Furnace in a box

[Mobuck]

This may end up being a poor choice but with the time crunch and all the other 'stuff' I just had to make a decision. Last year, I bought a new wood pellet stove that was advertised as providing enough BTU's to heat my house at an acceptable rate of fuel use. That was a dismal failure but after a lot of complaining and back and forth with the manufacturer, I got a full refund(didn't cover the cost of excessive fuel use and 250 miles of gas to return) so guess it could have been worse.
With cold weather on the horizon, I've been trying to get a HVAC guy to at least show up and make an estimate w/o success. Monday morning, I ordered a new high efficiency gas furnace and it's scheduled for delivery TODAY. Now that's on-the-ball service. Good, bad, or insane is yet to be determined but it's not the first furnace I've installed and all the ductwork is still in place.
Biggest concern I have is getting the 24' tall steel pipe chimney down w/o damage to people or equipment. I built it with hinges at the bottom to facilitate raising/lowering but that was 30 years back and the corrosion from the corn burner has taken a toll on the metal. Son says he remembers the raising operation which means it must have been a significant event from his perspective(he would have been about 10 years old).

 

[Dave P.]

The last gas furnace I installed four years ago was a Lennox and it used a 3 inch PVC pipe for both combustion
air intake and exhausts.
Dave

 

[Mobuck]

Yupper, this new one does also.
I made a start on removing the steel pipe chimney. When I was using the corn furnace, there was an issue with condensation in the chimney so I added an outer shield of galvanized 8" duct pipe on the outside allowing a buffer between the hot pipe and cold air. This worked OK but had to be removed for the lowering process that's coming up. I got all that off this morning. Now I'll have to wait for Son to bring his pole saw so we can prune a couple trees to clear the cab on the loader tractor. Probably going to leave the base since I remember it being a 3' diameter x 5' deep hole filled with concrete and the pipe goes all the way down. With a little carpentry, that base would be a good shooting position for the long coyote shots across the bottoms from my house.

 

[gramps]

Maybe I missed it? Why not use the Stainless pipe that is up? PVC pipe and heat don’t do well together as a firefighter.
gramps

 

[Dave P.]

Maybe I missed it? Why not use the Stainless pipe that is up? PVC pipe and heat don’t do well together as a firefighter.
gramps

Modern "stuff"....
There's almost no heat left to exhaust.
The Lennox I bought is rated at 99% efficiency by whatever standard the manufactures use.
The exhaust pipe gets warm near the furnace but you can comfortably hold your hand on it.
Totally variable burner and blower speeds depending on heat required and feedback from
the thermostat.
Dave

 

[gramps]

Maybe I missed it? Why not use the Stainless pipe that is up? PVC pipe and heat don’t do well together as a firefighter.
gramps

Modern "stuff"....
There's almost no heat left to exhaust.
The Lennox I bought is rated at 99% efficiency by whatever standard the manufactures use.
The exhaust pipe gets warm near the furnace but you can comfortably hold your hand on it.
Totally variable burner and blower speeds depending on heat required and feedback from
the thermostat.

Dave

Wow, I didn’t know that. We still get chimney fires in my area.
gramps

 

[blume357]

Yep, the new gas furnaces rob so much heat from the fire that the exhaust will not go up.... you are pretty much exhausting carbon dioxide and water.... I can explain the physics if anyone is interested.... basic is mater is neither created or destroyed and to burn gas you are using hydrogen, carbon and oxygen and all of those come out of the exhaust ... H2O and CO. Thus the furnace has an exhaust fan that blows this out through PVC.

The reason the old corn pellet vent pipe went bad was the sugar and starch in the corn will eat just about anything including most stainless steels.

Oh and don't do like the guy I heard about when I was taking a gas class a while back ... he lived in Kentucky and installed his own furnace and it died after a year... company replaced it and the next one went after a year and so they sent someone out to see what the deal was... seems the guy had 'plugged' into the side of the mountain where gas was coming out... raw gas....

 

[eveled]

PVC pipe was never meant to be used as flu pipe. The equipment manufacturers said it was ok. So it was allowed. The PVC pipe companies said we don’t recommend using our pipe that way. It is not meant for it.

There was a lot of problems with joints pulling out after they were glued. They say it’s because primer wasn’t used. So they mandated that purple primer be used. So you could see it was used. That did seem to take care of the pull out issue. But the pipe gets brittle over time and breaks down.

It is illegal in Massachusetts to use PVC. We switched to using Centotherm pipe. 1738 pipe is another option.

Bottom line if PVC is still legal in your state and you chose to use it be sure to use primer.

No matter what make sure you have Carbon Monoxide detectors on every floor and within 10 feet of every bedroom.

Blume there was school in Texas that blew up killing around 300 students. They were using raw wet gas to heat the building. There were leaks and natural gas has no odor.

 

[Mobuck]

"Bottom line if PVC is still legal in your state and you chose to use it be sure to use primer.

No matter what make sure you have Carbon Monoxide detectors on every floor and within 10 feet of every bedroom."

Duly noted, thanks .

 

[Mobuck]

Thumbs up to DAYTON freight company. Dispatcher called yesterday to let me know the delivery would be today 1-3PM. I needed the driver to call about 30 minutes out so I could get the loader started and meet the truck. Driver called and I gave directions. By the time I reached the highway, the truck was waiting to unload. Five minutes later, my stove pallet was on the loader forks and I was headed back. That's the way it's supposed to work.

 

[gramps]

WooHoo! “ I love it when a plan comes together”—Hannibal
gramps

 

[Dave P.]

Thumbs up to DAYTON freight company. Dispatcher called yesterday to let me know the delivery would be today 1-3PM. I needed the driver to call about 30 minutes out so I could get the loader started and meet the truck. Driver called and I gave directions. By the time I reached the highway, the truck was waiting to unload. Five minutes later, my stove pallet was on the loader forks and I was headed back. That's the way it's supposed to work.

Never...ever...celebrate till the job is done.
Some part of it is smiling right now with razor sharp
teeth.....just quietly waiting.....
Dave

 

[blume357]

When the new high efficiency furnaces first came out they were using some type of badge plastic pipe and that stuff seemed to break....

I see a lot of gas furnaces vented with pvc pipe now and I think I've seen one joint come loose...... not rocket science to use primer before the glue in my opinion... also to check every year.... also, and I know this is nuts... but guess what.... even if the pipe breaks the chances of you diving from CO2 is almost impossible... I could explain why but you would find it quite amusing.... and I've worked in an industry that loves to scare folks half to death about dieting from it. I've know one person who did (using a ventless wall heater to heat his house) and one person who ended up in ER (30 year old gas heater with a stopped up chimney).

Another interesting thing is in all the old movies people are killing themselves by breathing gas... I can't quite figure this one out... because neither natural gas or propane is toxic... the only way to do it is to aficiate yourself by displacing all the oxygen in the room with gas.

 

[Dave P.]

the chances of you diving from CO2 is almost impossible...

Blume,
Did you really mean CO2 or CO ?
Dave

 

[eveled]

Blume357 You are a straight shooter I have an immense amount of respect for you, but that is a really irresponsible post. People really do die from CO poisoning every year. Gas appliance venting is potentially a life and death situation. It is not rocket science but needs to be done right.

Sticking your head in the oven to commit suicide always made me wonder too. Almost like they didn’t want to give you an idea that would actually work.

Mobuck. read the manual about the total lenght allowed. They usually allow a certain number of elbows then after that each elbow counts as x number of feet. Sometimes it’s a combined length intake and exhaust sometimes it’s individual lengths.

Long sweep elbows are better than short sweep elbows. Pay attention to the details and the install will be fine.

 

[eveled]

Any questions you have I’ll be glad to help with. I wish I could actually help you with the install, but you’ll do fine.

 

[Mobuck]

Thanks.

 

[kmoore]

My 2019 home has a gas furnace and gas tankless water heater vented out through the roof with PVC. Same with all the newer homes in the area.

 

[Mobuck]

I was told that high efficiency furnaces like to run more rather than less. I used this as a consideration in sizing the BTU output. Hope I didn't make a mistake.

 

[blume357]

the chances of you diving from CO2 is almost impossible...

Blume,
Did you really mean CO2 or CO ?
Dave

Sorry, of course I meant CO.... even though it seems you can die from the other... remember the movie Apollo 13?

 

[eveled]

I was told that high efficiency furnaces like to run more rather than less. I used this as a consideration in sizing the BTU output. Hope I didn't make a mistake.

That is true. Of all high efficiency heating equipment. Think slow and steady. It’s been a problem on forced air systems that also have air conditioning. The high efficiency furnaces are in effect too small to cool the house.

 

[wolfsong]

I love this forum, and the wisdom of its members.

 

[Mobuck]

"I love this forum, and the wisdom of its members."
Worth more than it's weight in gold.
I'm hoping today is a short day in the field so I can get Son and Gson to help move the new furnace into the basement. Once I get it uncrated, I can begin to figure out how it's going to set in order to utilize the hot air plenum from the previous furnace. Once that's established, I can make a supply list for the intake, exhaust, drain, and LP connections.
After reading the installation instructions, I've noted one thing: Older furnaces had 3 basic requirements. Electrical, fuel, and exhaust. These high efficiency units have all sorts of minimum/maximum on sizing EVERYTHING-very narrow parameters. This old house has a very basic heat circulation system. There's a warm air duct that runs the length of the house with vents in each room. There's a stairway into the basement at the end of the house opposite the furnace which allows the cooler air to flow downward and return to the intake for the furnace fan. This has worked well enough for 70 years but not up to the type of system this furnace is designed to work with.

 

[blume357]

I think you are going to need to consult with Eviled for a minimum... I've never seen a duct system that did not have a return side and I think newer ones don't just have one big return but often two or more. I used to deal with the exhaust on gas furnace systems all the time but for the last 10 years or so mostly I just walk around the house and see the PVC pipe sticking out of the side of the house and I'm done... except:

You may need to run a PVC line from the outside to the air intake on the furnace. One issue that has been drilled into me with these new high efficiency furnaces is to never use the inside air for combustion if it is near the laundry room. If you do you will be pulling the phosphates and chlorides from the laundry wash into the combustion of the furnace and these will condense inside it and cause premature corrosion.

 

[eveled]

There should definitely be some sort of return from upstairs. For air quality if nothing else. You’ll go crazy with all those parameters on the duct work. So much is out of your control anyway. A lot of that should have been looked at when sizing the unit. Just put it in and see how it goes. Adjust the blower speed accordingly. Paying attention to the air temperature immediately after the heat exchanger.

 

[Mobuck]

Bingo, I like that advice.

 

[eveled]

On a furnace taking the return from the basement works fine. But basement air is not the healthiest. Mold mildew dust etc. So they require a return from the living space. The first floor is fine.

If you have an A coil on a basement furnace to use it for air conditioning then you must have a return from the top floor preferably on the ceiling. You are fighting gravity forcing cold air up.

 

[Dave P.]

And no discussion about return air would be complete with out provision
for a filter.

 

[blume357]

Actually all home air is dirty, much dirtier than outside air. What I was alluding to was the air that goes into the combustion chamber and all of these new fangled high efficiency units have the ability to bring outside air directly into it. That is the best way to do it....it should be another round pipe connector on the unit right beside the one that you put the pvc exhaust pipe on.