Furnace Freed

Continuing the NewOld House construction, today's post is about disconnecting the furnace, and considering our options for what's next.

Hapy Update

I know I have not written much about cars lately, so here's a quick update on Hapy. I don't drive every day, but Hapy has been my main vehicle all summer. The other night, I grew frustrated with someone driving at least 10 mph below the speed limit in the left lane. I was cruising around 2k RPM in 3rd (around 30mph in a 45mph zone). An opening appeared in the right lane, so I stepped on it and started changing lanes. I guess I stepped on it too hard because I smoked the tires for a second before they grabbed, launching us forward. Goes to show, the KermaTDI bigger nozzles and Malone Tuning CPU chip were significant improvements. Since I have been driving him so much, it is now time to do his front brakes. I am still questioning the brake booster, so once the front brakes are done, I may revisit the booster and master cylinder. Since Hapy has become the gear-hauler for the band I've been playing in, taking him off the road has larger implications than ever. Anyway, back to the furnace.

Exhaust

furnace freed

Because of the way the furnace was installed, I had to get the exhaust stack out of the way first. The furnace is not a 95% efficiency-or-better, so the exhaust is both double-walled and transfers more than just water vapor. Still, it is put together the same as one of the high efficiency ones, it is just double walled instead of single. Some pieces twist-lock together and others are held together with sheet metal screws. With a 1/4" hex socket on the cordless torque driver, I made quick work of all of the sheet metal screws. I was able to remove the exhaust in sections and set them aside. Once the entire exhaust, from furnace-to-chimney-liner was removed, I shifted to the cold air intake or "return" in HVAC parlance.

Cold Air Intake

On this furnace install, the cold air return/intake enters from above. So, while warm air rises and cold air drops, our cold air return was installed 6 feet up into the wall. Genius. It was simple to take apart, though. The protective grill was held on with 3" long screws, which also held the air filter in place. Behind that the HVAC flashing was bent to create a flute or trumpet-bell shape to route air from the grill through the hole in the wall into the main intake. From there, the intake took a 90* turn down into the top of the furnace. Easy-peasy. The intake was similarly held together with sheet metal screws, and it came apart just as easily as the exhaust had. The sole difference was that each seam had the fancy shiny duct tape. That came off fast too. Once in pieces and the trumpet-bell bits bent straight, the whole unit came free.

Hot Side

exhaust removed

Once the "cold" air passes into the furnace, the squirrel-cage blower pushes it through the heating element and down into the chase below. In our case, that chase is large, rectangular and takes an immediate hard 90* turn along the main beam. From that chase, the round insulated heat conduits attach, routing the air to the various registers around the house. None of that needed to be touched for the furnace removal. All I needed to do was detach the furnace from the floor. Again, sheet metal screws held a double-thick 90* bend of HVAC flashing between the side of the furnace and the top of the chase interface. Once removed, the furnace was free-floating. We intend to re-use as much of the original "hot side" as we can. The round insulated tube things were all replaced when the crawlspace was done, so they are effectively new. The places where heat needs to go remains the same and whichever furnace we put in the crawlspace, it can send heat (or should I say processed air) down the same paths.

Electric

Next came the electric stuff. I started by removing the thermostat and the trigger cable from it to the furnace. We don't know if we are going to retain that thermostat, nor are we sure it is going back in the same spot. Either way, it was a standard 5-wire control cable, so re-installing it or doing net-new is very little difference in cost. Having it all out so we could make decisions was worth the few minutes.

Obviously, a gas furnace still needs electricity to run the squirrel-cage fan, so I flipped the breaker for the furnace and disconnected it at the furnace end. I pushed the wire through the hole in the floor. Next, I disconnected the ground wire which the prior installer had connected to the gas line. While I would like to accept that this was safe, it really didn't feel like it. I think we will run a fresh 3-wire line if we reuse this furnace. Since an electric furnace requires 220V, that would also get a new line.

Gas

gas and electric shutoffs

All that remained was the gas line. After our little excitement a few years ago when Zed went crashing into our gas water heater at the old house (See One of the Many Joys of Home Ownership), I was not exactly wanting to do this part. Our pipe-fitter (also licensed plumber) friend offered to do it. So, Lana came by, shut off the gas at the meter, disconnected the gas line under the house where it bent up to the furnace and capped it off. Together we push/pulled the disconnected end up through the hole in the floor, leaving the furnace completely disconnected.

Considerations

We have a curious cat, so we are leaving the furnace pretty much where it was while we figure things out. Otherwise, we would have a cat stuck in the heat system as fast as you can ask "where'd the cat go". Meanwhile we have some things to figure out. The furnace was manufactured in August 2019. The house was vacated around a year later, so the folks who installed the furnace got one winter out of it. We bought the place last year and used it this past winter so this furnace has 2 years of use. There are at least 15 more in it. Knowing that natural gas prices will continue to climb, eventually this furnace will be more expensive to run on a month-to-month basis than an electrical one, but that isn't the case today. Today, a gas furnace is considerably less expensive to run. A heat pump is different, but we don't have one of those. Adding a heat pump to this system would be a $8-10k upgrade. We are not in a financial place to do that. Assuming either system can reuse the existing hot side, and routing the cold return from the hole in the floor will be effectively the same, we can eliminate those from the decision: its a wash.

August 2019

So, we are looking at electric-only or gas-only. Since this furnace is practically brand new, and in-hand, it probably makes the best financial sense to keep it, and install it under the house. Before we jump in, we need to route the gas and the exhaust -or- get 220V under there and set up the trigger cable. The gas is already right there. We may need to add some flex-pipe depending on where the furnace ends up, but the gas part seems easy. For 220V, we have multiple extra slots in the breaker panel, so it would just be a matter of adding a breaker and threading the wire through. I know how this furnace was set up so re-introducing the trigger wire is easy. I don't know anything about a new furnace, so while it is probably not that hard, it would be something new and potentially challenging. Last, the gas furnace needs to have the exhaust routed. The chimney goes through the floor, but we don't know if there is a clean-out at the bottom. That would tell us if the chimney is hollow below the floor (we think it is), and therefore available for having the exhaust run into it. This mystery needs to be resolved if we are going to retain the gas furnace for a few years. I think, for the bigger financial picture, it makes sense to relocate this furnace rather than spend even $1500US on an electric one. I cannot imagine routing the exhaust would cost half that, and the 220V routing versus gas routing is a cost-wash. So, really it comes down to the cost of the exhaust versus the cost of a new furnace plus the increase in monthly cost to run the electric... even if we could sell the gas furnace to offset some of the initial outlay. I think, the gas makes better cost-sense. Once we make a determination about the chimney, we'll know.

Well, that's it for now. thanks, as always, for following along-