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  1. #27
    Join Date
    Aug 2003
    Posts
    1,311
    75 degrees set point and ten degrees offset while running and trying to keep up. ouch! the argument of it's a/c not refrigeration is a mute point.

  2. #28
    Join Date
    Sep 2002
    Posts
    3,708
    Shoot my feeling are hurt,and I thought I was being helpful.







  3. #29
    Join Date
    Nov 2002
    Location
    lancpa
    Posts
    260
    sometimes the problem is that technicians look too hard because the homeowner tells them they have a major issue, and sometimes the answer is right in front of the techs nose. My opinion, of course is easy to give because im sitting here but with a 10 degree split out of the duct that he mentioned is , duct leakage, refigerant problem ie. overcharge, orfice not seating, undercharge , no orfice, wrong orfice, unit cycling on safties , t stat dropping out, or my vote, no flow control or problem with flow control from boiler, or low voltage wiring problem. good luck. It may be easy for someone .

  4. #30

    Lightbulb Some Advice...

    Looks like your issues are being well addressed by my colleages. I have read the thread from start to finsh and heat gain has been brought up in reference to the ducts, ect.

    Attic FANS are great as long as the make up air is avialble and your not creating a negative pressure in the house. m You actually may bring the attic temperture down but at the cost of occupied space. You literally can pull the conditioned air out thru the attic. Follow any manufactures recommendatiosn for their fans, allowing ample intake air for the balance...

    I once installed a very nice 3-1/2 High efficent System to have the home owner call and complain it couldn't keep up. All the ducts were in the attic as usually are here in California. I couldn't help but notice the air around me rush in when the homeowner opened the front door. When my helper left me at the FAU and exited the front door I heard above me a slight thud... The crawl hle lid was dropping into place and when the door shut, was lifting up..

    This homeowner had installed 3 large electric whole house attic fans. each fan was rated for 2000 sq ft , a total of 6000 . This home was a modest tract home 1400-1600 sq ft :-)

    Didn't mena to ramble jsut thoguht I'd throw that wor dof caution out there. Coolingthe attic temps is a good idea but you need the system to be balanced and I'm sure you can tell my this stroy why ... :-)
    AllTemp Heating & Cooling

  5. #31
    Join Date
    Oct 2003
    Location
    Sherman, TX
    Posts
    254
    Originally posted by simpleman

    Right now,I know of several company in my area that do things by the book,and they are setting at the shop with
    nothing to do,but there hardnose in maintain there ethic
    on doing it right.

    We reap what we sow,when price is the only issue,then it
    pushes out the contractor that have highly skill tech and
    gives way to the I dont know parts changer.Sad but true.

    How can we as hvac contractor send our people to schools,
    to make them better at there skill and be more efficent at there jobs,when no one is willing to pay for it?




    The techs that do it the right way are sitting on their butts because they only have to go out and fix it once.

  6. #32
    Join Date
    Jun 2004
    Posts
    43
    Thanks for all the great info. Lmtd... your 2 questions are right on. I don't claim to know how to do a heat loss calc but I see there is a tool to help do one?... I'll try it and tell you how confident I am with my input... after all - Sh*t in usually equals sh*t out.

    I will take all measurements as accuratly as possible and document all test conditions. I take it by the comments that the 75 deg. set point is OK and that the 10 degree delta is not (I kind of figured but its nice to have confirmation from the experts).

    Here are some obvious things that I have checked just so you know I'm not overlooking the trees becuase of the forest.

    1) Low voltage wiring has been checked. The T-stats (Robertshaw 9000 series) are less than 1 year old (replaced due to lightning strike... and no, this probelm didn't start after the lighting). Capacitors in condensing units were also replaced (same reason). All equipment, relays and controls verified operational at that time. Handler fan relays and fans clearly audible and air flow verified but not measured. No overloads tripping or controls releasing... the system just runs and runs but doesn't cool well.

    2) Ducts don't appear to be popped off - Been in attic and confirmed all visible vents are intact. Some are not visible but connections verified by register flow (using smoke).

    3) The attic is freakin hot! I would expect that if there were a substantial leak in the duct work, it wouldn't be as hot as it is?

    4) All ducts are very close to roof sheathing due to vaulted ceiling design. Radiant heat infiltration has me really concerned... I will confirm with duct temp readings.


    5) Air handler could use some sealing... the entry point for lines as well as fliter and access panels are not sealed very well. Filter panel seems to be sucking some air and other holes appear to be leaking some cool air.

    6) Working in the attic SU**s! I don't envy you guys!


  7. #33
    Join Date
    Feb 2004
    Location
    Midwest
    Posts
    9,932
    All Temp brought up an excellent point about attic ventilation fans.

    They can sometimes cause more problems than they solve. I think most people use them *instead of* correcting the problem of inadequate attic vents. You have to remember that the fans need to draw the air they're moving from someplace. If the intake vents in the attic aren't adequately sized and the floor of the attic isn't air tight, the air is going to be drawn from the conditioned space below.

    2 attic ventilation fan efficiency studies have been done and both concluded that the power usage of the fans exceeds the energy savings realized by the a/c system. The exception to this was the voltaic (solar powered) attic fan. But the initial cost of the voltaic unit was so high that a 20 year payback period was estimated.

    After researching attic ventilation a bit, I think that there are cases where the fans may actually work, but sizing and placement would be critical, and the attic space would have to be well sealed from the conditioned space below. These would be special cases which weren't part of the 2 efficiency tests.

    From what I've been reading, conventional wisdom about the nuts and bolts of the thermal draft mechanism of attic ventilation may be flawed. The effect of it may be much less than previously thought. Wind driven cross ventilation from the lower inlet vents may be a much greater factor than previously thought. In other words, the cfm of hot air removed from the attic by outside air entering the inlets and moving the air up through the roof vents may be less significant than wind driven air entering the lower inlet vents on one side of the house and exiting the lower inlet vents on the other side of the house. This is making me rethink attic ventilation fan applications.

  8. #34
    Join Date
    Jun 2004
    Posts
    43
    Midhvac - I read the same study that concluded attic fans failed to perfrom from an energy stand point, But, wasn't that study evaluating energy savings only? In my case, the primary goal is more effective cooling without re-inventing the wheel. If an attick fan improves cooling and saves no energy, or even uses slightly more...I would still consider that a success. Obviously, I'd like both but, with such little attic space and such high temps, my situation can't be helping things.



    Ok - downloaded trial version of program and did quick tutorial - looks very detailed and no problem using it BUT -
    Being a trial version, it doesn't look like you can save your work... I may just buy the homeowner version if there is way to deal the following.

    Here's my problem - I have one room that has always been problematic for HVAC design... and as far as the program goes, its no different.

    The room is a first floor- sunken great room measuring 32' x 18' but, the ceiling starts at 13 ' on the first floor and slopes up to over 22' high, ending over a second story balcony. The southeast outside wall extends to the second floor as well and has 4 trapazoidal windows that span from the first to second floor. The ceiling (northeast facing) has 2 large skylights. Being open to below, there is no floor. Obviously this room needs to be included in both the first and second floor calculations but how would you do that??? I don't see a simple method to deal with this large open area.

    Just so you know... this space of conditioned by both the first and second floor HVAC systems.

    Any suggestions??

    [Edited by jav on 06-18-2004 at 10:09 AM]

  9. #35
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,338
    Just had a thought about your ductwork. Since they are close to the roof decking, it's a sure bet they're picking up some radiant heat if they aren't wrapped in a reflective foil backed insulation.
    You asked earlier about radiant barrier after the fact of construction. I've heard of a radiant paint that can be sprayed on the underside of the roof decking, but I don't know how effective that is. I think Sherwin Williams sells that paint, but I'd like to meet someone who's actually used it to see if there's any real world benefit from it.

    As for your large room that spans two floors, I would try treating it as having two separate floors. Imagine an invisible floor separating below from above and compute sq. feet, solar load, etc, from there. Maybe Don Sleeth (author of the program) might have a better suggestion.

  10. #36
    Join Date
    Jun 2004
    Posts
    43
    Shopgound,

    even painting the sheathing isn't an option. If you can picture it, my ceiling cross section is a sandwich as follows:

    Outside air
    -------------
    asphalt shingles
    Felt paper
    5/8 plywood sheathing
    airspace
    styrofoam air space baffle
    insulation batt
    insulted rigid oval duct
    3/4" strapping
    1/2" blue board
    1/8" plaster skim coat
    --------------------
    inside air

    this whole sandwich is about 14" thick so I can't access anything other than the outside surfaces. In the center od the attic, there is some room above the collar tie which is where the air handler and main trunks are. So you see, my options up there are limited.


  11. #37
    Join Date
    Sep 2002
    Posts
    3,708
    And that the problem with this type envelope,the upstairs
    system become over loaded because the heat from the first
    floor make it way up,and the cool air from upstair wants to
    go down.This is why the downstair run less while the upstair
    never shut off.

    The type of enevelope you have would be idea for one system on a zone damper system,put the btus where they are needed.

    If I had to do that house I would add the load of those two room to my upstair zone,for me the vent that are there now
    would be more for heat,even tho They would supplement the
    cooling in that room,if it would run long enough to help.

    But thats the problem imho ,and that why the upstair is being overloaded.










    [Edited by simpleman on 06-18-2004 at 03:03 PM]

  12. #38
    Join Date
    Mar 2004
    Location
    NJ
    Posts
    1,214
    The real problem is there were too many chiefs " an engineer, supply house, a manufacturer, and a contractor." All them minds and they didn't even think of making the unit accesible for a replacement. I suggest try to put your faith in the best contractor you find then leave him alone and let him do his job. I have walked away from a few customers who kept saying "well don't ya think ...this , that, or the other thing..." NO I told you what i thought its on your proposal If you want to design your system go ahead and install it while your at it.
    thehumid1-------I live in NJ, a state where it's free to come in but you have to pay to leave!

  13. #39
    Join Date
    Nov 2002
    Location
    lancpa
    Posts
    260
    i agree completely to the last thread.Find a referenced guy to troubleshoot, and leave him alone . And the lightning strike comment and the replacement of caps and thermostat is exactly what i was fearing he would say. That means this new system has taken a jolt in the control wiring and high voltage. FOr me , if you told me that, i would assume that the stat and caps are not the only damage. And the system running all the time, is that just the air handler or the condenser 24 hours a day. This doesnt sound like a complicated problem. please somebody come to this guys house hhhhhelp him

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