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  1. #1
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
    Posts
    209
    I've gotten a lot of help here in making the decision what type of system to put in a new house. I've pretty much made up my mind except for one big issue, and that is zoning.

    Zoning is attractive to me as a concept. The zoned system allows me to afford a higher efficiency unit than I might have if I had 2 units, and the concept of shutting off unused zones seems like it might be an energy saver. It also seems as though VS and zoning could be a good match. My local Trane dealer (who I have worked with from the beginning) is about the only local dealer who is enthusiastic about zoning. His son has a Trane zoned system and he is so impressed with the zoned system that he is installing a new zoned system in his house later this year in conjunction with a room addition.

    I have called several other dealers who sell other brands I was interested in but they have never done a zoned system. (Another interesting experience I have had is that in a town of over 450,000 the only Lennox dealer does not do new residential construction and 2 of 3 Rheem/Ruud dealers also expressed no interest in new residential construction or zoning. There are, however, about 15 York dealers in my town).

    So here's my issue: The architect's load calculation calls for 2 split system units totaling 6.5 tons. The house is 3139 sq ft in Bakersfield, CA (hot dry summers and mild winters). I have asked for but have not yet received a copy of the load calcs. Previous responses on this site have questioned that much cooling for 3139 sq ft for a new home built to Title 24 specs.

    Aside from issues of whether the load calc is correct, does using a zoned system allow you to change to size of the units? My guess is no, in that whether you are using 1 or 2 systems the house's demands remain the same.

    The reason I ask is that the dealer mentioned above has quoted me a 5 ton single system (Trane XL19 and XV90) used in conjunction with the zoned system (3 zones). He is confident that the system will handle the demands of the house. If a properly prepared Manual J shows 6.5 tons then would it prudent for me to have a 5 ton zoned system?

    The Trane dealer told me he has never had county building inspector question a smaller zoned unit when the plans called for more capacity. I am worried that a building inspector would challenge my 5 ton unit when the plans called for 6.5 tons.

    Have you ever done a zoned system that had less capacity than a 2 unit set up? What issues or concerns should I have and what questions should I pose to my dealer? Is it the HVAC contractor's responsibility ot insure that the system meets local code requirements? I am building the house with a construction manager without a general contractor, so I want to make sure I don't have an inspection problem.

    One last zoning issue having to do with IAQ. With 2 units I was going to go with 2 Aprilaire 2200 filters. With a zoned system I will only have 1 filter. Is this a problem (more frequent filter changes, etc.)?

    Thanks very much.

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428
    Originally posted by nathan9999
    Zoning is attractive to me as a concept.

    .. concept of shutting off unused zones seems like it might be an energy saver. It also seems as though VS and zoning could be a good match.

    .. about the only local dealer who is enthusiastic about zoning.

    ... load calc calls for 2 split system units totaling 6.5 tons. The house is 3139 sq ft in Bakersfield, CA
    (hot dry summers and mild winters).

    Aside from issues of whether the load calc is correct, does using a zoned system allow you to change to size of the units? My guess is no, in that whether you are using 1 or 2 systems the house's demands remain the same.

    5 ton single system (Trane XL19 and XV90) used in conjunction with the zoned system (3 zones). ... the system will handle the demands of the house.

    What issues or concerns should I have and what questions should I pose to my dealer?

    Is it the HVAC contractor's responsibility to insure that the system meets local code requirements?

    I want to make sure I don't have an inspection problem.
    The answer lies in
    How does the calculation which is based on Design Conditions ( close to 96'F Outside temperature with ~73' Wet Bulb temp) as defined by ASHRAE and the selected indoor temperature ( normally ~75'F) address YOUR requirements?

    The amount and type fo windows on the WEST side of the house governs the Worst Case loading on the zones/ total system.

    I would recommend a Grey Tint which results in a Solar Heat Gain Coefficnet < 0.5 on the windows and < 0.4 on the sliding glass doors. I am not aware of the CA Budiling Code requirements.

    BAKERSFIELD " Design Conditions" from Weather.com
    ........Daily.................Record
    ....Hi...Lo...Avg...Precip..High..........Low
    May 84F 57F 70F.. 0.24 in 107F (1982) 37F (1988)
    Jun 92F 64F 78F.. 0.12 in 114F (1976) 44F (1943)
    Jul 97F 69F 83F.. 0.00 in 115F (1950) 52F (1987)
    Aug 95F 68F 82F.. 0.08 in 112F (1981) 52F (1942)
    Sep 89F 64F 77F.. 0.15 in 112F (1955) 45F (1948)
    Oct 80F 55F 67F.. 0.30 in 103F (1980) 29F (1971)

    Seems like during ~10 weeks [early/mid June to late August] late afternoon 2 to 6 pm, the system may be challenged but ADEQUATE to handle the load, if YOU do NOT wish to maintain 75' on EXTREME [ > 95' ] Days.

    Of course, if > 100'F {perhaps upto 15 days in some years), you may expect inside temperature to be >> 80'F.

    The EXTREMELY DRY 5-month period indicate that you will definitely not have a Latent Load concern.

    The Average Exposure Diversity [ AED ] in the Manual J calculation may shed some light on whether One zone will have a high late afternoon load while another zone has a lessened load.

    The AED indicates the load over the course of a day due to amount of glass area and orientation of the windows in each zone.

    If you are satisfied, that the 2 PM to ~ 6:30 PM Load Combination is < 5.5 tons for YOUR Room temperature set-point, a TRANE 2TTZ9060 /TWE065E 3-zoned system will likely be satisfactory >>90% of the late afternoon hours.

    You may wish to have the person responsible for the Manual J calc to run the calc based on YOUR actual Room Temperature set-point(S) (i.e. 78'F). The capability of the 5-ton unit can be investigated to determine what temperature a 5-ton system can maintain when the outside temperature is at, say, 94'F.

    If no one is home during the week in late afternoon, then there is lessened concern for maintaining Design Temperature except for maybe 20 days per year ( Saturday & Sunday * ~10 weeks).

    The number of average annual and monthly hours above 94'F for Bakerfield CA is known from the local Bin-Temperature Data. This data tells you the number of hours that you may expect the system to be near Full Load conditions and still maintain a reasonable temperature.

    For example:

    80'F day-time set-point in the bedrooms, 78'F in common area versus a simultaneous 75' Design Temp in all areas.


    Nathan,

    A 5-ton / 3-zone TRANE high-efficienct variable speed system handling a 3,139 Sq Ft residence in your area Completely Depends on the desired room temp, Zoned areas, the West Side windows area & S.H.G.C., roof overhangs and interior window treatments.

    If no one is able and willing to assist, you may wish to e-mail ACAD floor plans WITH Window schedule AND Solar Heat Gain Coefficient { S.H.G.C. } to racingdan11@comcast.net.

    We can then ( after I perform Manual J calc) more realistically discuss anticipated conditions versus your expectations.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,764
    Zoning can often reduce system size by 80%, and some times more.

    When you use set back stats, and don't keep your bedrooms, and or other used rooms, at occupied temps, it works very well.

    Dan is making you a good offer.
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  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428

    Question Overall Capacity Reduction

    Originally posted by beenthere
    Zoning can often reduce system size by 80%, and some times more. and don't keep your bedrooms, and or other UN(cr) used rooms at occupied temps
    .. I assume you meant Reduced By > 20%
    (i.e. TO ~70% or 80% of calculated capacity).
    .......___________
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,764

    Re: Overall Capacity Reduction

    Originally posted by dan sw fl
    Originally posted by beenthere
    Zoning can often reduce system size by 80%, and some times more. and don't keep your bedrooms, and or other UN(cr) used rooms at occupied temps
    .. I assume you meant Reduced By > 20%
    (i.e. TO ~70% or 80% of calculated capacity).
    .......___________
    ROFLMAO!

    Yea, thanks, thats what i meant to type.
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  6. #6
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
    Posts
    209
    Dan, thanks for a very detailed and helpful respnse. I'll take the time to read this carefully and then discuss with my dealer.

    What about the model choice? My dealer is proposing XL19 dual compressor (R-22 and recip compressors). I was thinking about the XL16 dual stage (R-410A and scroll). R-410A and scroll compressor were on my original list of preferred features.

    Dan and beenthere, any opinion on which system would be the better choice for a zoned system? Mark Beiser, a forum member who installs Trane in North Texas, said he thinks the XL19 would be the better choice for a zoned system. He also said Trane did not originally recommend the XL16 for zoning but have since changed their advice and now recommend the XL16 for zoned systems.

  7. #7
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428

    Lightbulb XL 19 i

    Originally posted by nathan9999
    What about the model choice? My dealer is proposing XL19 dual compressor (R-22 and recip compressors).

    Mark Beiser, a forum member who installs Trane in North Texas, said he thinks the XL19 would be the better choice for a zoned system.
    XL 19 i seems to be a Simpler, more proven configuration.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  8. #8
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
    Posts
    209
    Is there any performance difference between a 2 stage compressor versus a dual compressor? And when you say the XL19 is a simpler solution. Can you explain how the XL19 would be a simpler option? I know the XL16 is a newer product with fewer installations.

    [Edited by nathan9999 on 05-29-2005 at 06:17 PM]

  9. #9
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,764
    I like the scroll 67/100 2 stage systems.
    Simple 2 stage operation.


    On a zoned system I prefer the bristol 50/100 compressor, but since trane doesn't use them, I say go with the 16i.
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  10. #10
    Join Date
    Sep 2003
    Posts
    1,311
    If a properly prepared Manual J shows 6.5 tons in your area (Bakersfield) then do not go with the 5 tons unless you like it warm inside. As you pointed out your area is dry; Dry climates require more airflow to match the Sensible Heat/Latent Heat ratio.

    For example, if the Manual J shows 6.5 tons total then it is probably broken down to about 70,000 BTU sensible and 8,000 BTU latent. The total airflow requirement to match this is about 3,800 CFM. The proposed system is 60,000 BTU total (approx) with about 2,000 CFM available. If this is installed then your actual sensible heat removal would be about 42,000 to 45,000 BTU - only a little over half of what you need. You will have a toasty house on those toasty days.

    I would recommend going with 2 systems properly matched to the airflow (IE Manual D duct sizing method) and, if you want, zone what you want from them. I would also recommend not going less than the Manual D even if a system is zoned; When the heat sets in you'll need the capacity to remove it.

  11. #11
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428

    Lightbulb REAListic Equipment Capacity

    Originally posted by sadlier
    If a properly prepared Manual J shows 6.5 tons in your area (Bakersfield) then do not go with the 5 tons unless you like it warm inside.

    As you pointed out your area is dry; Dry climates require more airflow to match the Sensible Heat/Latent Heat ratio.

    For example, if the Manual J shows 6.5 tons total then it is probably broken down to about 70,000 BTU sensible and 8,000 BTU latent.
    _____ IT's ALL ABOUT SIMULTANEOUS LOADS! _____
    .... that is Windows SHGC / Area & House Orientation ...

    6.5 Ton Equipment capacity
    = 78,000 BTUh
    = Sensible + Latent

    However, no more than 57,700 BTUh would be SENSIBLE Load based on TRANE residential equipment properties.
    The maximum Sensible load would NEVER actually be reached with Maximum Design Load for Each room occuring Simultaneously. Unless, of course, the sun could provide Direct Radiation onto the East and West walls at the same time. L.O.L.

    5.0 Ton unit provides ~ 45,000 Sensible BTUh.

    So if loading difference on the East facing Windows between morning and afternoon sun is ~8,000 BTUh,
    a 5.0 Ton, 3 zone system is surely adequate > 95% of the time ( except for the " Pampered Set ").

    Nearly 180 square feet of windows ( ... ~9,000 BTUhs morning design load) on the East side may be expected in some 3,129 Sq. ft house designs. I suspect that the total glass area may average in the 550 Square Foot range (something like: 20 windows and 3 sliding glass doors).

    Is the Manual J load based on a differential temperature of 22'F (i.e. 97'F-75'F) and the owner is satisfied with 18'F or 19'F for the section of the residence used in late afternoon?

    If yes, the actual equipment capacity needed would be reduced BY upto ~14% (57,700 x .86), TO ~50,000 BTUh.

    Additional window tinting or Interior Shading on the West facing units could account for an additional ~4,000 BTUh reduction.

    Would closing the drapes (blinds), when it's > 96'F, be a significant inconvenience?

    Also, I would antiicpate one would have the ceiling fans ON when the outside temp is > 96'F ( assuming the utility is still able to provide power)?

    REAListic evaluation of one's lifestyle and Needs affect the A/C Systems CAPACITY Design.

    Have a Pleasant Memorial Day!
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  12. #12
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    To down size ,if that 6.5 ton load is correct(doubtful),they should do a "block" load,to see what the peak load will be.Then the zones need to be arranged by which way the glass faces ,not by bedrooms,versu linving ,kitchen areas.

    This way each zone wiil have same/simlar glass to take advantage of the diversity of the load as the sun travels over.

  13. #13
    Join Date
    Dec 2002
    Posts
    174

    I will have...

    .... to go with Sadlier...always go with the heat load sizing. Even companies that make zoning equipment will tell you to size the unit by heat load calcs.

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