Hi,
I'm hoping to get some opinions from the experts about a new A/C unit that was recently installed in my house in southwest Ohio. I have some suspicions all is not well. I've been reading up on things but a little knowledge is a dangerous thing and I want to make sure I'm not seeing issues that really aren't there.
Background:
Original owner, very little HVAC experience, house built in 2003. Anderson Low-E windows, Original A/C unit was a 3.5 ton, single stage, 10 SEER Trane. Home is a 2 story, 3200sf, unfinished basement. Upgraded the attic insulation to R-46 @ 4 years ago when the furnace was replaced - Bryant Preferred 2 stage, multi-speed ECM blower, 9X% efficient.
Had a couple of local Carrier HVAC companies come out and give me quotes on replacing the current system. Both have been in business for some time, residential/light commercial, Carrier awards, good reviews on the standard consumer sites. They both started the sales call with the "how's your comfort?" query, to which I replied: no real complaints other than the second story is a little warmer than first floor and it can get a little stuffy/humid at night if the A/C isn't running a lot. Discussions proceeded and both suggested upgrading to a 4.0 ton unit (one of the salesmen measured and ran the ductwork dimensions and said the system was designed for 4 tons). I'm not aware that they actually did what I've come to learn is called a Manual-J/Manual-S calculation to confirm the size.
Final system that was installed was a:
4 ton, Bryant Performance 2 stage 17 SEER until with matching coil
Cor7C thermostat
upgraded from a 1" filter to a 4" filter media
Since the unit was hooked up, I'd have to say that the house has been experiencing higher humidity (52-56%) and bigger temperature swings than I remember with the old unit. The unit also seems to run for much shorter periods of time than I remember the old one running. This surprises me as I expected the unit to run for longer stretches at lower capacity (being a 2-stage). I'm wondering if the unit has been oversized. The COR t-stat is configured to allow 4 A/C cycles per hour, so a cycle runtime of 4 minutes doesn't really pull much moisture out of the air and the stat keeps the A/C off until the 15 minute timer from the start of the previous cycle elapses (4 cycles/hr) even though the temp rises above the set point.
I've done some timings on the compressor cycle time and here are some examples over the last week. All values are all based on what the COR7 and my trusty stopwatch is reporting:
Formatting issues so trying this differently:
Outside Tmp, Indoor Tmp, Set Point, In timer lockout at start, Runtime, Highest Stage
82 74 72 Y 0:05:08 Stg1
82 74 72 Y 0:07:06 Stg1
78 76 74 Y 0:04:38 Stg1
78 75 74 Y 0:04:43 Stg1
74 75 74 Y 0:03:10 Stg1
91 75 73 Y 0:13:09 Stg1
92 76 74 Y 0:13:10 Stg1
*** For the last two entries, they were in lockout because the previous/subsequent cycles kicked off shortly after the long cycles ended and only had to drop the temp 1 degree and ran a short period of time.
There have been some issues getting the new A/C & thermostat wired up correctly to the furnace board/blower, and getting the proper refrigerant charge for which the company has been good about sending people out. Based on my discussion with the last tech, I suspect next time I'll have the service manager out. At this point, I'm not sure i the problem is with the unit size and/or thermostat or if everything is fine, so would like to have a better sense from some neutral HVAC experts before I make my call.
A couple of simple questions:
Are the cycle times I'm seeing reasonable with the info I've been able to provide?
Should I have been seeing stage 2 on the 90 degree days (I thought it was supposed to kick in after 10 minutes at stage 1).
Does it look like the the unit may be oversized?
If it is oversized, what is the best way to approach the company about downsizing it?
I know the thermostat can be configured to allow 6 runs/hour, but is that just working around a problem that shouldn't be there?
I would appreciate any/all thoughts (other than I should have insisted on having a Manual J done - water under the bridge and I, like a typical homeowner, didn't know any better).
Thanks
I'm hoping to get some opinions from the experts about a new A/C unit that was recently installed in my house in southwest Ohio. I have some suspicions all is not well. I've been reading up on things but a little knowledge is a dangerous thing and I want to make sure I'm not seeing issues that really aren't there.
Background:
Original owner, very little HVAC experience, house built in 2003. Anderson Low-E windows, Original A/C unit was a 3.5 ton, single stage, 10 SEER Trane. Home is a 2 story, 3200sf, unfinished basement. Upgraded the attic insulation to R-46 @ 4 years ago when the furnace was replaced - Bryant Preferred 2 stage, multi-speed ECM blower, 9X% efficient.
Had a couple of local Carrier HVAC companies come out and give me quotes on replacing the current system. Both have been in business for some time, residential/light commercial, Carrier awards, good reviews on the standard consumer sites. They both started the sales call with the "how's your comfort?" query, to which I replied: no real complaints other than the second story is a little warmer than first floor and it can get a little stuffy/humid at night if the A/C isn't running a lot. Discussions proceeded and both suggested upgrading to a 4.0 ton unit (one of the salesmen measured and ran the ductwork dimensions and said the system was designed for 4 tons). I'm not aware that they actually did what I've come to learn is called a Manual-J/Manual-S calculation to confirm the size.
Final system that was installed was a:
4 ton, Bryant Performance 2 stage 17 SEER until with matching coil
Cor7C thermostat
upgraded from a 1" filter to a 4" filter media
Since the unit was hooked up, I'd have to say that the house has been experiencing higher humidity (52-56%) and bigger temperature swings than I remember with the old unit. The unit also seems to run for much shorter periods of time than I remember the old one running. This surprises me as I expected the unit to run for longer stretches at lower capacity (being a 2-stage). I'm wondering if the unit has been oversized. The COR t-stat is configured to allow 4 A/C cycles per hour, so a cycle runtime of 4 minutes doesn't really pull much moisture out of the air and the stat keeps the A/C off until the 15 minute timer from the start of the previous cycle elapses (4 cycles/hr) even though the temp rises above the set point.
I've done some timings on the compressor cycle time and here are some examples over the last week. All values are all based on what the COR7 and my trusty stopwatch is reporting:
Formatting issues so trying this differently:
Outside Tmp, Indoor Tmp, Set Point, In timer lockout at start, Runtime, Highest Stage
82 74 72 Y 0:05:08 Stg1
82 74 72 Y 0:07:06 Stg1
78 76 74 Y 0:04:38 Stg1
78 75 74 Y 0:04:43 Stg1
74 75 74 Y 0:03:10 Stg1
91 75 73 Y 0:13:09 Stg1
92 76 74 Y 0:13:10 Stg1
*** For the last two entries, they were in lockout because the previous/subsequent cycles kicked off shortly after the long cycles ended and only had to drop the temp 1 degree and ran a short period of time.
There have been some issues getting the new A/C & thermostat wired up correctly to the furnace board/blower, and getting the proper refrigerant charge for which the company has been good about sending people out. Based on my discussion with the last tech, I suspect next time I'll have the service manager out. At this point, I'm not sure i the problem is with the unit size and/or thermostat or if everything is fine, so would like to have a better sense from some neutral HVAC experts before I make my call.
A couple of simple questions:
Are the cycle times I'm seeing reasonable with the info I've been able to provide?
Should I have been seeing stage 2 on the 90 degree days (I thought it was supposed to kick in after 10 minutes at stage 1).
Does it look like the the unit may be oversized?
If it is oversized, what is the best way to approach the company about downsizing it?
I know the thermostat can be configured to allow 6 runs/hour, but is that just working around a problem that shouldn't be there?
I would appreciate any/all thoughts (other than I should have insisted on having a Manual J done - water under the bridge and I, like a typical homeowner, didn't know any better).
Thanks
