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Problems??? with my new HVAC system.

Posted by april_love (My Page) on
Tue, Jun 19, 12 at 7:45

Hello all,

We bit the bullet and purchased a Carrier Infinity system. However, we've had nothing but issues with it since installation.

Here's my question: How fast should an air conditioner cool a house?

We live in Michigan and we generally run the air conditioner as needed from May-June and August-September. For the past five years, we've ran the unit everyday in July.

We turned on the air conditioning unit for the first time about a month ago. It was about 89 degrees outside; The main level cooled in a few hours and the second floor never cooled. Of course, I called for service.

When the HVAC company came out to take a look they discovered that the heating and air were running backwards - the low stage was kicking out high and the high stage was kicking out low. After changing what the technician referred to as "the module," "the motor," "the board," and "the infinity controller." (which sounds like the whole furnace to me) he stated that the unit was working correctly.

Fast forward to this past Saturday - The weather was 89 degrees and we turned on the AC around 6:00pm. The house cooled on average 1 degree per hour. At that rate the house really didn't get cool until the middle of the night when temperatures are low anyway.

The olde AC cooled the house within 2 hours. The technician explained that the newer units don't cool as fast.

Can someone help? Do I have an issue?


Follow-Up Postings:

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RE: Problems??? with my new HVAC system.

whoa, sounds like a headache. I would call the owner of the company and tell him to get himself and lead tech on the job right away. If that doesn't work call carrier and tell them to get a feild rep over right away. Do you mean the tech changed out the module the board the motor and the infinity controller? What an idiot.


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RE: Problems??? with my new HVAC system.

April

I am going to be a little bit contrary. I will assume there is nothing mechanically wrong with your new system and even more important, that you are sized correctly. You don't say the model of your outside condenser. If it is two stage unit, then you want to be certain that both low and highbstagevare operating correctly. And that your refrigerant charge is correct.

With var speed blowers whether from a furnace or air handler, you do not get the quick recovery in either heating or cooling. Don't expect it. Perhaps you can provide a little more info such as:

Outside temperature
Inside house temperature
Your thermostat setting before and after
Length of time to reach thermostat setting
And take several temperature readings from different supply registers in home

Keep in mind, it is difficult to get even temperature from main floor to second floor off one system without zoning controls. Plus you need better than adequate returns on each floor for best airflow and comfort.

Tell us a little about your system-model numbers of furnace and condenser
Size living area main floor and second floor.

Post back.

Without additional information to indicate a problem, then I believe you may be overreacting. If you don't think you are, then start recording specific information to share with dealer. While your story is interesting, it is just anecdotal with little to no facts.

IMO


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RE: Problems??? with my new HVAC system.

Hi Tigerdunes,

Thanks for the great questions.

Here are the model numbers: Furnace: 59TN6A100V21--20; Air Conditioner: 24ANB748A0030010 (This is a 4 ton 17 SEER unit). The units were installed in March.

Last Saturday, specifically, we turned on the AC at 5:15pm when the temperature was 89 degrees. The room temperature was 82 degrees. I had the cooling set to 65 degrees for 2 hours (on override). The cooling is set at 70 degrees normally.

I checked the temperature again at 8:53pm. The room temperature was 78 degrees. The outside temperature was 82 degrees.

I went to bed shortly after but when I woke up about 6am the house had reached 70 degrees inside. It seemed that the house was getting colder and colder after the 70 degrees had been met, rather than maintaining a steady temperature. The tech told me initially that the stages were working backwards. However, that problem was supposed to be fixed.

My concern is that it takes so long for the house to cool.
The old AC would cool the house in about 2 hours.

I could feel the air on the first floor but didn't feel anything on the second floor. Surprisingly, the basement was an ice chest. The house is a two story colonial. We have 2400 sq feet.

The technician told me to keep the air turned on to maintain a consistent temperature. However, here in Michigan I can have the heat on one day and air on the next day. We also have days like today where it's not humid and it's best to open the window to get fresh air.


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RE: Problems??? with my new HVAC system.

April

Thanks for the additional info.

You are not going to like my reply.

I see nothing unnusual with your new system. You will not get quick recovery like your old system. And I dislike high setbacks both in heating
and cooling (or shutting system off) as they lead to false economy along with comfort issues and some homeowners like yourself think something is wrong with the lengthy time to reach normal thermostat setting. I would set thermostat where you like it and monitor your systems operation over several days. Now if the system can not
maintain the normal setting, that does present an issue that should be addressed by dealer.

You may need some airflow balancing between the floors. I hopenyour ductwork supply lines to each floor ave damper controls that can be adjusted. Obviously with the basement, you are getting too much air. Keep
in mind basements at or partially below grade have low heating and cooling loads.

Where is your thermostat located? What was the temperature difference between the main floor and top floor? I would let system run several days to take this reading. Again keep in mind hot air rises so the load on the
second floor after system being shut off is going to be larger than normal and the temperature differential should improve after several days of normal operation.

Monitor this over several days and post back.

Again what is living are for main floor and top floor?

IMO


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RE: Problems??? with my new HVAC system.

Why are you setting the theromostat to 65 when you want the tempertaure to be 70? The AC in your house does not work like the AC in your car. It will not cool any faster if you set the thermostat 5 degree below the desired temperature.

A 70 degree setting is cold. I would be wearing a coat if it were my house. You can't expect the AC to lower the temperature by 12 degrees in a few hours.

What humidity level are maintaining in the house?


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RE: Problems??? with my new HVAC system.

Hi Tigerdunes,

Actually, I do like your answer.

I guess it wasn't properly explained to me that the new system would not cool as quickly as the old system.

The thermostat is on the main floor. I'm not sure of the actual square footage. However, I would guess that the main floor is 1300 sq ft and the second floor is 1100sq ft. I'm guessing that the difference is temperature was about 10 degrees. What kind of device can I buy to check the temperature at the vents?

I believe the supply lines have dampers. However, I have no idea of how to adjust them. Is this something that I can expect the HVAC company to do for me? Is it a DIY project?

Our kitchen is being redone right now so we don't run the air while they're here during the week.

I'm not for sure what the humidity is set to but I believe he told me 54%.


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RE: Problems??? with my new HVAC system.

Get a digital temperature and humidity gauge at one of the big box store. They are reasonably cheap and accurate.

If you have damper controls on your trunk lines to each floor, the damper control to be basement should be 3/4 closed, the one to the main floor 1/2 open and the one to the top floor completely open. That would be my advice as a starting point. Perhaps more adjustments to follow. You want to verify you have those dampers and please be clear. I am talking about
the supply trunk lines, not the runs to each room.

Humidity setting should be reduced between 45-50%. Take care of that
ASAP.

You can't get a good feel of your system's operation by stopping and starting. Begin close monitoring when kitchen project has been completed.

Then post back your findings.

IMO
Good Luck


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RE: Problems??? with my new HVAC system.

April,

You should try to keep the humidity in the 45-50% range. You will be more comfortable even if you raise the temperature level 2-3 degrees. You should also keep the windows closed as much as possible. I know it is a temptation to open them when it is cooler, but this lets in humid air.

The HVAC installer should show you how to balance the dampers. Depending on your set up, you may want to do this between the winter and summer seasons.


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RE: Problems??? with my new HVAC system.

"I dislike high setbacks both in heating 
and cooling (or shutting system off) as they lead to false economy"

"You should also keep the windows closed as much as possible."

You guys really want to jack up the electricity bill. Set backs do save energy. If the humidity is low, and the day is cool, opening the windows is very useful as long as the AC is not running at the same time.


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RE: Problems??? with my new HVAC system.

There is are some really important question that has not been answered that flow from this:

"The olde AC cooled the house within 2 hours. The technician explained that the newer units don't cool as fast."

What size was the older system compared to the new one? Why was it replaced? Were the ducts modified or replaced? Was humidity control an issue with the older system?

If BTU old = BTU new, and cooling is not as good as before, something must be wrong with the new system.


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RE: Problems??? with my new HVAC system.

"With var speed blowers whether from a furnace or air handler, you do not get the quick recovery in either heating or cooling"

Why not?


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RE: Problems??? with my new HVAC system.

Variable speed furnaces and air handlers normally start up in the low stage for some period of time. In addition if the thermostat is near the set point, the blower may stay in the low stage until the thermostat is satisfied. This is some of the reasons why it takes longer.

The OP stated the room temperature was at 82 degrees, and the thermostat was set to 65 in an attempt to get to 70 degrees quickly. I find it hard to believe that the old AC could drop the temperture 12 degrees in 2 hours.

My gut feeling says there are installation and duct problems which have yet to be addressed.


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RE: Problems??? with my new HVAC system.

April: what thermostat do you have (model number)?

When it comes to thermometers, I have several. I sometimes use a simple meat instant-read thermometer for checking vent temperatures. $7. Just make sure it is one that covers the temperature range you need (down to 40f).

When it has been running for a while (15 minutes or more), check the inlet temperature (wherever that is in your house) and an outlet temperature (some vent nearby on the main floor).


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RE: Problems??? with my new HVAC system.

"My gut feeling says there are installation and duct problems which have yet to be addressed."

That I can not argue with that :-D I fear that the installer downsized the system without taking into account the lifestyle of the users, they shut off the system, come home and then want it cool in a hurry. (Sounds like me.) It seems like a variable system should be able to do this well and not be oversized when demand is relatively low. Mine does. The OP might, however, need to learn to use the programable thermostat or maybe even a thermostat that can be controlled via a smartphone.

"Variable speed furnaces and air handlers normally start up in the low stage for some period of time. In addition if the thermostat is near the set point, the blower may stay in the low stage until the thermostat is satisfied. This is some of the reasons why it takes longer."

I agree that they might take longer reach the set point as they approach it because they shift to lower speed, but that would be eliminated by setting the t-stat to 65. Starting up in the low stage should not affect things when you are talking about a couple of hours. That start-up low phase should only be for a few minutes at most. Am I wrong?

"I find it hard to believe that the old AC could drop the temperture 12 degrees in 2 hours."

It might if the humidity was low enough.


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RE: Problems??? with my new HVAC system.

You are correct that the start up phase should only add minutes to the time. I know for heating the Carrier Infinity controller will go immediately to the high stage in heating mode when the thermostat set point is more than 5 degrees than the room temperature.

Old systems tended to be oversized. This allowed rapid heating and cooling.


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RE: Problems??? with my new HVAC system.

How long is your fan running in the furnace stack? Given your floorplan & hot upper floors it sounds like the fan is not running as often as it should (thus mixing the cold air on the bottom floor with the air from the top floor). These fans are extremely efficient @ low speed. I would suggest trying to run the fan 24/7 for a day or so and make adjustments to the vents such that the temps are about the same between floors (upper may be 2-3 degrees hotter). If that works you can dial back the fan run time to your comfort level.


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RE: Problems??? with my new HVAC system.

Hi everyone,

The older system was also a 4 ton unit. When we first moved in, almost 5 years ago, the air worked fantastically. However, last year, we received an outrageous electric bill AND the unit wasn't cooling properly so we decided it was time for a new one. It was the original HVAC system which was about 50 years old so it lasted exceptionally well.

The ducts were not modified or replaced. Humidity was not an issue. The previous owner installed a new humidifier so that hasn't been an issue.

I don't know how to balance the dampers. In the winter my bedroom, on the second floor, is unbearably hot. Now it's summer and it's still unbearably hot.

The salesperson is listening to the tech and I've been told to let the system run. It was over 100 degrees here today so I turned the system on late this afternoon. The upstairs is more than 5 degrees hotter. It seems to be more like 15 degrees.

I'm not sure how ling the fan is running in the furnace stack. I have the fan set to high in hopes that it would drive some of the cooler air upstairs.

The salesperson is not being very helpful now. I almost feel like the attitude is "We have your money, now what?"


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RE: Problems??? with my new HVAC system.

Get the temperature and humidity gauge.

All this guessing accomplishes nothing.

You will not know if you really have a problem as long as you continue to cut system on and off.

Did you adjust the humidity setting as suggested?

If you have access to your ductwork system, you will be able to see easily if you have manual damper controls on trunk lines to each floor.

Until you are able to run your system continuously for 3-4 days, you are just wasting your time, ours, and whistling in the wind.

IMO


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RE: Problems??? with my new HVAC system.

Was the system installed as heating only 50 years ago or heating and cooling?


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RE: Problems??? with my new HVAC system.

Was the system installed as heating only 50 years ago or heating and cooling?


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RE: Problems??? with my new HVAC system.

Here is the fast and easy way to test your home AC. Simply get the difference between the cold register air temperature and the return air temperature. If it is between 16 and 20 degree F, your AC is OK. (You can measure the temperature by using a thermometer about 1 inch from the register grill.)


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RE: Problems??? with my new HVAC system.

The system was heating and cooling.

I'll have to go and get a thermostat.


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