Plenum Repair

ekulrenlig · 10-03-2009, 03:27 PM

The house I bought used to have some kind of water boiler or geothermal unit (not really sure) but they left the heat transducer in the furnace with the water pipes connected. I was told that the furnace will be more efficient with that removed. My question is, is there a certain gauge sheet metal that I should use to repair the hole once I remove the heat transducer? It is probably about 2 to 2.5 feet above the burners in the verticle portion of the plenum. Would galvanized sheet metal cause any poisonous gasses? What else do I need to know to do this?

Grampa Bud · 10-03-2009, 03:45 PM

You have a jury rigged forced air furnace by the sound of it. If it really has been 'modified' to place a water pipe in the combustion box area with an opening out into the room from the fire box red tag the whole affair immediately and get a contractor in there. The water pipe could be a REDNECK water heater, not sure. If the plenum you refer to is just the discharge side of the heat exchanger you can just run a 1/2" bead of silicone around the opening and cut a tin sheetmetal patch 1" bigger than where you have the silicone. Shoot it down with 1/2" sheet metal "shooters" and you will be ready to heat/cool.

yuri · 10-03-2009, 04:06 PM

Post some pics of it and the name of it. Hopefully it is not a Brock.

tinmanrob · 10-03-2009, 04:29 PM

Outdoor wood boilers use this type of coil.
I've installed several of them.
It's a flat coil that looks a lot like an automotive radiator.
It's installed in the supply air plenum, and has 2 connections for the boiler system (usually 1" copper).

Grampa Bud · 10-03-2009, 04:50 PM

AH HA That answers that. I do remember a set up like that, and if it is a radiator rather than just a hunk of pipe like tinmanRob says you can actually heat your house using the alternative heat source. Thanks Rob I find myself forgetting more than what I thought I once knew.

ekulrenlig · 10-03-2009, 06:56 PM

Yes, it is pretty much exactly has tinmanrob describes. Here are a few pics if I can figure out how to post them.
http://thumb18.webshots.net/t/96/96/...8ndfiXj_th.jpg
This is the heat transducer
http://home-and-garden.webshots.com/...98834518zlnhpk
The other side
http://home-and-garden.webshots.com/...98834518HKvyHT
The furnace setup
http://home-and-garden.webshots.com/...98834518ZngLot
The water pipes connecting to it.

So what is that thing anyway? Can I use galvanized sheet metal to patch the hole once it's removed? Do I need a certain gauge?

ekulrenlig · 10-03-2009, 07:04 PM

Here we go.

ekulrenlig · 10-04-2009, 10:22 AM

So do I need a certain gauge sheet metal to cover the hole once I remove this thing?

tinmanrob · 10-04-2009, 06:11 PM

Well, we generally build plenums out of 24 gauge or 26 gauge, but, for a small patch like that, I wouldn't worry about the gauge.

On a side note, your single wall vent looks like it's very close to combustibles.
Could just be the angle of the picture.

ekulrenlig · 10-04-2009, 07:56 PM

The "single wall vent" being the vent coming directly out of the furnace? Yes it it quite close to the 2x4 construction. What do the codes say about the required distance? I've got about 4 or 5 inches.

Another question about heat transducer: Is there any danger running the furnace without any water running through that thing?

tinmanrob · 10-04-2009, 08:03 PM

I believe the code for single wall pipe is 6".
I don't think you have anything to worry about with 4" or 5".
As far as the coil goes, no danger in leaving it in there.