Carrier AC question

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I'm hoping someone here can help answer my question. Just bought a house with a Carrier Performance air conditioner and Carrier Infinity furnace with an Infinity thermostat. It also has a 3 speed blower motor.

The problem I'm having is when the AC comes on I can't get the fan to run on anything but low speed. I've confirmed that the blower can run at the faster speeds, just not with the AC on.

The only code that comes up is 56, which is a faulty outdoor temperature sensor. The outdoor temperature on the thermostat shows as hot as 200 degrees. I get conflicting info whether that prevents the fan from running anything other than low speed. I just bought a new one and will be installing it, but doubt that will fix the issue.

I've also read that this is how the system is designed, which if it is I'm changing it as on low speed the fan doesn't move the temperature inside the house. I haven't checked freon levels, but the air that does come out is cold.

Any ideas? One of my friends thinks that it is hardwired as such and I need to change it physically on the control board to make it work.
 
Originally Posted By: SVTCobra
I'm hoping someone here can help answer my question. Just bought a house with a Carrier Performance air conditioner and Carrier Infinity furnace with an Infinity thermostat. It also has a 3 speed blower motor.

The problem I'm having is when the AC comes on I can't get the fan to run on anything but low speed. I've confirmed that the blower can run at the faster speeds, just not with the AC on.

The only code that comes up is 56, which is a faulty outdoor temperature sensor. The outdoor temperature on the thermostat shows as hot as 200 degrees. I get conflicting info whether that prevents the fan from running anything other than low speed. I just bought a new one and will be installing it, but doubt that will fix the issue.

I've also read that this is how the system is designed, which if it is I'm changing it as on low speed the fan doesn't move the temperature inside the house. I haven't checked freon levels, but the air that does come out is cold.

Any ideas? One of my friends thinks that it is hardwired as such and I need to change it physically on the control board to make it work.




I think that unit has a 2-stage compressor; will probably run on LOWER speed stage most of the time (for HIGHEST efficiency, and best moisture removal).
Low speed will run LONGER; this is NOT a defect, or failure - supposed to work that way.
Also Lower fan speed = better moisture removal (if t-stat has humidity control) while it cools; has it been very humid lately ???

You can probably FORCE the 2nd stage (full) by dropping the temp setting SEVERAL degrees on the thermostat, OR override/disable the humidity setting; this will 'trick' the system that it needs to 'work harder' to 'catch up' ; this mode will of course use MORE AMPS (= less efficient), and NOT do as good of job at humidity removal.

If you outdoor temp sensor is sitting in the sun - or somewhere where the hot air from condenser blows on it, or both - that can cause problems; also if varmints chewed the wiring to it ... or it got soaked with water.
 
Originally Posted By: SVTCobra

Any ideas? One of my friends thinks that it is hardwired as such and I need to change it physically on the control board to make it work.


If, as suggested, dropping the set temperature several degrees doesn't force the second stage and the outside temp. sensor doesn't fix the problem, then I think your friend might be right. Check the board if it was wired correctly to engage the second stage. The thermostat might not be wired correctly either.
 
Thanks for your responses. The main complaint from my end is that I typically don't turn on the air until I get home and the air conditioner wouldn't catch up till the next day. It's a 3.5 ton unit on a 2400 sq ft house (1/2 of which is a finished basement), so there is the desire to get the fan speed faster.

It is a two speed compressor, but a large temp difference between set and actual hasn't made the fan speed faster (84 actual and 70 set point). The temp sensor is somewhat in the sun in the morning for a brief period, but is underneath a deck and even when completely dark it can read 200 degrees. I checked the resistance with a multimeter and seemed to be within range, but the temperature got wonky again after installation. I will check the wires to the temp sensor as well.
 
If the blower is a multi-tapped AC motor, you may have to change taps to change speed. Slow speed works for those who rarely change the t-stat. Works lousy for those like yourself.

To change speed on my old unit, I have to remove the metal panel, disconnect the motor wire, connect the other motor wire (2 speed AC motor), then replace the panel.
 
The infinity systems are 4 wire communicating system, there is no speed taps to change or anything. It has a variable speed blower motor and condenser fan motor I believe. 3.5 ton for a 2400 sq ft house is perhaps a little undersized. Infinity units only operate with their own controller ( thermostat ), if it's not throwing any codes I'd say it's just running on low speed maybe because of low humidity in the house to conserve energy.
 
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Also the OTS may affect the blower speed, they are very sensitive units, I wouldn't recommend them, problems outweigh the savings IMO.
 
For those that say the low speed is fine I ask, what's the point of having an expensive multistage AC system and not be able to fully utilize its potential?
I would keep digging until this is fixed, or hire a pro that knows Carrier. On their website you can find authorized installers/service shops.
 
Originally Posted By: KrisZ
For those that say the low speed is fine I ask, what's the point of having an expensive multistage AC system and not be able to fully utilize its potential?
I would keep digging until this is fixed, or hire a pro that knows Carrier. On their website you can find authorized installers/service shops.


It's not necessarily that.. but an air conditioner will be most efficient (in terms of perceived effect to the owner) when it runs continuously (rather than cycling on and off). This is why a unit needs to be sized correctly for a home with a Manual J Load Calc, which most HVAC guys don't know how to do.

More often than not, and with improvements in building materials, you end up with oversized units that are so quick at getting the air cold that it turns off early and doesn't run long enough to extract humidity from the air. If you've ever stayed in a cheap motel with one of those in-wall units, you may remember a feeling of "cold and clammy" because often those units have way more tonnage than is needed for a small motel room.
 
Originally Posted By: Reddy45

More often than not, and with improvements in building materials, you end up with oversized units that are so quick at getting the air cold that it turns off early and doesn't run long enough to extract humidity from the air.
I always hear that, but what about places like Phoenix where we don't have hardly any humidity? Units are sized at around 400 square feet per ton, so my 1,400 square foot house has a 3-1/2 ton unit. It cools it just fine, doesn't cycle too much and doesn't run for too long.

Is there much of a downside with having an oversized unit in a low humidity area?
 
Originally Posted By: Reddy45
Originally Posted By: KrisZ
For those that say the low speed is fine I ask, what's the point of having an expensive multistage AC system and not be able to fully utilize its potential?
I would keep digging until this is fixed, or hire a pro that knows Carrier. On their website you can find authorized installers/service shops.


It's not necessarily that.. but an air conditioner will be most efficient (in terms of perceived effect to the owner) when it runs continuously (rather than cycling on and off). This is why a unit needs to be sized correctly for a home with a Manual J Load Calc, which most HVAC guys don't know how to do.

More often than not, and with improvements in building materials, you end up with oversized units that are so quick at getting the air cold that it turns off early and doesn't run long enough to extract humidity from the air. If you've ever stayed in a cheap motel with one of those in-wall units, you may remember a feeling of "cold and clammy" because often those units have way more tonnage than is needed for a small motel room.


I don't think you understand the concept behind multistage AC units. While what you described is true for single stage AC units, that's not how it should work on multistage units.
Multistage units allow exactly the type of usage OP wants, that is to knock down the temperature quickly using the high speed stage and then maintain it using the low speed stage. This saves electricity and controls humidity in a comfortable level . That's the whole point of having such a system.
 
I just checked Carrier website, their Performance AC units are single stage, even the 16 seer one. So everything works as it should for OP. He would have to install the Infinity unit in order to take full advantage of that Infinity furnace.

In light of this new info, I would suggest to keep the AC on all the time, just program the thermostat to increase the temp a little bit when no one is home and set it to the desired temp. for the time when family members start coming back.

From their website:
Quote:
Features
STANDARD FEATURES
Up to 16 SEER cooling efficiency
Sound: as low as 72 decibels1
Single-stage operation
Compressor sound blanket
Filter drier system protection from moisture and contaminants
WeatherArmor Ultra™ protection
Non-ozone depleting Puron® refrigerant
10-year parts limited warranty2
 
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Thank you for clarifying KrisZ, I thought I had read it was a two stage air conditioner. A dumb follow-up question then is does that mean I can't change the blower speed to circulate air inside the house while the AC is running? In other words, the fan speed is fixed when the AC is on? I know when the furnace is on I can change it, but that's an Infinity model.
 
Originally Posted By: SVTCobra
Thank you for clarifying KrisZ, I thought I had read it was a two stage air conditioner. A dumb follow-up question then is does that mean I can't change the blower speed to circulate air inside the house while the AC is running? In other words, the fan speed is fixed when the AC is on? I know when the furnace is on I can change it, but that's an Infinity model.


Not with the thermostat. The furnace fan speed is set with the connection on the control board.
Below is a link to the installation manual for the infinity models. On page 41 the diagram shows that a single speed air conditioner connects to cool stage 1 on the thermostat and Y/Y2 on the furnace. From the diagram I gather that the Y/Y2 switch should be the higher speed because for the two stage models, stage 1 (which is the lower speed) should connect to Y1 connector.
I would check the thermostat and board connections to make sure they match the installation manual. If they do, then everything is connected as it should be.

The furnace fan speed can be adjusted a little bit via the SW2 on the control board, but this is to fine tune the furnace fan speed to the evaporator core and the compressor, so that it can all perform optimally.

Infinity Furnace installation manual
 
I did open the panel up last night and found the wiring diagram to the board and there are dip switches. The set position of the switches was DEF, and I changed them for the AC setting (underneath the CF in the bottom left corner) and checked the CFM and blower RPM. Neither changed. I then switched it to have both the CF and AC dip switches all up, which should have been the max setting of 1225 cfm. Looked at the output on the thermostat and it was still the same (around 700) and the vents didn't blow any harder or sound different.


KrisZ, once I get home I will double check the wiring and get a bigger picture of the wiring diagram above. I see the Y/Y2 on the picture above, and for some reason I don't remember anything being hooked up, just the comm wire, but I will double check.

On a side note, I did install the new outdoor temperature sensor and although that corrected the display temp, it didn't change anything in relation to fan speed.
 
Originally Posted By: KrisZ
I just checked Carrier website, their Performance AC units are single stage, even the 16 seer one. So everything works as it should for OP. He would have to install the Infinity unit in order to take full advantage of that Infinity furnace.

In light of this new info, I would suggest to keep the AC on all the time, just program the thermostat to increase the temp a little bit when no one is home and set it to the desired temp. for the time when family members start coming back.

From their website:
Quote:
Features
STANDARD FEATURES
Up to 16 SEER cooling efficiency
Sound: as low as 72 decibels1
Single-stage operation
Compressor sound blanket
Filter drier system protection from moisture and contaminants
WeatherArmor Ultra™ protection
Non-ozone depleting Puron® refrigerant
10-year parts limited warranty2


Just to follow up I'm pretty sure I have the 24APA7 model, which is similar to the 24ACB7 model on the website, which has a two stage compressor. Sorry for not having all of the details correct and organized, literally just moved last weekend and still sorting through that.

STANDARD FEATURES
Up to 17 SEER cooling efficiency
Sound: as low as 72 decibels1
Superior humidity and temperature control
Two-stage compressor operation for ultimate comfort
Filter drier system protection from moisture and contaminants
WeatherArmor Ultra™ protection
Non-ozone depleting Puron® refrigerant
10-year parts limited warranty2
 
Read the manual and check the wiring and all the dip switches. Here is an interesting note for connecting the thermostat:
"11. Optional connection - If wire is connected to W2 on furnace control board, either dip switch SW1-2 or SW1--LHT on furnace control
should be set in ON position to allow thermostat to control furnace staging.
12. Optional connection - If wire is connected to Y2 on furnace control board, ACRDJ jumper on furnace control should be removed to
allow thermostat to control outdoor unit staging."
 
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