Trane Unit Runs All Day

[rsamerica]

Hello,

Had a new Trane 2 ton compressor and coil installed last July to replace the 18 year old Lennox 2 ton unit, as the outdoor fan motor seized and I figured it would be best to have new/efficient units installed, even though the original system was working well until the fan motor seized. We retained the original Lennox furnace/blower. Since the day of install, the new system has not cooled properly - contractor will return now that weather has warmed up to continue working on it, but I am not confident in their abilities. Here are some basic facts:

Location: Connecticut
- House type: Two Level townhouse (not an end-unit), lower level partly below ground ; 2100 sq/ft. w/ 9ft. ceilings upstairs.
- Thermostat A/C Set Temp: 74F
- Airflow out of the vents seems adequate (by hand feel)
- Natural gas forced air heating system works fine in the winter and cycles on / off normally to keep at set temps. of 70-71F.
- The thermostat is located on the upper/ground level and this area feels warmer than the downstairs area, which is cool (70F or lower).

Problem example:
Today, outside temp at 2:00pm is mid-80's, not terribly humid. Unit started up at about 11:00am and is still running (6:22pm) and temperature has gone from 74 to 75 to 76 to 77 where it stands now. It has not cycled at all, and will continue to run into the night until inside temp finally drops to 74. This is what happens all of time, even with outside temperatures in the low 80's.

Does this sound like a situation where the unit is not sized correctly, even though the original Lennox unit was 2 ton? I'm trying to better understand the effects of tonnage/capacity on situations like this, to determine whether this is something to press with the contractor. They did not do a load calc. originally, but eventually did a one late last year which according to them came back right on the edge of 2.0 vs 2.5 ton (I did not see these details).

Basically, I'm trying to get some ideas as far as what the problem here might be and how to proceed with this so that we have properly functioning system.

Thanks.

[beenthere]

Did the old 2 ton unit cool the house ok.

It could be a problem with the charge.

Or an air flow issue.

Is the duct work sealed.

[rsamerica]

The old unit cooled properly, and from what I remember cycled regularly. The installed messed around several times with the charge, so I am not sure where it is right now. I am thinking of having a the local premier Trane retailer/installed in the area come in as a third party to observe what's been done, do a charge-check and give recommendation. I have done nothing with the vents/ducts, so I am not sure if there is a problem with them. It is now 7:57pm and the unit is still running, trying to get down to 74 (its only 75 outside and dusk now). The downstairs is 68F.

Thanks.

[pstu]

Your experience with constant multi-hour runtime and slowly rising indoor temperature, sure sounds to me (as a homeowner) like proof of inadequate sensible capacity. While the "easy answer" is a bigger system, things are often not as simple as that. You can regard several detail areas as opportunities to improve.

I would concern myself first with duct leakage and airflow. Measuring supply airflow with tools rather than hand feel, would be valuable here. If you find any significant duct leakage, fixing that would give you a bit of extra cooling capacity. Next, I would investigate what airflow you currently have, and also whether your duct system can handle any more. The classic airflow setting is 400 cfm/ton, however you can get about 6% more cooling capacity if you run at 450/ton -- with a corresponding reduction in humidity removal. Is humidity removal a large concern in your climate?

Anything to reduce load of course, will help your sizing problem. This might be an opportune time to consider any energy saving home improvements -- beginning with air sealing which sometimes is very cost effective. A dehumidifier can take away some of the latent load (i.e. humidity removal), and that might make you comfortable a few degrees higher than your 74. I run 76-77 and am comfortable, however my climate is hot-humid and my indoor humidity averages around 50%.

In my climate a radiant barrier in the attic could be expected to reduce cooling load by 8-12%, but that is a Southern not a Northern opportunity. Possibly you could use additional insulation instead, after doing a thorough job to minimize infiltration.

All the above assumes you will not have a tech find any AC problem which reduces cooling capacity. If you do find such a problem, there is your solution. You might try using a tech certified by the National Comfort Institute (NCI):
http://www.nationalcomfortinstitute.com/

Their specialty is to measure what your system is actually doing, and look for opportunities to improve system efficiency. It is doubtful the average tech would do that as systematically as NCI.

A knowledgeable tech might investigate the latent and sensible capacity of your 18 year old Lennox, and find that the new Trane is actually rated at a lower cooling capacity -- that is just speculation but it would fit your experience. Contrary to what most people normally think, "2 tons" can be a range of capacities.

Best of luck -- Pstu

[beenthere]

If they have adjusted the charge acouple of times, then its time to call someone else.

[iamcanadiandave]

I would disregard comments on duct leakage, sizing, etc. The fact is that the old 2 ton unit cycled and the new one does not. There is a problem with the new A/C install. Period. Call someone who's competent.

[dan sw fl]

Originally posted by rsamerica
new Trane 2 ton compressor and coil installed last July

Since the day of install, the new system has not cooled properly -

contractor will return now that weather has warmed up to continue working on it, but I am not confident in their abilities.

Here are some basic facts:
Location: Connecticut
- House type: Two Level townhouse (not an end-unit), lower level partly below ground ; 2100 sq/ft. w/ 9ft. ceilings upstairs.
- Thermostat A/C Set Temp: 74F
- The thermostat is located on the upper/ground level and this area feels warmer than the downstairs area, which is cool (70F or lower).

Unit started up at about 11:00am and is still running (6:22pm) and temperature has gone from 74 to 75 to 76 to 77 where it stands now.

Does this sound like a situation where the unit is not sized correctly, even though the original Lennox unit was 2 ton?

according to them came back right on the edge of 2.0 vs 2.5 ton

Basically, I'm trying to get some ideas as far as what the problem here might be and how to proceed with this so that we have properly functioning system.

... Seems like an Air Distribution problem
when the there is
>7'F difference ( 77'f Upstairs and < 70'F downstaris)
between the two floors.

Did someone crush a duct or two?

What is the total air flow?

What is the temperature across the air handler?
( hand does not usually measure
temperature very accurately)

What is the air flow for upstairs?
What is the air flow for downstairs?

What is the R.H.%?


If you are not confident of their abilities

WHY would you have them return?

Anyone competent would perform the
set-up in a MAXIMUM of two attempts
if done @ > 83'F !

[mayguy]

When they changed out the system;. did they change the line set? Indoor coil? what do you have now for furnace/air handler?

[rsamerica]

Thanks for the feedback. Some more details:

Installer installed new outdoor compressor (Trane XR12 - R22 version) and indoor matching coil, along with adding a thermal expansion valve. An line filter was added on the outdoor freon line running to/from the outdoor compressor. No lines were replaced.

The furnace / air handler is a Lennox G12Q3E-82-8 built in June 1987. It continues to work well for heating the home, but I am not sure if this would negatively effect the air conditioning.

I do not have any airflow - distribution data / information: how is this obtained?

As far as I can tell, no duct damage has occurred. Again, this is only determined by hand airflow measurements - all registers upstairs have seemingly similar airflow coming out, and it seems to be adequate (unprofessional opinion).

During the installer's last visit here in September, as well as during previous visits, they measured the "split" temp (intake vs. outgoing) at 17-19 degrees which they said was good to very good (for instance 75F in / 58F out). I routinely measure temps in the mid-high 50's with a digital thermometer placed on the air registers.

One part I left out earlier, and partly explains why I continue to have this group back is that I have withheld $1000 in payment to this group until this gets resolved.

[rsamerica]

One other comment, the thermal expansion valve hisses / gurgles slightly when A/C is running. Is that normal?

And a general question: What is the impact of a greater capacity compressor, for instance a 2.0 ton vs. a 2.5 ton. This is something I am trying to understand the theory of. For instance, does more air flow occur as the result of a larger unit? Is more humidity removed? What is the "metric" that can be used to explain what a larger unit does. I am probably looking at it too simply by thinking either one needs to lower the temperature coming out of the vents, or increase the amount of air coming out, neither of which seem to me to be impacted by the size of the compressor. I'm sure I"m missing something here. Any clarification would be great.

[nina]

rsamerica wrote:
> hermal expansion valve hisses / gurgles slightly when A/C is running. Is that normal?

no, you're low on R22

[RoBoTeq]

Originally posted by nina
rsamerica wrote:
> hermal expansion valve hisses / gurgles slightly when A/C is running. Is that normal?

no, you're low on R22

Well, a txv will do that under heavy load as well.

That's quite a bit of house for a two ton system, and newer units are no longer as close to their tonnage rating Btu wise as older systems were.

Are you positive the Lennox was a two ton? Do you have the model number of the old Lennox?