Upgrade my furnace to central air?

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kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Upgrade my furnace to central air?

Post by kevm14 »

Not surprisingly I'm all over the place here. First I thought I wanted an 18k BTU mini-split heat pump for my great room. And maybe I still do. But that's $1,500 for a Mr. Cool DIY system and while that gives me an extra heat source, and avoids me having to schlep my heaviest window A/C twice a year, I started wondering what it would cost to upgrade to central air. One HVAC guy quoted me a VERY ballpark number, over the phone, of around $7,000 after I told him what my situation was. Of course this same guy also quoted me $4,500 for a single 18k BTU mini-split so obviously he is not into those because that price is whacked.

I don't necessarily want to just throw away my hot air furnace. Yeah it's old, I'm guessing 30+ years old. However, it works fine. And ever since I bought the house I noticed the sticker on it that says something like "Equipped for air conditioning." I'm not sure what would make it equipped unless it just generically would fit standard size A coils.

So I started by looking up the cost of a condenser and coil.
Here is a Goodman 4 ton unit with coil and a 50 foot line set for $2,316.95.
https://hvacdirect.com/goodman-4-ton-14 ... d1662.html

I would need a bunch of other stuff and that's why I'm posting this.

But like...probably $3,000 or less? Not including refrigerant work which I may be able to borrow some stuff from my brother in law and get that done, too. Also that's only twice the single mini-split. Seems worth a look.

So it seems I can buy what I need.

No pro is going to retrofit A/C to my old-ass furnace. And the guy who is coming tomorrow is probably going to tell me that my ducting is insufficient (too small). Yeah, for modern cooling efficiency standards. But what if I want 70s standards? I'm not redoing my ductwork. And maybe I can just retrofit A/C into my furnace as if it was 1991 or whatever. What's the difference? It's not going to be as efficient as a brand new modern system but it also won't be as expensive. The idea is it would be as functional as a period system would have been. And the Goodman system I linked above is 14 SEER which is probably still quite a bit better than a standard 30 year old system so I'm still doing better.

Fortunately I found some manuals for my furnace in the basement...on the furnace. Here are some key pieces of info.
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One thing my furnace is missing is the controls for A/C. And look at that - the manual says exactly what I need. Honeywell Cooling Center R8325A. That has the fan controller and talks to the thermostat.

Even better, here's one on eBay:
https://www.ebay.com/itm/New-Open-Box-H ... SwlxNeqtI1

$71, not bad. Also my furnace manual shows how to wire it all up to my existing stuff.

I would also have to run a new like 5 wire thermostat wire down but my basement is unfinished so this would be a cinch. I am not sure what else I'd have to do. I would have to cut a giant hole in the duct on top of my furnace and mount the coil inside, on top of the furnace.

Other items I'd need, listed randomly:
- Condensate pump and tubing/pipe ($47)
- Disconnect switch for the condenser ($28)
- TXV ($90, https://hvacdirect.com/goodman-3-5-to-5 ... tx5n4.html), not required but should help efficiency
- Misc electrical stuff, like, uh, 8/2 or 8/3 wire and a 40A 240V breaker, or 10/2, 10/3 and a 30A breaker. 50 ft of 10/3 is $83 at https://www.homedepot.com/p/Southwire-5 ... /202316239. Maybe I can even use 10/2, not sure
- Pad and whatever else for condenser

Here are some other thoughts.

For sizing I came up with probably in the 4.5 ton range. So then it becomes a question of 4 or 5 because there is no 4.5. Part of me wants more, but you don't want to oversize A/C systems because it can lead to short cycling and poor dehumidification (from shorter running times). So maybe 4 ton would be sufficient. I have 3.6 tons of window unit normally and the upstairs bathroom and kitchen are not really cooled and tend to be warmer than the rest of the house. So it's probably closer to 4 tons than 5 based on that. The other thing is, if my ducting really is inferior (the guy will tell me tomorrow) then perhaps I am better off on the smaller end (4 ton) to avoid other issues like evaporator freezing. I think this makes sense. It makes even more sense because the coil linked above is actually a 4-5 ton, depending on the condenser used. So it's really a 5 ton coil with a 4 ton condenser. That sounds like efficiency to me, bigger coil, higher CFM, etc.

For brand, Goodman is cheap and made in the USA. Some people bag on them but I have been watching HVAC videos for the past few years. What I have learned is the installation is more important than the brand. Since I'm controlling the install, for better or for worse, no sense in spending big bucks. The other reason not to spend big bucks is there are some seriously diminishing returns for the very cutting edge super high efficiency stuff like 20+ SEER. These units have all kinds of electronic controls, variable speed compressors and all this nonsense that is likely A) less reliable and B) more expensive to fix when it breaks. So a Goodman 14 SEER is just right for me. Single speed. Simple. Cheap and easy to get parts for.

Down the road when I need a new furnace, there's no reason some or most of this couldn't be used. Worst case I'd need a new evaporator coil to fit a different furnace. The one above is $500. Should be able to reuse the condenser outside.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

The AR Heating and Cooling guy came and many things were discussed. There are many options but let me highlight the two primary ones that I was considering:

Option 1: Add 18k BTU single mini-split system to great room. He had a great suggestion on another wall to use which would make simple work of the whole job. I would mount the air handler above the window next to the chimney where the window A/C used to go. This helps with airflow, blowing it back toward the opening to the rest of the house. And I would have the condenser just below it sort of behind the chimney. This would be easy. Even the electrical would be pretty easy. However, he rough quoted an LG install at around $3,800 which isn't much different from the other guy quoting $4,500 without even seeing the house. That is just way too much for what it is. Ironically this quote and discussion may enable me to simply execute this option myself.

Option 2: Whole house central air, necessitating the replacement of my oil furnace with a new oil fired furnace and air handler. The good news is, he didn't see any glaring issues with the size of my ductwork. The only real issue was it was not insulated but that is a project I could tackle myself either way. It sounded like this option was going to be over $8k still.

Other interesting options:
Whole house heat pump, with a single condenser outside. Multi-zone. Either 3 ton for whole house + 1 ton for great room, which would help by giving independent controls in the great room for heating and cooling. Or add an air handler to the attic and have 3 zones, adding an upstairs zone. These options likely require me to give up oil UNLESS I just go full mini-split and keep the oil system in place as a backup (or when the power goes out). All of this is probably over $10k and possibly higher than that.

So I admit a whole house 22 SEER system would possibly be worth it from a heating/cooling cost standpoint, I don't know that I'm in the market for dropping like $12k on HVAC. That's way more than my other options. Of course attempting these options as DIY is the other avenue I could take to split the difference so I guess I should pull that string just to be fair. All that really means is whole house mini-splits. I don't think I'm up for that. His option would remove my oil furnace and replace it with an LG air handler, tie into the ducting, etc. Not doing that DIY either.

I'm still leaning toward one of the following:
DIY single zone 18k BTU mini-split in my great room. I could even buy something other than Mr. Cool since I think they all come pre-charged. So I'd have to flair a couple ends of the line, possibly nitrogen purge, but at a minimum just vacuum down before releasing the charge. I need to price some stuff other than Mr. Cool. If the LG stuff for example is $2,000, that doesn't include electrical.

Or, my DIY whole house solution with adding a coil to my existing furnace, the controls, condenser and all that for perhaps around $3k.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

Another permutation is to block off the vents going to the great room and use the 18k mini-split as the year round full heating and cooling in that room. I could downsize the oil nozzle on the furnace and this would probably have a real energy savings.

I could also pair this option with whole house central air. And still just have the great room on a zone controlled by a separate mini-split. With this plan, I would probably start with the mini-split and maybe isolate the great room from the furnace. Down the road I'd pursue a central option for the house and likely keep the mini-split.

Interesting.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

LG 18k mini-split (20.5 SEER) is $1,838.99. To match the Mr Cool I'd have to add a line set which is $63 for 15 feet.

Also they have many pricing and efficiency options just in 18k so I should look at those. Like a 24 SEER for $1,888.20. Or a 19 SEER for only $1,393.20.

I will have to check the Mr. Cool kit to see what other nickle/dime stuff I'd have to buy on my own but it looks like $2,000 would do it for theG vs $1,4xx for Mr. Cool.

I may consider wall mount.

He also just quoted me $2,850 for a Gree if I do the electrical. The other prices also don't include electrical. I have to look up Gree costs but he was not too thrilled with them in terms of having call backs. LG would be a 12 year warranty with him and he has a great relationship with the regional rep so the coverage is real rather than theoretical.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

So I just put in my 4 window A/C units for the main part of the house. That's 2.6 tons of cooling. When I add the 18k unit to the great room, that will be 4.1 tons, which is probably perfect.

Anyway the plan is just not to put the great room A/C in. We will tough it out until I finalize the mini-split plan, purchase the parts, and install. Hopefully this project doesn't take all summer...
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

https://mrcool.com/diy-3rd-generation-e-star/

Apparently this is now available in a 16' line length which would be perfect. It's the only system I know of with a DIY warranty (5 yr parts and "labor" and 7 yr compressor). Also there will be $412 of rebates (federal and utility). I should be able to do this for well under $2k. In fact I may be able to do it for $1500 all in. Just can't seem to find where to actually buy the one with the 16' line option. It may have just come out so maybe I'll have to wait. I did contact Mr. Cool.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

16 foot line set, pre-charged: https://iwae.com/shop/12k-18k-btu-mrcoo ... 20975.html

I'd rather buy as a kit and that may not be an option. I may either have to just spend the extra $200 and end up with the 25' set as a waste or buy the kit in pieces which couldn't possibly be a good value but may offset some of that $200...
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

Ah, foo.
Am I able to buy this package with 16' precharged lines instead of the 25' lines ?
0
BEST ANSWER: Not at this time. Any 16' line would have to be purchased separately.
Kyle Davis Expert on May 5, 2020
I just don't like the idea of coiling up 9 feet of unused line behind the condenser, even though that is sanctioned.
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

Drag my feet and I shall receive!!

They are now offering a 16' line set option which saves $200. The 16' option isn't cheaper as a combo even though the set alone is $40 cheaper than the 25'....

Current price from Ingram's is $1,466.10. I may just want to pull the trigger on this soon.

https://iwae.com/shop/18k-btu-20-seer-m ... 20869.html
kevm14
Posts: 15200
Joined: Wed Oct 23, 2013 10:28 pm

Re: Upgrade my furnace to central air?

Post by kevm14 »

Total fail on my part. After being back ordered for months, it is now $1,972 and I no longer see the 16' line option. I suck.

Oddly if I press scratch and dent there is still the 16' line option and the price is $1,420.35 but then it still says on back order. How can a scratch and dent be on back order?
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