Has Carrier Infinity 96 _always_ been variable speed?

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Old 06-27-19, 09:22 PM
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Has Carrier Infinity 96 _always_ been variable speed?

House we bought awhile ago has 3 Carrier Infinity 96 furnaces (2 w/ AC, one heat only). They're from 2006, per the label inside.

I keep reading online that this is a variable furnace/fan unit with custom control interface that requires a specific carrier controller not a thermostat. But we have very standard looking thermostats w/ 4-wires labeled R/G/Y/W.

Have Infinity 96 units _always_ been variable-speed and the original installer just used the wrong thermostat type? Or did Carrier re-use the name and upgrade them at some point in the past 13 years?

Is there a way to tell if this is a 1-stage, 2-stage, or variable heat and/or variable speed fan furnace directly by looking inside it?
 
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Old 06-28-19, 08:41 AM
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popped open the cabinet to check how it's wired....and whatever it may or may not be capable of, it's currently being controlled as a single-stage. connections from the t-stat to W1, Y1, Y and R only (and, as it happens, an aprilair humidifier). So an ecobee certainly won't be a step backwards, but I'm still unclear if this furnace is capable of more than it was wired up to do.
 
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Old 06-28-19, 11:02 AM
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The infinities have always been variable speed,

Variable speed simply refers to the type of blower motor. The blower automatically compensates for duct pressure to maintain proper airflow in each mode of operation.

Has extra features like low speed continuous fan and being able be slowed down to dehumidify better in cooling mode.

The amount of airflow is dictated by the mode of operation, not the thermostat directly.

Your furnace is either 2-stage or modulating/3 stage - unsure of if 3 stage/mod was out in 2006.

2-stage enables the furnace to run at 66% capacity most of the time and bump up to 100% when the demand for heat is high.

3 stage has a low stage around 40%, medium 66%, high 100%.

For 2-stage:

With a normal thermostat, it runs on low at the beginning of each cycle and switches to high after 16 minutes or less, stays there until the stat is satisfied. The colder it is outside, the shorter the delay. This is not optimal but saves the contractor some money.

You can get a 2-stage thermostat for $150 or less that uses W2 and allow it to stage based on the needs of the house.

Only brings on high when low isn't sufficient to maintain the setting and h drops back down to low after running on high. Allows for continuous operation in brutally cold weather if your furnace was sized correctly.

The infinity thermostat does the same thing but communicates digitally with the control board, allows error code reporting, setup from the stat instead of setting switches on the board.

To me the communicating thermostat isn't worth hundreds of $$ it costs when you have a 2-stage furnace unless you have a complex setup or can't run an extra wire for a regular thermostat - like 2 speed a/c as well, wanting to
dehumidify on demand by slowing the fan, dual fuel with heatpump.

The infinity stat is required for 3 stage or modulating to take full advantage though.
 
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Old 06-28-19, 11:13 AM
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Is there a way to tell if this is a 1-stage, 2-stage, or variable heat and/or variable speed fan furnace directly by looking inside it?
Post the full model number for each furnace.

It's at least a 2-stage with variable speed blower as stated in my post above.

You should know that all the 58 series high efficiency furnaces from carrier have problems with heat exchangers - there's a plastic coating that fails and plugs them up, when the coating fails the heat exchanger also rusts out from the inside out.

This style of unit needs a combustion test every year. If bad, the part can be replaced under warranty and there's some labour coverage as well due to a class action lawsuit.

The major parts in these infinities are very expensive though so if/when the heat exchangers fail, can be better to just replace the furnaces when they're well over 10 years old.

Its actually wise to get a comprehensive parts/labour protection plan from a reputable contractor in your case. Normally, its not worth it.
 
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Old 07-02-19, 08:39 PM
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Thanks for the very clear explanation. It was definitely previously wired up only as a single-stage heating and cooling system. I'm hooking it up to an ecobee4, which could handle the 2-stage if I was willing to run the additional wires...but at least won't be any worse than what was already there just hooking it up. Seeing as it's the 2ndary heating system (hydronics handle most of it) I'll probably just leave it.

thanks for the advise re: having the heat exchange checked. Will do.
 
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Old 07-04-19, 08:11 AM
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If these furnaces are used in extremely cold weather, it's absolutely worth having the staging controlled by thermostat.
 
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