HE Furnace Condensation

[inspectorwill]

What causes this much condensation to accumulate in this high efficiency furnace (see pic)? The condensate pump seems to be functioning correctly.

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[Jim Katen]

What causes this much condensation to accumulate in this high efficiency furnace (see pic)? The condensate pump seems to be functioning correctly.

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Does the picture show condensation on the *outside* of the collection box?

If so, the box would have to be cold and warm, humid air would have to be present on the outside. I'd speculate that negative pressure in the furnace room was drawing outdoor air in through the plastic vent and causing the box to become chilled when the furnace wasn't running. Was the furnace in the same room with a clothes dryer or other exhaust fan?

If this is the case, and if the furnace draws its combustion air from this room - as it would have to for my theory to work - then there's a high risk of spillage when the furnace is running.

[Brandon Whitmore]

The main byproducts when you burn nat. gas are CO2 and water. With a high efficiency furnace, there's less heat loss, so moisture condenses in the furnace& vent, hence the reason for the condensate management system.

You just don't usually see a clear collection box like that, so the moisture isn't typically visible.

[inspectorwill]

Thanks for the replies. I should have been a bit more detailed with the installation. Furnace is located in the garage next to a water heater and draws combustion air from the garage. I have never seen a clear collection box so I was a thrown off by the amount of condensation inside. An important note is that this home has been vacant for a few months and I presume the furnace has not been run in that time. My photos were taken prior to my operating the furnace. I've attached another pic of the installation area.

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[Brandon Whitmore]

Was there any spillage @the water heater draft hood by chance? Not related, but just noticed a 3" connector run into a very large common vent, or what used to be a common vent anyways.

I wouldn't expect to see any condensation in the box if the unit hadn't been run in a while........

[inspectorwill]

Thanks Brandon, I thought the same with water heater vent but there was no spillage.

[Jim Katen]

OK, then. If that's a clear collection box, then it looks exactly as I'd expect it to look. There's a reason these are called "condensing" furnaces.

[Brandon Whitmore]

That's a crazy looking discharge pipe installation by the way......

[hausdok]

Yep,

I see those all the time. One of the selling points that the salesmen like to make for these is that they extract the heat from everything, even the condensate; and I think this is the manufacturer's way of showing that to folks. As long as that condensate is inside the furnace and the drain system is functioning properly, and there isn't any leaking out of that plastic cover onto the electronics (Had one of those once), it's fine.

ONE TEAM - ONE FIGHT!!!

Mike

[inspectorwill]

Thanks all. It is the clear collection box full of water and the fact the furnace has not been run in at least a couple months that peaked my curiosity. Unless, the thermostat was left on automatic and it has been coming on during the cold morning hours. I switched it on without checking the setting.

[Yooper]

The clear rectangular box is the very end of the heat exchanger and meant to collect condensate from the combustion process. Some other furnace brands are black and you just don't see the condensate. If it is draining properly and the furnace is running, all is well.

[Eric B]

Not enough info for me. Was this found with the furnace not operating. Was it during heating or A/C mode? What were the weather conditions? Where is the evaporator coil in proximity to the furnace - up or down stream?