How to Balance Cooling in a Two Story Home

[jmatthew]

My wife and I am spending time with our daughter and son-in-law while they prepare to have thier first child. 

The home is located in the southeastern US.  The home is about 8 -10 years old, and HVAC is a heat pump(?) with the heat exchanger located in attic.  Compressor was just replaced in autumn. My son-in-law changes the filters about every couple of  months.

 

From morning to mid-afternoon, the thermostat temperature would be at setpoint.  By early evening, the displayed temperature would be up to two degrees higher than setpoint.  System is on, and a very small trickle water does flow from the drain line outside while the unit is on. 

 

We find the ground floor is much cooler than the upstairs.  I understand that cooler air sinks and warmer air rises.  But, the upstairs is really warm.  We tried closing the ground level vents.  I expected a noticable increase in the volume of air blowing out of the upstairs registers, but did not feel an increase.  Not very scientific, but I don't have acess to a manometer, and not sure that is the best method to assess system performance.  Then, I was concerned that I could cause the system to malfunction by not allowing the air to flow through the heat exchanger, so I opened some back up.

 

To keep my future granddaughter comfy, what is the best method or process to adjust the cooling in two story house?  Or, is there a bigger issue we are missing?

 

 

[BryanS]

So you don't have a system for each floor? Most places typically have one for the bottom floor and a seperate one for the top. When I was in tech school my instructor told us it isn't easy to get a two story house cooling evenly off of one unit. If you only have one system, which floor is the thermostat located? Are their windows upstairs without blinds? Have you been in the actic to check out if any of the ducts could be leaking out or attic air may be pulling in from the return side? Sometimes installers use a foam board called ductboard and flex runs. I'm mainly an appliance guy, but I've done HVAC on the side. I've retapped and applied mastic for some family members who had older units with air leaking into the attic. I also fixed one for one of my dads coworker who's upstairs unit would cool at night, but it couldn't keep up during the day. It turned out to be a loose thermostat wire connection up in the attic randomly kicking the blower motor off. There are a lot of factors to consider, and many many things that can be wrong with any cooling system.

[BryanS]

Also closing off vents just puts extra strain on the blower motor. They are designed to work with all vents open. It's like people closing them in empty rooms thinking they are saving money, but they are in fact not saving anything and making their system run harder.

[jmatthew]

Thanks for the fast response BryanS.

Questions:

Two units? I noticed each floor has a grille with a filter. How can I tell if two units? Why wouldn't each floor have a thermostat?

Closed vents causing stress on blower Motor. So if two units, really did not add anything to fixing the issue.

All windows have blinds.

[BryanS]

Well you would have two condensing coil outside and two different thermostats. I haven't seen a two story house with only one system around here yet. I've seen a one story with vents into the basement, but basements typically stay cooler anyway. Yea, closing vents off increases the back pressure the blower has to blow against. If your thermostat is on the first floor, then that could be why the upstairs is warmer then the downstairs. It could be a refrigerant issue, but you have to check superheat or subcooling depending on what type of metering device it has. The best thing to do before hooking gauges up is to verify it isn't any outside factors and airflow is good. I would think if the tstat is up stairs it should be able to maintain temps. Is it a mechanical thermostat? Sometimes they aren't as accurate as digital. Has it always had this issue cooling the upstairs? Could be a design issue. How hot is the outside typically? The one I had with the loose thermostat wire at the air handler through me for a loop because he just moved into a house with zero blinds. It was getting up to about 100 degrees outside. He had some dude come out and put refrigerant in it, which wasn't the issue. I changed his fan relay thinking that's all it could be because the thermostat is new. That's when I bumped the bundle of thermostat wire and heard the fan shutoff Then I found the loose wire nut causing the whole problem.

[m_west5]

Make and model number?

"Compressor changed last autumn". How long was it used after change-out last autumn? Was service done by a reputable technician or company who will warranty their work? Possible leak issue over the winter.

How much insulation is in the attic? How large is the home in sq. ft.? Flex duct or sheet metal rigid duct?

I would recommend a check up of the entire system. Especially in the air handler in the attic to get thier eyeballs on the blower motor with an amp meter and blower wheel and evap coil cleanliness. And especially need to check refrigerant level, as BryanS recommended also.

This does not sound like an air balancing issue. The system worked when it was new if it was properly matched to the home's size. My guess would be that it was.

Edited May 6, 2014 by beam current

[jmatthew]

BryanS:

1. Honeywell digital thermostat (came with system I believe)
2. The home had one outside unit when home was purchased.
3. This is the Charleston, SC area, so they get a lot of hot days I expect - more than Wisconsin, where I live.  They said it 'worked' before, but reason for the change was the system was not heating as it should.  They were told systems usually lasted about 6-10 years.  I questioned that, but no experience with these integrated heating and cooling systems.

Yamabushi:

Make and model number?

Nordyne "Air Temp"

Model: VT4BE-042K (3.5 TON)

"Compressor changed last autumn". How long was it used after change-out last autumn?

Installed after cooling season and just before heating season.  House was cold a few nights before it installation was completed.

 

Was service done by a reputable technician or company who will warranty their work? Possible leak issue over the winter.

Installer plans on coming back later this week.  However, the installer was a coworker of son-in-law.  He works for a HVAC contractor part time.

 

How much insulation is in the attic? How large is the home in sq. ft.? Flex duct or sheet metal rigid duct?

I will have to look in attic, don't know.

2,024 sq. ft.

Again, will have to eyeball the attic, but I believe my son-in-law stated flexible duct.

I would recommend a check up of the entire system.

Especially in the air handler in the attic to get thier eyeballs on the blower motor with an amp meter and blower wheel and evap coil cleanliness.

The air leaving the registers is very weak.  In the morning, the temp is at stpt.  by afternoon, it is 6 degrees from stpt.  System is in operation nearly non-stop.  Just isn't right.

 

And especially need to check refrigerant level, as BryanS recommended also.

From the generous sharing of technical knowledge by BryanS and you, I would agree.  Old story: Had an issue with my new home that was completed after cooling season.  Next summer, the AC  did not keep up.  Called contractor, and he found the system low had to add refrigerant.  He was a reputable sub for my home builder.

This does not sound like an air balancing issue. The system worked when it was new if it was properly matched to the home's size. My guess would be that it was.

I was not around when they purchased the home.  They did state it was inspected and told it was in working order, and I have not heard it did not keep up with the cooling in the past. 

 

Okay, thanks.  We will keep all of you updated on progress and the ending of this problem.

[BryanS]

Thanks for the update. Hopefully you get it figured out soon

[m_west5]

BryanS:

1. Honeywell digital thermostat (came with system I believe)
2. The home had one outside unit when home was purchased.
3. This is the Charleston, SC area, so they get a lot of hot days I expect - more than Wisconsin, where I live.  They said it 'worked' before, but reason for the change was the system was not heating as it should.  They were told systems usually lasted about 6-10 years.  I questioned that, but no experience with these integrated heating and cooling systems.

Yamabushi:

Make and model number?

Nordyne "Air Temp"

Model: VT4BE-042K (3.5 TON)

"Compressor changed last autumn". How long was it used after change-out last autumn?

Installed after cooling season and just before heating season.  House was cold a few nights before it installation was completed.

 

jmatthew, thanks for the detailed feedback.

 

Unit is sized properly to the home.  This would indicate a fairly significant (fast) leak in 6 months.

 

Your son-in-law's system is a R410 14 SEER heat pump. It provides heating and cooling in one system by reversing refrigerant flow by way of a valve.  These are common in the southeast and extremely common in the southwest where temperatures are mild in the winter.  It has a fixed orifice metering device, which means it is properly charged (refrigerant level) by superheat.  R410 systems are more charge sensitive than say the older R22 systems.

 

This system may have electric heat strips to provide additional heating help to the heat pump on more colder days.  These are located in the attic air handler.  Have these checked too as they have a high fail rate.

 

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Was service done by a reputable technician or company who will warranty their work? Possible leak issue over the winter.

Installer plans on coming back later this week.  However, the installer was a coworker of son-in-law.  He works for a HVAC contractor part time.

 

Have your son-in-law check the warranty from Nordyne.  Some manufacturers offer a 10 year coverage on the high dollar components.

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How much insulation is in the attic? How large is the home in sq. ft.? Flex duct or sheet metal rigid duct?

I will have to look in attic, don't know.

2,024 sq. ft.

Again, will have to eyeball the attic, but I believe my son-in-law stated flexible duct.

 

Insulation can be upgraded  fairly inexpensively, if it is sprayed in.  I'm sure you are aware that most of the cooling loss is through the ceiling.  Flex ducts can develop kinks in the runs over time if they are suspended from the rafters by straps. (Main trunk, straight out of air handler plenum, for example.) You are correct, get the eyeballs up in the attic.

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I would recommend a check up of the entire system.

Especially in the air handler in the attic to get thier eyeballs on the blower motor with an amp meter and blower wheel and evap coil cleanliness.

The air leaving the registers is very weak.  In the morning, the temp is at stpt.  by afternoon, it is 6 degrees from stpt.  System is in operation nearly non-stop.  Just isn't right.

 

If it is ALL registers, than this points to the blower motor, fan wheel, evap cleanliness, and ducting.  Make sure they test/look at these.  It's best to schedule EARLY, EARLY morning when the temps are cooler in the attic.  It gets very hot in the attic and this would not only keep the technician safe but also gives them the time to thoroughly inspect/test the system.

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And especially need to check refrigerant level, as BryanS recommended also.

From the generous sharing of technical knowledge by BryanS and you, I would agree.  Old story: Had an issue with my new home that was completed after cooling season.  Next summer, the AC  did not keep up.  Called contractor, and he found the system low had to add refrigerant.  He was a reputable sub for my home builder.

 

When the technician returns to service the unit, he or she should not just "top it off".  You stated above that the system runs constantly, which most likely indicates an inadequate system charge.  The problem will return, most likely on the hottest day of summer, when the system is under the heaviest load.  Hottest day equals highest head pressure equals fastest leak rate.  The refrigerant provides to the compressor cooling and lubrication, so lack of a sufficient charge will shorten the life of the new compressor.

 

The proper way of doing this is to hook up a manifold gauge set to "see what the mechanical side" pressure is, recover any remaining refrigerant and pressurize the system with N2 to find the leak(s) or use a leak detection device.  After the leak(s) are repaired, a sufficient vacuum (<500 microns) should be maintained for at least 20-30 minutes to ensure all moisture and non-condenseables are evacuated.  The filter/dryer may also have to be replaced.  Then the charge should be WEIGHED in as per the manufacturer's placard, most likely found on the outside (condensor) unit.  If the technician does not do the above, chances of future problems are pretty good.

 

I understand this may be cost prohibitive for your daughter's family with a new baby coming soon, but in the long run it will actually save them money on maintenance and operating costs.

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This does not sound like an air balancing issue. The system worked when it was new if it was properly matched to the home's size. My guess would be that it was.

I was not around when they purchased the home.  They did state it was inspected and told it was in working order, and I have not heard it did not keep up with the cooling in the past. 

 

Curious.  Did your son-in-law say why the compressor was changed?  Did the technician mention amp draw, winding resistance values or short-to-ground to require condemning the compressor?

 

Okay, thanks.  We will keep all of you updated on progress and the ending of this problem.

 

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This should help with what to expect when the technician arrives.  Please reply if you have anymore questions.  There are alot of other folks on here that can provide valuable advice also.   You definitely came to the right forum to find help.

 

btw, congratulations on the new grand-baby !!!!! 

Edited May 7, 2014 by beam current

[m_west5]

jmatthew,  a fews more points to add:

 

 This would indicate a fairly significant (fast) leak on the system high side (condensor) in 6 months time.  If not properly repaired, and by just topping off, the problem will quickly return because of the higher pressures.  Especially in R410 systems, which operate at much higher pressures than R22.

 

and.....

 

Comparing your son-in-law's and your own systems, it sounds like your leak was on the low side (evaporator).  Topping off will work without finding and repairing the leak(s) on the low side.  Here we are talking extremely low leak rates, somewhere in the order of < 1/2 ounce per year.  Over time (years), insufficient cooling will be noticed.  If the leak is on the high side, insufficient cooling will be noticed much sooner, as perhaps the case of your son-in-laws.

Edited May 7, 2014 by beam current

[BryanS]

Yep. Low charge can take a compressor out. I checked a classmates heat pump one time when we were in school. His superheat was very low like 1 degree. A few summers later his compressor went out I didn't have the tools or refrigerant to fix it at the time. I installed a new compressor a few years ago and it's been working fine ever since. Probably an evap leak, but his funds were low. I was so busy working my regular job, I just didn't have the time to run a thorough leak check. I did pump it up with nitrogen and it held pressure for a few hours no problem.

[jmatthew]

....a shameless plug for this forum and the website:  when Yamabushi states, "There are alot of other folks on here that can provide valuable advice also.   You definitely came to the right forum to find help."  This site is a shining example of the good the internet can do and this site in particular.  Thanks to Samurai and his team.

 

Spent quality time with my grand daughter after work.  She is gorgeous!

 

Now, thank you to BryanS and beam current.    I am grateful for your willingness to share your expertise and experience.

 

When my AC system was tested and found low on refrigerant, I do remember the technician recommending a stop leak additive, or a refrigerant that had this additive in it already.  I believe the technician stated, if the leak is small, this will fix it.  Again, my records are home, but it cost me more to have this added.  The charge was checked the next year and found to be at spec,

 

For my daughter and son-in-law, I was told the 'plan' is to do a check, and most likely recharge the system.  I hope to have him review your answers before the technician arrives.  I have learned much from your comments.

 

I will keep all updated.

Edited May 8, 2014 by jmatthew

[jmatthew]

Hello All!

I want to update all on the status of the HVAC system repairs.

 

Although I was there during the work, the tech was communicating with my son-in-law, and I did not 'dog' him with questions.  I offered him whatever assistance he felt I could give, and then let them go to work.  He did ask me to help him with a ladder to access the attic, so I did contribute.

 

First, the work started at approximately 0800 and continued until 1530 later in the day.  The tech started in the attic, then went out to the compressor.  Several trips between the attic and compressor.  He shut down the system for an hour while away at lunch.  Came back and fired it up, and checked temperatures at registers.  Still not cooling to meet whatever spec. he was trying to achieve.  He called another tech and the two of them brought in a tool that was in a case about 24 inches square and 4 inches thick.  The system was shut down a final time, During that time I heard hissing or rushing of fluid in lines.  After about 30 minutes, it was again turned on, and cool air started flowing.

 

All they told me, prior to leaving the home, was there was a 'major restriction' in the system. 

 

Once they finished the work, I believe all the ducts seemed to blow more air.  And, the system could keep the home temperature at set point.  The tubing that would exit the compressor and then enter the home, before repairs were encrusted with ice, and after were bare.

 

Again, I appreciate all the information that was passed along concerning this issue.

 

 

[BryanS]

Sounds good Thanks for the update.

[m_west5]

Glad we could help.

Now enjoy the family time !!!!!☆