[rnk]

Can you explain a little more what you did? Just a little bit, like what brand, did you replace an existing home system. Who did the electrical, did you need duct work? I already have a forced gas system, you can just connect it up? If I only had say 4-5 rooms on one story it would be a lot easier.

[sokoloff]

Lots of good YouTube videos and good DIY HVAC content on garagejournal.com (the latter will have good discussion on brands as well as DIY installs).

For a case where you have a ducted gas furnace, you are probably better off with a traditional A coil evaporator, especially if you want invisible in the living area of the house. Those are not as DIY-friendly (but anything is DIY-able if you're skilled and bold enough, willing to learn, and willing [or eager] to buy some tools :) ).

[abakker]

Durastar 36k Dual head unit from ACwholesalers, buy 2 stage harbor freight vacuum pump, micron gauge from amazon, a bunch of manifolds, and fittings and adaptors from amazon, some NICE shredder core extraction tools, a NICE line set flaring tool, a pipe cutter, pre-insulated line set, 14/4 cable from outdoor unit to indoor units, 5/8 AC condensate pipe from indoor units outside, lots of zip ties, pipe wrap, and line hide. I pre-provisioned a 40amp breaker and an outdoor disconnect/breaker panel (and an extra 120v GFCI plug so i could easily run the vacuum pump). Sub-panels are your friend.

I used all Aluminum SER cable to run the sub panel and a copper whip from the outdoor unit to the breaker (terminals on the AC unit are rated for copper wire).

If you had a forced air gas system, you can get a heat pump coil and condenser to replace the AC unit. ACwholesalers has those too. If you are able to, you can add one to your system and run "dual fuel" where the heat pump runs down to about freezing, and only kicks on the gas for heat when it is outside the efficiency range of the heat pump (model dependent).

My house is annoying to condition. It was built in 1987 by people who had interesting notions about efficiency, space usage, and material selection. As a result, the surface area to volume ratio is pretty poor and it is not very efficient. the duct design is...TERRIBLE...and so a lot of the house wasn't served well by the HVAC.

I added a mini split to address the considerable heat load on the southern side of the house, and am working to replace the air handler and duct work entirely for the rest of the house.

Central air can do several things mini splits can't do, and that's why I want to keep it instead of just adding 4-8 more zones of minis splits, which would be WAY easier. 1. Air filtration, 2. Fresh air intake 3. Humidification 4. air mixing. it also seems to be the cheapest way to solve heat/cool + the things I just mentioned. Even with ducting. Design/Sizing/install is worse and harder. Leaking/poorly insulated ductwork can also cost a lot of energy and so takes a lot of effort to prevent.

HVAC as a mechanical system in homes is pretty awful, and the load calculations are frequently not well in line with the "theory" of system capabilities. Static pressure, air exchanges, etc all play Major roles in system sizing and make it very hard for technicians who do not live in a house to accurately evaluate the "real" load vs the theorized one.