A/C advice

[wendow]

Our neighbor is an HVAC guy and he said he could install a 4-ton, 16 seer Carrier unit for $4,000 OR a 5-ton, 13 seer Carrier unit for $3,500. There is a $300 gov't rebate on the 16 seer so the cost is pretty comparable.

I will be talking more to him but just wondering if anyone knows how to choose. I know there are many variables to this. Basic info though, house is a/c ready but has never had one, furnace has been checked and can handle a/c, 2700 sq ft on 2 levels, 1300 sq ft finished basement and we live outside Denver so a/c isn't necessary for a large part of the year. Oh and we did have another company give us a quote and I believe they were trying to sell us a 5-ton, 13 seer unit.

Can anyone advise? Thanks.

 

[BridgetBordeaux]

Definitely get multiple quotes. Tonnage recommendations may vary a bit from quote to quote. Also do some research on brands. Some are great, some are good, and some are not so good.

Do more research on how long the higher seer design has been offered by the brand in question. Sometimes the "newer" technology may not be as reliable as "older" technology.

Also...............we got slightly burned because we had an issue under warranty, but only the parts and not the labor were covered for 5 years. Be sure to ask about the standard and optional warranties. Electrical boards, motors etc are a lot more expensive now than they were 10 or 15 years ago. All this modern computer controlled equipment is expensive to repair.

I hope this helps.............

 

[dvczerfs]

Our neighbor is an HVAC guy and he said he could install a 4-ton, 16 seer Carrier unit for $4,000 OR a 5-ton, 13 seer Carrier unit for $3,500. There is a $300 gov't rebate on the 16 seer so the cost is pretty comparable.

I will be talking more to him but just wondering if anyone knows how to choose. I know there are many variables to this. Basic info though, house is a/c ready but has never had one, furnace has been checked and can handle a/c, 2700 sq ft on 2 levels, 1300 sq ft finished basement and we live outside Denver so a/c isn't necessary for a large part of the year. Oh and we did have another company give us a quote and I believe they were trying to sell us a 5-ton, 13 seer unit.

Can anyone advise? Thanks.

I have designed hvac systems for 30 years, I can try to help. a/c systems are measured in tonnage. there are 12,000 btu per ton. as a rule of thumb, each ton requires 400 cfms to move across the indoor coil. so a 4 ton unit delivers 1600 cfms and a five ton is 2000 cfms. duct work must be sized to move the amount of cfms that come across the coil. if the duct is not sized properly, the unit will not work properly and can burn out compressors and parts well before there life expectancy. hence the issues people have.manufactures will not cover "defective" parts that are not installed properly.
the first thing that has to be done is your house has to be measured room by room. a heat gain calculation done to determine the proper size unit for your home. you cant go off of square footage. window sizes, exposure, and internal heat gain all are factors. its like going for a pair of shoes and you are a size 8 and the sales person says but I can sell you a size 9 cheaper.

If the person didn't start by measuring your home room by room, I would tell them to have a nice day.

 

[dvczerfs]

I have designed hvac systems for 30 years, I can try to help. a/c systems are measured in tonnage. there are 12,000 btu per ton. as a rule of thumb, each ton requires 400 cfms to move across the indoor coil. so a 4 ton unit delivers 1600 cfms and a five ton is 2000 cfms. duct work must be sized to move the amount of cfms that come across the coil. if the duct is not sized properly, the unit will not work properly and can burn out compressors and parts well before there life expectancy. hence the issues people have.
the first thing that has to be done is your house has to be measured room by room. a heat gain calculation done to determine the proper size unit for your home. you cant go off of square footage. window sizes, exposure, and internal heat gain all are factors. its like going for a pair of shoes and you are a size 8 and the sales person says but I can sell you a size 9 cheaper.

If the person didn't start by measuring your home room by room, I would tell them to have a nice day.

existing system:

1) measure home for proper size unit. do heat gain calculation to determine unit size.

2) after size of unit determined, measure existing duct and size supply and returns making sure proper sizes in each room and duct is sized properly. if not, change,add or subtract as needed to properly deliver the proper air exchanges in each room.

3) after all that work is done, then decide on the unit you want. in most cases the further north you are, the less the unit runs thus higher seer units are not worth it. you wont run the unit long enough to get your money back on the higher seer unit.

 

[wendow]

Thanks dvczerfs. So I have a question, if you don't mind. I really don't know much about all this as you can tell. I am wondering if you can get away with less tonnage if the seers is higher. Why would this guy recommend a 4 ton, 16 seer or 5-ton, 13 seer?

Again, we did get a quote from the HVAC place we have used for years. The said they would install a 5-ton, 13 seer for $5400. And they did measure our house. My neighbor is offering to do the system for a lot less (almost $2000). He bought last year's model. Our regular HVAC place would install an Amana system and my neighbor has a Carrier system.

 

[wendow]

Electrical boards, motors etc are a lot more expensive now than they were 10 or 15 years ago. All this modern computer controlled equipment is expensive to repair.

This is my worry with everything these days. I so miss simplicity. Before everything was computerized.

Thanks for your input!

 

[tvguy]

I would get several quotes, not only for price, but to learn what these companies are saying about tonnage and why.

I know my wife's stepfather had his bar buddy put in his a/c, a 4 ton unit for an 1150 square foot house. Boy did it cool that house down fast, but it never ran enough on humid days to lower the humidity. Never knew that you could put in too big an a/c unit.

 

[wendow]

Never knew that you could put in too big an a/c unit.

Yep, weird, huh? I didn't realize that either until recently. Our old house had too little tonnage and our upstairs was never cooled as we would like on the hottest days. That house was 2100sqft and we had a 2 1/2 ton system. This house is 2700 sqft (minus the basement) so it seems like 4 tons should be plenty. But I know it's not that simple

 

[dvczerfs]

Thanks dvczerfs. So I have a question, if you don't mind. I really don't know much about all this as you can tell. I am wondering if you can get away with less tonnage if the seers is higher. Why would this guy recommend a 4 ton, 16 seer or 5-ton, 13 seer?

Again, we did get a quote from the HVAC place we have used for years. The said they would install a 5-ton, 13 seer for $5400. And they did measure our house. My neighbor is offering to do the system for a lot less (almost $2000). He bought last year's model. Our regular HVAC place would install an Amana system and my neighbor has a Carrier system.

no problem. tonnage has nothing to do with seer. tonnage is the size your house requires.that is just a fact calculated by doing a heat gain calculation.the only way to do one is to meassure each room . my house takes 3 ton of air. that's it, no more no less. seer is an efficiency rating. seer is like miles per gallon you get on a car.
the calculation also takes in consideration if you live in florida or Alaska. here in pa, we figure for a 15 degree split. if it is 80 degrees outside, the a/c system will bring the house to 65 degrees. split is another question I ask people. sometimes we get to 100 degrees here. that means your ac will bring your house down to 85 degrees. I ask is that ok?
a lot of people tell you to get multiple bids which is fine. but make sure you get multiple bids from contractors, not fly by nighters who take a guess at what you need. it maybe cheaper but is it installed properly? you burn out a compressor (aprox. $700-$1000 item) because your duct work is sized for a 3 ton and someone puts in a 5 ton. the manufacture will say sorry mam, the compressor was not defective but "burned out" due to not being installed correctly, how much did you save? you are going to be upset.

if you have any questions just pm me, ill be more then happy to talk to you on the phone or you can call any manufacture and read to them what I have posted for verification before you get more prices. its complicated. that's how companies take advantage of people. its not only about price, people go with the cheapest and that's how a lot of time they get taken for a ride.

I work for a hvac supply company, I am not a contractor, I design hvac systems. I do the calculations for the contractors and give them the info they need. most hvac companies cant afford to keep someone like me on staff and just don't know how to calculate or don't have the time to learn so they call us. like I said, if you like verification on what im telling you, just call any manufacture.( not even trying to sell you a brand unit )



now in your case, you have to live next door to the guy. if you don't get him to do it, what do you do?

 

[dvczerfs]

I would get several quotes, not only for price, but to learn what these companies are saying about tonnage and why.

I know my wife's stepfather had his bar buddy put in his a/c, a 4 ton unit for an 1150 square foot house. Boy did it cool that house down fast, but it never ran enough on humid days to lower the humidity. Never knew that you could put in too big an a/c unit.

perfect example. it is what we call the morgue effect. a/c system is a big dehumidifier. it has to run to take out the humidity. the area is cold and clammie. the unit is so big it ran, dropped the temp in the area and satisfied the thermostat and shut off. it never ran long enough to take out the humidity.

go to the mall in the summer time, be there at rope drop. walk into a store or department. its cold and clammie. why, when you calculate a store, church , theater you have to take into consideration the people. 400 btus per person. you sitting on your sofa produces 400 btus per hour. so the store was calculated for capacity of 100 people. when those 100 people are not there putting off heat, you get the morgue effect. once the day gets goingand people are in and out, its comfortable. it is called internal heat gain. lighting, people, ovens even tvs. walk by your 80 inch flat screen tv and feel the heat.

tonnage is the size you need, its not negotiable and the calculation process has been in place for years and is standard to the industry and will hold up in court.when I started, IBR was the standard and we did the math by hand, now, its all done by the computer.


seer is like the mpg on your car. let me talk a bit about seer. here in pa your ac runs for about three months. we see a lot of 14 seer units and I will tell you why. just for ease of explaining I will use numbers just for using a number:
if a 14 seer unit is $2000. a 16 seer unit is $3000. how long will it take to get your $1000. back in savings? here in pa it will take about 25 years. in florida, 2 days. you decide how you want to spend your money. a few years ago, the fed. government offered a rebate on replacing your gas furnace with a higher efficiency unit. sound good? you can buy a 86 percent unit for $1000. the min eff. unit the gov. wanted you to buy cost $3500. they will give you $500 back for buying the more eff. unit. so I just spent an extra $2000 for saving 7 percent of my gas bill. at 7 percent savings off my gas bill, that unit would have to run for 45 years before I break even on my investment. why don't the installing contractors tell you this info? they mark there products and parts up on a percentage of what they pay for it. so 25 percent of 3500 is more then 25 percent of 2000.
also remember they have bills like every other business. they pay taxes, health insurance,truck insurance,liabilty insurance,gas,empolyees like every other business. so when they say its $100 per hour and you think,geez, I make $20 per hour what gives? that's why. in most cases a company that has been around for a long time, is a good company. pete the ac pumper driving a station wagon may be cheaper but????

companies who have "list" of contractors. call "xyz list before you have any work done?these companies are not lying to you, you don't have to pay to be on the list.but they do pay on where on the list there company is located. type in plumber and 5000 names come up in your area. are you going to read them all? most likely read the first ten or so and those are the companies who paid to be there.

a lot of time to get the best info is through the manufacture. see a service truck in your uncles driveway, ask him what he thinks of the company. also the guy may be cheap but will he come out to fix a problem o a Saturday night and its 90 degrees out? just something else to think about.

 

[dvczerfs]

Yep, weird, huh? I didn't realize that either until recently. Our old house had too little tonnage and our upstairs was never cooled as we would like on the hottest days. That house was 2100sqft and we had a 2 1/2 ton system. This house is 2700 sqft (minus the basement) so it seems like 4 tons should be plenty. But I know it's not that simple

here is another problem. "bigger" homes should have multiple units in them. the temp on the second floor is hotter then the first floor. in our area , its about 10 degrees in the summer. I put one big unit which sized properly is fine but where do you put the thermostat?? put it on the first floor, you are going to be hot on the second floor. put it on the second floor and you are going to freeze on the first floor. two smaller units, one in basement, one in attick is the way to go. not the cheapest but most comfortable. who ever installed that system or builder who wanted it that way saved themselves a lot of money and you paid for it every time you tried to go to sleep in the summer and paid your electric bill.
in most cases basement don't require ac. again the morgue effect. the unit cant run long enough to take out all the humidity in the basement. most basement require a dehumidifier. there are a lot of factors but if it does require ac, a separate unit is required for the same reason as I gave for the first and second floor. all different levels,lighting,people,tvs,outside wall exposure, direction the room faces etc... all have a factor in sizing a proper system.

I go into a church and start counting the seats. the person from the church will ask what are you doing? I explain internal heat gain. heres what I get, no no no at the most we get 50 people on a sunday. what will happen? a person from the area will pass on, its 100 degrees outside, the church is packed full of people.it august 15th, churches turn the ac off unit an hour before they need it so the unit is starting from a dead start. two board members are sitting in the back and here is the conversation " geez frank, we paid x amount for an ac system, it don't work! all that money and it don't work? why? I never had one of these phones calls. I tell them what size they need, if they don't want it, I will sell you what you want but it will say. designed by others on the contract. so if it don't work, your on your own.
I get the "why four ton? my uncles house is only three ton and its about the same size. your trying to rip me off!" I reply, here are my calculations let me see yours, maybe I hit a wrong button. dead silence.

 

[wendow]

now in your case, you have to live next door to the guy. if you don't get him to do it, what do you do?

First, I really appreciate your help dvczerfs. You answered many of my questions as to what all the tons & seers stuff means

I don't know the answer to your question quoted above. These people live right next door. We haven't lived here all that long and they have been very friendly. However, I know nothing about their workmanship and I cannot find their company online to find any reviews or anything. Makes me nervous

 

[dvczerfs]

First, I really appreciate your help dvczerfs. You answered many of my questions as to what all the tons & seers stuff means

I don't know the answer to your question quoted above. These people live right next door. We haven't lived here all that long and they have been very friendly. However, I know nothing about their workmanship and I cannot find their company online to find any reviews or anything. Makes me nervous

not sure in co but in pa they must display a state lic. number on the truck. the one good thing is if it isn't done correctly, you live next door, he cant hide from you. make sure you get a contract. make sure the model and serial numbers are on the units. they scrape them off if they are stolen.
the manufactures warrant the units not the contractor, the only thing he can do is offer a warranty on his labor which most contractors will give you one year on there workmanship. good luck and if you need any help just let me know.

 

[wendow]

not sure in co but in pa they must display a state lic. number on the truck. the one good thing is if it isn't done correctly, you live next door, he cant hide from you. make sure you get a contract. make sure the model and serial numbers are on the units. they scrape them off if they are stolen.
the manufactures warrant the units not the contractor, the only thing he can do is offer a warranty on his labor which most contractors will give you one year on there workmanship. good luck and if you need any help just let me know.

Hmm, good thought on looking for a lic number on the truck. Our HOA doesn't allow them to park it here so I rarely see it but next time I do, I'll "go for a walk"

It's very true that he cannot hide from us. That is what I told my dh. If you were looking to do shoddy work for someone, you wouldn't choose your next door neighbors who you have to see all the time!!

Thanks again! You've been so helpful

 

[Claire&TheBoys]

We just had a new a/c installed in our house. We live in Florida, so our cooling requirements are probably different from yours - we need to have a lot of humidity removed from the air and our summer temps are higher. Ours is a heat pump because it functions as both our a/c in the summer and heater in the winter.

But, FWIW, we had a Carrier 4 ton unit installed for right at $5000. It was supposed to be a 14 SEER unit, but the distributor messed up and sent a 13.5 SEER. The SEER has to do with the efficiency of the unit and how much it costs to run it. It was supposed to be a 14 SEER to get a rebate from the power company but since the distributor made the error, they are covering the rebate amount back to the company we purchased from, plus sending us some extra money for our "trouble." Our house is just over 2700 sf. The unit that was taken out was only a 3.5 ton unit but the a/c company we used (which is co-owned by a friend that I trust implicitly) recommended a 4 ton unit. Both kept our house plenty cool without running a lot. (The old unit was from 1995 when the house was built, so it lasted almost 19 years.) We keep our thermostat set at 78 and it's comfortable for us.

 

[Anthony1971]

Carrier is a good unit BTW but in the end most brands use the same compressor but may offer lesser of a warranty. The other difference between brands is a 4 ton unit by brand A may go as high as 50,000 BTU and by brand B may go up the rated 48,000 BTU and brand C a little under 48,000 BTU. Does that matter in the end.. maybe not. Another question you must ask is how cool do you want your house.. If you keep it 68 bigger is better and you need to pay for any modifications they may need to be done... If you keep it 75 well in your area 4 tons may be to big... Sometimes a unit will be undersized or oversized to meet needs... oversized for colder undersized if you keep you house warmer so it will run longer to get the humidity out....
A lot of people in the northeast will get for example a 3 ton compressor with a 3.5 ton blower as a humid 80 degree day the unit will run for 10 minutes unless you like it 70 or lower in your house. This is done to undersize the compressor so it runs longer to get the humidity out but the house really requires a 3.5 ton unit to move the air properly.

 

[wendow]

Thank you both. We had a/c in our last house and kept it about 75 all the time as I am a SAHM and here most of the time. Humidity tends to be low most of the time here in our area though. We run a dehumidifier in our basement b/c without it, the humidity down there climbs to 65-70%. The humidity in the rest of the house stays about 40-50% in the summer.

 

[EMAW_KSU]

here is another problem. "bigger" homes should have multiple units in them. the temp on the second floor is hotter then the first floor. in our area , its about 10 degrees in the summer. I put one big unit which sized properly is fine but where do you put the thermostat?? put it on the first floor, you are going to be hot on the second floor. put it on the second floor and you are going to freeze on the first floor. two smaller units, one in basement, one in attick is the way to go. not the cheapest but most comfortable. who ever installed that system or builder who wanted it that way saved themselves a lot of money and you paid for it every time you tried to go to sleep in the summer and paid your electric bill.
in most cases basement don't require ac. again the morgue effect. the unit cant run long enough to take out all the humidity in the basement. most basement require a dehumidifier. there are a lot of factors but if it does require ac, a separate unit is required for the same reason as I gave for the first and second floor. all different levels,lighting,people,tvs,outside wall exposure, direction the room faces etc... all have a factor in sizing a proper system.

I go into a church and start counting the seats. the person from the church will ask what are you doing? I explain internal heat gain. heres what I get, no no no at the most we get 50 people on a sunday. what will happen? a person from the area will pass on, its 100 degrees outside, the church is packed full of people.it august 15th, churches turn the ac off unit an hour before they need it so the unit is starting from a dead start. two board members are sitting in the back and here is the conversation " geez frank, we paid x amount for an ac system, it don't work! all that money and it don't work? why? I never had one of these phones calls. I tell them what size they need, if they don't want it, I will sell you what you want but it will say. designed by others on the contract. so if it don't work, your on your own.
I get the "why four ton? my uncles house is only three ton and its about the same size. your trying to rip me off!" I reply, here are my calculations let me see yours, maybe I hit a wrong button. dead silence.

I had a class in college that the text book we used was the ASHRAE Handbook. I kind of wish I would have gone that direction for a career.

My house would be more comfortable if it had two systems instead of one system for both floors.

 

[wendow]

My house would be more comfortable if it had two systems instead of one system for both floors.

My in-laws went with two systems instead of one and their upstairs stays much cooler now. Cost them 9k or something like that! But they live outside Dallas where their a/c runs all but a few mos of the year. Just not sure that makes sense for us since we only need a/c 8 weeks of the year or so. And even then, there are many cooler days within that 8 weeks where you can just open your windows.

 

[Ed J]

Where is your duct system located?

If it's accessible a damper zoning system could allow you to have a separate zone up & down with 1 piece of equipment.

Zoning with units vs zone dampers is the difference between the designers ability to do math and apply industry standards and not. 2 systems is very common but it's such a waste of resources and $$$$$$.

Contact zone first or Arzel directly and they can recommend a contractor in your area.

I've spent some time in Co. It's a rather arid climate, so humidity control is no so important. You could also be at elevation if someone wants to use rules of thumb, they are not who you want working on your stuff. You need to move a lot more air to move heat at elevation, so make sure you get someone who knows what they are doing.