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  1. #1

    Unven temps - What are other possible causes/fixes?. North Dallas Area

    I have a new construction home. Based on some issues I've had from the start, I feel the system is unbalanced and needs one or more fixes.

    This is rather drawn out, so please feel free to take on question or area and focus on that.

    The HVAC company has been out 20+ times(NO, really - I have all of the invoices. Talk about a tremendous waste of my time!)

    ... Does anyone have any recommendations for HVAC repair in the future for the North Dallas area?



    Problem:
    The front room(study/Bdrm 4), master bedroom, living room, and kitchen have been warmer by approx. the following(these are actually better than before the contractor made several 'fixes').
    During the cooling months...
    Study - 5-6 Deg.
    Master bedroom - 3-5 Deg.
    LR - 4-6 Deg.
    Kitchen - 3-7 Deg.

    The winter is here, and swings/variations are not as bad but I'm still seeing the same trend. The study seems to be affected to a lesser degree, but I believe that can be easily explained by the addition of a new home file server(As of November - Approx a 60W average heat-load).



    Advice/solutions?
    There are few things I've thought of as possible solutions. I feel wasting my time with the HVAC company will prove frivolous - At this point they claim the variations are very normal, and they have zero obligation to make any corrections.

    Possible solutions I've thought of include:

    1 - Alter angle of supply box in attic to 45' from the current 90' bend in the 16" flexible duct coming off of plenum supply. Also would facilitate correcting angles/beds in most of the supply lines to registers at or near supply box.
    2 - Return air; transfer air grille (Master? LR?)
    3 - Ducting size changes in rooms. LR needs one more? Master needs one more; or even a Y?
    4 - Perhaps one of the variable and constant on blower setups?(ECM or VS?) I've seen several options for installing a multi-speed blower - I'm very confident I could do this on my own given I have the right wiring diagrams in front of me.(IE, Emerson 5521ET). Or perhaps an IAQ with my current blower or a new blower?(Factory blower has 3 speeds, but low speed is still high for 'circulation' mode).
    5 - Thermostat relocation? If I turn the fan on - The rooms seem to balance out fairly quickly. Perhaps the issue is the location. It's by the two rooms with the least amount of heat production. Only 2 windows, South facing wall.
    6 - Zoning out the system? I have a strong electrical and mechanical background due to occuptation.... but I don't know enough for placement, location to put makeup air return, etc. Any thoughts based on my floor plan?




    Additional information:
    -Pictures provided do mark location of return, registers, duct sizing, and thermostat.
    -All ducting is R6 Flex. Return is direct - no ducting, just a large non filtered register.
    -Home has a central updraft style return in the hallway. Return grille in filtered;filter at handler.
    -All doors left open 24/7 with two exceptions - Pantry & Master Closet. Doors also have a 3/4" undercut
    -Insulation for problems rooms on outside walls has been inspected by 3rd party utilizing a thermal camera as well as a blower door test. Apparently, as far as air leaks go... my home exceeds Energy Star standards by 2-3 times.
    -The supply box is currently level on a horizontal plane. All but one of the takeoffs are taking some rather harsh bends within a few feet or less of the box due to truss webbing and cords. Changing of the angle should allow the 16" return from Plenum to Box be more of a 45' then the 90' plus. It'd also allow more direct ducting to the other supply's from the box with fewer bends(or any at all).
    -Contractor has modified the duct run to the study. Now it's 8" all the way to the study. They did a flip on the ducting for Dining and Study. Damper added to 8"run for Bedroom 2 and 3 - These two rooms receive little if any air right now, but they still stay in comfortable temperature ranges


    Specifics/Technical specifications:
    Heat pump make/model: Lennox 14HPX-036-230-12
    Air handler make/model: Lennox CBX26UH-037-230-1 (1/3hp 1.7 FLA 825 RPM motor; 37,000BTU)
    Geographical loc: North Texas(North Dallas Area)
    Filter size: 20x25x1
    Fan rated CFM(set on Med): 1,354 CFM

  2. #2

  3. #3
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    What you need done is a Room by Room heat load done (Manual J). Then have them balance accordingly. Without this I'm making some generalized assumptions and suggestions, so remember that.

    The size of your return is good for approx 1000Cfm of incoming airflow. Your system is rated at approx 1200cfm. So this should be your first fix. Second all your ducts look like they are WAY undersized. And if it was our company the placement of the grills is non-optimal (should be positioned closer to the outside wall as that is where your major heat gain/loss is. We also do not like seeing Y's that go to multiple rooms, if we did a Y both terminations would go to the same room.

  4. #4
    Quote Originally Posted by cuchulain View Post
    What you need done is a Room by Room heat load done (Manual J). Then have them balance accordingly. Without this I'm making some generalized assumptions and suggestions, so remember that.

    The size of your return is good for approx 1000Cfm of incoming airflow. Your system is rated at approx 1200cfm. So this should be your first fix. Second all your ducts look like they are WAY undersized. And if it was our company the placement of the grills is non-optimal (should be positioned closer to the outside wall as that is where your major heat gain/loss is. We also do not like seeing Y's that go to multiple rooms, if we did a Y both terminations would go to the same room.
    I appreciate your response, as well as the disclaimer in regards to Manaul J.
    They 'assure' me that it's been done, but they aren't 'allowed' or 'able' to give, or show me any of that info. Suffice to say that I do not believe them.
    I believe, as you mentioned, that a manual J followed by a manual D is vital.

    What do you think of HVAC calc? http://www.hvaccomputer.com/
    I'm not sure how they'd react to a 3rd party doing both Manual J & D, and providing those results as a "Hey look... this is all wrong. Your responsible for fixing it"

    Regarding your other thoughts on ducting - Undersized was my thought. Not a professional or scientific backed up opinion though.
    I am contemplating asking a third part to install a Jump duct from the LR, possibly above or near the windows or door, to the hallway were the main return is.

    Where or how are you getting the 1,000 CFM? Based on the single return being 20x25x1? So a return would be the first start. However, this will be very difficult given location the air handler. It could only be fed from the food pantry - doesn't seem ideal or even advisable. The other two walls are shared by bathrooms.
    Last edited by Stamas; 02-12-2012 at 10:00 AM. Reason: //

  5. #5
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    If they won't show you the manual J and D results then I don't believe they were done. There is nothing against showing someone the results. Infact here we have to turn them in to even pull a permit. You may just have to have someone else come in and do them, and while they are at it they can confirm everything was done up to snuff, and if not give suggestions to fix it. Since you have a pretty open concept Home design having a R/A jump from the living room isn't going to help you.

    the system you have depending on if they calculated at 350cfm/ton or 400cfm/ton is either 1050cfm or 1200cfm. if they calculated at 350/ton then the R/A is only minimally undersized. If that is the case then your main problem is all on the supply side. If they calculated at 400/ton then your system is rated at 1200cfm and then your R/A is grossly undersized and your problem is on both the incoming as well as the outgoing side.

    I'd get the Manual J and D done and go from there. This will let you know from an airflow side as well as a system size side of things where you stand.

  6. #6
    Join Date
    Mar 2011
    Location
    Galveston Texas
    Posts
    530
    Looking at your drawing a bit closer for your bedroom 4, if your measurement is correct and you have an 8" at the plenum and an 8" at the grill yet they are also pulling a 6" off to go to the dining room then that will never work.

  7. #7
    Quote Originally Posted by cuchulain View Post
    Looking at your drawing a bit closer for your bedroom 4, if your measurement is correct and you have an 8" at the plenum and an 8" at the grill yet they are also pulling a 6" off to go to the dining room then that will never work.
    That's right - that was their 'fix' for bedroom 4/study.

    The study was a brazing 85 during the summer... after the first 13 or so visits, the finally made it better by choking at the dining room and increasing the size to the study. It helped - but I really don't think it was a correction, just a band-aide.

  8. #8
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    Since you said the house is very tight (hope you have fresh air ventilation) and since the rooms even out quickly when the blower is turned on, you may want to replace your blower psc motor with an ecm replacement motor, and maybe a new t-stat with "circulate" option, and just leave the fan running 24/7 and call it a day.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  9. #9
    Quote Originally Posted by tipsrfine View Post
    Since you said the house is very tight (hope you have fresh air ventilation) and since the rooms even out quickly when the blower is turned on, you may want to replace your blower psc motor with an ecm replacement motor, and maybe a new t-stat with "circulate" option, and just leave the fan running 24/7 and call it a day.
    House is tight - But I know there are places for it to find makeup air.
    No noticeable negative pressures yet.

    Actually - that was one of the thoughts.

    How do installers go about that without replacing the complete air handler?
    I have 2 extra wires running to the t-stat; Are there particular stats that use a separate call for 'circulation' mode? Or would it need to be a true ECM fan with the 16-pin setup, along with a retrofitted controller inside the handler? (Cant even seem to find controller upgrades...)


    I like to do my research - and I've gotten really tired of the "There's only one solution" approach from contractors. Could you point me in the right direction?

    Also - I did a Heat Load calculation with that program. It would seem that system is actually over sized. If I assume .6 pressure, the airflow would be more like 900-950CFM.

    Program reported
    Heat gain: 24,670 ( 2 tons )
    Heat Loss: 21,220

  10. #10
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    The people doing the blower door test should have told you how much fresh air you need mechanically introduced for health & safety. Do a little google searching "evergreen motor" and you should find information on them. They are not a variable speed motor, just an ecm, and they will replace a psc motor without anything else needing to be done and they use much less electricity than a psc.
    There really is no reason to guess as to whether or not your home is getting the proper amount of fresh air changes. What did your blower door test report say?
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  11. #11
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    From the basic design layout you've posted, I can tell you I would never do a system that way. Quick and dirty, yes. Even temps, even without a Man 'J', not likely. Read the attachment and then render your own opinion.

    Regards
    Attached Images Attached Images
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  12. #12
    Quote Originally Posted by tipsrfine View Post
    The people doing the blower door test should have told you how much fresh air you need mechanically introduced for health & safety. Do a little google searching "evergreen motor" and you should find information on them. They are not a variable speed motor, just an ecm, and they will replace a psc motor without anything else needing to be done and they use much less electricity than a psc.
    There really is no reason to guess as to whether or not your home is getting the proper amount of fresh air changes. What did your blower door test report say?

    I don't have it in front of me, so i couldn't tell you exactly what it said.
    I certainly don't recall them telling me I need so much makeup air. I do know a new set up codes went into effect this year requiring whole house vent systems to go in the homes in the area.
    I will certainly keep this in mind.

    Quote Originally Posted by skippedover View Post
    From the basic design layout you've posted, I can tell you I would never do a system that way. Quick and dirty, yes. Even temps, even without a Man 'J', not likely. Read the attachment and then render your own opinion.

    Regards

    I appreciate that, I'll take a read.
    Any light reading for the Manual - D methods?

  13. #13
    Quote Originally Posted by skippedover View Post
    From the basic design layout you've posted, I can tell you I would never do a system that way. Quick and dirty, yes. Even temps, even without a Man 'J', not likely. Read the attachment and then render your own opinion.

    Regards
    Ha, not sure where you found that... but interesting read indeed.

    Funny that you buy a new house only to find the need to have someone come and do it right. My first new home; Think the price of those customs homes dont look too bad now

    I have a saying that I(Actually, the company does... but I like it!) follow everyday I walk into work...
    Fix it RIGHT
    On TIME
    The FIRST time

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