Infinity system not keeping up on hot days

[dafreerider]

Folks,

We have a one year old Carrier Infinity system (heat pump, hybrid fuel, dual zone) installed by a very reputable contractor. It was installed last April. Last summer there were a couple of heat waves in Philly area and the 2nd floor temps were creeping higher than the set temp by 2-3 degrees. The contractor first suggested to not set back the t-stat at daytime, saying that the system is not designed to catch up on hot days. We did that - set it at a constant temp. The system still did not keep up. Then the contractor said the system was not designed to keep up when temps exceed certain average temp. I forget what it was for Philly, but something like 85F. Then the heat waves ended and I had no way to argue with them or to diagnose the problem.

Now there were 3 days with upper 80's temps in May. The 2nd floor unit was again not able to keep the temp at a set level, even though we were not setting back the t-stat (baby at home). I called and now their response was: "2nd floor will always be hotter (even though I have two separate units) and you should set the 2nd floor 2 degrees lower than the 1st floor." It made no sense to me, but I did that. The system was still not keeping up. I'd think that with 2 zones the 2nd floor would just have to work harder to keep up, but should be able to do so, if properly sized and installed.

As a consumer I am worried that after shelling out lots and lots of hard earned money, I got a system that was improperly sized or improperly installed. What are your thoughts? I really don't feel like settling for less than stellar performance, since I paid premium for such a fancy high end system.

Details:
House - 3,500 sq ft. Living room and foyer are 2-story. Skylights in living room and master bath.
Systems: 2 units (one for each floor) Carrier Infinity 25HNA636A (3 ton). Coils CNPVP4221. T-stats Infinity SYSTXCCUID01. Variable speed air handlers.
Old system was Trane XL1200: 3 ton for 1st fl and 2.5 ton for 2nd fl. I never had that problem with old Trane, even though 2nd fl unit was 1/2 ton smaller.

Your thoughts and advice are greatly appreciated.

[catmanacman]

mabe the upstairs unit is not going into second stage

[brian in mass]

Check the ductwork for a less then perfect install. I just left a house last week that had holes in the attic duct I could literaly stick my arm in ! Not to mention it was way undersized. Make sure your not a/c'ing the attic as well !
And in another direction.....is your home real new and supper sealed ? Maybe some new attic fans ? Just a shot in the dark....

[BobbyBJr]

I agree with the other posters. I'd check out the staging to make sure it is going into second stage, but the duct work is very important too. Leaks as has been mentioned and also undersized duct can choke the system and not let it perform like it should. You mention that one unit was upsized a 1/2 ton. Was the duct work for that system upsized too?

[dafreerider]

The new install was in place of the old system. The duct work was not changed. The house is 20 years old. Unless the ducts developed gaps during the installation, which I doubt, the leaks should not be a problem. I don't believe I have many ducts in the attic.

The system does go into 2nd stage (high stage), I checked that, and the air comes out cold.

When I was getting estimates most contractors were suggesting 4-ton units for our size of the house, but their suggestions were not based on Manual J, just on rule of thumb. I ruled them out. I hired the contractor who, supposedly, calculated the needed size by measuring the house, the windows, etc. He came up with slightly less than 3 tons each. So we went with 3 tons. Now I am wondering if he made a mistake or didn't consider something. The air travels up easily through our house due to 2-story rooms. But I was hoping he'd take it into account. Maybe he did. But the result so far is less than satisfactory.

Summers in Philly are pretty hot and it would be very upsetting if 25% of the time my house is hotter than I'd like.

Should the system be able to maintain set temp during 85F days? 90F days? If not, does that mean that everyone's house is hotter than desired on those days?

[bmathews]

Maybe a bad expansion valve on the coil or undercharged. If a 2.5 ton kept up and a 3 ton won't. Something isn't right. The ductwork could be a contributing factor, but probably not the entire issue. Maybe a plenum or a duct fell off and you're sucking hot attic air in. How about your insulation in the attic. Maybe it got crushed when the changeout was done.

[BobbyBJr]

Well, you said the old equipment worked and it was smaller. I wouldn't question the load, if that is the case. There should have been some duct changes to go from a 2.5 to a 3 ton, maybe nothing really major, but some changes like additional return and possibly a supply.

The system should be able to maintain set temp on whatever temperature the contractor based his load calculation on. I don't know the design temps for Philly, but here we use 95 and do pretty good until the temps exceed that. When it gets above 95, our indoor temps do start to creep up on marginally sized equipment. If the old 5.5 tons kept you comfortable, then the new 6 tons should be able to with all things being equal. If there is a problem, it has to be something has changed with the home, the sytems aren't working properly, or you have duct issues, which would prevent the systems from working properly. Thats about all we can say from a keyboard.

[beenthere]

If it was designed to maintain temp when its 90° out, then it should maintain temp.

If the 2.5 ton maintained temp. The 3 ton should also.

They could have an air leak where the supply and return are connected to the air handler.
Could be an improper refrigerant charge.

Call them again, and remind them that the 2.5 ton maintained temp.

Are they a member of BBB. If so, report them.

[KGBster]

The suggestion about sucking attic air or settling or crushed attic insulation is possible....

Air conditioning has three crucial needs:

1 Correct sizing of Ductwork and equipment
2 Proper charge of refrigerant
3 Proper air flow

If the airflow isnt enuff it will not satisfy the demand for cooling. Without actually coming to your home myself and seeing the dilema your in, i cant offer much help. Hopefully they set your infinity control to 36k btus....or maybe eliminate first stage cooling via the control(not sure about that).

I'm a hvac business partner and we pride ourselves on getting things figured out.

My suggestion to you is to talk with another company that has been in business for 50 years...Carrier or Bryant dealership doesnt matter, same equipment only with different model numbers. If it is an equipment malfunction the Bryant dealership can warranty it too. If your lucky, you will find a company that will come over and inspect the system free of charge as we sometimes will do as a courtesy.

Ask around to see which is the ONE company that usually can fix any problem...Keep in mind they are usaully not the cheapest.

[Joe Harper]

Im going to bet that the installers didnt remove the txv bulb when the lines were brazed.

[dafreerider]

One thing that is different with the new system is that I am using MERV 10 Lennox pleated filter. The old system has those electrostatic filters (that were broken anyway). Do you think the restricted airflow through the pleated filter would be the culprit? (By the way, the filter is clean - just changed). But I would think they'd count it in, when suggesting the air handler.

I have 10 year warranty - parts and labor that I purchased, but I'd hate to have to repair it for 10 years and never get it to work, even if it doesn't cost me any additional money.

So far the suggestions are - duct leaks, refrigerant charge, txv bulb (?).

[bmathews]

Remove the filter and see if it works better. Who knows?

[beenthere]

A 20 x 6 supply for a 5 ton system?

[smittyii]

One thing that is different with the new system is that I am using MERV 10 Lennox pleated filter. The old system has those electrostatic filters (that were broken anyway). Do you think the restricted airflow through the pleated filter would be the culprit? (By the way, the filter is clean - just changed). But I would think they'd count it in, when suggesting the air handler.

I have 10 year warranty - parts and labor that I purchased, but I'd hate to have to repair it for 10 years and never get it to work, even if it doesn't cost me any additional money.

So far the suggestions are - duct leaks, refrigerant charge, txv bulb (?). thats the first place i would look (filters) put a cheap fiberglass filter in and run it for a couple of warm days. log your temps at the infinity controller. i don't care for higher merv filters especially on older houses unless there are returns added.

[allan38]

Pay to have a 3rd party Bryant/Carrier dealer check it out.
I've seen leaks in the evap coil, malfunctioning TXV's and one defective start kit.
All that should be covered under the 10 yr parts and labor contract.
I love the Infinity/Evolution stuff. A real joy to work on. I work for a Bryant dealer and we've installed a lot of them. Most of them I only see during annual maintenance.

We install the pleated media filters, both the Bryant and Lennox ones and havn't seen any problems with them.
We use 16X25, 20X25 and 24X25 5 inch media filters on almost all of our installs.

[dash]

In a typical two story home,the second floor requires more cooling then the first,due to the attic.

Are you sure the old second floor unit was 2.5 tons??

If so tell the installer and ask why the difference!