View Full Version : 3 stories 2 zones, upstairs still too hot
I'm trying to figure out what to do here. My upstairs unit runs all day on hot days. Temperature still gets up to 80 degrees upstairs. Down stairs unit keeps the two lower levels comfortable.
Upstairs bedrooms all get hot. The master, where the stat, is gets up to 80 and the other 4 rooms get up to 78 to 80, so I can't do any balancing. The attic has ridge and gable vents and there is one attic fan.
Did the builder just under size my upstairs unit? Should I add insulation, additional fans or suck it up and get a bigger unit up there?
06-06-2005, 06:00 PM
If its less then a year, call your builer, and have him send his hvac contractor back to check it out.
If its more then a year, have you checked oyur air filter lately.
How much insulation is in your attic.
I change the filters about once every month or two.
I had baffles installed to help direct air toward the master bedroom, which gets the hotest, but then the other rooms get too hot.
The house is about 8 years old and we bought it when it was 3. We've had this problem since moving in.
I had the freon (sp?) checked and topped off last year.
I think it may be lack of insulation (blown in to the depth of the joists, I think about 10 inches), bad duct work and an undersized unit. Our house has a 400 sq. foot builder bump out on the top floor and I'm almost positive they didn't upgrade the a/c to account for that.
I have one side of my trunk that is not used, would it make sense to add additional ducts in the bedrooms off that side of the trunk?
Also, the ducts are those round flexible ducts and they are hanging from my framing in midair instead of down in the insulation...they are insulated themselves, but could it help to get them down closer to the rest of the insulation?
They seem to be kinked in some places and the junction boxes where the line splits into many directions seems to leak some cold air too. Could that really cause me to loss that much cool air to the rooms?
06-06-2005, 08:49 PM
Kinked flex, and air leaks can cause you to loose more then enough capacity to cause high temps in your rooms.
It never hurts to add more insulation.
Remmember, if its blowing air into the attic, its putting the rooms into negetive pressure, meaning its drawing in air from the outside.
If you mean all the take offs are pointing in the same direction from the trunk line, that has no effect.
The 400 sq. ft. addition could could be the straw that broke the camels back.
You still didn't say what size the unit is.
06-06-2005, 09:34 PM
What is the downstairs temp at the cieling?
Maybe you are trying to cool the whole house with the upstairs unit. Put a probe at the cieling downstairs. Also shade your windows will help alot.
06-06-2005, 09:35 PM
Let's see, I am terribly sick. What do I do?
a) call mother
b) call grandmother
c) call Madam Whackola, the famous psycic
d) whine about it and sleep it off
e) ignore it, it will go away
f) call a doctor
I know you dont want to hear this, but you need an A/C doctor to check things out. We are trained to solve problems like this. You should do nothing until a professional looks at EVERYTHING (load calc to determine the proper sizing, a ductwork analysis to make sure it is sized right, etc.) Anything else is a guess and is waster $$$$$
That's interesting, the upstair unit might be trying to cool the entire house...I never thought of it that way. Makes sense, warm air rises and cool air falls. The down stairs unit still cycles a bit, but thinking along those lines...
My foyer is open and with that theory,what do you suggest? Closing all the bedroom doors during the day to isolate the cool air in those rooms? I'm going to give that a try and look for your suggestion here.
I'm not sure of the tonnage on my units. Where do I look to determine it?
I'd like to troubleshoot a bit on my own with your suggetions before calling someone. I've called people before and paid to have dampers/baffles put in, which didn't really help.
My upstairs is about 1400 sq feet, 1st floor is about 1550 with the foyer open to the upstairs. Basement is about 1500 sq ft, but it is alway freezing down there. I have all of the vents shut down there to direct more air up to the first floor. The foyer has a vent about half way up the wall (10 feet up I'd guess). I've been told that is there to create a 'wall' between the two floors....just trying to give you all more info until someone can tell me how to figure out my tonnage.
Thanks for all the help!
06-06-2005, 11:12 PM
Post the model numbers of the outdoor units.
Each unit had two model numbers listed.
Unit one (up stairs compressor):
Comfortmaker ACS024A2C1 or FBA024GC1
Unit two (down stairs and basement compressor):
Comfortmaker ACS036A2C1 or FBA036GC1
06-07-2005, 12:02 PM
2 ton on upper level, and 3 ton on the lower level. Just at face value, the 2-ton would not be able to take care of your square footage as indicated, and would explain the continous operation without an appreciable affect on cooling the space. The fact that you have tolerated this for 5 years probably doesn't allow you to go back to the original contractor. If you want to correct the situation once and for all, call a qualified contractor and have them perform a load calculation of the upper floor only. This is where you are having the problem so I don't suggest reinventing the wheel by messing with the lower level system. This load will tell him and you exactly what size system should be in place. Also be sure if a change in size is made, that the existing air distribution can handle the increased airflow. You will need expert advice to fix this once and for all, and be willing to compensate for that expert advice. What you are attempting to do by closing doors, etc. will not only 'mask' the real problem but may in fact cause some additional problems. Any other questions?
Before my counterparts jump on me with both feet, I am confident that we will all agree that with a second floor square footage of 1400, the 2-ton won't keep up, as is obviously the case. I stand by my position that the ONLY definitive way to properly size the system is with a load calculation.
p.s. just for your information, I would not be surprised if the builder told the contractor to put in the bare minimum. Hey guys, you know it happens!
[Edited by John Lloyd on 06-07-2005 at 12:04 PM]
06-07-2005, 03:04 PM
It is highly unlikely that the top floor AC is not large enough. Most homes that are only 8 years old are reasonably tight, have dual pane windows, and are well insulated. Under these circumstances, 2 tons should be more than adequate.
However, you could have a lot of air leaks -- particularly if you have recessed lighting in the upstairs ceiling or if the attic hatch is not gasketed to prevent leakage. Other ceiling penetrations could be leaking also. You'd be surpised how much air can leak out -- or in -- through these seemingly insignificant holes, gaps and cracks.
It is likely that you are losing 25% or more of your cooling thorugh duct leakage. If you have a ceiling filter grille, make sure you use a fiberglass filter (like Grainger sells) instead of a pleated paper one. This will reduce any leakage in the return duct. Consider having a Duct Blaster or other test done to determine the amount and sources of leakage. Then fix all the leaks and get a retest done.
It is also likely that your system has a fixed orifice rather than a thermostatic expansion valve. If the refrigerant charge if off just a little, a system with a fixed orifice will suffer substantial degradation in performance. Few technicians know how to correctly adjust the refrigerant charge and are willing to spend the time required to do it right. With a TXV the charge does not have to be quite so exact.
Panama gave you some good advice.
What type of windows do you have?R-value of insulation?
You could click on the bullseye above,Hvac-Calc,and do your ouwn load calc,for a reasonable cost.
Then you'll know if two tons is enough,if it is, look at the list above as a place to start locating the cause.
Panama, thanks for the advice.
I have had to recharge the unit a few times, I wonder if it may have been done improperly.
I do have dual pane windows, though I don't know the R-Factor. We're the second owners of the home and the builder has since gone out of business....surprising in this area, we're the fastest growing county in the nation.
My attic hatch is basically a peice of sheet rock sitting on some molding, so I probaby lose a lot right there. My master bedroom is above a 2 car garage too, which the insulated the ceiling and the walls against inside rooms, but the outer wall and the doors themselves allow a lot of heat to build up on there.
I'll check the ceiling for other possible areas, I'm pretty sure the duct work isn't well insulated around where it attaches to my vents and pumps the cool air into the rooms, I guess that could let a lot of the air leak back out too.
What type of contractor would I contact for the Duct Blaster and what kind of questions do I ask to ensure I'm getting it done right? How about the re-charge on the A/C unit?
Sorry to be so naive...I'm trying to get away with the useful life out of my unit before I have to potentially replace it with a larger one.
06-07-2005, 04:36 PM
Where are you located? Is your AC equipment in the attic? Do you have vaulted or cathedral ceilings upstairs? This creates more space that must be cooled, and can cause ventilation problems in the attic if the insulation guys didn't put in baffles to allow air flow from the soffit vents to the vents at the top of the roof. I had this problem, plus a skylight that added to the heat load, plus a dark roof, plus AC equipment in the attic. Plus a big two story entry that allowed downstairs heat to rise upstairs. Plus no shade on the upper roof. Replaced the 2-ton with a 3-ton and it still works hard.
Check the floor system under the master and above the garage for insulation.If it's trusses ,and insulation is at the garage ceiling level,hot air from the attic can circulate above the insulation and warm the master floor.
The space should be sealed off, air tight,you can use High R 1" foam board from the home supply store.
If any walls in the master or other second floor walls ,back up to the attic ,they should be sealed with the same.This can make a big difference.
Call the electric utility ,they may do ,duct leak testing,check the yellow pages ,or http://www.aeroseal.com
[Edited by dash on 06-07-2005 at 04:56 PM]
06-07-2005, 07:42 PM
Originally posted by gzgg
Panama, thanks for the advice.
What type of contractor would I contact for the Duct Blaster and what kind of questions do I ask to ensure I'm getting it done right?
You might find someone here http://www.energyconservatory.com/contractors/contractors1.htm
As for the recharges, often an inept technician will decide a system needs more refrigerant by just looking at his pressure gauges instead of following the manufacturer's instructions. This can lead to overcharging. If a system really is low, the technician should look for a leak.
How many times have you had to recharge the refrigerator in your kitchen? Basically, they are the same as an AC system.
The a/c unit is in the attic. My roof line is lower above the garage/master bedroom side of the house by about 4 feet. The master bedroom also has vaulted ceilings. I went in the attic last night and the powered roof fan is running and keeping the higher roof line part of the attic relatively cool. The lower roof line and vaulted ceiling on the other side of the attic almost make it a seperate space. When I went over there, the temp was noticably higher. I do have baffels around the soffet vents and have a ridge vent as well. To top that off, I have gable vents. I ended up adding a gable fan to the side of the attic where the master bedroom is and it make a noticable difference, though it rattles a lot.
I'm going to keep the upstairs doors shut to avoid the warm air from the downstairs rising up into the rooms and the cool air running back down coupled with the new gable fan and see how that does.
I'm also going to look into the garage ceiling / master bedroom floor insulation and see about sealing the entry to the attic a little better.
Someone suggested that if the walls in any rooms back up to the attic to use foam board. I'll check that too, the vaulted ceiling in the master has a few walls that are against the attic, though there is pretty thick insulation against them already.
03-20-2006, 06:56 PM
there is a company in oregon that offers a zone solution usually installed in 1 day with little to no construstion needed http://www.homecomfortzones.com give these guys a buzz. they just started selling their product here in california and i hear it really works and is affordable just off the hip usually runs less than XX
http://www.my-smileys.de/smileys2/033102sor_1_prv.gif (No pricing, due to site rules (http://www.hvac-talk.com/vbb/showthread.php?threadid=1241) )
[Edited by arpa on 03-20-2006 at 07:52 PM]
03-20-2006, 08:36 PM
1. Call service company
2. Have them check out your system
3. I bet you have a refrigerant leak and the system is low on refrigerant....
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