[jethro00]

We have a 2 story raised house in New Orleans. The house is built as a double, with a center wall on each floor. Each side is upstairs and downstairs. The downstairs has no internal opening. The downstairs is about 800 sq.ft. each side. The ceilings are 10’. The floor is 100 year old cypress without insulation underneath. The walls do not have insulation. The outside wall on each side has a number of windows about 6' tall. The windows are original, single paned.

We are redoing the A/C and heat downstairs. We have considered proposals from various contractors. We are looking at quality of the contractor, brand, equipment rating, price, and warranty. The best overall proposal for a separate system for each side would run about $ for 2.5 ton, 2 stage, Trane 16 SEER A/C, gas furnace, rigid duct, with a 10 year parts and labor warranty on one side and a similar system with 2 tons on the other side. Tonnage recommendations are all over the place. One contractor furnished a J calculation and says it comes in at just under 2 tons per side. Some contractors says the J calculation does not sufficiently account for the uninsulated floor and walls, so 40% has to be added to the tonnage.

Alternatively, we are looking at one zoned system for both sides downstairs. It is impractical to put a large opening between the sides downstairs, so zoning will be needed if we go with one system downstairs. It looks like we can save $ to $ in equipment and installation costs as compared to using separate systems, plus a lower operation cost. We have limited usage of the downstairs, and rarely use both sides at the same time, so a large cost savings is a major factor in our decision.

A complicating factor is that the contractors (We have met with 8.) do not seem to have a great deal of experience with zoning. In particular, each company may have one technician who really knows about zoning, if they have one at all. We believe 2 companies could design and install a good system with zoning. We have concerns about whether, over time, technicians who come out to service the system will be experienced with zoning. That said, zoning seems like a good fit for our needs.

A Trane dealer proposes a 4 ton Trane XR17 A/C, 2-stage variable speed gas heater, high efficiency evaporator coil and Honeywell electronic 2 zone zoning system. That would cost $. That system will not have a bypass. The dampers will be set to stay open at least 20-30% to avoid the need for a bypass. The Trane 20 SEER system with Trane communicating zoning would cost $, which is more than we hope to spend.

A Carrier dealer proposes Carrier Model 24ACB748 4 ton up to 17 Seer two stage condensing unit, Carrier Model 58CVA090116 variable speed gas furnace, Carrier Model CNPHP48 evaporator coil, and Carrier ZONECC4KIT01 B Performance zoning. The Carrier system would cost $.

The Trane warranty is 10 years parts and labor, 5 years on the Honey well zoning. The Carrier warranty is 10 years parts, 1 year labor.

We would like comments on our choice between 2 separate systems and if we go with one system with zoning, our choice between the Trane and Carrier proposals.

Thanks for any light you can shed.

 

[Mr Bill]

We have a 2 story raised house in New Orleans. It looks like we can save $$$$ to $$$$ in equipment and installation costs as compared to using separate systems, plus a lower operation cost. We have limited usage of the downstairs, and rarely use both sides at the same time, so a large cost savings is a major factor in our decision.

You will get many varying opinions, here is always my thoughts on a two story. If your zoned system goes down for any length of time until a tech can get out, your family will be hot, and also humid in your part of the country, with two systems you will have air or heat in one area until then. Also, I have never understood how you save money on your power bill with a zoned system, example, if you have two 2-tons systems, and at night the sleeping quarters are say upstairs, you can turn the downstairs up, and mainly use one 2-ton system. If you have one 4-ton system it will run no matter where you are up or down, you will be paying to run 4-tons all the time. You also said you rarely use both sides at the same time, just proves more that 2-systems would be the way to go. So you have to weigh the extra cost up front for two systems, because there really are no benefits or savings after that, in my opinion.

 

[jethro00]

zoning plan

You will get many varying opinions, here is always my thoughts on a two story. If your zoned system goes down for any length of time until a tech can get out, your family will be hot, and also humid in your part of the country, with two systems you will have air or heat in one area until then. Also, I have never understood how you save money on your power bill with a zoned system, example, if you have two 2-tons systems, and at night the sleeping quarters are say upstairs, you can turn the downstairs up, and mainly use one 2-ton system. If you have one 4-ton system it will run no matter where you are up or down, you will be paying to run 4-tons all the time. You also said you rarely use both sides at the same time, just proves more that 2-systems would be the way to go.

Thanks for the input.

The zoning plan at this point would be to put one system for both downstairs sides. We would leave that system turned up most of the time and then turn it down on the side that is being used when in use. We have a separate system that covers upstairs where we work and sleep.

 

[George2]

Okay, help me understand………you have two 800 sq. ft. areas downstairs and (I assume) two 800 sq. ft. areas on the 2nd floor. Does the 2nd floor have its own system(s)? Thanks

 

[Mr Bill]

Thanks for the input.

The zoning plan at this point would be to put one system for both downstairs sides. We would leave that system turned up most of the time and then turn it down on the side that is being used when in use. We have a separate system that covers upstairs where we work and sleep.

Ok, I see now, so my way you would have 3 total systems, well you can rule out the one system breaking down and waiting for service. :grin2: That's a unique setup you have there, so unless I was going to personally live there, and knew the amount of time spent or use in the two areas, I really don't know what my advice might be, that's a head scratchier.

 

[beenthere]

Sorry, no prices allowed.

 

[btuhack]

We have concerns about whether, over time, technicians who come out to service the system will be experienced with zoning. That said, zoning seems like a good fit for our needs.

I agree with both statements.

Having seen the numbers, the proposed Carrier system would be my choice. Spending 50% more for zoned 20 seer or two independent systems doesn't provide a noteworthy benefit IMO.

BTW, what's the deal with the segregated 1st floor? How come?

 

[jethro00]

The upstairs is a bit larger (maybe 925 sq.ft.) on each side, due to a closed in "sleeping" porch. We work and sleep upstairs in the tree tops. On one side downstairs, I have a workshop and rooms where we meet with people (not often). On the other side downstairs, we have a kitchen and exercise room and the other rooms (at this point) are basically used for storage. We have a surplus of space for 2 of us and renovate rooms as needed for use. Since we do not use the downstairs all that much, we are more price conscious than on the second floor. On each side, the downstairs and upstairs are connected by an internal staircase. Since this is an old house, the duct work has to go in the attic or under the house to preserve the aesthetics.

 

[George2]

The upstairs is a bit larger (maybe 925 sq.ft.) on each side, due to a closed in "sleeping" porch. We work and sleep upstairs in the tree tops. On one side downstairs, I have a workshop and rooms where we meet with people (not often). On the other side downstairs, we have a kitchen and exercise room and the other rooms (at this point) are basically used for storage. We have a surplus of space for 2 of us and renovate rooms as needed for use. Since we do not use the downstairs all that much, we are more price conscious than on the second floor. On each side, the downstairs and upstairs are connected by an internal staircase. Since this is an old house, the duct work has to go in the attic or under the house to preserve the aesthetics.

I still need to know if the 2nd floor has a (separate) system or two for said area. I can not give you my 2 cents worth until I have more information. Thanks.

 

[jethro00]

I still need to know if the 2nd floor has a (separate) system or two for said area. I can not give you my 2 cents worth until I have more information. Thanks.

The upstairs has a separate system that covers all of one side and part of the other side. We plan to do the downstairs on both sides in the next 30 days. We plan to redo the upstairs and expand coverage to all of the upstairs before the summer of 2014.

 

[jethro00]

I can't figure out how to edit the original post that started the thread. The administrator says I can state the percent savings of 1 zoned system versus 2 separate systems, etc. as long as the actual price is not stated. So, here goes.

The best overall proposal for a separate system for each downstairs side would run about 25% more than the zoned system for both sides, a 4 ton Trane XR17 A/C, 2-stage variable speed gas heater, high efficiency evaporator coil and Honeywell electronic 2 zone zoning system.

The best overall proposal for a separate system for each downstairs side would run about 35% more than the Carrier Model 24ACB748 4 ton up to 17 Seer two stage condensing unit, Carrier Model 58CVA090116 variable speed gas furnace, Carrier Model CNPHP48 evaporator coil, and Carrier ZONECC4KIT01 B Performance zoning.

The best overall proposal for a separate system for each downstairs side would cost about the same as the Trane 20 SEER system with Trane communicating zoning (about 35% more than the Carrier system and about 25% more than the Trane system with the Honeywell zoning.

 

[George2]

The upstairs has a separate system that covers all of one side and part of the other side. We plan to do the downstairs on both sides in the next 30 days. We plan to redo the upstairs and expand coverage to all of the upstairs before the summer of 2014.

Okay, thanks for that important information. First, let me say that I'm a big fan of zoning (I have a 3 zone in my home), but it depends on the situation. In your case, I would recommend separate systems. A 4 ton system, when only one side is calling (which you said will be most of the time), will not dehumidify, plus it'll be noisy unless you have a by-pass to dramatically reduce the airflow. This reduces the efficiency as well. Your downstairs doesn't have much load because of the system above. I think you would be much happier with two 2 ton systems…………IMHO.

 

[jethro00]

A 4 ton system, when only one side is calling (which you said will be most of the time), will not dehumidify, plus it'll be noisy unless you have a by-pass to dramatically reduce the airflow.

George2, thanks for the input.

Most of the time, I expect the thermostat to be turned up (or down) on both sides to avoid extreme heat or cold, depending on the season. We keep the upstairs comfortable. Since we are not downstairs a lot, we only need to get one side comfortable on the 3 or 4 times a month when we meet with someone or when cooking is going on in the kitchen on the other side or when I get time on a weekend to work in my workshop. I was thinking that the system would run at a low rate most of the time, and then run at 4 tons when it is late August and brutally hot and we need to be comfortable for a few hours to meet with someone or to cook.

Dehumidifying is a big concern in New Orleans.

Will a zoned system be loud when running at full tonnage if the ducts are sized properly?

Attached is an article "Navigating the Twilight Zone: The Hidden Flaw in a Zoned Duct System" that claims a bypass should not be used in a zoned duct system. We read the article after an American Standard contractor proposed a system with a bypass and a Trane dealer told us a bypass should not be used. The American Standard dealer says he has installed about a dozen zoning systems with a bypass and not had a problem. But, he is not that old and the problems might show up down the road. The Trane proposal plans to handle the excess air when only one side is calling by leaving the dampers 20-30% open on the other side and (I think) sizing the duct larger. The American Standard proposal for a zoned system with the Honeywell zoning costs about 15% less than the Trane proposal. But, the American Standard contractor seems less knowledgeable and we are uncomfortable with the bypass, so we are inclined to pass on his proposal.

 

[George2]

The article is correct……..most of the time I don't install a by-pass damper. I thought you were dealing with existing ductwork. If the new ductwork is sized properly, it'll be quiet. But even on low speed, you'll be moving 2.5 tons (1,000 cfm).
The Trane guy is going about it all wrong leaving the supply damper partially open. That defeats the purpose of zoning.

The lack of de-humidification is my concern. I know humidity is a problem where you live. You might consider a 3 ton zoned system and a "whole house" (put on the 1st floor system) dehumidifier. That would be my recommendation.

 

[jethro00]

The article is correct……..most of the time I don't install a by-pass damper. I thought you were dealing with existing ductwork. If the new ductwork is sized properly, it'll be quiet. But even on low speed, you'll be moving 2.5 tons (1,000 cfm).
The Trane guy is going about it all wrong leaving the supply damper partially open. That defeats the purpose of zoning.
.

George2, thanks for the reply. The current duct under the house is 22 year old flex duct. Feral cats and/or possums and/or raccoons have had their way with it. We're going with rigid duct in our new system. I am relieved to hear that a zoned system will be quiet if the ductwork is sized properly. Your comments about the Trane zoning plan weigh in favor of the Carrier system, even though the Carrier system only has a 1 year labor warranty. For some reason, Carrier seems to have lost market share in New Orleans these days. You see American Standard and Trane equipment and dealers everywhere. It is rare to see Carrier equipment and we had to call Carrier's 800 number to even find a Carrier dealer. One dealer told us that Carrier's parts distribution has become a problem in New Orleans.

 

[Mr Bill]

Attached is an article "Navigating the Twilight Zone: The Hidden Flaw in a Zoned Duct System" that claims a bypass should not be used in a zoned duct system.

One of the biggest problems I have with the bypass in a zoned system is, your mixing unconditioned air from the home/returns with conditioned air, air does take up space. If your mixing conditioned air with unconditioned air, the conditioned air from the bypass is taking up space were the unconditioned air from your returns should be, to me this would create a slight inefficiency to the total system efficiency.

 

[George2]

Regarding your concern about the warranties, every manufacture offers extended warranties. Sometimes dealers"include them "free" in the overall price and sometimes they are listed as an option.

With some minor arm twisting, you can have the extended warranties "thrown in". Extended warranties always cost the dealer something, sometime.

 

[btuhack]

What you do with the return(s) may impact your zoning due to the dividing wall too. You'll need a return for each side and if you don't zone the return, you'll be cycling air thru the unoccupied space defeating the zoning benefit. Putting a common return outside the zone..equally bad outcome. Make the solution fit the problem, not the other way around.

Skip the zoning, skip 2 systems, put in a 1 or 2 stage unzoned system, be nearly as comfortable, and blow the 5 figure savings on something fun.

 

[beenthere]

One of the biggest problems I have with the bypass in a zoned system is, your mixing unconditioned air from the home/returns with conditioned air, air does take up space. If your mixing conditioned air with unconditioned air, the conditioned air from the bypass is taking up space were the unconditioned air from your returns should be, to me this would create a slight inefficiency to the total system efficiency.

Since the return is sized to move a lot more air then it is. The bypass air isn't taking up any space that the return duct doesn't have ample room for.

 

[jethro00]

If we go with zoning, does anyone have a basis for recommending EWC zoning, Honeywell zoning, or Carrier ZONECC4KIT01 B Performance zoning?

Thanks for all of the suggestions so far.