AC Issues and Repair/Replacement Quotes

taysdadJune 17, 2011


I have a two story house in Cincinnati, OH with two split gas furnace systems that heat and cool the place. The second floor of the house (approximately 900 square feet of finished living space and approximately 800 additional square feet of "2 story living area" comprise the second floor. The house is 7 years old (as are the HVAC systems) and is well insulated.

The upstairs system today is comprised of a 60k BTU 90% carrier furnace (58MCA060) with a 2.5 ton coil (CK3BXA030) and a 2.0 ton 10-SEER, R22 Carrier outside condenser (builder's grade). We have only lived in the house since October, and the furnace seems to heat the second floor without too much issue and keeps the place comfortable in the winter. This summer, when we turned on the AC for the first time, we discovered we were low on freon due to a leak in the evaporator coil. We have had the unit filled with R22 and the house is cool (for the time being). Unlike the heating, the cooling of the house is challenging in some rooms. The furnace sits in our attic and feed 11 registers and have four return air registers. The air flow just seems a bit low. Also, humidity is a bit of an issue on the second floor of the house. However, it is presently keeping the second floor at 76F without issue.

The registers are fed with a series of insulated, flexible ducts in different sizes. Most are reasonable in length (4'-12'), a couple are a bit longer (about 15-16'). The flex duct is taught and not kinked.

At first, we thought we'd just replace the coil. However, quotes for replacement are running $1500-$1800 and universally all the contractors have advised against just repairing the existing unit.

Instead, all have recommended replacing the coil and outside unit with a new system. I have received quotes from three different dealer on replacement units. Also, two of the three dealers are recommending changes to the existing ductwork. I'd appreciate any expert opinions on these systems and their recommendations:

DEALER # 1 -NATE Certified

Trane XR15 (2 ton)

Trane CC 17.5 SEER coil (cc)

10 year parts / 1 year labor

Flush & clean existing lines. Use existing programmable thermostat (Carrier)

recommends installing new unit first and only making changes to duct work if issue persists with new unit. Says current duct work appears "ok" and new units are stronger than older ones and may be fine. Duct work changes could be addressed after installation if issues continue. Says that might increase diameter of longer runs.

Price $3,529

DEALER # 2 - NATE Certified

Trane 4TTR5024 2 ton

Trane 4TXCB025 coil

Clean, flush, and reuse existing line set.

Use existing thermostat (Carrier programmable)

Change 2 supply runs (further away) to larger diameter (included in the bid)

10 year parts / 3 year labor warranty


DEALER # 3 - NOT NATE Certified

Install 2.5 TON Trane system (not 2.0)

4TXCB030BC3HCA coil

Clean existing line set with RX-11 and nitrogen and reuse

Trane XR13 system with 10 year parts / 5 year labor $3,620

Trane XR15 system with 10 year pars / 10 year labor $4,445 - includes 4TTR5030A1000A coil

Trane XL15i system with 12 year compressor / 10 parts/10 labor $4,810 includes 4TTTX5030A1000A coil.

This dealer also recommended reinstalling (8) 6" RIGID supply pipes in place of the flexible duct that lead to the bedrooms and bathrooms. - $1,110

Sealing off (3) supply ducts in attic (these currently supply closets) - $185

I have mixed feelings about the contractors, but I would love to hear what this group thinks about these bids and recommendations.

Also, I'd be interested in what this group would think about possibly replacing the furnace as well with a variable speed unit (this would allow us then to qualify for $900 in rebates). How much extra cost could I expect to add for this? Would you think it worth it?

Many thanks,


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Chances are they have the blower speed set too high already but 11 runs for a 2 ton, they won't be that strong. If turned back where it belongs, will be even weaker but better humidity control.

Someone should look at the duct static pressure to see how restrictive it is. That will help tell if you need to replace ductwork.

If you don't get a new variable speed blower, no point in getting more than an XR13 system. You'll get only 13 SEER out of the 15 and 15i units and pay hundreds or more for them.

Upgrading to an XV95 probably would add $3500 or more to the project.

    Bookmark   June 19, 2011 at 9:21PM
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You are correct about the fan speed setting. It was checked and it is definitely on the highest setting.

What are you thoughts on moving to a 2.5ton and keeping the setting on high? This seems like it should provide better humidity control? This is what the third contractor was recommending, as well as sealing off (3) of the runs that only supply walk in closets.


    Bookmark   June 20, 2011 at 10:27AM
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OK - after another couple of weeks of living with the A/C system, the humidity in the whole house (but particularly the upstairs) is high. While it's cool inside, it is very humid and muggy. Does anyone have a suggestion on the best way to address high humidity?

    Bookmark   July 6, 2011 at 10:39AM
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Let's get some facts.

What exactly is the humidity level that you describe as high?

What are the normal runtimes for AC cooling upstairs?

I would move the fan speed on the blower down to low and see what effect that has on upstairs comfort level both on maintaining temp and lowering humidity level.

If you do elect to purchase new system for upstairs, I would recommend a system that has var speed blower and a thermostat that can be set up for
DOD-dehumidify on demand feature.


    Bookmark   July 6, 2011 at 2:47PM
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Thanks for your follow-up. I don't have a humidistat to measure the humidity level (yet), but here is what I can describe qualitatively.............

The top row of windows in our two story family room have fog/condensation on them every morning that completely covers the windows (they are 72" tall windows). Also, many of the windows in the upstairs bedrooms also have condensation on them each morning (albeit to a lesser degree). By late morning, the condensation is all gone. Also, many people who come in the house comment on it feeling "muggy" (and they typically are just on the first floor and not the second floor where it is worse).

I will try to pick up a meter tomorrow to measure the actual humidity levels at different spots in the house and different times of the day.

As far as run times, when it is working to cool, the a/c unit will run almost non-stop for the peak periods of the day (both units actually).

Are there particular systems that I should be looking at? So far, I have constrained my searched to only Trane equipment, but I am open to other choices if they better address my needs.


    Bookmark   July 6, 2011 at 4:23PM
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Obviously you have a lot going on here.

The condensation/fog as you describe is not normal. What kind of windows do you have?

How would you describe the insulation qualities of your home?

Has your ductwork been inspected for any obvious leaks and/or insulation problems?

I would get a combo digital humidity/temperature gauge and measure both at various supply registers serving the upstairs.

If your AC runs continuously most of the time, then this suggests your condenser may be undersized.

When was the last time your evaporator coil was inspected and refrigerant was added? Any idea how much refrigerant was added? If the leak was
not located and repaired, then you can expect the same problem to re-occur.

If you intend to keep your existing furnace, then I would stick to a good 13 SEER AC with matching evap coil. If your electric rate is reasonable vs nat gas rate, you might even consider a 13 SEER heat pump.

Do you have a basement or crawl space? If crawl space, does it have vapor barrier? Any evidence of mildew on either floor?

I would turn down the blower speed for AC cooling at first opportunity.

Filters are regularly changed out?

Post back.


    Bookmark   July 7, 2011 at 10:53AM
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OK, I got a temperature and humidity gauge and I spent the last day taking measurements at different times. I took measurements of the house under two different conditions: (1) when the fan for the HVAC were set to "on" (2) when the fan setting was "auto"

I had been keeping the fan switch set to "on". Under these conditions, the house was kept at 76 degree set point (and it also measured 76 on my thermometer in various points -- very good temperature control). However, the humidity in the downstair reached 67% and the upstairs measured 86%.

I then moved the HVAC switches to "auto" and waited almost 12 hours. The humidity in the house was noticeably lower. It measured 41% in the first floor and 47% on the second floor. There was a bit more temperature variation than with the switch to "on", but it was on 1-2 degree differences.

All filters are changed regularly and are very clean - they were just replaced.

It does seem that the house is much more comfortable with the "auto" setting and I have no windows with condensation.

The insulation quality of the home is actually quite good. The walls are 2x6 construction with fiberglass insulation. The attic has loose fill fiberglass measuring at 20-22" in depth. The windows are Pella Proline casement windows. They caulking is mostly good - some small drafts but nothing major. The house is built over a full basement (no crawlspace) and the basement walls are insulated . No evidence of mold or mildew.

My evaporator coil was inspected in early June and found to be leaking. About 2.5 lbs of R22 was added to the system then. They performed an leak check and determined the coil was "leaking badly" and needed replaced as opposed to repaired. At that time they suggested total A/C replacement and not just the coil. While I am sure I have lost some refrigerant, the registers are still putting out ice cold air today.

We do have pretty reasonable electric rates .0778 /kWh.

I am open to replacing the furnace if that is what is the best thing to do. My priorities are: increased comfort and then energy efficiency and reliability. I intend to be in this home for about 15 more years so I am trying to think long term.


    Bookmark   July 8, 2011 at 6:50PM
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Well, after a few more days of experimenting, it seems that I get the best results (most comfortable conditions and the least amount of condensation on the windows) when I leave the first floor HVAC fan to "on" and the leave the second floor HVAC fan at "auto".

Does this indicate the issue is with the upstairs unit somehow?


    Bookmark   July 11, 2011 at 9:05AM
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Both AC modes should be on auto because with the fan "on" setting, you run the risk of re-introducing humidity off the evap coil.

Blower speed on both settings should be on the low or next to lowest speed setting.

Then re-evaluate with new temp/humidity readings on both floors and directly at supply registers on both floors.

Condensation on windows indicates an unacceptable problem.


    Bookmark   July 11, 2011 at 9:25AM
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Well, after MANY, MANY load calculations, inspections, and load calculations, I have finally signed a contract. I wanted to post my decision back here for others to use in the future.

I ended up going with an HVAC contractor that I have used for a number of years (about 12 years on three different houses). His pricing was middle of the road to slightly higher than most, but I do trust his expertise and his work.

After careful inspection of ductwork in both my attic (second floor) system and my main (first/basement) system, it was found that my returns were in adequate for the second floor system. He has proposed to add two returns from our central upstairs hallways to compliment the individual returns in each bedroom. Additionally, he recommended dampering all the runs and replacing two of the longest runs with a larger diameter duct. Additionally, he is replacing the leaking Carrier coil and condenser with a TRANE 2.5T XR15 (4TTR5030) A/C unit and 4TXCB031 coil. He will reuse the existing lineset (and flush, wash, rinse, and vacuum procedure). He assures me the lineset is in good shape and correct in size. We will also resuse the existing thermostat that currently runs the system (a carrier). He will also resuse the 6" Aprilaire media cabinet. Further, he will seal all ductwork with a brush on mastic. He is doing all this for $3774 which includes a 10 year parts and 3 year labor warranty.

The net outcome of all the inspections for this system was that (1) my A/C unit was oversized (2) my ductwork was poorly sealed and not dampered (3) I needed a "wrap" added to my furnace along with a second filter to allow adequate return air flow to the furnace. The other determination was this furnace was in poor condition and the blower motor needed replacement and the furnace did not burn cleanly and efficiently. It was repairable, however, I decided to replace it and pair my main system with a very new high efficiency VS furnace to take advantage of a 2 stage A/C unit for this level that could help drive out the high humidity levels in the house better. What I am purchasing for this system is:

Trane 95% XV95 Furnace variable speed, 2 stage heating (TUHMC100ACV4A)
Trane 4.0T XL20i dual compressor A/C unit
4TZCC008CC3HCA coil
Trane Comfortlink II Thermostat
(2) 4" pleated media filters (along with a furnace "wrap" for return air)
Trane humidifer
Dampering all runs for main system and balance all registers with CFM meter
Sealing all ducts and returns with paint on mastic to prevent air leakage
New Lineset
This system qualifies for $500 federal tax credit and $400 Duke Energy credit
10 year parts (12 on compressor) / 3 years labor

In the end, I think we will have a system that not only works, but hopefully increases our comfort in the home.

I'd like to thank everyone who helped me gather information and pointed me in the right direction to asking good questions and getting the real issues with this system (particularly Tigerdunes and Baldloonie). I doubt I would have made as wise a choice without your help.

The systems will be installed in (3) days. (1) day for the upstairs unit and (2) days for the downstairs system. I'll post after the system is up and running with my opinions on how it works.


    Bookmark   July 28, 2011 at 4:48PM
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It's great that proper load calculations were performed and ductwork was given attention. I'm impressed that they will go the extra step to test and balance the system airflow -- a practice "required" in commercial applications but often ignored in residential (changeouts, at least).

    Bookmark   July 28, 2011 at 6:11PM
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Not my intent to muddy up the water when new install seems imminent.

However, I want to point out a few things.

You will have a mismatched system on 2nd floor including the fact that you will be pairing a high eff AC condenser with a non var speed furnace. This means that you will not achieve the performance/eff numbers that the condenser is capable of achieving. Perhaps this choice is made looking down the road when the furnace is replaced. Also, it seems doubtful since you are going up in condenser size that your line set is the correct size. I'm sorry but I don't like a shortcut like that. What does dealer have to say about your humidity problem? I will come back to you about that evap coil selection.

For the main floor system, what size is the living space area both first floor and basement? What size are your existing systems?

Why two media filter cabinets for downstairs?

Post back as time is available.


    Bookmark   July 30, 2011 at 10:42AM
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Thank you again for taking your time to help me. Here are the answers to your questions:

Your assumption about looking to the future for the second floor condenser is spot on. Our dealer pointed out the exact same thing about our furnace not being variable speed, but the additional investment from the XR13 to the XR15 was very small and might give us better flexibility in the future. The furnace for now seems fine, but we may decide to replace it in the future either for the comfort of a VS system or if maintenance starts to become an issue.

As for the humidity problem, he concluded a few different things. (1) the ducts in attic (whole house actually) are poorly sealed (not sealed at all) and we are getting a lot of air from the attic into the system. This is part of the problem. Both systems are to be properly sealed at all joints with a brush on mastic (2) the fan setting is on "high" and there is simply not enough cooling capability in the current system to pull any moisture from the air while the system is running. The fan speed needs to be adjust down. (3) both our systems were low on charge. As a temporary measure, he put 2.5 lbs of R-22 in our main system and another 2 lbs into our upstairs system (this was recharged about 6 weeks ago). The air coming out of the registers is again very cold (not just cool) and this has already made a big difference in the humidity in the house. While its already improved to the point that we no longer get condensation on the windows anymore, my installer tells me that it will improve even more with the new system.

As to the question of the lineset. Multiple installers have looked at the lineset and said its fine for a larger system. I don't know what size it should be, but I think they said it was 3/4 - 3/8. Does that mean anything to you? What should the lineset be for a 2.5T system?

The living space for the main system is: approximately 4,000 square feet of first floor space and about 1200 square feet of finished basement. The current system is for this space is a matching system to the Carrier system in the second floor, just larger in size. It is a Carrier 58MCA120 120K BTU furnace paired with a 5 ton 38CKC060 builder grade A/C unit. It currently has one Aprilaire model 2400 filter media on the furnace and an Aprilaire humidifier. The installer suggested adding a second media cabinet to the downstair system because he wants to install a "wrap" to the return air feed to the furnace to increase the return air supply to feed the furnace air from more than one point.


    Bookmark   July 30, 2011 at 11:14AM
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Coming back to the line set size, I am a trust but verify kind of person. This is an important detail. If you were going from a two ton condenser to a two ton condenser, I probably would accept his word. However, you are going from a two ton to a two and half ton. You should take the measurement of line set, small line and large line. Post back and I will verify the correct size.

Have you even wondered why dealer is installing new line set for downstairs system? Humm...It appears you are going down in size from a 5 ton to a 4 ton condenser. Correct?

Since you have confirmed that you are looking down the road by selecting the XR15 condenser for upstairs, I did a little research on your behalf to try to find the best matching coil that would be compatible for possible future furnace selections. I looked at the XV95, XV80, and XT90. Based on the AHRI directory, the consensus choice would be 4TXCC044BC3.I would review this point with dealer.


    Bookmark   July 31, 2011 at 1:16PM
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I went outside to my two units and this is what I measured for line sets: Main unit (7/8" - 3/8") and for my upstairs unit (3/4" - 3/8').

As for the upstairs furnace, it's currently a high efficiency unit that has not had an issue with the condensate freezing up to date, but my installer thinks it was a bad idea to put this furnace in the attic. If we do replace it down the road, he said he would recommend a XV80 unit. Does this sound right to you? I know that this unit doesn't run much at all in the winter (there is A LOT ) of two story space and it seems like a lot of heat comes up from the first floor causing most of the heating load to be carried by the main system.

As to why they are putting in a new line set for the downstair unit, I don't know. I think this is a great question to ask my installer tomorrow (along with the coil recommendation for the upstairs unit :)).


    Bookmark   July 31, 2011 at 4:44PM
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