Installing a new system!

[glee314]

I started a thread about a couple of days ago. Since I am installing a new system for the home, I am starting a new thread. If this is a problem, let me know. Please help me to find the right this time.

1. I have the heat load calculation with me, but seems like it could be wrong because it was done by a dealer.
2. This is Atlanta area.
3. Cathedral Ceiling.

Below is what a Trane dealer proposed.

For the downstairs,

Trane 60KBTU Furnace and 2 Ton A/C.

For the upstairs,

Trane 60KBTU Furnace and 3 Ton A/C with a new return vent made on the hallway of the 2nd floor.

He measured the house; upstair and downstair. But he did not do heat load calc. He proposed this based on measurement and houses in the surrounding neiborhood. After he came back to the office, he said that he did heat load calc and consulted this case with an install manager.

I asked him if 60KBTU is oversized. He agreed that it is oversized, but the one below in Trane line is 40KBTU. He said that is too small for the house and the blower capacity is not big enough.

I asked him why he suggested 2.5 Ton for the upstairs. He said that the upstair gets heated and needs more cooling especially in the cathedral ceiling. And since there are only four return vents, additional one needs to be created to accomodate 2.5 Ton A/C.

He also suggested to change to the supply plenum for better air distribution. He pointed out that the air distribution is not good because the original one is not properly installed.

Seems like this guy is the best I ever met. He kind of meant that the heat load calc is not always right because a lot of contractors sometime don't enter right information.

Do you think what he suggested is correct? Does it make sense?

Looking at the heat load calc the previous dealer created for me, something does not make sense to me. The upstair heat gain is smaller than the one downstairs. Heat gain on the 2nd floor has to be bigger, doesn't it?

[captube]

He measured the house; upstair and downstair. But he did not do heat load calc. He proposed this based on measurement and houses in the surrounding neiborhood. After he came back to the office, he said that he did heat load calc and consulted this case with an install manager. Wrong

I asked him if 60KBTU is oversized. He agreed that it is oversized, but the one below in Trane line is 40KBTU. He said that is too small for the house and the blower capacity is not big enough. right

I asked him why he suggested 2.5 Ton for the upstairs. He said that the upstair gets heated and needs more cooling especially in the cathedral ceiling. And since there are only four return vents, additional one needs to be created to accomodate 2.5 Ton A/C. His load probably takes more accurate account of ceiling heights,glass. I would say he is right.

He also suggested to change to the supply plenum for better air distribution. He pointed out that the air distribution is not good because the original one is not properly installed. I.m sure hes right he doing good job so far.

Seems like this guy is the best I ever met. He kind of meant that the heat load calc is not always right because a lot of contractors sometime don't enter right information. You found a winner:)

[glee314]

Captube,

First I do appreciate your comments. Serisoulsly, unless you have technical background, it is not easy to figure out what is wrong or what is right. I really hate to verify what they are saying, but there is a old saying "Trust, but Verify!"

1. So, usually, the upstairs needs more cooling than the downstairs in a 2 story open design?

2. If I ask them to install Trane 2 Stage Variable speed 60KBTU, will I solve the oversizing problem? I never seen a variable speed furnace. Does it make a real difference?

3. The previous dealer did the heat load calc as below.

Upstairs Total Gain 19897 Total Loss 31085.

Downstairs Total Gain 22466 Total Loss 35640

The above cals shows that the downstair is hotter than the upstairs. Is it
wrong heat load calc?

4. At least, is the proposal he did close to the spec of our house? Our house is about 2200 and 2300 sq. And family room is a two story open design.

5. This time, we will get the line replaced. What he found is that tubing that was connected to the evap coil is bigger than the one in the wall. So, there are two different line sets conncted through welding. He said that is acceptable, but not recommended. If I want, he will replace it, too. Of course, the tubing will be done outside the wall. I don't care about the look because the system safety and efficiency are far more important to me.

6. This time, I will go with R-22. To me, R-22 has been longer in the market. Seems more dependable to me. Yes. there could be many arguements about it; note that this is my personal preference. And R-22 units are less expensive.

Tomorrow, I will have a new guy coming out for a new proposal. If there is a huge difference, I would need to reconsider everything. I will post what other guys propose.

[seatonheating]

Man, sounds to me like you found a guy already that will do a good job. You should stop there and not waste anymore hard working contractor's time. Not trying to sound like a jerk, but you can only compare so much.

[glee314]

Oh, Sorry, I did not mean to waste contractors' time.

Last time, my biggest mistake was I got one bid from a well known dealer and purchased the system from them. This time, I want to have two bids at least. Like someone advised me, I should not get pressured and should spend enough time for the new system because I will live with that over many years.

Also, different dealers have different pricing and options.

[steve3871m]

Man, sounds to me like you found a guy already that will do a good job. You should stop there and not waste anymore hard working contractor's time. Not trying to sound like a jerk, but you can only compare so much.
I'll have to chime in here with Seatonheating. There was another post here about a guy had 6 contractors out and wanted Manual J done for free from each one.

Be respectful of their time. Anything over 3 or 4 is a waste and the customers that do so tend to be looking for cheap. We pass these type up and let the low end contractors have at em.

Not all are that way but experience is the teacher and 8 out of 10 that over shop are just that. They want all the specs, engineering, hard input done by a pro, then give the low bidder the info.

[dash]

"The above cals shows that the downstair is hotter than the upstairs. Is it
wrong heat load calc"

They likely included the second floor ceiling in the first floor calcs,or made some other errors,assuming second floor sits directly on top of the first floor,and glass is not extensive on the first floor.

[glee314]

Oh, don't get me wrong. Believe me, I am not comparing the bids, and I am not negotiating their price down based on heat load calc or something like that because lowering the price will not bring the good installation.

What I want to do is to hire an independent contractor who is not tied with any company and have him do the heat load calc. but where can I find that type of pro?

What confuses a lot of consumers are that many sales engineers bash each other, throw in different systems, which brings a lot of confusion to consumers. So, consumers don't know which one to pick. I have reading a lot of posts, but every one agrees that there is only one size for the house. Why so many different people after heat load calc come up with different sizing?

And this is the second bid. I don't have time to bring more contractors in to our house. My best interest is to put the right system in our house.

Please if you are a pro, just comment on my situation. I appreciate your time and expertise.

Today, I got a new one. This guy also did heat load calc.

What he suggested is

1.5 Ton A/C for the upstairs after one supply vent is converted to the return vent. So, all supply vents will be located in three bedrooms. There is no supply vent in the hall way of the 2nd floor. Note that our ceiling is a cathedral ceiling. There will be no cooling in the second floor.

2 Ton A/C for the downstairs.

I found a sizing estimater on the Internet. In Atlanta area, it shows 4.5 - 4.9 cooling is needed for 2200-2300sq house. The total of 3.5 ton for the whole house seems very low. When I said one engineer said the upstair needs 2.5 Ton, he said that is a way too much.

Hey, what about this?

Maybe, I need to meet in the middle. Just put 2 Ton for the upstair and 2 Ton for the downstair. The total output for the house will be 4 Ton. If I put 2 Ton for the 2.5 needed space, will it be significantly undersized?

[captube]

Go with the guy you said you liked he is calculating good in my onion. You may very well need 2.5 up with the heat gain on that cathedral ceiling. Cathedrial ceilings are usually 2*6 rafters and than the decking, doesn't leave much room for insulation and ventilation does it.

[glee314]

Cathedrial ceilings are usually 2*6 rafters and than the decking, doesn't leave much room for insulation and ventilation does it.

What is the 2*6 rafters? This is too technical for me. Can you explain in plain English?

[dash]

What is the 2*6 rafters? This is too technical for me. Can you explain in plain English?

Nominal 2" by 6" lumber for roof joists,no room to crawl thru,limited space for insulation.

More likely you have cathedral trusses ,so plenty of room for insulation.IMO.Climb thru the attic to see which if it's important to you.

[captube]

Yes dash is right i was thinking vaulted ceiling :o

[glee314]

Hey, guys,

I appreciate your help.

I went up to the attic. I saw a lot of insulation material on the top of the ceiling. I think the insulation itself does not have any problem.

So, if that is the case, I don't really need 2.5 ton a/c unit. Right? How big of a difference does that make if we have 2.5 ton verus 2.0?

We were fine with 2 ton unit before. Only the problem was the 2nd bedroom and the 3rd bedroom were not cool enough because they are facing south and the rooms are not big. I don't believe that is the size of A/C. The rooms did not hold temperature good enough. So, they are easily heated and cooled. But if we have variable speed furnace, we want to leave the blower on all the time to reduce the temperature swing.

So, 2 Ton is good enough?

[MB1211]

A heat load calc can vary alot by the stated "tightness" of the house. A loose house, alot of infiltration, will need more capacity where a tight house, little infiltration, will need less capacity.

[glee314]

I heard oversizing A/C will hurt comfort very much more than oversizing the furnace. My conclusion is that 2 Ton is big enough, and 1.5 is too much undersized.

Seems like their sales needs drive heat load calc results. If so, heat load calc is a very subjective approach unless it is governed by some regulations and law.

I will go with the old unit size. At least, it worked very well. I don't want to risk anything.

It is not that I did not trust the contractor, but it is more likely I will need to make my own decision because they are also humans who make mistakes.

[MB1211]

I feel that you are experiencing the need to have your home tested. Find out exactly how "tight" your home is and then the calculations will be right on. Take out the variables and you get good results. You may also find that your home needs insulation in some areas and sealing in others. This will increase the efficiency of your home and save money. You will also be more comfortable. If you can have one ton less cooling you can potentially save 30% in cooling cost. Thats money in your pocket. I can go on and on but the biggest problem with oversized A/C is high humidity. That's exactly opposite of what you want.

[glee314]

You may also find that your home needs insulation in some areas and sealing in others. This will increase the efficiency of your home and save money. You will also be more comfortable. If you can have one ton less cooling you can potentially save 30% in cooling cost. Thats money in your pocket. .

Your are right, Everett. If we need more cooling eventually after we put 2 ton, we can tight-seal the house. But if we put 1.5 Ton, that is too small. Some one in this forum told me that the smallest size for the upstair is 2 Ton because of heat. But if we go with 2.5 Ton and it is too cool, we should create crack in our windows and leave the doors open in summer :).

Today, I signed the contract with a dealer in our area. He still insisted that we need 2.5 with modified vents, but I disagreed. My wife and I came to the conclusion that he might have proposed that spec to increase his sales. The other guy proposed 1.5 Ton, and we think he did that to impress us that he knows better than the original builder. He just wanted to change everything. Then, what about the builder who put 2 ton in our house? He was too wrong? We have just decided go with 2 Ton which is the size of the old unit and 60KBTU 2 stage variable speed furnaces which gives us a lot of flexibility. This way, we can't go wrong. At least, we will have the same old heating and cooling, which was not that bad.

I appreciate you guys help.

[pstu]

While Manual J is the gold standard and the only way before you build a house, the fact you have an existing system is an important fact. I am a S.Texas homeowner and have been using runtime measurement as a way to estimate sizing, I did Manual J early on but felt the need for something to double check my own calcs. I trust Manual J in the hands of an expert, better than my own.

If your new 2-ton system puts out the same number of cooling BTUs as the old one, you will have equally good cooling results. But beware that not all systems cool the same for a given size, some are a little higher and some a little lower. My old system is said to be a "light" 3 ton Intertherm, for example. This is something which can be checked by your tech, he probably has access to all the relevant numbers.

One detail, that room which does not heat and cool adequately, is not getting enough airflow to do the job. Enlarging the supply duct to that room is the obvious way to increase airflow. If you *did* heat and cool it well, you might be consuming a little bit more BTUs. But probably you are running less than 4-6 hours uninterrupted in a hot summer day, so you would have that capacity to spare even with the same sizing as your old system.

It sounds like you would benefit from having that additional return installed, many houses including mine were built with too-small returns. That is one factor which reduces airflow, makes the equipment work harder, and robs your system of energy efficiency. If you were to add a half-ton capacity it would demand 25% more airflow to do its job, and that strongly suggests enlarging your ductwork. I think your #1 tech already understands the principles I describe, and you will do well to work with him.

Best of luck -- Pstu