HVAC replacement

Question

we just recently purchased an older home- 1978 - 2200 sqft, 2 stories, 2 14x20 returns - one downstairs, one upstairs, 5 ton 10 seer system, 10yr old goodman air handler but the condensor is unkown but looks very old and worn - attic insulation is cellulose but needs more. We've been living in it for about 30 days now with fairly cool weather. (Central Texas) The system heats very well (natural gas) but almost too well, the upstairs gets very warm compared to down - but this may be a separate issue. Now the temperatures are starting to pick up (83 forcasted today) and we've noticed the current AC system is not capable of keeping up. I installed a Nest because the old thermostat was shot plus I already had it from the old house and yesterday with 80 degree temperatures, the nest reported 77 degrees inside and could not get below that despite being set to 70 - this notion is scary considering the days are only going to get hotter.

So, a local company has had an ad in the paper for full system swaps (nothing else in terms of ducting, etc, just system swap including air handler, furnace, coil, condensor, etc) There were two packages in which pricing expires this friday that we are considering - they deal primarily with Lennox systems.

The first package is with an undisclosed (in the AD anyway) Lennox system, 16 SEER gas system, Media Filter, UV Light, 10 year P&L, 6" blown-in insulation - this was recommended by the salesman - for $5,898

The second package is with a Lennox XC21 system, (21? seer or "up to"?) "super efficient system" 2 stage with variable speed motor and media filter - for $7,998. To get the same "package" as the first one, which includes the UV Light, 10 year P&L, 6" blown-in insulation adds $2,000 for a total of $9,998. The salesman said this is of course a really nice system but you're going to pay for it and persisted that the first package was the better way to go.

Now to my questions:

1. We're considering the XC21 (second package) because we like the sound of the greater efficiency and the decreased utility bills, but is it worth the extra money compared to the first package?

2. That being said, since we seem to have a balance issue between the first and second floors, the salesman recommended increasing the size of the first floor air-return to a much greater dimension than 14x20 but this doesn't make much sense to me since the size of the return duct will remain the same...? This was recommended despite the system we choose.

3. The possibility of a Zone system came up but this particular company charges $3,500 for a zone system though if we went this route we'd probably go with package 1 to offset the cost. However the salesman insisted that we try increasing the size of first floor return first to avoid potentially un-needed costs upfront. I'm assuming the system in either package is capable of "powering" a dual zone system

Thank you guys for any help. I've been a long time fan of "Stack Overflow" which is the computer programming equivalent of diy.stackexchange and has been a great help with my day job. I look forward to any help you guys might offer! Thanks again.

Answer 1

It's hard to say for sure one way or another without evaluating your specific circumstances, but the SEER 21 option is probably not worth it. You get diminishing returns from increasing SEER. Going from SEER 10 to SEER 16 should get you close to a 40% reduction in your cooling costs; going to SEER 21 only brings that up to about a 55% reduction. An extra $4000 is quite a bit to pay off, and between SEER 16 and improved insulation, there probably won't be enough potential savings left to cover it.

Also, make sure you take care air sealing in the attic before adding in the insulation. And make sure the ducts are well sealed with mastic or foil tape, and well insulated. Those will be much more cost effective than a higher efficiency AC unit.