What thermostat is proposed on each quote?

It should be a true two stage thermostat for best operation.

What size are the furnaces quoted?

Post back.

IMO

Hi tigerdunes,

I already have Honeywell Vision Pro 8000 TH8320U1008 stats that can be used for the furnaces based on installer. Not sure what size they are.. specs for the Carrier 59TP5A E21-20 indicate rated heating output on high is 97K and low is 63K which seems appropriate for a 5000 sq ft home (excluding basement)

The Carrier furnace is muti-speed, while the Trane is a variable speed. This plays into the price difference.

The Carrier 59TN6 would be the equivalent furnace.

Do you have central AC? If not a muti-speed furnace should be sufficient for your application.

Not only that but the 59TN6 Infinity furnace would require the Infinity controller for best operation. Why buy a great furnace and then cripple it without the best controller?

IMO

@mike_home - Yes, I have a central A/C so assuming you are not recommending the Carrier 59TP5 for my needs? Don't know what the difference between multi-speed and variable speed since the dealers just told me two-stage is the way to go.

@tiger_dunes - As above, would you not recommend the Carrier? Cost is a concern for me.

A mutli-speed means that the furnace can operate at two fixed speeds which are set at the time of installation. There is sometimes a third speed option for the AC operation.

Variable speed means the furnace can adjust the speed to produce a constant air flow for each stage. If the filter gets dirty or you have a restrictive duct work then the blower motor will increase the RPMs to compensate for the restricted air flow. The variable speed motor can support a 2-stage AC.

If your AC is a single stage then the 59TP5 should work. If you have a 2-stage AC, then you are going to need a variable speed furnace. As Tiger points out getting the Carrier 59TN6 will require the Infinity controller which will add more cost.

What AC and coil are going to use with these furnaces? It sounds like you are creating a mismatched system.

I would not purchase a new furnace for that size home that was not at least two stage with a var speed blower.

In fact, I would be looking at one of the nice modulating furnaces that can move up and down based on demand for best overall comfort.

Any existing hot/cold spots in home should be evaluated and addressed for improvement. Also adequate and properly sized returns are important. I assume you have multiple returns.

IMO

@mike - thank you for the explanation. Very helpful. I believe we have a one-stage A/C because its original to the home. The AC is a Comfortmaker Model AJ048GA1. Also have a Comfortmaker Heatpump model YG030GB1

@tigerdunes - thank you again for the input. I don't know what a modulating furnace is; these installers are telling me I need a condensing furnace. I very much appreciate all this information as its really difficult to understand everything since I don't know what I don't know. Yes, we have several returns around the house, 3 on the upper level that are in the ceilings, a large one on the main level and a large one in the basement.

I feel we are not getting the complete picture on how you heat and cool your 5000 sq. ft. house. You are not going to get good advice unless you explain how your house is currently set up.

It seems like you have a 100K BTU furnace connected to a 4 ton AC condenser. You also have a 2.5 ton heat pump which I assume is connected to an air handler. Is this correct? How is the house divided between these systems? What amount of area does each serve?

A modulating furnace is a condensing furnace...

Go to Google...

@mike - I'm sorry, I'm very new to this and am trying to get educated. You are correct that I have a furnace connected to the AC. The heat pump is connected to an air handler that sits in the attic. The heat pump takes care of the upstairs which is 4 bedrooms. The main level and basement is handled by the furnace, etc. I don't know the exact sq footage split between both.

@tigerdunes - thanks for clarifying. Next time I will google it as suggested.

One thing a variable speed (as opposed to variOUS speed) blower can do is run at a lower speed on AC in order to perform humidity extraction. My Trane starts very low, then low and stays there for a while (several minutes). It then slowly picks up speed and reaches its highest setting. At shutdown, it slows down quickly then blows at very low for about 30 seconds before stopping.

The heat profile is similar though the highest setting is more like medium.

A modulating furnace will modulate (or change up and down) the gas flow to match the amount of heat that is needed. A single stage 'regular' furnace is all on / all off. A 2-stage would be off / half / full or something similar.

I generally like to think (and others will correct me) that a condensing furnace is so efficient that the gas exhaust temperature is low enough that water vapor 'condenses' in the flue. A less-efficient design would have hotter exhaust and the vapor would not condense but go out the vent.