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Old 02-11-2012, 09:14 PM   #1
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Uneven temps - Solutions? Looking for advice/opinions


I have a new construction home. It's 2,100 Sq. Ft. ft ceilings. 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'. Eliminates the 90 degree 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?
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? Probably something I could not do myself... or could I? I have a strong electrical and mechanical background, and repair electronics for a living. I could wire and install duct work, but I don't know enough for placement, location to put makeup air return, etc.




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. I want to change the angle to 30-45 deg. This would allow the 16" return from Plenum to Box be more of a 45' then the 90' plus. It'd also allow me to get 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 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


Last edited by fuzzball03; 02-11-2012 at 09:19 PM.
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Old 02-11-2012, 09:18 PM   #2
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Old 02-11-2012, 09:37 PM   #3
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To me I go to zoning system if you can. You got to remember that one stat is reading what is temp around it. Other room get control by that stat only. Plus if you had same company came out and had not took care of it then you should call some other company. It will not hurt your warranty. If anything you can call lennox and maybe they can find another dealer for you.
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Old 02-11-2012, 09:55 PM   #4
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Originally Posted by Tator1076 View Post
To me I go to zoning system if you can. You got to remember that one stat is reading what is temp around it. Other room get control by that stat only. Plus if you had same company came out and had not took care of it then you should call some other company. It will not hurt your warranty. If anything you can call lennox and maybe they can find another dealer for you.
This is a new house, so the issues are due to design... Lennox warranty wont help me here, unfortunately.

Any specifcs on the zoning?
Where would possible or ideal area be for zones, and the return for makeup air?
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Old 02-11-2012, 10:07 PM   #5
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Uneven temps - Solutions? Looking for advice/opinions


Did the original HVAC company do a manual J or D. These are the only way to tell how many heat runs and sizes are needed for each room. Also will tell you if system is sized right for the house.
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Old 02-11-2012, 10:27 PM   #6
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Originally Posted by hvac122 View Post
Did the original HVAC company do a manual J or D. These are the only way to tell how many heat runs and sizes are needed for each room. Also will tell you if system is sized right for the house.
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 was told by the same company who did the blower test that my Heat Pump was unsually small compared to what they usually see - They also dont see many new homes though. In addition - they swear they've never seen a better result after doing the blower door test.

I dont think I should take that opinion to heart. 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.hvaccalc.com/main.asp
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Old 02-11-2012, 10:33 PM   #7
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It's a good program for manual j. I use it all the time. Don't fudge or add. The program will do that for you. I would guess your system is oversized verses undersized.

It's a good starting point.
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Old 02-11-2012, 10:40 PM   #8
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Quote:
Originally Posted by hvac122 View Post
It's a good program for manual j. I use it all the time. Don't fudge or add. The program will do that for you. I would guess your system is oversized verses undersized.

It's a good starting point.
Over-sized? Really - I'm not saying your wrong or right, but your the first to voice over-sized seems more likely then undersized.

Now the question is... pay a contractor to come out and due it?
Or try out HVAC calc and go from there?
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Old 02-11-2012, 11:11 PM   #9
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if your drawing is correct, you do not have a true duct system, rather what you have is a plenum and heat runs...........with this type of system, you tend to have more dips, turns sags and radius in a heat run......all of which kill air flow. Also do you have just 1 common return, or many and of course is your filter clean?
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Old 02-11-2012, 11:27 PM   #10
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Why are the suppies all toward the interior walls in your drawing,is that where they actually are located?
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Old 02-11-2012, 11:35 PM   #11
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if your drawing is correct, you do not have a true duct system, rather what you have is a plenum and heat runs...........with this type of system, you tend to have more dips, turns sags and radius in a heat run......all of which kill air flow. Also do you have just 1 common return, or many and of course is your filter clean?
Air filter replaced religiously. The thermostat I put in will tell me to replace it after 10 days of 'usage'.
I honestly cant even tell their dirty when replacing them - but I've kept them all to cover my ass if I need to with these guys.(contractor)

I'm not sure on your distinction of the kind of system. But there is a large box in the attic. Each run/duct connects to that. It's almost directly above the air handler - I was trying to draw this as best as I could, I apologize for the lack of detail.

The drawing is correct. And yes, just one common return.
"Home has a central updraft style return in the hallway. Return grille in filtered;filter at handler."

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Why are the suppies all toward the interior walls in your drawing,is that where they actually are located?
Yes, it's almost dead on.
I've been told that they SHOULD be near the greatest heat loss area. Windows, door, outside walls, etc
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Old 02-11-2012, 11:51 PM   #12
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I would suggest that you get a couple of different HVAC companies out there to give you suggestions on how to fix this mess.

My experiance (limited) is that flex duct is really not very good. I would consider having the ductwork re- designed by a professional and then an all metal system installed if you have attic access.

so one of the things that you can do in the mean time is to pull all the flex duct really tight. google "why flex duct is bad" and then check out the first sight that comes up. You will be amazed.... others may have a different opinion.

You could also replace all the bends (90, 45 etc) with metal adjustable elbows..

you could also find a manometer (ebay!!) and test your own static pressures in the system. that would tell you a lot!!! about the amount of air you system can push out (and of course pull in!!)

you could also get an anometer and check the flows from the supplys and the return for FPS and or CFM. This would give you an idea of the amount of air each room is getting. You could then, tune the system to your needs,,, but watch the static pressure!!!

I would suggest also that the 20 by 25 return grill and filter might be too small. consider adding more return filter area and or upgrading to a 4 inch media filter. The media filters at 4 inches are much better then the 1 inch ones from HD.....

Its really great that it sounds like you have a very tight home.
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Old 02-11-2012, 11:55 PM   #13
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Im no tinner (Service guy here)but from my experiance they should have run a metal trunk line to each end of house and had short drops coming off of it as needed for each area along the exterior walls.
That flex is junk,in short time what airflow you do have will be reduced as it settles into itself.
Id also have a return in each room instead of that central return crap,this is why I never got into much new construction period.
Builders want the cheapest subs and cheapest materials possible,then the homeowners are stuck living with it
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Old 02-12-2012, 12:05 AM   #14
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Quote:
Originally Posted by bobinphx View Post
I would suggest that you get a couple of different HVAC companies out there to give you suggestions on how to fix this mess.

My experiance (limited) is that flex duct is really not very good. I would consider having the ductwork re- designed by a professional and then an all metal system installed if you have attic access.
I have attic access. All metal due to the truss system would make the already difficult attic even more difficult to get too.
Personally, I believe the flex has it place - but I have one run that is greater than 25 ft - That should have been solid at least till it was 5-6 feet from the register.

so one of the things that you can do in the mean time is to pull all the flex duct really tight. google "why flex duct is bad" and then check out the first sight that comes up. You will be amazed.... others may have a different opinion.

You could also replace all the bends (90, 45 etc) with metal adjustable elbows..

you could also find a manometer (ebay!!) and test your own static pressures in the system. that would tell you a lot!!! about the amount of air you system can push out (and of course pull in!!)

you could also get an anometer and check the flows from the supplys and the return for FPS and or CFM. This would give you an idea of the amount of air each room is getting. You could then, tune the system to your needs,,, but watch the static pressure!!!

I would suggest also that the 20 by 25 return grill and filter might be too small. consider adding more return filter area and or upgrading to a 4 inch media filter. The media filters at 4 inches are much better then the 1 inch ones from HD.....
I cant do this. The air handler shares 2 walls with a bathroom, and 1 wall with my food pantry. I can add a return in the pantry. I'm not sure if this is to code or even advisable at all. I cannot make the other return any larger due to the framework there. According to a friend that's an architect, it's very possible the king studs that reduce that's openings size could be a load bearing wall. Alas, the builder wont tell me jack about the truss design or maker.(10 months in my 'new' better than a 'old' house now)

Its really great that it sounds like you have a very tight home.
Yea, looks like one thing was done well.
There've been some other issues - well, several(electrical, bath vents, roof, door frames...). But at least that one has been good.

Last edited by fuzzball03; 02-12-2012 at 12:14 AM.
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Old 02-12-2012, 12:10 AM   #15
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Uneven temps - Solutions? Looking for advice/opinions


If the ductwork is all in the attic why didnt they set the air handler up there also?

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