Home AC advice

[elcom]

The collective wisdom and experience on this forum is amazing! I wonder if you could comment on my AC issues. Apologies in advance for the long post...

I live in Houston (hot!) in a home that according to official records is just under 3900 sq ft, two stories + finished attic/third floor built in 1994. I had two Trane units, 5 ton downstairs and 4 ton upstairs. These worked well for the 13 years that we lived in the house (meeting set temps), but recently died (leaking coils). The 5 ton was original (1994) and the 4 ton was replaced in 2001. I decided to replace both units.

I decided to go with variable speed Tranes (XV20i) and asked for a manual J calculation. The contractor that ended up choosing told me that he would do the manual J if we ended up choosing him, but not while I was still shopping. OK, fair enough. However, it never got done.

The two units were installed. The downstairs 5 ton unit is working fine and meeting set temps.

The upstairs unit is not meeting set temps (set to 75, only reaches ~81-83 when it is 96 outside). The unit is running at 100% (not much benefit of the variable speed) all of the time.

The contractor now did a manual J and found that the house is actually closer to 4700 sq feet and the upstairs unit is grossly under sized. This is why the upstairs unit is not cooling appropriately.


Options are:

1) Add a third system
2) Add insulation to attic (radiant barrier foil + blown in insulation)
3) Replace upstairs windows with double pane
4) Increase capacity of upstairs unit to 5 ton (currently 4 ton)

Per contractor, if we do 2-4, it ends up being on the border of appropriately sized. He is reluctant to replace the 4 ton because he cannot return the unit (used for 1 week).

At this point, I don't have a concrete offer/plan from the contractor.

Questions:
1) Is it common to have 3 systems for this sized house?
2) Would you recommend a mini split for the third system?
3) What would be fair in terms of correcting the problem? Should I insist on replacing the 4--> 5 ton upstairs unit?

Thank you in advance for your advice!

 

[rsanter]

If they were both replaced with the same rating sized unit then why is the upstairs one not getting the job done. I would want to know for sure that it is working right and was installed right first.
If you have three units then you have the opportunity for more energy efficiency in how you operate them. You will have more options is which one you run and which you don't. I have one unit and really wish I had two.
What size is the added third floor? Rule of thumb is 500 to 700 sq ft per ton of cooling

What is fair? Not a penny over his cost and prefer that it is a little under his cost.
If the agreement was that if he gets the job and he would do the calls then he screwed up.
The other way to look at it would be what is the added cost of the bigger unit if it was installed at the time? Pay that difference

Bob

 

[brewchief]

If the house cooled fine with the two units before and the capacity is the same it stands to reason that it should cool now.
First thing I would do is to verify that the 4 ton unit is operating at full capacity.

Next thing I would do is look at the house itself and see if anything changed or if there is anything that can be done to reduce the cooling load. Old leaky and poorly insulated ductwork could be losing a lot of capacity.
Fixing ductwork and adding insulation to the attic may reduce the load so the current system will work.

Sent from my SM-G900V using Tapatalk

 

[CNGsaves]

Pay for a "blind" system evaluation from competing Trane HVAC EXPERT in suburb town - - - ie remove any tags/labels from guy who did the job !! Tell the story that you just bought house and "prior owner" put in these new systems recently and you're not happy with effectiveness.

That will give you INDEPENDENT opinion on what you really should have done in the first place.

How can the first guy miss the square footage by 800 ft ??

Is that first Trane guy competent?? Would you trust him to do anything more??

 

[AndyCBR]

Make sure the 4 ton is wired correctly. If it cooled with a 4 ton before a new 4 ton should be equivalent. It could just be running on just the low speed compressor and not kicking in the 2nd stage, effectively making the unit act like a smaller tonnage.

I have heard some negative things about the Trane variable speed 2 stage units not dehumidifying well and would be interested in your experience with that. Complaint I heard is the units run continuously and meet the temperature set point but do not dehumidify well.

I have an XR16 single speed compressor with a variable speed blower that works well.

 

[elcom]

Thank you for the thoughtful responses:

1) The explanation that the contractor gave is that the cooling capacity of the newer higher efficiency units is actually slightly lower than the older units. This is the first time that I was told about this difference between old and new units.

2) The contractor assures me that the unit is working properly. He tells me that he has contacted Trane and is convinced that the unit is working as designed. At this point, I have no independent verification. He also installed an additional return in the ceiling on the second floor (at no charge) -- this was not part of the initial estimate/plan.

3) No problems with humidity either upstairs or downstairs. You can actually adjust for temperature or humidity using the Trane thermostat. Current humidity is 52% downstairs at 75 degrees and 47% upstairs at 80 degrees (set to 78 and outdoor temp 92).

4) Third floor is ~500 sq feet not including attic space. At current tonnage, I have ~4700/9=522 sq ft/ton.

5) To be fair to the contractor, he was going by what I reported as the square footage and what is listed in the official records. I have never actually measured the house myself, so I was just going by the records.

6) To the best of my ability to judge, the contractor seems competent and well-meaning.

7) How would I determine the contractor's cost for installing a third unit?

 

[brewchief]

If you have both indoor and outdoor model numbers you can look up the exact btu rating that the unit should produce by doing an AHRI matchup. FWIW most units will still be within 1000-2000 btus of what the nameplate rating would be, your 4 ton might 46 or 47k btu instead of 48k btu, you would have to have had a very marginal system prior for it not to work now.

What are your humidity settings that you are trying to get to? Have you tried turning the humidity controls off and just set your cooling temp? If not try it, all the system that I know of that provide dehumidification control do it by slowing blower speed, this can lower your system capacity somewhat.

Can you get some pics of the indoor unit that serves the upstairs along with it's ductwork.

What does the man J show as far as total heat gain?

 

[elcom]

This is what the contractor sent me:

1st Floor:
Total Load: 43,491
Sensible Load: 39,105

Current Equipment 5 ton:
AHRI 7066831
Total Load Capacity: 53,500
Sensible Load Capacity: 39,200

D/S 5 ton is sufficient - note the sensible load is nearly perfect in line. Design specs are to ACCA houston default of 96 degree outdoor. As temps go higher the load increases as well.

2nd Floor:
Total Load: 47,278
Sensible Load: 42,443

Current Equipment 4 ton:
AHRI 7159574
Total Load Capacity: 46,000
Sensible Load Capacity: 35,200

System Sensible Capacity is short 7,243 to the home demand for the 2nd floor and 17,249 when combined with the 3rd floor.

3rd Floor:
Total Load: 11,595
Sensible Load: 10,006

 

[Stuff]

If you push hard enough Trane will send a company tech out to review the system. Just keep on saying that the old system worked and the new one doesn't.

 

[Bruce4310TX]

contractor screwed up by not cking the SQ ft of the home switch that unit out

 

[Radix2]

3) Replace upstairs windows with double pane


I find it very hard to believe that a house built in 1994 does not already have double pane windows. Maybe he is talking triple pane ?

 

[elcom]

Pushing for the Trane tech will make sure that the unit is installed properly. That makes sense, though the contractor tells me that they are in contact with Trane and that the unit is functioning properly. This seems plausible since the cooling capacity has decreased compared to previous system and heat load has not changed.

I am pretty sure that they're single pane windows. Don't know if that was common in 1994 or not.

This is very helpful. Thanks again to everyone who responded.

I don't like the idea of having 3 systems -- seems complex, expensive, more difficult to maintain, etc. However, the contractor tells me that swapping the 4 ton to a 5 ton would not be enough.

If the best solution ends up being a third system, would you suggest matching the existing systems (i.e., another XV20i perhaps a 2 or 3 ton) or would a lower end system be sufficient (e.g., XR16)? I am leaning toward matching, any suggestions?

Thanks!

 

[dsimatt]

IMO he said he would do the manual J then didn't follow thru and had he done it wouldn't have installed a inadequate system, also he should have known the new one didn't perform as good as the older one.

I don't see adding a 3rd unit as a option since the older ones handled the load before even being older. My move would be he takes back the 4 ton, you buy the 5 ton and split the install cost to sweeten the option and if he's a busy dealer he will move the 4 ton pretty quick or have to sell it at his cost but its not your problem.

I think the insulating or windows is something to look into but to save energy costs in the future and not for trying to fix this mess.

 

[elcom]

The contractor came out again today to look at options.
He feels that substituting a 5 ton for the 4 ton is not likely to resolve the issue.
His argument is that the manual J shows a deficit of 17,249.
Upgrading to a 5 ton system would only address 4,000 -- therefore it would still not be adequate.

Thus, the radiant barrier, windows and additional insulation to reduce heat load. According to the contractor, these changes + changing to a 5 ton would be borderline. That's why he is suggesting a third system +/- measures to reduce heat load. He brought up: 1) a mini split (most efficient), 2) an additional 2-3 ton XV20i and 3) a less efficient 2-3 ton system (e.g., XR14).

He is NOT proposing to install a third system for free. We have not discussed costs.

 

[Mike007]

If the house cooled fine with the two units before and the capacity is the same it stands to reason that it should cool now.
First thing I would do is to verify that the 4 ton unit is operating at full capacity.

Next thing I would do is look at the house itself and see if anything changed or if there is anything that can be done to reduce the cooling load. Old leaky and poorly insulated ductwork could be losing a lot of capacity.
Fixing ductwork and adding insulation to the attic may reduce the load so the current system will work.

Sent from my SM-G900V using Tapatalk

What he said. Something just doesn't sound right. I would ask around, find someone you know is competent and get a second opinion. Have them determine if the system is actually running properly.

 

[brewchief]

Remember a manual J is only as accurate as the person inputting the info and the info itself. Some programs want more info then others and can create a more accurate number.


If the ductwork for the second/third floor is in the attic consider having it tested for leakage, you may want a company that does energy audits to do this as they may be able to find other areas of heat loss/gain as well.

Do you have a digital thermometer that you can measure return and supply temps both in the rooms and at the unit?

 

[dsimatt]

The contractor came out again today to look at options.
He feels that substituting a 5 ton for the 4 ton is not likely to resolve the issue.
His argument is that the manual J shows a deficit of 17,249.
Upgrading to a 5 ton system would only address 4,000 -- therefore it would still not be adequate.

Thus, the radiant barrier, windows and additional insulation to reduce heat load. According to the contractor, these changes + changing to a 5 ton would be borderline. That's why he is suggesting a third system +/- measures to reduce heat load. He brought up: 1) a mini split (most efficient), 2) an additional 2-3 ton XV20i and 3) a less efficient 2-3 ton system (e.g., XR14).

He is NOT proposing to install a third system for free. We have not discussed costs.

Did the old units struggle to cool the house? I would at this point demand a trane factory guy comes out and goes thru the system because this is BS that you just dumped all this money upgrading units and now are told to shell out even more for a another unit or do expensive home upgrades.

The numbers you posted before a 5 ton should be able to keep up so he should install that and see what happens and in the future you can work on insulating and new windows to be more efficient and save you money versus just costing more like the other options.

Might be time to get a 3rd party in there to do a manual j and see what they come up with and go from there. The mini split would be the best I think to use it as a booster when its really hot and maybe just run it when the temps are just warm enough you need some ac upstairs.

 

[elcom]

Thanks again for the good advice.

I admit to increasing frustration (dsimatt's post summarizes my position well).

Not sure how to answer the "did the old units struggle to cool the house." I told the contractor that I was 95% happy with the 21 year old units in terms of upstairs cooling. Actually, that was the reason that I specifically requested the manual J; to make sure that an upgrade to 2 x 5 tons was not advisable. I believe that even a slight increase in capacity would have made me 100% happy with the upstairs cooling. However, the contractor's calculations do not agree.

The contractor appears to be acting in good faith and I have not heard any "final" offers to resolve the issue. At this point, I hesitate to officially involve third parties and make the situation more confrontational than absolutely necessary. That having been said, I was quite clear with him verbally and in writing that I am not happy with the current situation, that a solution requiring a third system is not likely to make me happy and that I believe that failure to do a manual J prior to system selection/installation is a significant issue.

I have a Fluke IR thermometer (62 Max+) and have measured the temps:

Downstairs: return 73.2, supply 58-61 degrees depending on the vent (there are many in the house and I did not measure all of them, but the contractor did).

Upstairs: return 75-76 (two returns), supply 57-81 degrees depending on the vent (there are >15 vents on the second floor). 70-81 in the vents in the master bedroom alone.

 

[slice]

I am retired ac contractor houston. 25 yrs, The new 4 ton and old are not the same. Old unit outside. probably was right at 42,000 btu compressor ( mfg always undersized comp on unit) check new comp and see what its btu are. Are you sure the variable speed Ahu are set up correctly. Moving too much or not enough air. ? There a many "variables" of how to set up Ahu unit.
Man j. It would get you close. But as u know. Units are designed houston tx for 95*. Anything over that good luck. That's why most units are slightly oversized here.
If it takes 72 degrees on a normal day to be " comfortable". Then your unit is oversized Houston tx. Ie: We dehumidify more than we cool here.

 

[elcom]

Thanks slice. I can only report that the contractors assures me that he has been in contact with Trane and that the units are set up correctly. I do not know enough to determine this myself.

The contractor confirms what slice wrote -- the new and old unit are not the same and, per the contractor, the new unit has a lower capacity. Not sure how to determine the "compressor btu"; is that the "total load capacity"? Per the contractor:

Current Equipment 4 ton:
AHRI 7159574
Total Load Capacity: 46,000
Sensible Load Capacity: 35,200

It seems reasonable to expect that a contractor in Houston would be aware that he is reducing capacity compared to the old system... Especially if he was explicitly asked to perform a manual J.

Contractor tells me that the standard cooling design specs are: meet 75 degrees when it is 96 outside. The downstairs unit is clearly doing this... Currently set at 72, achieves 72 and thermostat reports that it is 99 degrees outside.

Humidity does not appear to be an issue. 50% downstairs, 46% upstairs (presumably because the 4 ton is running continuously).

 

[brewchief]

I have a Fluke IR thermometer (62 Max+) and have measured the temps:

Downstairs: return 73.2, supply 58-61 degrees depending on the vent (there are many in the house and I did not measure all of them, but the contractor did).

Upstairs: return 75-76 (two returns), supply 57-81 degrees depending on the vent (there are >15 vents on the second floor). 70-81 in the vents in the master bedroom alone.

While I prefer a probe type thermometer over the IR style the fact that there is very little temp drop(and in some cases it appears temp gain)leads me to believe that there could be some pretty major duct issues.

Can you get some pics of the upstairs unit and it's ductwork?

 

[Milton Shaw]

Can you block the air flow/exchange between the floors to see if all your upstairs cold air is going downstairs. This is a common problem with houses that have two or more floors that have open staircases between floors. Some plastic and masking tape would block for a single day to check cooling results.

 

[slice]

You see that sensible btu numbers. Right at 3 tons. Not 4. Unit seems not to be big enough. Hope all works out for you. Keep at em.

 

[zmaxmotorsports]

Thank you for the thoughtful responses:

1) The explanation that the contractor gave is that the cooling capacity of the newer higher efficiency units is actually slightly lower than the older units. This is the first time that I was told about this difference between old and new units.

2) The contractor assures me that the unit is working properly. He tells me that he has contacted Trane and is convinced that the unit is working as designed. At this point, I have no independent verification. He also installed an additional return in the ceiling on the second floor (at no charge) -- this was not part of the initial estimate/plan.

3) No problems with humidity either upstairs or downstairs. You can actually adjust for temperature or humidity using the Trane thermostat. Current humidity is 52% downstairs at 75 degrees and 47% upstairs at 80 degrees (set to 78 and outdoor temp 92).

4) Third floor is ~500 sq feet not including attic space. At current tonnage, I have ~4700/9=522 sq ft/ton.

5) To be fair to the contractor, he was going by what I reported as the square footage and what is listed in the official records. I have never actually measured the house myself, so I was just going by the records.

6) To the best of my ability to judge, the contractor seems competent and well-meaning.

7) How would I determine the contractor's cost for installing a third unit?

The guy should be able to look at the house and size the equipment without having to know the exact square footage if hes been doing this any amount of time.

 

[magicrat]

Sorry to hear of ur problems.....Get a competent professional to make sure AC is running at
full capacity(sometimes hard to find)...Anyways in my experience with radiant barrier u might try just that first.....U might be pleasantly surprise what the insulation and radiant barrier do.....Good chance it corrects ur problem and if not then worry about upgrading ac.....Im not 100% sure how it works but the radiant barrier is amazing sometimes.....seen it firsthand make a huge difference ESPECIALLY ON THE UPSTAIRS FLOOR.

 

[elcom]

1) Slice -- I agree (as does the contractor), upstairs is unit not big enough. Given your experience in Houston, what do you suggest as next step? Contractor suggests a third unit at my expense - perhaps with some discount (undetermined at this point). Understand that he does not want to lose money, but...

2) I bought the XV20i x 2 to realize greater efficiency. Seems like a third system is likely to kill any efficiency that I would have realized with the high end system. Correct?

3) Magicrat -- Getting quotes on radiant barrier on Monday. Any suggestions re: "blown in" vs "foil." Contractor suggests foil is better.

4) Can't isolate floors. Would be impractical at my house.

5) There is at least one duct that traverses the attic which is very warm, I think that this is the 81 degree output that I am measuring upstairs. Will try to get some pictures tomorrow.

Thanks to everyone!

 

[Charles (in GA)]

Sounds like you have a third floor "attic" bonus room that was finished out at some time and is not on the tax assessors description of the house. If this room is separated from the rest, does it have its own return? and would a minisplit not be the best option for this single area?

 

[Radix2]

1) Slice -- I agree (as does the contractor), upstairs is unit not big enough. Given your experience in Houston, what do you suggest as next step? Contractor suggests a third unit at my expense - perhaps with some discount (undetermined at this point). Understand that he does not want to lose money, but...

2) I bought the XV20i x 2 to realize greater efficiency. Seems like a third system is likely to kill any efficiency that I would have realized with the high end system. Correct?

3) Magicrat -- Getting quotes on radiant barrier on Monday. Any suggestions re: "blown in" vs "foil." Contractor suggests foil is better.

4) Can't isolate floors. Would be impractical at my house.

5) There is at least one duct that traverses the attic which is very warm, I think that this is the 81 degree output that I am measuring upstairs. Will try to get some pictures tomorrow.

Thanks to everyone!

Radiant foil is mostly snake oil. About the only place it could work as well as claimed would be on the top of your roof where it can reflect into the sky and stay reasonably clean.

I will say that by 99% probability you have double pane windows (single pane have not been used since the 1950s). If you by some strange possibility you do indeed have single pane windows ( this area was once outside if the conditioned space like an attic?), you should definitely change them since it will lower the heat transfer there by at least 100%.

Yes, insulate ducts in unconditioned spaces!

How much attic insulation do you have now? R value/inches.

Hate to see you spend even more on equipment until you you have at least a decent amount of basic insulation and contruction since that is one of the few investments that pays.

 

[CNGsaves]

OP . . . are you saying that the contractor put bare duct in attic WITHOUT insulation??

. . . . and that duct (when running A/C) is pumping out 81 degree air ???

If yes to above, get your MONEY BACK from hack installer for labor/profit. Only pay ACTUAL DEALER COST for units put in (ie equipment), and get somebody competent to work on your HVAC needs.

Did he even ask about and inspect your insulation BEFORE proceeding ??

 

[slice]

Have outside unit removed and replaced with strong 4 ton or weak 5 ton. Determined by comp btu. U don't need a third unit. U need the correct unit for upstairs. It worked before. Fine for how many yrs. the upstairs units coil heater does not need to be changed out. Only the condenser unit. The coil can handle different tonnages, If it has a expansion Valve. Not prob. If it had flow rater. Then it gets matched to new outside unit.
Point still goes back to he did not do as u ask with heat load clacs. I know why as two unit change outs are big money. So times you win and other times not so good as ur cases.
See if Trans can help. Contact state license board file a complaint. That usually perks a contractor up your serious and mean business. And for him to stop slow playing you.

 

[magicrat]

Yes calling TDLR really works.......I had a friend which i advised that his 2 ton ac was in no way big enough for his brandnew 2100 sq foot home....He argued with the contractor for a year and they told him it was right even tho I had him get 2 other evaluations saying he needed 3 to 3.5 tons......Well i told him he could try tdlr.....they sent there own tech out to evaluate and then the homebuilders ac guy magically appeared a couple weeks later and installed a new AC and they will maintain it for 3 years free of charge.

 

[elcom]

I want to be reasonable and, to be fair to the contractor, he never suggested that the unit that he put in is correct. He has said that based on the manual J, swapping the 4 ton for a 5 ton XV20i will not be sufficient to meet demand, even if I add insulation and radiant barrier.

Slice -- per the manual J, a 5 ton would still be ~3,000 (btu?) short in terms of sensible capacity. Isn't that an issue?

I appreciate the suggestion to call the TDLR and Trane. I don't think that I am at that point yet and hopefully will not get there. I have not even heard the contractor's specific plan to solve the problem.

Also, the old 5 + 4 ton units worked pretty well for 21 years (13 years that I was in the house). However, to be perfectly fair, I was considering a modest increase in capacity. That was the reason that I requested the manual J. I told the contractor that I was 95% happy with the previous system's cooling capacity. If the old system continued working, i would not have even considered replacing it to increase capacity. However, it is possible that the old system was a *little* small -- again, that's why I requested a manual J. I did not know that the systems that the contractor was going to install were actually smaller than the ones that I had, even though they were nominally the same tonnage.

 

[magicrat]

Yes work WITH him.....just giving a worst case scenario......And like i said try the radiant barrier and maybe everything will be corrected and u get ur efficiency. That 81 degree duct does sound fishy tho......IF you have an add on on thre 3rd floor(im not saying you do) i would disconnect that duct and put in a window unit and be done with it.

 

[slice]

That 5 ton Trane unit may not be the one you " need" to meet man j. I am sure there is one that will meet the needs. My past with man j is it way under shoots our capacities. School of hard knocks rules with our weather extremes. Keep at them till your happy.
You can take a five ton cond with variable speed Ahu. Custom dial in a perfect setting.
Btw. In past post u said humidity was 49% upstairs. That's idea. But temp was not. That a clue to the sensible load not being meet.

 

[brewchief]

The AHRI numbers appear to be for a A/C and evap coil, are there existing furnaces that the units were installed on or are they air handlers or what?

Where is the second/third floor unit located in the house and where does the majority of the ductwork run? Basement? Attic?

Where the existing linesets(the copper piping connecting the A/C units) reused or were they replaced? If reused were they chemically flushed? Mineral oil left from an old r-22 system is said to inhibit heat transfer in a new r-410a system.

 

[elcom]

1) The units were installed with new furnaces. They are Right --> Left; if I understand correctly, that limits some of the combinations. The combination was chosen by the contractor. I believe that the furnaces are XC80 with variable speed blower -- I confirmed that the blower motor was variable speed (not two speed).

2) Both units are located in the third floor, in unfinished attic space. The duct work to the second floor runs in the attic. I asked about the ducts and was told that they were in good shape.

3) The copper piping was reused for both units. The old system was r-22. I know that they flushed with nitrogen. I don't know about a chemical flush -- not saying that they didn't do it, just don't know.

4) I was told that the temperature drop across the coil was 17 degrees and that the goal was 15-20.

5) I will ask again re: a solution that does not involve a third system. When we met yesterday, I expressed significant reservations re: third system. I suggested what I thought was a reasonable option. Specifically, I was willing to explore increasing the unit from 4 to 5 ton and was willing to pay the difference in price between the two units (~$750). I would also look into adding insulation and radiant barrier. The contractor said that this may not be enough. This plan would cost me an extra $3,000-$5,000 -- seems like the consensus here is that it may be too generous to the contractor...

I have asked the contractor to explore options, including costs and get back to me on Monday. Will report back when I hear from him. I have no evidence that he is dragging this out and, in fact, has been quite responsive.

Thanks again to everyone for their thoughtful comments. I am finding this VERY helpful.

 

[brewchief]

17 degree drop across the coil sounds about right, problem I see is by the time it gets to the rooms it's only 5 degrees or less in some cases.

Is the ductwork flex or wrapped metal? I would assume flex. Is there an R value printed on the insulation? Around here something from that time frame would have R-4.2 Is it tightly sealed at the register boots and at the main trunk or plenum? Some pics of the ductwork may provide some more insight here.

Are the returns properly sealed to the furnace? Some leakage here will draw in the hot attic air and hurt capacity as well.

Duct leakage of 15% or more is pretty common, fix it first if needed rather then simply throwing more btus at it.

 

[elcom]

Pictures of ducts and systems attached...

 

[elcom]

Update:

1) I have quotes from insulation (~$5,600) to insulate the attic. Not sure that I understand that quote because they are talking about insulating ~3300 square feet. Attempting to clarify. In addition, they are suggesting attic vents to be installed by a roofer. They "do not believe in any kind of radiant barrier."

2) Quotes from Window World to upgrade all windows in the house to double pane. I have verified that all current windows are single pane. I am told that current building codes require at least double pane in Houston. However, my house was built in 1994-5, under previous building codes. This would cost approximately $21,000 for the entire house ($8,000 for the upstairs and $13,000 for the downstairs). The solar heat gain coefficient on the windows is 0.19-0.21 (depending on the grid pattern, if any) and the u value is 0.28.

Although they are very expensive, I am leaning toward the window replacement plan as they offer additional benefits (e.g., quieter, less UV-related fade on furniture, etc.).

3) The contractor found a 5 ton configuration that would provide a sensible load capacity of 41,000 which he tells me is likely higher than my old 4 ton. His analysis:

- From the Load requirements, and the pre-existing disconnect box the whole home was intended to have 3 system.
- No two systems are capable of satisfying the demand of the whole home as is.
- My understanding is that you've been able to have "livable" 76ish degree 2nd floor air for 10+ years.
- Since installing our system my understanding is that your hope has been to reach closer to 72 degrees.
- 75 degrees at 50% relative humidity is the set point for average human comfort.
- Current Sensible Capacity on your current 4 ton XV is 35,200
- The highest sensible capacity available on any 4 ton within Trane's current line across all efficiencies is 38,000. Likely at or higher than the capacity of your previous system.
- The highest sensible available on an XV20 5 ton is around 41,000
- This is a higher capacity than your previous 4 ton was capable.
- Still, we are short of the design conditions to satisfy fully by about ~1,400 CFM
- I am willing to replace the 4 ton with a 5 ton XV which will be better than the previous system but still short of ideal without modifying the load via, improved windows, insulation etc.

Should I accept the swap of the 4 ton for a higher-capacity 5 ton?

 

[jacob_coulter]

I just think the window issue is completely separate and I wouldn't bring that into finding a solution as you had adequate cooling before with the same windows. That factor should have been accounted for before installation.

Just out of curiosity, what did you spend on both of the the Trane XV20i? Isn't that an incredibly expensive AC unit? Like $15k + installed times 2? So you've easily spent like $30k+ with this outfit? The fact that you can't get it lower than 81-83 when it's set to 75 is a big problem that should be put squarely on the company/contractor that installed it.

What is he charging to go from a 4 ton to 5 ton to fix his mistake? My opinion is the charge should be zero and completely out of his pocket, that is part of the service and especially when you're talking about a pretty massive outlay of money for such a sophisticated system.

I just can't believe their solution are things like adding a 3rd system and putting in more insulation or double paned windows when they took your house from cooling properly to this and you dropped that kind of money on them.

I really think the "train" left the station as soon as they started pushing for a 3rd system and you immediately should go up the corporate food chain. They know they made a mistake and they're doing everything they can to try and get you to buy band-aid solutions on your own dime.