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  1. #1
    I've had several contractors out to look at my house. It was built about 15 years ago. 2 story 3100 sq ft. House is in So. California (that means hot!) All double pane glass- R11 walls- R30 attic. Upflow furnace is in garage on stand.
    Here's the problem- it does a poor job of cooling on hot days- now it's dead. Compressor burn-out. House has only 1 system for house. Furnace & coil are original to house. 80,000 btu Comfortmaker furnace I was told is a 4 ton. Coil is a 5 ton (60,000 btu). Condenser was replaced 3 years ago w/ a Goodman by previous owner. It's a 4 ton, but the factory compressor is only 42,000 btu's (I'm repeating what HVAC guys told me BTW.
    I want a 5 ton. No one on this street has a system that works well & we entertain alot during the summer months. I wanted a 14 SEER but it won't fit in working area of platform. So- I'll go w/ a 12 SEER- probably the Rheem 2 stage for the short furnace so we can install an EAC or media filter under it. A couple of the guys who came out say no problem. A couple more weren't sure. I don't know who to believe. I had a Manual J performed (cost me $250.00!) & it requires 53,800 BTU's for cooling based on a 90 degree temp (it was 105 yesterday & humid as heck) so I'm not sure how accurate that calc was. Return grille is a 14x36- they say that's good. The supply may be a problem. I had the guys pull out the coil to see what size ducts were running from garage. The plenum box is 24x24- is about 18" tall & is capped off on top. What we have is 2- 12" flex lines & 1- 9" flex lines into the side of the box. The guy who seems to think it will work (the 5 ton) says the total square inches of the 3 ducts are slightly larger than 18" & will probably be ok. They have installed them many times on same duct size w/o problems.
    What do the pros think? Will it work? Will I have problems w/ too much backpressure? I don't want to do this twice. BTW_ there's no access to the supply box to either increase duct size or add more outlets. I'm stuck w/ what we have. I really want 5 tons of air if it's do-able- but will settle for the 4 ton if that's my only other option.
    This is suppose to be EZ- pick up phone & get it installed. The more people I call- the more stories I hear. I'm beginning to think some of these people will tell me whatever I want to hear to land the sale. I hope not.
    That's why I came here- for neutral advice.
    Help!

    [Edited by tri-five nut on 07-27-2005 at 01:46 AM]

  2. #2
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Sounds like that is exactly what is happening, you are being told what you want to hear and believe. I would have to check my duct calculator but your supply air seems awful small for that amount of air. You have no way of knowing what is all connected to those flex lines or how good of air flow you are going to get through it if you can't access the ductwork at all. 4 Tons might be a more realistic expectation on this system even though your manual J calls for more than that.
    "Go big or Go Home"

  3. #3
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Equipment Selection

    Originally posted by tri-five nut
    A couple more weren't sure. I don't know who to believe. I had a Manual J performed (cost me $250.00!)

    & it requires 53,800 BTU's for cooling based on a 90 degree temp (it was 105 yesterday & humid as heck) so I'm not sure how accurate that calc was.

    Return grille is a 14x36- they say that's good. [Edited by tri-five nut on 07-27-2005 at 01:46 AM]
    I recommend
    a ..4-Ton + 2.5-Ton.
    ... 48,000 + 30,000 =
    ... 78,000 BTUh Total
    ..= 57,720 BTUh Sensible.
    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

  4. #4

    I'd look at

    What the two 12's are serving if the down stairs is on one and the up is on the other, you might be a good candiate for zoning. do you have return air on both floors. That's just a thought to add to the confusion. You may want to ask the contractor for copies of the preformace of the unit, with the condensor, indoor coil and the furnace, there is a wide range of btu and seer ratings on the Rheem / Ruud ( most likely on all brands) He should be able to print the rating for the system off Rheemote web site. Well I'm only a few thousnad miles away, What about a Two stage, Two speed blower, with zonig and a 12 seer Ramc-048JAZ condensor that will give you 48,000 btu's of cooling and more control over the temperture in the up and downstairs. Throwing 5 tons at you duct system may not be the best thing to do, Ask the contractors about possible zoning, if you get a straight NO! he's either very good or doesn't know what he's talking about, if he comes out again and check out the duct system then explains why he would zone it he may know what he's talking about.

  5. #5
    The guy who seems the most knowledgeable (performed Manual J & pulled coil) also tested the 2- 12" ducts for possible zoning. I forgot to mention that as I was getting quite winded w/ my response before. He taped up 2 of outlets & placed some sort of smoking device into the 12" duct & then stuck a fan into it (run is horizontal). There seems to be no rhyme or reason how the 12" was split to feed the house. The 1- 12" run serves the downstair's den kitchen & bathroom- then also feeds 2 bedrooms & 2 baths on 2nd floor. The other 12" feeds both 1st & 2nd floors- as well as the 9" feeds 1 bedroom on 1st floor & 1 on 2nd floor. With the height they have to work with- EAC- furnace- coil, that leaves a whopping 3" to build the adaptor to fit the existing box in ceiling. He said he would love to install a horizontal in 2nd floor attic but splitting this house up into 2 zones w/ 2 separate systems would be a nightmare & cost a fortune. Plus- attis is extremely tight w/ the truss construction- it's hard enough just moving around up there- can't imagine how they would get a system up there. He said if the runs were separated into floors- he could have zoned the 2 runs w/ 1 system.
    Who the heck designs these homes when they are built?
    When I talk to my neighbors- all have cooling issues from day houses were new. One did go to a 5 ton (same floor plan) & his house was 74 degrees on the 100+ degree day! That's what I want. But he doesn't know if his layout & sizing is the same, his build was in different phase & they had a new contractor for every new phase. Red flag?
    Looks like I may be stuck w/ the 4 ton.
    Return? Only 1 on 1st floor behind the unit. It sits on a platform in garage & the return backs up to platform. it's 14x36 He looked at construction of house & said there's no way to get a return to 2nd floor. Note platform is 33" deep & 48" wide. Tight fit & no room to do much of anything, as the water heater sits right beside furnace. Behind water heater is a boxed out area where the sewer runs to 2nd floor & a linen closet backs into.
    So- my question is- is the equivilant of 18" round too small for a 5 ton?
    One contractor (large company) told me on rooftop units he sizes like this- 14" good to 3 tons, 16" good 3 1/2 to 4 tons, 18-20" good for 5 tons. I realize this isn't a rooftop unit but many who came out seemed to use that guide to size ducts quickly in field.
    Thoughts?

  6. #6
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295

    Exclamation Responsibility

    Originally posted by tri-five nut
    Who the heck designs these homes when they are built?

    When I talk to my neighbors-
    ALL have cooling issues from day houses were new.

    One did go to a 5 ton (same floor plan) & his house
    was 74 degrees on the 100+ degree day!

    That's what I want.

    So- my question is- is the equivalent of 18" round
    too small for a 5 ton?

    BUILDER IS RESPONSIBLE !__!!___!!!____!!!!

    I smell " CLASS ACTION " in the near future.

    18" diameter (1.766 Square Feet, 2,000 CFM = 1,132 FPM ) might be OK
    if the run is VERY Short (< 10 FEET) and
    splits into TWO 16" diameter.
    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

  7. #7

    I wouldn't

    Even try to guess how many cfm's you can move thru your 12" ducts, the guy that ran the flex may have not installed it just right.

    Back to the fellow that actualy looked what you got and what might work the best, throw him a curve in the old days you could run the furnace and using the temperture rise and some other information ( it's not a seceret, I'm just getting old) an calculate the air flow. My guess is that he may charge more and not want to throw 5 tons on it just to see if it works. 4 tons that's inline with airflow that you can actually move will work better than 5 with low air flow, too many BTU's and not enough air sounds like M&m's (Thats Mold and Mildew) A good contractor will lose interest in a job like that hurry. New construction, the builders have all kind of money for gold fixtures, solid counter top's and hardwood floors, but don't let that HVAC contractor try to add good return system . See if you can find a post by BIGBIRD, I think he's a hippy but may know someone around LA. He out there in the hills some where.

  8. #8
    Join Date
    Mar 2004
    Location
    Gone
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    5,340
    Your ductwork will not even flow 3 tons of air.

    Your return will not even flow 3 tons of air.

    Go get a lawyer, and do not waste your time trying to make this system perform what it is unable to produce being it is limited by the duct system.

    The quick repair is to throw something in, and sell the house. It will never work right, and nobody will ever pay all the money it would take to rip all the sheetrock out to rerun the ducts correctly. You will waste money for years in this house with larger than normal electrical bills, and be uncomfortable the whole time.


  9. #9
    Well- it's all in & installed & works like a charm.
    Turns out a contractor who is a pro member here was doing a service call across the street & came out for free to look at my home. He came back later that evening when he had more time to spend. He spent 3 hours at my house one night measuring everything & looking at plans (I had a set from builder). He installed a 4 ton 12 SEER Rheem w/ a 2 stage Criterion 2 furnace & Vision Pro 8000 thermostat. The area just above furnace in garage was a dropped ceiling so he opened drywall to access front of supply air box above the coil. He then installed a big duct to it- ran it across garage 10 ft horizontal in front of this dropped area & up through floor into the walk-in closet on 2nd floor Then it runs into 2nd floor attic & he installed a supply grille in ceiling over spiral staircase (vaulted & open right there- and always hot). Then he pulled out the water heater & installed a rectangular duct behind it through the platform- then a duct following the other one which he framed & drywalled around- even painted it. It goes up in closet as well to a grille above hall on 2nd floor- also framed- drywalled, textured & painted. He then performed some sort of pressure test while it was all running using some big gauge w/ 2 rubber hoses running from it to the box above furnace & another into the side of furnace where blower is. He said readings were what manufacturer recommended.
    System works great! Couldn't be happier! I'm not sure if he wants his name mentioned but he knows who he is. I came home tonight- 95 degrees outside- 75 degrees inside & as you walk through the house- every room feels same temperature! It's really true you get what you pay for. It wasn't cheap but he was the only one who came out & had a fix for my delima. I'm very pleased! Best part? Doesn't look like anyone was even here! Talk about a nice job!
    Glad I found this site!

    [Edited by tri-five nut on 07-30-2005 at 01:59 AM]

  10. #10
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Love to know which contractor installed it. It is a nice feeling to know you have done a difficult job well. As contractors we here far more negatives than positive comments from our customers. Let us know who installed the system if you can get his permision. Come on now no need to be shy. LOL
    "Go big or Go Home"

  11. #11
    Join Date
    Mar 2004
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    Gone
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    You are a very lucky person to get someone who was knowledgeable and could correct all of this for you. Obviously you were willing to pay to have it done right if possible, most are not. Happy endings are sweet.

    Quick question. Manuel J showed you needed a 5 ton, why didn't you get a 5 ton? Was it because they could not increase the duct work enough for it?

    [Edited by madeinusa on 07-30-2005 at 02:47 PM]

  12. #12
    Join Date
    Jul 2002
    Posts
    962
    WOW, looking at the time frame from Wed. to Saturday, this guy is fast. How many installers? Its almost to fast to be true.

  13. #13
    Join Date
    Oct 2004
    Location
    So Cal
    Posts
    3,525

    Talking

    I'm the guilty party.
    The 2 12" ducts were smashed oval to fit construction & one 12" run was mashed over a ceiling joist & showing it's intrusion. The 9" had the sharpest turn I've ever seen w/o an elbow! I did install an elbow when I opened front up to access supply plenum. No excuse for that- just sloppy work. No way was a 5 ton going to work w/o a major tear-out & re-duct. I was pretty confident I could get a 4 ton in there & have it work well too. I was pretty much stuck w/ what builder left us.
    Quick install? You bet! In & out in 2 days. Me mostly w/ a helper for several hours 1 day to run the ducts- and I'm no young kid! I had a friend I use drywall, texture & paint boxed out areas in a couple of hours- I framed them before he got there using my compressor & nail gun. Both days were long- until nearly 10 pm- running service & office stuff off & on through the day. The old equipment was removed by previous contractor so that saved some time. I'm waiting for all the neighbors to come running now, as they are in the same boat. I like a challenge & this was a interesting one.

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