaching target temperature
 
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Hi all,

I have a gas furnace which works OK "most" of the time. However, there are times it will shut off prior to reaching it's target set temperature. I have changed the filter, changed the setting on the thermostat to try to get it to reach the target temperature. And I am not sure why it is inconsistent (sometimes works, sometimes does not). I have had this furnace for less than 1.5 years.

Today, I removed the cover and noticed a build-up of water inside. I am not sure what is causing the water build-up. Anyhow, I am thinking this may be causing my furnace to shut down prior to reaching the set temperature.
Anyone with any ideas on next steps?

yuri 01-21-2013 05:31 PM

What is the brand name. Ducane or AirFlo? Hard to tell where the water is coming from but it may be the gasket behind the exhaust fan is faulty or a different problem. I would get the installer to fix it as removing the ventor fan is not easy and the gasket is not a easy DIY fix either. There should be a LED in a viewing window in the lower door. Check for an error code when it ias acting up. Check your vent pipes outside for obstructions.

That unit is a clone of a Lennox as they own those 2 brands. Get the installer to make sure it is sloped to the front 1/2 an inch for better drainage AND to make SURE they followed the installation instructions PERFECTLY for the condensate trap. If the vent pipe on the trap is too long they don't drain properly.

iwannadiy 01-21-2013 06:13 PM

Thanks for the reply.

Brand name is Ducane.

Only LED I see is a red one on a circuit board that stays lit while the unit is running. Is this the one to look at once the unit shuts off?

yuri 01-21-2013 06:56 PM

Yep. But that is a bad water leak that needs fixing or the water will get into the circuit board and blow it and void it's warranty

ben's plumbing 01-21-2013 07:58 PM

there is a issue with the drain on the left side of unit ....there is a black hose that drains the exhaust... trace it down to beside inducer motor... see if its clogged ...bet it is ..or at least restricted..ben sr

JScotty 01-21-2013 08:48 PM

Quote:

Originally Posted by ben's plumbing (Post 1099026)
there is a issue with the drain on the left side of unit ....there is a black hose that drains the exhaust... trace it down to beside inducer motor... see if its clogged ...bet it is ..or at least restricted..ben sr

Yep I'd bet this is your problem. 90% furnaces make water in the exhaust. So there is a drain built it. (also why they use pvc pipe instead of metal because the water rusts the metal pipes)

What can happen is the drain partially stops up. When the unit doesn't run a lot it is given plenty of off time to drain down so you have no problems. When it runs a lot it makes water too fast to drain through the restriction. Water backs up into the inducer motor causing the fan to not move enough air. Then the pressure switch shuts the unit down.

iwannadiy 01-22-2013 03:51 PM

Thanks for all the replies. Appreciate it.

It turns out that it was a drainage problem. Water was getting backed-up. Although there was no clear blockage or anything like that. Once I removed some of the drain (and trried to blow water out of it). It drained a whole lot of water and once it started up again, it ran until it reached desired emperature this time.

So it looks like I will have to keep monitoring it to ensure there is no water backing up.

Thanks again to all for your comments/tips.


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