[microcraft]

We've put off replacing our 2 HVAC systems long enough.

Scenario:
Raleigh, NC
2 story House is appox 3100 sqft built in 1996.
Downstairs unit is an old Goodman/Janitrol Gas pack, PGB030075-1 (original). I love this thing, very little trouble over the years, but only 10 SEER.
Upstairs is split, AC unit outside is a slightly newer Trane XR-12. Rest of that system is in the attic.

We have Natural Gas, both furnaces use it.

Ducts need to be replaced, all of them.

For the downstairs, I'm going to stay with a package unit. Never had issues keeping the 1st floor cool/heated.

My main question is that our upstairs AC never, ever could keep up during the hot summers. It would be running 20 hours a day, only getting a break around 4 AM when it could catch up. I had to get a portable roll around AC unit to put in our bonus room to get the temp below 80. That leads me to think the system was undersized for this area. I forget what the tonnage is (1.5 or 2 Ton?)
(In addition to new HVAC's, I think I will also need to be looking at some form of better attic/roof insulation to keep it cooler if possible)


I'll let the local HVAC guy do the load calculations. But what can you guys tell me as to what type of equipment I should be looking at for the upstairs?
Do they make super insulated ducts for the attic? The original ducting (R-8) was run around the perimeter of the attic (it is a walk up attic) to give as much floor space for storing junk as possible. I'm guessing that increased the length of some of the ducts by at least 2X.

Variable speed compressor & blower? Any other new tech that would help?

Advice, comments appreciated.

Walt

 

[bobboan]

I'd suggest Bosch for both the package and split system, but you'd better do your homework on finding a competent, reliable contractor. He's 95% of the equation.

 

[rider77]

Many contractors will not do a load calculation. You will tell them the old unit struggles, and they will automatically add a ton or two to whatever you have now.

 

[Makeitcold]

Manual J to figure out how many btu's your home gains/losses during the year. Do one for yourself for free at loadcalc.net. Your going to meet lots of contractors that want to be lazy with your money ad will reassure you that its unnecessary, they have X years of experience etc. The best way to save money is to insulate as best you can afford or is reasonable for your climate, this allows you to buy smaller sized equipment which is a bit less money but it will use less power to run, saving potentially thousands of kw/hrs over the equipments life.

From your description of the ducting I'm guessing your running a really high static pressure, losing capacity and airflow. Probably will need to redo the ducting to ensure indoor comfort this may or may not mean losing some storage space in the attic. Variable speed a/c does not maintain constant airflow, airflow drops to match compressor staging, so not a good idea if you've got a bad design like yours

 

[microcraft]

Bosch, huh! Didn't know they made HVAC stuff. I'll definitely look into it..

I have a friend that did his own Manual J calculations years ago, so I'll pick his brain. Thanks for the loadcalc.net site. Attic/roof insulating really does need to be done. Nothing on the rafters now, so anything we put up will help.

Thanks for the info & help.

 

[BaldLoonie]

Bosch doesn't make it, the Chinese do. Bosch just markets it. Looks like a nice idea and low priced way into inverter/variable capacity heat pumps. The split systems can be put on a gas furnace. The packaged unit is all electric.

Foaming the roof deck would really keep the attic cool. Friend who was a foamer did his and said the attic stayed about 10° above room temp rather than 140-150 typically.

 

[vstech]

First things first.
Before bothering with a load calculation or new equipment and ductwork...

Decide and implement the insulation of the home.

It is primary, and will drastically alter the load calc.