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  1. #1
    I live in a two story, 3800 square foot house in Pasadena CA that was built in 1901. The house originally had gravity heating. This was upgraded by a previous owner to forced heat. There are two zones: on the first floor, the heater is forced gas where the old gravity heat ductwork was converted to return vents and new supply vents were added. The second floor is a gas heater and air conditioning located in the attic. New supply and return vents were installed. The system in the attic is manufactured by Payne, The condenser has the following Prod# 565AJX04800AEAA.

    Id like to add AC to the first floor. The installed unit on the second floor is inadequate to cool the whole house. When it is 90+ degrees outside, the house is about 77 degrees. My wife would like the house to be between 69 and 73 degrees year round.

    Questions:
    1) What is the age and size of the unit in the attic?
    2) The heater in the basement must be at least 20 years old. Does it make more sense to replace the heater and install a matched heater and AC?
    3) Does it make sense to keep two separate systems? I dont see how I could install one system with two zones since there doesnt appear to be an easy way to extend the ductwork from the basement to the attic. I dont want to start opening walls!
    4) What would be the proper size unit for the 1st floor? It is about 2000 square feet with 10 foot ceilings and lots of windows. Ive been getting quotes from local contractors with sizes from 2.5 to 5 ton ACs.

    Ive been doing a lot of research and reading the postings on the site. All the contractors Ive talked to so far seem to come up with the unit size based on experience. I have yet to see any of them pull out a calculator. Im inclined to run to Sears and purchase a couple of window units :>).

    Any suggestions and help would greatly be appreciated.

  2. #2
    Join Date
    Feb 2004
    Location
    Maine
    Posts
    483
    You could certainly use a couple of window units to get you by until you decide which contractor to use. Whoever you use make sure they do a load calc to size your new system. Ask a lot of questions and get some referals from friends and neighbors who have had similar work done. Ask your potential contractors to show you proof that they are insured and licensed. Get refrences from people they have done work for. You need to put more effort into choosing your contractor than you would for equipment choice. Even cheap builder grade equipment will perform great if it's installed correctly. Top of the line equipment could fail in a year or less if a bad contractor just hacks it in. Hope this helps.

  3. #3
    jdenyer,

    Thanks for the response.

    I have been doing pretty much everything you suggested. The one exception: having the contractor do a load calculation. How can I be sure a contractor did perform a load calculation? So far I haven't seen any of them pull out a calculator, computer or manual.


  4. #4
    Join Date
    Feb 2004
    Location
    Maine
    Posts
    483
    Ask the contractor for a copy of the load calc, now some contractors may not want to give you a copy for fear that you will take that load calc and give the job to the lowest bidder. This is a legitimate concern on the contractors part, after all he did do the load calc at no cost in hopes you would buy from him. The contractor however should at least let you see it. Don't let someone tell you that because they have been doing this for 20+ years they can tell just by looking around your house. Even 2 identical houses right next to each other can have different cooling requirements, as one may receive less sun, have more trees shading the structure etc. When the load calc is being done let the contractor know how cool you want the house to be. Most load calcs are based of 75-77 indoor temps. If you want it to be 72 let the contractor know so they can adjust for that. And yes now would be a good time to replace your heating system if it is 20 years old. And yes 2 seperate units are common if duct work can't be run, it is preferable to have one unit for both zones but there is nothing wrong with a seperate unit for each zone. One benefit of 2 seperate units is that if one stops working you have a place in your house to keep cool until the service guy can get there.

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    jd...

    Do your lad calculations consider trees? (just asking)
    I would take 2 seperate systems over zoning anyday. Zoning is a lower cost version of 2 systems, in fact thats the goal is to have 2 different controls. Wit zoning your limited in how well you can control different loads.

    Homeowner, you may not get a contractor that knows how to do a proper load. You can do it yourself by downloading the load calc software here. However, a contractr who cant do manual J, surely doesnt do everything else the way it is supposed to be done either. It simply cannot be done, how could he balance the system without knowing the individual room loads? How could he designg the duct? Your conversation with a contractor should start with you asking that a proper load calc be performed. You definately want to replace the furnace when you have the new AC installed. BTW, a load calculation is not done on a calculator per se, its a calculation format, requires more than a hand held calculator on the jobsite. Ther should be a worksheet.

    Also we would need a serial number to date the unit, the model number doesnt tell us much about the age, only the generation. Its like me telling you I have a son in school, he could be anywher between 4 and 22.

  6. #6
    Originally posted by docholiday
    jd...

    Also we would need a serial number to date the unit, the model number doesnt tell us much about the age, only the generation. Its like me telling you I have a son in school, he could be anywher between 4 and 22.
    Doc,

    The serial number is: 2383A 00376.

    Let me know the year and size of the unit.


    Thanks!

  7. #7
    Join Date
    Jan 2002
    Location
    East Grand Forks, MN
    Posts
    1,373
    Prod# 565AJX04800AEAA

    A 4 ton unit.

    2383A 00376.

    Manufactured in 1983.

    Homeowner, you may not get a contractor that knows how to do a proper load. You can do it yourself by downloading the load calc software here. However, a contractr who cant do manual J, surely doesnt do everything else the way it is supposed to be done either. It simply cannot be done, how could he balance the system without knowing the individual room loads? How could he designg the duct? Your conversation with a contractor should start with you asking that a proper load calc be performed. You definately want to replace the furnace when you have the new AC installed. BTW, a load calculation is not done on a calculator per se, its a calculation format, requires more than a hand held calculator on the jobsite. Ther should be a worksheet.

    Ditto that!

  8. #8
    Join Date
    Dec 2004
    Location
    Derby City
    Posts
    3,964
    This is a 4-ton unit, and was probably manufactured the 23rd week of 1983. I am sure of the size, and reasonably sure of the age, i.e. approximately 22 years old.

    Get some referrals from neighbors, friends, and/or family on some good contractors (per their experience.) Then have them provide you with their recommendations AND what their basis is for those recommendations.

    The contractor or contractors who look at your home, are in the best position (much better than us) to make recommendations.

    What was done on the first floor (converting old supplies to returns, etc.) is done here quite often to turn-of-the-century homes. Usually those outlets were toward the interior walls which is where you want the cold air return on conventional systems of today, with the supplies toward the outside walls to 'blanket' the perimeter.

    Sounds like you're on the right track to add a/c to the first floor system to give you zoned cooling between the different areas ( a good and efficient arrangement.)

    If a contractor indicates that he is basing his sizing and recommendations on Manual J load calculations, then even if he doesn't want to make it available to you beforehand, insist on it as part of the closeout paperwork upon completion. A competent contractor will be more than happy to provide you the documentation by which he determined the system he recommends. The problem that WE as contractors have is unfortunately some of your other homeowner friends, want a quality contractor to come out, calculate a load, make the proper recommendations, only to have them call Joe Kool, and say, "do it this way." This is very unfair and takes advantage of the conscientious contractor.

    If you update your existing equipment, you can get a system in place that will be extremely efficient, and provide you the expected cooling and heating throughout the house. Good Luck!

    p.s. don't hesitate to put questions forth on this site. There is a genuine wealth of knowledge that exists here. We just won't try to diagnose problems sight unseen, or try to give opinions on someone's pricing (per the site rules.)
    Everyone has a purpose in life..........even if it's to be a bad example.

    Seek first to understand, before seeking to be understood.

  9. #9
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,296

    Exclamation Testing Leakage

    Originally posted by homeownerx
    I live in a two story, 3800 square foot house in Pasadena CA that was built in 1901.

    4) What would be the proper size unit for the 1st floor? It is about 2000 square feet with 10 foot ceilings and lots of windows. Ive been getting quotes from local contractors with sizes from 2.5 to 5 ton ACs.
    Even though I very experienced in performing ACCA Manual J calc, I would have a very hard time determing unit size on a 104 year-old house. Infiltration would simply be a guess. I recommned a _blower door test_ to determine the actual leakage.

    http://www.infiltec.com/inf-btst.htm
    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

  10. #10
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,296

    Re: Testing Leakage

    Originally posted by dan sw fl
    Originally posted by homeownerx
    I live in a two story, 3800 square foot house in Pasadena CA that was built in 1901.

    4) What would be the proper size unit for the 1st floor? It is about 2000 square feet with 10 foot ceilings and lots of windows. Ive been getting quotes from local contractors with sizes from 2.5 to 5 ton ACs.
    Even though I am very experienced in performing ACCA Manual J calc, I would have a very hard time determining A/C unit size on a 104 year-old house. Infiltration would simply be a guess. I recommned a _blower door test_ to determine the actual leakage.

    http://www.infiltec.com/inf-btst.htm
    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

  11. #11
    Join Date
    Feb 2004
    Location
    Maine
    Posts
    483
    Doc,

    No my load calc doesn't include trees, but a house that is shaded most of the day has less of a heat gain than one that is in the hot sun all day. Of course there really is no way to tell. I was just using that as an example to show that 2 houses built exactly the same can have a different heat gain. Good point on asking how the contractor who didn't do a load calc would balance the system when they don't know how much heat gain there is to each room.

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