It is time to replace our furnace and air conditioner. We have had multiple bids and brought in an independent expert to confirm everything. So we are down to two options that we were wondering if the SIGforum brain trust has any suggestions regarding. Our home is 1600 square feet at ground level with a 1650 square foot basement. We live in Northern Utah — cold and hot. We are looking at the following systems:

100,000 BTU 95% furnace with a 4 ton 13 seer air conditioner or

100,000 BTU 96% 2 stage variable speed furnace with a 4 ton 14-16 seer air conditioner.

We are upgrading from a 3 ton 80% furnace as we are finishing our basement and the systems are getting rather old.

There is a $1600 difference between the two systems. Is the higher-end worth the cost or with a house our size, with half being the basement, would we be fine with the cheaper system?

THANKS!

Just very quickly, I am concerned they are increasing you to a 4 ton system from a 3 ton system...

With A/C, airflow is critical, and if not sized properly, then you will be in real trouble.

Can't put 3 lanes of traffic on a 2 lane road, so, is your ductwork sized properly to handle 4 tons of air. ie, 400 cfm per ton as a minimum, if your duct is currently only allowing 1200 cfm, and you need 1600, then???

Why is airflow critical? Because liquid does not compress, and your compressor can't handle liquid, only gas... If it can't pick up enough heat to turn from a liquid to a gas, your compressor will have a greatly reduced lifespan.

Airflow is critical. It is why sizing and filtration matters so much.

That aside, I am a trailing edge of leading edge technology guy. I like to keep it simple, less that can break, etc. Once you start getting fancy equipment, it goes up in cost, and less likely service techs will have parts on their van, meaning, longer to get back online.

I'm not a HVAC pro so keep that in mind. We are in Illinois 35 miles north of St Louis. We have a 1600 square foot ranch, 4" walls and full basement with 12" attic insulation. Our furnace is 70,000 btu 92% and our AC is 2 1/2 tons and it does fine and is relatively economical. An in-ground basement doesn't take much to heat or cool. The original furnace in our 1973 home was 150,000 btu and probably 60% efficient. The 70,000 replacement does very nicely. How far north you are in Utah and how well insulated your home is would have a definite bearing on this.

Thanks everyone for your replies and emails with advice!!! To answer some questions/concerns, the house has struggled with the 3 ton system, when it is really hot, since we bought it 17 years ago. This year has been OK but it has been a cool spring/summer so far.

The question of the ducting size has been a question we’ve had to address. I had one guy tell me to tear everything out and start over. Everyone else has said my ducting is properly sized for a bigger system. In as much as the basement is completely unfinished. I think if it was really a problem, we would have multiple suggestions to start over with the duct work.

You all raised an interesting point regarding size/BTUs. The upstairs floor has always been cold as the floor (basement ceiling) has never been insulated. We are planning on putting in sufficient insulation to help with noise in the basement. Plus we are going to do the outdoor walls which only had the “blanket” insulation partly down the the walls. We do think the insulation will make a difference we just don’t know how much.

Reliability is a concern. Simple is best in my book so the 2 stage has been a concern. Everyone’s comments and emails has really turned me away from it.

Thanks!!!!

Last year we got a two stage furnace with the variable speed fan and love it but we have a two story house and the new furnace puts out plenty of air volume to do a good up on the second floor from the furnace in the basement which the old one did not. In your case though I agree it is not going to do as much good. If the house has not been cooled adequately with the 3 ton AC then it makes sense to try the 4 ton or maybe 3.5 ton. We went with 5 ton after being advised that 4 should work fine and don't regret it. I told the guy my wife wants the house to be at 72 if it is 100 outside and if it is not she is going to be down at your office making sure you know she is not happy and with that he said then 5 ton makes sense LOL. I know so many people who complain that their AC does not cool well on a hot day and the government says we should set the thermostat at 78 in the summer, screw that. We have been really happy with our new system. Good luck.

Maybe it's different for the area but here in Texas the Professional rule of thumb is one ton for every 500 SF.
Too little it runs all the time, too much and it doesn't dehumidify correctly.
YMMV but let the Pros figure it out.

Something seems off that you have two contractors and and 'independent expert' all say you should up your system size. Did they say that the old one was undersized for the house? Like maybe it was designed with ductwork to handle a 4 ton system and they accidently or mistakenly installed a 3 ton system? It really seems unlikely you could jump two sizes with the existing setup, but I am no expert.

quote:

Originally posted by BB61:

Reliability is a concern. Simple is best in my book so the 2 stage has been a concern. Everyone’s comments and emails has really turned me away from it.

Its sad that you'd compromise your COMFORT, while being concerned about a 'non-issue' reliability concern.

quote:

Originally posted by Excam_Man:

quote:

Originally posted by BB61:

Reliability is a concern. Simple is best in my book so the 2 stage has been a concern. Everyone’s comments and emails has really turned me away from it.

Its sad that you'd compromise your COMFORT, while being concerned about a 'non-issue' reliability concern.

My American Standard 2-stage furnace and A/C has been flawless for the 5 years I've had it installed. I really like it and would recommend without hesitation a 2-stage system for anyone thinking of a new furnace and A/C.

...

quote:

Originally posted by Skins2881:
Something seems off that you have two contractors and and 'independent expert' all say you should up your system size. Did they say that the old one was undersized for the house? Like maybe it was designed with ductwork to handle a 4 ton system and they accidently or mistakenly installed a 3 ton system? It really seems unlikely you could jump two sizes with the existing setup, but I am no expert.

We’ve been told for years that it was too small. The home was originally built by the local school district. Anything that the students and their teacher did has been fantastic. If there has been a problem, it was by the non-student sub-contractors. Everyone thinks (is guessing) the HVAC contractor bid a 3.5/4 ton AC unit and put in a 3 ton and nobody caught the swap. If I ever build, I’ve learned a lot about how contractors and/or their subs can take advantage of you.

quote:

Plus we are going to do the outdoor walls which only had the “blanket” insulation partly down the the walls. We do think the insulation will make a difference we just don’t know how much.

Is your basement a walkout with a long exposed wall? Ours is not a walkout. I'm not sure what you mean by "blanket insulation partly down"? I was involved in the building of our house in 1973 and I used the blanket insulation full length of the first floor studs. There is no insulation on the concrete basement walls. I used the best blanket insulation I could get in a 4" wall which I think was either R11 or R13. Going back and improving that now would be difficult and costly. We have no insulation in the basement ceiling and it is comfortable down there all year. I did check Salt Lake City climate with St Louis and it is pretty comparable. When our system was installed in 1973 by a pro, the thinking was to be able to raise or lower temps quickly. I think current thinking is that on the very hottest and coldest days of the year, your system should run most of the time. In AC, a quick cool down will not remove humidity very well. Our replacement system in 2003 was an Amana (Goodman) which has run efficiently and been fairly trouble free. I think Amana is considered a builder quality unit rather than top of the line. We will be replacing in a few years I suspect. It sounds like you need to get a good recommendation for a quality installer and and let them figure it out (and pray that they are correct). How can you correct your insulation problem?

I like American standard. We don’t use furnaces here so I cannot comment on that. But, insulation makes a huge difference and pays for itself within months and can easily allow for a smaller Ac unit. I’d do that first since your Ac is working Asap before the hottest part of the summer, see how your 3 ton does and then go from there on the Ac sizing.

quote:

Originally posted by Gene Hillman:
How can you correct your insulation problem?

That’s a good question. Fortunately, as the basement is unfinished, we just pulled down the blanket (rolls of insulation wrapped around the top 1/3 of the basement’s walls.). We are going to put insulation between the studs and in the ceiling like you would normally see.

Not sure in UT but here we need a continuous R10 on the basement walls to bring it up to code (has gutted basement and is at this stage right now). A 2" Foamular rigid-type insulation for example. Johns Manville has a similar product to Owens that is R13 rigid. The insulation is attached to the concrete with adhesive and also provides a moisture barrier. Leave a small gap between the foam and the wall framing to run your electrical.

The other option would be to put up a moisture barrier, frame it and use fiberglass in-between the studs. Believe this requires a R13 equivalent rating for our code.

I have no interest in insulating between the basement and main floor. It's not required and I doubt I'd get the money back. I'd put extra into the attic insulation or a more efficient HVAC.

Obviously you local codes would take priority but maybe this gives you some idea of options.

quote:

Originally posted by BB61:

quote:

Originally posted by Gene Hillman:
How can you correct your insulation problem?

That’s a good question. Fortunately, as the basement is unfinished, we just pulled down the blanket (rolls of insulation wrapped around the top 1/3 of the basement’s walls.). We are going to put insulation between the studs and in the ceiling like you would normally see.

Have someone come in and do the spray foam on the open walls. It has terrific R value and works REALLY well as it also seals up any draft issues.

quote:

Originally posted by smschulz:
Maybe it's different for the area but here in Texas the Professional rule of thumb is one ton for every 500 SF.

When my local contractor was estimating the size of a unit, he took into account not only square footage, but ceiling height (volume of room), and windows, how many, how big, facing which way, and type of glass.

You would need a guy who would run a proper heat load calculation to make sure the final system selection would satisfy the requirements.

Load calculation would include all the details of the structure, kitchen equipment, number of people.

Good lucks,