Come join us for a round about look at the final piece of our all electric to propane conversion: replacing our aging and ineffective heat pump with a gas furnace. Just like our roof, we were well aware that this HVAC system was at end of life expectancy. Similar to the roof, an episode in the summer of 2018 caused Eric to jump in the attic to see why condensation was draining from the secondary line outside, instead of draining properly down our sink drain.
Overall standard of living improvements can be attributed to a reduction in power bills, a much quieter AC compressor that cannot be heard inside of the house, the soft starting/stopping of the blower unit that doesn’t wake anyone up like a cheap motel unit, and finally the ability to run the furnace on backup power.
It was tough to really document what was going on here with a phone camera, but you can see a lot of corrosion inside the coil box. What was happening is the entire air handler was too low in relation to the drain lines, and this caused the entire drain pan to fill with water during normal operation. We are talking six plus gallons of water here, which is significant if it were to leak. The secondary result was moisture was not able to drain away effectively in the coil, causing the corrosion present. The system had to go.
August 2018 had triple digit temps consistently, but the heat was no match for January’s cold for electric use! This was just the realization that our heat pump was not what we wanted to continue to use for heating. Our location sees temps in the low 30’s for months of nights, dipping into the high 20’s occasionally. This HVAC system was in good working order, but just could not heat effectively or efficiently for us.
Proof of concept: January 2019, our house was all electric. By January 2020, we had converted our cook top, dryer, and water heater to gas. Even with our poor HVAC performance, we successfully reduced our electric consumption by 37%. Our cost for gas in lieu of electric was a 69% reduction in budget for this month, and has been a consistent $200ish savings per month since.
Now we can see where the rubber meets the road! January 2021’s bill endured a cooler overall temperature, and the reduction in use of the heat pump for only 2 weeks of the 2021 billing cycle is dramatic! Another 30% decrease in electrical use, equivalent to $100 per month for heat. That said, our gas consumption is up 75% per day running the furnace, but we are still saving money after paying for propane.
January 2021 bill was almost 1000 KwH less that January 2019, which is a $450 savings! In one winter season, the conversion will pay for itself on the furnace side.
If you are curious why we didn’t stay electric and just add solar, see our video here detailing our prior use case and why we didn’t think spending $40,000 on solar would be a good fit.
Months of vacillating on what type of system we would install culminated with top of the line efficient models for both heat and cooling: a 100,000 btu 96% efficiency two stage furnace, and an 4 ton 18 SEER two stage compressor.
Our previous HVAC was a 3.5 ton unit, which translates into 42,000 btu worth of heat. We also upgraded our compressor half a ton, to help those peak days that are 115F or higher. Based on amperage draw of the new compressor, it uses half of the electricity our old unit did. Summer savings will be another post later in 2021.
We bought our system from an online retailer with great reviews, HVACDirect. Eric was a little nervous about spending $5500 with an out of state online retailer after getting burned by one in 2004, but HVACDirect delivered. Here our pallet is being inspected for damage prior to accepting the delivery, despite the delivery driver insisting that the shipment be signed for prior to. That little distinction is the difference between the freight company owning any damage, and us having to fight our vendor.
Many measurements were taken in the attic to define our available installation space. Our existing ducting at both the intake and exhaust manifold were hard stops for the scope of this project. Luckily there was just enough room to accommodate the new coil after the air handler. Now was the time to mock up the configuration to start making sheet metal adapters to get everything working together.
Our furnace required a conversion from natural gas to propane, as propane has 2.5x more btu per cubic foot. Our unit is known as a condensing unit, and it requires a drain from the heat exchanger to release the accumulating water that does not turn to vapor. This meant reconfiguration of the drainage system as we were changing the orientation from vertical to horizontal left.
Phillip loves to help around the house, and this was no exception! He had a blast playing with all of the extra hoses that we didn’t need for our conversion, as both left and right horizontal orientations had different needs for drainage.
We began the sheet metal process by sizing the intake and exhaust of the coil to match the exhaust of the air handler, and in the intake of the duct manifold. They were close in size, but nearly an inch different in height and width. It meant a little extra work since mirrored pieces couldn’t be duplicated.
All seams were sealed with foil tape.
The metal brake we were allowed to use broke in the beginning of this process. This is 1 inch thick piece of cast iron just let loose.
Unbelievable! We transitioned over to a pair of drill powered snips to complete the rest of our cuts.
Time to test fit the transition from the air handler to coil. All joints were riveted and sealed with tape.
Fits perfectly on the coil!
Like a glove on the air handler! Now to make sense of the rest of the install, and find an opportune time to demo our existing heat source in December…
As luck would have it, December 23, 2020 was the day of demo, and it worked out perfectly for us. Outside temps were almost 16F warmer in the evening, and 19F warmer in the morning than the 22nd. No need for the heat this night, and one of the first strokes of good luck our projects have seen.
Our plan was to remove the 20 inch by 30 inch intake, and use the hole to remove and install the components.
Pictures of the low voltage wiring were taken to make sure what was at the thermostat would line up with the furnace and compressor outside.
Eric rented the same lift we used briefly during the re-roof, and staged it to catch the old coil and air handler.
Trying to align the air handler vertically was a major challenge. Being nearly 100 pounds and lacking any good grip, it was difficult to manage.
As seen from below, so close, but so far!
An eye bolt was installed temporarily to aid in lifting the unit vertically, to no avail.
Eric was working solo this entire time, and the decision was made to cut the air handler in half with a reciprocating saw. The fresh blade made quick work of the sheet metal, and the unit was in bite sized chucks ready to set on the lift.
All three metal components ready to go to the recycling yard.
Almost out of the house! Our pest control service had just showed up, and was wondering what craziness we were up to this visit.
An exciting time, loading the new components into the attic! Time was getting long in the tooth, and it was evident at this point that we would not have any heat source until the next day.
Progress in the making!
It took some effort to get the furnace loaded, but it happened.
A VERY tight squeeze.
Damage to the drywall was unavoidable as the furnace was getting pushed in.
That is as high as she would go, and would need to be man-handled in the rest of the way.
Phew! What a sight to see, and a great feeling of accomplishment so far. But we aren’t ready to hook everything up just yet.
We have a mini sub panel in the attic for the 60 amp circuit that feeds the old unit. The sub panel needed to be converted to 120volt service, and an appropriate breaker installed for the new furnace. A double breaker was all that was available at the big box store, it was amazing to see how much inventory was not in stock.
Next up on the task list was mapping and installing the concentric vent that would house the intake and exhaust vent for the new appliance. You can see the 3/4 inch CSST gas line and valve capped and waiting to be put into service on the left. We did not want to chance any fuel supply issues and went one size up on everything in the house. This branch line has over 250,000 btu capacity, even though we only need 100,000 for the furnace.
New vent is hung as suggested with plumbers tape.
What it looked like from above. This was installed right before new underlayment was rolled onto the roof.
Flashed and ready for tile! Back inside to the attic again though.
I will apologize for the coming wall of text… This was going much slower than anticipated, and there just wasn’t much time to document the leveling and sloping of the manifold, coil, and furnace. That said, it was critical that the entire assembly sloped downward to the left on the X axis, and downward to the front on the Y axis.
Concerns and considerations: the exhaust manifold with ducting could be moved up and down a few inches, but not left or right. The coil had to fit in between the rafters and under the concentric vent, while still being high enough to allow the needed drainage to occur both internally and with the drain pan as a secondary relief. The furnace needed to be high enough to allow the condensation drain clearance, and allow it to drain effectively while being higher that the coil to prevent any backup from that component.
All of these individual components needed to be supported underneath, as they are not meant to “hang weight” off of each other. Another project left us with a smattering of 2×6, 2×4, 1×4, and 1×2 scraps that worked perfectly for this balancing act.
It started with the manifold to coil interface, and worked right to the furnace. First the X axis slope was determined, then the Y axis was built on top of that. This was one shot I had after adjusting the 100 pound furnace prior to it’s final placement. Needless to say, it was a bear shuffling these things in the limited work area; but the attention to detail now will pay dividends later. (Maybe more than GME and AMC as of Jan 28, 2021 Gamestonk! :P)
A nail gun was used to tack everything in place, and everything was lined up and set together with sheet metal screws, then all of the seams taped over with foil.
One snag: the new low voltage wiring needed to be extended a few feet, and finding a short piece of 18/8 thermostat wire was not in the cards. If you go back to Day 3, you will recall that we used 18/5 irrigation wire to relocate our sprinkler timer. Some leftover pieces of that saved buying 100 feet of wire to only use a 5 foot section. Again, taking pictures to help know what wiring is translating to which piece of wire since there are duplicate colors being used in lieu of the 18/8.
Since this was converted to propane, the internal pressure regulator needed to be manually set. After multiple tries to start ignition, we finally had success! The funny thing was, the furnace heats so well that all of the windows in the house needed to be opened to set gas pressure and allow the unit to heat cycle for 20 minutes. Again, this furnace has almost 2.5x the heat output of our prior unit.
At this point, you are probably looking at this picture and wondering what the eff is going on here. The furnace was patched in and operational Christmas Eve around 9pm, but the work was far from completed. All of the drainage, the intake/exhaust, and AC lines needed to be mapped and finalized.
We will start with the white PVC: these are the primary and secondary drain like for condensation generated by both the furnace, coil, and drip pan. The furnace drain system is completely sealed with hose clamps and glue joints, and a secondary drain solution was not utilized at this time. It generates a drip at most during normal operation, a far cry from the gallons a day generated by the coil.
Both the furnace drain and coil utilize an airgap, the one for the coil being made of standard pipe fittings as shown toward the rear. All three drains were routed to allow the most room to work in the area.
Both suction and pressure lines to the coil needed to be extended, which was easier said than done. This paired in tandem with the change from a fixed orifice to expansion valve to allow dynamic changes in cooling capacity. After multiple trips to the hardware store, these lines were ready to sweat in.
Intake and exhaust lines for the furnace. In order to satisfy Code requirements for a fuel burning appliance, the trend is to simply use a concentric vent to guaranty the proper amount of intake air and exhaust routing. Otherwise calculations of square inches available for fresh air are required to make sure the appliance has access to enough air for proper function, while also proving that any combustion air cannot get into the living space. This is a 96% efficiency unit, and calls for the use of standard drain/waste/vent pipe. PVC was not available anywhere locally to a homeowner, and we had to settle for the use of ABS.
Measurements were mocked up, and transition adhesive was used to glue the ABS to PVC at the vent/furnace, then regular ABS cement was used for the rest of the joints.
The cacophony of overlapping tools and projects made a mess of the installation area.
The final layout of refrigerant lines ready to test for leaks.
The intake manifold all wrapped up!
Eric had what seemed like half of the garage tools up in the attic for the duration of this project. De-staging was a chore.
That’s a wrap in the attic! You can see the fuel line extend well beyond the top of the unit, as a scrap from the kitchen renovation was used. Trying to find homes for already purchased materials has been an ongoing project.
Time to move outside. Prior to starting, a local tech recovered the refrigerant for us. The old compressor was simply disconnected and lines cut.
All HVAC and Christmas trash ready to find respective homes at the recycling yard and dump.
Drywall damage from the furnace install… This will get tackled one day.
We waited to set the compressor until the exterior of our house was painted. This was the day that the unit was placed, leveled and plumbed.
First things first: sweat the refrigerant lines and vacuum test for leaks.
After a 30 minute vacuum to ensure all moisture was removed, it was time to seal the system and make sure vacuum was held. No leaks!
And the lackluster finale: 240 volt, 24 volt, and insulation are completed. The compressor was charged to include 15 feet of lineset. Eric added 1 pound and 6 ounces of R-410 to account for the additional line and new coil. This will be adjusted once the weather warms up enough to really cycle the air conditioning. Leak detection dye was added too, since it was available and works extremely well in the case of a hard to detect leak.
If you made it this far, thanks for hanging in with us on this one!