If you decide to keep furnace and only purchase new AC condenser with matching evap coil, you will be limited to 13-14 SEER models only since your old furnace has conventional blower motor. Considering age, I would replace both furnace and AC and go with high eff 2 stage var speed furnace minimum with rated 15-16 SEER AC condenser. I would ask quoting dealers about smell, can't tell from here.

IMO

Will my ducts be a problem? and what is the difference between a 13-14 seer and a 15-16? I do like the variable speed from my upstairs unit - it lets me control temperature better so I will definitely do that. But I am not sure on this high efficiency SEER (BTW, I hate efficient toilets that require more than one flush, dishwashers that take hours to clean and don't dry well, and shower heads that make you stay longer because you don't feel you get enough water to wash long hair!) So, I rather go with a full force unit than a delicate energy efficient. My apologies to all conservationists. Given this opinion, is 16 seer better how?

I forgot to mention, I need to replace my thermostat. Which one? I like programing for times and vacation. I am not to thrill with Carrier's infinity thermostat. The replace filter program has never worked!

Depends on brand/furnace Mdl selection. If Infinity furnace, then yes Infinity controller. If Trane XV95, then Trane's XL824 thermostat. Sizing important. If you have hot /cold spots in your home, this is usually due to ductwork design/sizing issues. Ductwork systems are usually the most overlooked of the 3 components of a quality new system.

IMO

I do have a hot spot in my house. But I am not sure if it is because of sun (full southern exposure). The room is the hottest in the house at all times. Someone suggested to put a return outside of this room. Does this make sense? Is it to better calibrate temperature of returned air? And if so, is this expensive? The room has attic access (unfinished).

My big thing is, why are the vents in the ceiling? I can understand for cooling but why for heat?

The equation to calculate the energy savings based on SEER ratings is:

1 - (old SEER/new SEER) x 100%

If you current AC is rated for 10 SEER going to SEER results in a 23% savings

Moving up to 16 SEER is a 38% savings.

Systems with higher SEER ratings can provide the same amount of cooling as a lower SEER rating. The amount of electricity used is less for the same number of cooling BTUs.

If you have a system installed in the attic, then the vents are going to installed in the ceiling. It would be possible to run the duct down through to wall have been near the floor but that costs more money.

Your Carrier Inifinity system should provide very good humidity control. If it doesn't then I suspect it is over sized or improperly installed.

If the duct work is the correct size then it can support a high efficiency furnace and AC.

As for someone telling you that your 'ducts' can not handle high efficiency units, they were probably talking about the exhaust vent for the furnace. Newer high efficiency furnaces might require a different vent pipe (condensing furnaces have water vapor).

Ductwork is invariably undersized (and systems are invariabley oversized) so the contractor may have been registering a valid concern that your ducts might have a high static resistance. Unfortunately, you have to rely in the expertise and integrity of the contractors that come out to bid on the job.

If the single 4 ton unit cools the basement and first floor adequately, then I would just replace this. A lot less expensive to condition the basement than to install a second system.

thank you all. I have gotten two quotes so far. which is best? Quite frankly, I am not looking for a lexus model - I am happy with a "honda" but. Yet, everyone quotes the lexus even though I have asked for a Bryant model.

I will say that Option A is from a company that i know to have superior service. Company B has excellent service but their technicians do not seem as knowledgeable as those from Company A.

So far,

Full replacement Options

Option A ($10,600): Indoor model: CNPVP4821ALA, Outdoor model: 24ACC448, thermal model: 58PHVB110-20, Thermostat: White Rodger , Non-electric air cleaner, power humidifier, SEER14

Option B: Indoor model ($11,500): CNPVP60, Outdoor model: 24VNA948, thermal model: 58CVA110 2 stage, Thermostat: SYSTXCCITN digital wifi touch screen, April Air Media Filter 2210

AC Only Options: (Same but Option A cheaper)

Option A ($6409): CNPVP48212ALA, 24ACC448

Option B ($6800):
CNPVP4821, 24ACC448

Any comments?

One more thing. My water heater is 19 years old. They also recommended I should replace it even though I have not had any problems with it. Should I? I really don'tt want to spend additional $ but I do realize the unit is old and this might be a prudent thing to do know. If I should, any recommendation? I need a big gallon for 5 bedroom house, family of 6

What is you location and how large is the first floor? Is the furnace going in the basement? Has anyone done a load calculation? Post back and I will give you my comments.

My hot water heater started to leak when it was 19 years old. You can wait until it starts to leak. I would recommend a 50 gallon Rheem Fury. I like the conventional type. It is a little less efficient, cheaper to buy, and will make hot water during a power outage.

I highly doubt the first floor needs 4 tons of cooling. If the basement is below ground then it has no cooling load. I would think 3 tons would be fine. You need to find a contractor who will do a load calculation, or you can do one yourself.

The furnaces quotes are 80% efficiency (I think the model number is actually 58PHA or 58PHB) and are rated for 110K BTU. The furnace has been over sized in order to match it to the over sized AC condenser. I recommend you get a 95%+ efficiency furnace. It will cost more but with your size house you will save on heating costs. I would think a 80K BTU would be fine, and possible a 60K BTU.

The Performance 24ACC condenser is fine, but it is only a single speed. You stated you have humidity problems so a properly sized 2-stage condenser would be my first choice. The Greespeed 24VNA9 is over kill for your climate in my opinion. It is being matched to a 5 ton coil. I not even sure if that is a legal match. It might be if the plan is to operate it as a 5 ton condenser which would be really bad.

Get more quotes. I like Carrier equipment provided it is sized and installed properly. If the Carrier dealers in your area can't do that then move on to someone else.

If the hot water heat is leaking then start shopping for a new one. In time the leak will get worse. If the leak extinguishes the pilot light you will have no hot water.

I would want to see a full load calculation especially for heating. Hard to believe you require a 110 KBTU furnace even at 80% efficiency. If sticking with 80% eff furnaces(which I don't recommend), you can get a 90 KBTU furnace with 4 ton rated blower.

IMO

Hi,

I am in the same boat as initial poster of this post. I live in Louisville and so far have received quotes from 3 service providers. However, none of them did the above load calculation. They looked at existing furnace, measured it and outside unit that is not functioning to determine the tonnage of the A/C Unit. Is that ok? All the service providers who gave the quote so far have a "A" rating in Angies List with majority being positive reviews. Should I be concerned that the measurements were not taken for windows etc?

The bottom line that I am getting from above conversation is that it is better to replace both A/C and Furnace at the same time even though the Furnace might still have 5 years of life for it. Is that right?

My unit is for the second floor of the house and the house has a great room with high ceiling that covers 2 floors.

The units that I have been quoted are Lennox XC14 ($3726) and Trane XR14 ($3704).

Thanks in advance for your suggestions and comments.

Not muc to add but but replacing is best way to go. I prefer brands that have the least amount of proprietary parts . When the break, like all machines I want to have the option of getting (generic) parts avialble from multiple sources.

Manual J came out to 3.28. Thus, a 4-ton is not out of the question? I do have many windows (63 to be exact!).

I got more quotes:

($9850) # 24VNA948A003, # CNPVP4821 Factory TXV is installed, 110K BTU Gas Furnace #58CVA110-20, touch screen WI-FI infinity control

($7480) # 24ACC648, evaporator coil # CNPVP4821 Factory TXV is installed, Carrier 110K BTU performance Gas Furnace Model # 58PHB110-16, new Carrier programmable Thermostat.

($6800) # 24ACC448, # CNPVP4824 with TXV installed, 100K Gas Furnace #58STA110-16, Carrier programmable Thermostat.

I am leaning to get the cheapest option. I realize it is a single state AC but this is exactly what I am replacing and I really cannot complain from noise or performance. If my infinity upstairs had been better (i found my old single stage to be better), may be I would consider the infinity for downstairs. And my electric bill is low relative to size of house (average $93/mth).

So, is the combination of A/C, evaporator coil, furnace ok for a manual J of 3.28?

kesavnag, the only provider to do a manual J was SEARS! and they were among the most expensive so I am not considering their offer.

If the cooling load was calculated to be 3.38 tons, then you should be getting a 3.5 ton condenser. Larger is not better when it comes to HVAC sizing.

What was the calculation for the heating load?

The only thing I would say about 3.5 vs 4.0 is what were the design temperatures used when computing the manual J?

In my case, they used 89f for outdoor and 78F for indoor. I told them to use 95f and 72f and recompute. That upped me from 2.0 to 2.5 tons and I have no regrets.

Thanks sconway. I have asked for a quote from Sears as well. Hoping they would do it for me also.

you need a load calc for heating!...and for your location you should be considering a 95+% eff nat gas furnace!..as far as AC, either a 3 1/2 ton single stage or a 4 ton 2 stage condenser.

IMO

"Why 95% efficiency for furnace? What is the efficiency really doing for me (except maybe save some money)?"

High efficiency (90%+) have become the norm in the northern part of the US. There was a legislation in Congress to mandate all new furnaces in the northern states be high efficiency, but it did not make it into law. The higher efficiency models tend to be better built and have more features. The 80% AFUE furnaces are mostly builder grade type equipment with a few exceptions.

If you don't want to run a generator, then it would be possible to power the furnace with a power inverter connected to a 12 V battery.

A 12 V battery isn't going to run a furnace blower for very long.

I agree a single battery is not going to be able to continuously power the blower motor for long periods of time. You could connect multiple batteries in parallel to provide a longer run time.

A generator could be installed outside your house and the wiring would run to a transfer switch to your electrical panel. Then you could power your whole house. You could run one circuit to the furnace and still keep the generator outside. The generator is a better solution than the inverter.

The size of the wiring is determined by the electrical load of the equipment and not the SEER rating. Someone is giving you bad information.

Your idea of having a gas furnace with a built in generator is interesting. There may be safety issues that could make it difficult to market.

The amount of heat a furnace delivers is the input rating times the efficiency. So a 110K BTU furnace at 80% efficiency delivers 88K BTU, a 90K would deliver 72K, and a 70K BTU would deliver 56K BTU. Now if your heating load is about 46K BTUs then which furnace do you think is the correct size?

"Please pardon my ignorance but if a generator is converting gas to power a house, why can't my gas furnace use such concept to power itself?"

A conventional generator has an internal combustion engine (like a gasoline powered lawn mower or your car) that turns a shaft to power a generator. So-called "built in" generators can be connected to a house's natural gas or propane supply and can run off of that. Automatic switches flick off the house's connection to the outside power grid and instead will connect the generator to the home circuits when the power goes off. A furnace simply burns fuel to produce heat, like a log fire. No mechanical forces are produced.

(Not that it matters, but an electrical generator is akin to an electric motor being run backwards. If you turn the shaft with an external force (for generator mode) , it produces electricity. If instead you apply electricity to the generator (electric motor mode), the shaft turns to produces an external force)

You don't need a 4 ton AC. Your furnace is being over sized in order to support your over sized AC condenser. It is one mistake compounding another.

There is not a big difference in cost when going up one size in a furnace. But that is not a good reason to buy a bigger furnace. I have no confidence in the contractors you are working with. They do a load calculation (assuming it is correct) and then ignore it and over size the equipment. You need to find a competent contractor.

Basements at or below grade carry little heating and cooling load. Did you get your load calc in writing. Was the load calc broken out by zones, ie main floor and basement? It should have. What design temps were used both inside temp and outside temp, both cooling and heating? If you have confidence in the heating/cooling calculations, this is what I would recommend. First off, your dealer(s) seem intent on grossly oversizing your furnace sizes. I would ditch them. If you prefer to stay with 80% eff furnace, then this is my recommendation. Go with Trane XV80 furnace 80 K size and 4 ton rated blower... This is 2 stage var speed furnace with low stage at 44 KBTUs and high stage at 64 KBTU. Pair with 3 1/2 ton XR16 AC condenser. XL 824 thermostat to control furnace stages. Exact same HVAC available from Trane's sister company, American Standard.

IMO

" So, how can I get them to explain to me why they recommend a 110?"

The contractors who did not do a load calculation will say it is based on the size of the house. This is wrong and leads to over sizing. The one contractor (Sears) who did a load calculation thinks the heating load should be doubled which is also wrong. It is hard to have a conversation about this with a contractor who has already predetermined what size should be installed.

"Also, if I do go with the bigger furnace (110k BTU), what exactly am I compromising on? You say bigger is not better. So what exactly is wrong then?"

Here is a list of problems caused by an over sized furnace:

Short cycling: The furnace runs in short cycles. This constant on and off creates a lot of wear and tear on the furnace and leads to premature failure. It also creates a blast of air every time it turns on causing excessive noise and discomfort.

High static pressure: A big furnace needs a lot of air. Your duct work is likely too small to handle the air flow and will cause a restriction. The restriction causes the furnace to run hotter which will overheat the heat exchanger. This will cause the heat exchanger to fail prematurely. This is a very expensive repair. The undersized duct work causing excessive noise.

Lower efficiency: During the first 5 - 10 minutes of operation the furnace is operating at a lower efficiency. If it short cycles it does not reach its rated efficiency level.

Less Comfort: The short bursts of air blowing at high speeds and the extra noise make the house less comfortable. This is the primary reason forced hot air systems had a bad reputation 20 years. Proper sizing and variable speed furnaces have greatly improved the comfort level.

"So, I don't know why you are saying I don't need a 4 ton AC."

You don't need a 4 ton AC because you said "Manual J came out to 3.28. " As Tigerdunes stated above you should get either a 3.5 ton single stage or a 4 ton 2-stage condenser. If I knew the city where you lived, and the summer design temperatures used in the calculation, I might be inclined to round down to 3 tons if you lived in an area that suffers from high humidity. I don't know what temperature you set your thermostat to, but I am comfortable at 78 degrees at 40% humidity. I find it more comfortable than 75 degrees at 60% humidity.

I am in the Princeton NJ area so our climates are similar. Your summers and winters are a little warmer than mine.

If you are going to set the thermostat to 68 in the winter then your furnace is going to short cycle. You shouldn't be including the basement in the area because it is mostly underground and has few windows.

If you are buying from a Carrier Factory Authorized dealer, then they are supposed to guarantee you will be happy or they will remove the equipment and refund your money. I would ask to put in the contract something about the furnace not short cycling. They will most likely object.

Good luck and keep us posted on how it goes.