Hello,
Make sure you have the right sized equipment. Using efficiency to calculate output of furnace is the first step. Don't let someone downsize you to the point of stupid. Yes new equipment is probably more efficient than your 50 year old furnace, but not necessarly. You can check the efficiency by dividing output by input and multiplying by 100. Many older systems were more efficient than people want to believe. Newer higher efficient equipment is smaller than older equipment, but the higher efficiency it is, the quicker it will fail. Heat exchangers are a common problem. As far as I know Heil is middle of the road good equipment. It is not popular in Texas, but never the less probably equal to most brands seen here.

Installation of an AC system, usually requires larger ducts to cool the same sized romm as to heating the room. With this said, just admiring the existing duct, does not tell if it is large enough for the layman. Using rigid pipe is probably best with custom designed duct the top of the list. This just don't happen in Texas. Most homes are ducted with flex duct. It is cheap to install, and low labor. Air flow is quite with flex duct, but it has it's problems. If animals get into the attic, they can easily damage the duct looking for fun. I have some unwanted visitors in my attic. Since the duct is steel, the only damage was to the insulation last winter. I will reinsulate a couple of small areas and all will be good.

Using round duct with insulation on the outside is a good comprimise for quality and durability. It cost about double of flew in material costs, and labor is probably triple, over using flex duct. Some areas of the country require metal duct. Just not Texas. if the unit is in a closet, it needs to be installed to local code. Proper exhaust venting and attic sealing. Fibre board is expected in some installations, but metal plenums are preferable. I recently saw a plenum make of 1/2 inch insulation foam board as found at Home Depot. I told the owner of the dangers of fire, but he was very cheap. This is not adequate and should not be used. Metal tape to seal joints at a minimum, and mastic joint sealer is prefered.

If the registers whistle, they are either too small or the system is operating at too high air flow. If you use a variable speed blower you will never know you are screwed until the cooling does not keep up.

IMO current practices are kinda overrated. I do not use nitrogen, I don't evac the system to 500 microns, but I also do not do 410. These practices are necessary with puron. Even then, the systems fail quicker than 22 systems.

I have nitrogen, but do not see the need to purge with it. If I purge, I use 22 and recover it. I believe in filters.

Duct sealing is tops on my list. The instructions in a box of flex duct will tell you how to install. Two raps of tape and a strap for the inside liner. And, a strap for the outside jacket. The return air duct size is of utmost importance. To control air flow better, we use 7 inch flex. We use 6 inch flex for small rooms such as closets and bath. All supply ducts have dampers. Ideally, a rigid main trunk with flex duct to the individual areas work well. All metal ducts will allow room noise to move to freely.

We use nitrogen only for leak testing the line-set and indoor coil. We use 18 gauge 8 conductor thermostat wire. If it is a heat pump, have an outdoor thermostat installed to control the heat strips or furnace for a dual fuel system.

Proper electrical breaker size. A receptacle within 25 feet of the equipment. And, a light for servicing the system. Oh, I am not one who believes in removing the furnace or air handler door to change the filter.

Phillip

"When the company does lousy braze jobs,Â"

Many new systems use TXV (thermostatic expansion valve) top meter liquid coolant into the evaporator coil. TXVs are not very tolerant of contamination, including the junk from traditional flux used in the brazing process. No flux brazing rods often use phosphorous (just a few %) to clean the surface during brazing.

"Âdoes not use nitrogen gas while brazing,Â"

Copper oxide scale will form inside the lines during brazing if oxygen is present. The scale can break loose and clog a TXV (most commonly the scale holds the valve open when it tries to close). The older orifice metering was not as prone to this since the pressure would often just blow any scale through the orifice. To prevent scale formation low pressure nitrogen is used to fill the lines during brazing. The nitrogen flows through since any real pressure would interfere with the brazing process.

"Âdoes not vac the system correctlyÂ"

A new system must be pulled down and held there to remove ALL moisture that is present. It is pretty common to pull a good vacuum, then wait and the vacuum goes away as moisture in the system boils off. Pulling a vacuum, waiting, then pulling again (repeat until the vacuum holds) ensures no moisture or other volatile contaminants are present.

"and purge at least one timeÂ"

Filling the system with nitrogen to operating pressure then pulling a vacuum again can help speed the cleaning process. If you are willing to spend more time (think hours) the purge is not really needed.

"and then use a digital vac gauge for the final micron reading you are already heading for trouble down the road"

This is a little exaggerated. The digital gauge has the same sensors as the older analog systems, but adds an analog to digital converter to allow numbers to be read directly.
An analog micron gauge works just as well, they are just not as convenient as a digital gauge.

Purging with nitrogen is kinda like using bar soap to brush your teeth. For this reason, I do not purge with nitrogen.

I like to purge with 22 and probably will for many years more. Working with 410 requires a different approach. Since it is a blend, you can never be sure of removing the crap with the purge. On other sites, Nitrogen is considered junk to purge with. Maybe to test pressures, but new beliefs say nitrogen is a poor second choice.

As to vacuuming to 500 microns, anyone can vac a system and not vac the moisture. This is what a purge is for. purge with the gas you intend to use and recover.

Since I have been doing the same old same old for many years, some snott nosed kid will have a hard time convincing me that f22 needs to be vaced to 500 microns. IMO this is just a way to sell a new toy to the ignorant.

When f22 is a blend, I may change my attitude, but I have a few years to go before I will make that decision.

Remember, I live in an area, where the climate demands quality or the system fails. At one time I fixed the screwed up installs for 2 companies. Also the higher standards were started by companies that pretend to be better than Goodman.