Not an urgent need - but we have had our HVAC system worked on a couple of times in the past two years.
Whenever I have a number of repairs to something I start thinking about replacements.
Our HVAC system is about 13 years old. It is an Amana furnace and heat pump. It is a 13 SEER unit, about 3.5 ton capacity. We have two zones - upstairs and the basement.
Our house is about 1600 sq. ft. upstairs with an approximately 1000 sq. ft. basement. We live in the mountains of North GA. The current system "struggles" a bit for controlling the 2nd floor. Primarily because of poor ducting - which cannot be easily remedied.
So - in planning for the future, I got a some estimates on systems.
16 SEER unit w/ 3.5 tons of capacity
16 SEER unit w/ 4 tons of capacity
18 SEER unit w/ 4 tons of capacity
They are all "dual fuel" w/ heat pump and propane furnace. TVA and our EMC are raising our electrical rates - which is another reason to consider a more efficient unit.
Right now I am leaning towards the 16 SEER unit w/ 4 tons of capacity. The extra capacity might help alleviate any problems we have w/ heating/cooling the 2nd floor.
Should I consider the 18 SEER unit? Should I consider the 16 SEER unit/3.5 tons?
This is all just planning and budgeting for the future. I don't like unforeseen expenses.
I'm curious as to what the condition is in your second floor that the A/C doesn't control. Is it too humid, or too warm? A common problem around here is that people have too large of a unit installed, so it short-cycles, bringing the temperature down, but because of the short run times, the humidity is not controlled, and results in an uncomfortable home.
We run a dehumidifier in the summer almost 24/7, which does put a little heat back into the house, but with the thermostat set to 76/77ºF, it's far more comfortable. I also tweak the diffusers a bit to send more of the cool air upstairs, and we have a fan setting on our thermostat for "circulate", so it will run say 10 minutes of every 30 whether there's a call for heating or cooling or not. That also helps filter the air and keep it cleaner.
Sorry I can't really help you with specs on a new unit--that's outside my wheelhouse.
JL, your question is much more complicated than it seems. Jason hit on much of it.
You need to look at the house as a "system" and try to diagnose the overall problems.
What is the problem?
Is the attic accessible and well insulated? Could you add more insulation. Attic insulation is very important. It's a 2fer. Rejects heat in summer and retains heat in winter. You might be able to spend a thousand or two in the attic and cut the size of the system substantially. Unfortunately, they sell HVAC systems "by the ton" and many think bigger is better so they push you toward bigger more expensive systems.
In fact, smaller may be better. Jason touched on it, Bigger systems, especially AC tend to short cycle and not do a good job of dehumidification. Also consider that (simplistically) they size systems for the hottest and coldest day of the year. So the AC is sized to handle the house and keep it cool on the hottest day. (Not really, but they use the statistically hot day and the similar cold day) Let's say that in your area that's 95 degrees and 10 degrees. (Whatever) So on every other milder day, the system is too big. Then if they sell you a ton or two extra, it's REALLY too big.
Think about what happens if the system is slightly too small and it goes to 98 Degrees one afternoon. You don't die, the system simply runs until after sundown, trying to keep up and the inside of the house is 78 instead of 74. Same with heating. Lets say it falls to 5 degrees on one bitterly cold morning. The inside of the house may fall to 65 instead of 72. Put on a sweater until the sun comes up.
In your case, its the furnace that controls comfort in winter anyway.
How about your windows? Could they be improved at a fair cost?
After a house is moderately well insulated, air leakage is the dominant factor. Look at eliminating drafts. A few house and cases of caulk can really help. Gaskets under receptacle covers. If there is access to the attic, caulk where wires and pipes pass from floor to floor. They are like little chimneys sucking conditioned air out to the house. (Try not to fall through the ceiling)
There are dampers and booster fans that can be installed inside the ducts to improve performance. And Jason mentioned tweaking the system. It's called balancing. Close down registers In rooms that are warm enough (winter) and open them wide in rooms that are cool. Force the warm air to go where it's needed. Try not to reduce overall air flow over abut 10% You may have to re-tweak it for AC Once you figure it out, you just change things slightly in spring and again in fall.
Anecdote: I built a very well insulated 1800 SF house over a unheated 1000 SF basement and sold it. Put in a 2 ton Heat Pump. (A toon for 600 sf was the norm and the Building official was so upset they made me put a letter in the file that if it were inadequate I wudl upsize it.) First owner finished off half the basement and just hacked into the existing ductwork. Second owner finished the other half and did the same thing. Third owner is living in a house with 2800 sf and a 2 ton heat pump. At about 13 years he complained, not that the HP was not adequate, but that it died. Turns out he apparently NEVER changed the filter and it had abut an inch of crud on it. Service guy put in a clean filter and pushed a reset button and the owner used the system for two more years.
So, if I were you I would cut air leakage, improve insulation, check the ducts for easy fixes, and install a middle of the road system. MAYBE 16 Seer and stay away form the exotica.
PS, is the basement wet? As you can see, I can go on and on.
There are no returns upstairs. When they did the ducting - I don't think they did a good design. Upstairs is colder in the winter and warmer in the summer.
About 5 years (or so) ago, I replaced all the cedar siding on my house w/ Hardiplank. At that time the house was wrapped w/ a layer of Tyvek house wrap.
When I painted the Hardiplank, I caulked ALL the seams before I painted. Before we had a problem w/ japanese beetles - now we don't. I don't have any problems w/ air leakage from receptacles or switches.
The insulation in the walls and attic are good. There is no insulation on the basement "ceiling" - but I did put up a suspended ceiling in the basement - and it is a "conditioned" space. The basement walls are cinder block on three sides (daylight basement) and concrete on the remaining side. The coolness of the basement does mean it is damp.
The windows are double paned - but are metal. Which means they do conduct some cold (and possibly heat - but we don't really notice that). I have contemplated replacing the windows - and that may be happening in the future. IDK if I would go for wood or what. The LOML doesn't like vinyl.
Our H&A guy is of the opinion that our system is fine for now.
What's driving my thoughts are:
Had $1.2K of repairs in the past 2 years. One was to replace the heat exchange unit - the unit was free - the labor is what cost. Had to do a number of minor repairs.
The price of electricity is going up. TVA and our EMC our raising our monthly rates.
The upstairs doesn't get enough heat in the winter or a/c in the summer. Ideally we'd have a third zone - but there is no way to put a 12" return from the air handling unit to the upstairs.
Two things not mentioned. One is a variable speed unit. I live in central FL. My variable speed unit is essentially a five speed unit, both the air handler and condensing unit. Because of its variable speed it will not short cycle. As it nears the set point it slows down. This help keep the air moving and in the summer with lower humidity and running at lower speed does not take as much electricity. The second thing to consider is zoning. Zoning is where cut offs are put into ducks so anywhere from one zone to the whole can air at a time. With variable speed if the whole house needs AC all ducts would be open and the speed of the unit might be a four or five depending on things like outside temp. Then when the downstairs hit it set point the duct cut off would close to the down stair and the unit would ramp down to a two or 3 depending on demand. As the air handler might be servicing only on half of the house when a zone shut down it cuts the air volume so as not to over pressurize the ducts in that zone. I currently live in a 2500 sq ft ranch. It is long and get the sun at different points at different times of day. There were always warm zones. I had it zoned into three zone and the temp never varies by a full degree in the whole house, unless you want to set one zone at different temp. I got an 18 seer from carrier, electric bill dropped a lot.. They determined my 2500 sq foot house in central fl (one of the hot spots in the states) only needed 3.5 ton unit. Had it four years and I am very satisfied.
I gather you have a two story house over a basement???? You are calling "upstairs" both levels above the basement?
Balancing is your friend. In winter reduce the air supply upstairs by 25 to 50% and open the ones on the first floor wide open. Dump the heat in low and let it rise. In summer, do the opposite. Choke down the ones downstair and open the ones upstairs. Dump the cool air in high and let it fall. If there are doors on the stairs that could isolate the floors, leave them open. And, sleep with the bedroom doors open if there are no returns in the bed rooms.
This is not as complicated as it sounds. I do it in my house and it takes about ten minutes.
I was a Home Inspector for 32 years. I am a fan of simplicity. Locally I saw very few zoning systems. They were poorly installed by companies who did not really grasp what they were doing. I saw several that had never worked and the owners did not even know. (The wiring to the dampers was just dangling and had never been connected.)
My friend flipped a house with a sophisticated thermostat. The buyer/owner couldn't figure it out and asked my friend to teach him. In short order he called the service company to come and give him a simple stat. In all my years of inspecting I almost never saw anyone using a programmable stat the way it was intended. They admitted they tried and gave up and just programed it to Hold 72.
The caulking I was referring to was on the inside. Air leakage is very subtle. I hate to suggest it because I am putting you in the hands of the Philistines, but you could have a Blower Door test done. They install a powerful fan in a exterior door opening and create suction of pressure on your house and trace the leakage. Sometimes its shocking. OTOH, some air leakage can be good.
I am still skeptical of high efficiency systems and zoning. The people locally who pass for technicians say things like "Gaulee! I ain't never seed one of these before! and then start charging you for replacing parts.
Somebody came to my cousin's house and did a very sophisticated thermal scan and blower door test. Then they suggested almost $15,000 in repairs and upgrades. (A fortune in caulking) Said it would cut his bill in half. His bill was about $1500 a year if you took out everything except heat and air. It would have taken 20 years to recoup if you disregard the interest cost for the money. Of course, If the interest was 5% he would have been treading water. Also, he was 80, I pointed out he was not going to live long enough to make this practical.
Be careful. A 20 Seer unit will not solve the balancing problem.
Upstairs is the 2nd floor. The 1st floor is fine in terms of heat and ac - as is the basement.
The 2nd floor - nope. Enough heat goes up the stairs to make the upper landing tolerable - but the bedrooms are cooler in the winter and warm in the summer.
There is a single duct in each of the upstairs bedrooms. The main duct for upstairs goes from the basement where the HVAC unit is to the upstairs via a large duct. The duct presumably ends behind the upstairs hall closet and has three smaller ducts (probably flex duct) going to the registers in the bathroom and the two small bedrooms.
There is no space for a return.
We've tried adjusting the registers to help w/ air movement. It has helped to a degree - but not enough.
Can you get to the three ducts upstairs? Are they in a knew wall or some accessible space? If you can maybe you could add a second duct into each bedroom. And if that does not work, there are booster fans available the can be inserted into the six inch ducts to increase the flow.
If heat goes tot he landing, are you keeping the doors closed, preventing it from warming the bedrooms?
Another possibility is a "relief". In this case, a hole through the floor and the ceiling below to let air circulate. You may be able to offset the holes in a joist cavity so you can't see through them into the other space, and it cuts down on sound transfer as well. They could have a fan in them also.
And, I saw your prices below. They seem high to me. My friend and I have flipped about 20 houses in the last few years and have joked the contractors come out and do all kinds of fanciful calculations and then announce "it's $4500". In the last year or two they have gone to about $5500. They replace both the indoor and outdoor units for that. These are standard 13 seer builder grade units If you can get such a unit at a similar price, it would take a very long time to recoup thousands of dollars.
I had a similar situation with the lack of a return duct on the second floor causing inadequate heating and cooling on the second floor. After consultation with an HVAC specialist we concluded that adequate cooling and heating on the second floor, with the air handler in the basement, could not be attained without a properly sized return air duct.
We ended up constructing a 16” x 16” duct chase in the corner of the first floor living room and the bedroom above it to route a return air duct into the attic where it could be branched out into the three bedrooms and the hall. The utility chase is almost directly above the air handler in the basement. The chase is concealed within a corner closet bookcase in the living room and enclosed in the corner of the 2nd floor bedroom by a partition that is dry walled and painted like the rest of the room.
The bottom line is that this solved the heating and cooling problem on the second floor.
That might be a thought. The main floor return is in the hallway by the master bedroom.
The return "box" or the back of the return is in the closet.
I could possibly frame a return chase to the 2nd floor - I would lose some shelf space - but it wouldn't be bad. I'd just have to figure out where it would come out on the 2nd floor. Probably right by the closet upstairs.
I think you need to have someone test your house with a blower door and a Flir camera. Is the house drafty, or is the duct work in the attic?
If the system is not keeping the temp correctly when it is 80° out and cycles on and off. Installing a larger unit will not fix the problem. You have other problems
If the system is not keeping the temp correctly when it is 80° out and cycles does not off. Installing a larger unit would work assuming the current system is working up to its design limits. Drills 3/16 holes in the supply and return ducts where the air enters and leave the unit. Check the air temps from the holes after the unit has been running for 15 minutes. The deference between the 2 readings should be more than 14° and less than 21°
Lack return duct work is not a likely problem. If the air is getting to a room it will find a way back to the fan. I found mine was open to the basement and pulling all its air from there, after the duct was fixed it made no difference.
If the 20 SEER unit is a good deal in dollars and cents for you depends on how long you plan on keeping the house, how much electric cost per kWh and the price difference between the units.
The 20 SEER may be a good deal in terms of comfort, in that it will speed up and slow down instead of stopping and starting.
The 20 SEER unit will have smaller and slower swings in temp and the longer run times that will remove more moisture from the air giving you better comfort.
I think you need more bids as $2000 is too much of a price difference from 3.5 to 4 tons if a change in equipment capacity.
I installed HVAC units for about 20 years as a second job, (Engineer at daytime job). One often overlooked issue when a room does not maintain proper heating or cooling is lack of return air. This is often due to Carpet installation closing off the room when the door is shut. Every 6" vent is approximately 30 square inches most doors are 30" wide so a 1" gap should be left under the door. If your stairway is open to the upstairs (no door) this should be adequate without any other "return air" for heating use. As has been mentioned "booster fans" can be installed in the upstairs ducting to facilitate air flow during cooling season.
Replacing most working systems with a higher efficiency system is not financially advantages. High efficiency systems do reduce your fuel and electrical usage, however the payback is (on most systems I have calculated) longer than the system will last! I have and do recommend calculating the additional cost of extremely high efficiency systems even when replacing a worn out system.
One other oft seen issue is that some contractors I have seen install the attic ducting using flex duct. This has about 1/4" of insulation incorporated into the "wrap", just enough to prevent condensation when using air conditioning. I always either installed the flex duct under the existing insulation or wrapped and taped a layer of standard aluminum backed wall insulation to prevent heat and cool air loss.
By the way if I were to replace my air conditioning unit I probably will look at the variable output units ~ I recently replaced my furnace with a 2 stage type and really like the results. A variable air conditioning unit should really provide some real advantages as it cycles like a small unit when possible and steps up output when required.
This will provide almost continuous operation keeping the humidity low and still cooling to your comfort level during extreme hot days (as well and the air filtration level being much better).
