[mcburton]

Hello,

I just had an American Standard Freedom 80 (2-stage, variable speed fan) installed with my existing (old single stage) coils and Rheem condenser along with the AcuClean filtration system. This is a two-piece system (outside condenser, inside coils/furnace). The contractor installed a basic digital thermostat but I want to upgrade it to a programmable model. There seems to be different models for the same thermostat product to deal with different stages of furnaces and AC units, but I am not sure what to buy in situation to utilize the dual-stage furnace with variable-speed fan with a single-stage A/C. Below are variants of the same American Standard thermostat, but I don't see a 2 Heat/1 Cool option. What do I really need? I don't necessary want to stick to an American Standard brand -- these are just examples.

Thanks in advance.


Model Description Used With Shipping Weight (lb)
ACONT800 7-Day Digital Programmable 1 Heat / 1 Cool All Cooling and HP Models 1
ACONT802 7-Day Digital Programmable 3 Heat / 2 Cool All Cooling and HP Models 1
ACONT803 7-Day Digital Programmable 2 Heat / 2 Cool with humidity sensor All Cooling and HP Models 1

[KISS]

The best place to start, is to see what terminals are connected to your thermostat..

3 heat can always be reduced to 2 heat or 1 heat by programming. Read the instructions for the stat.

There needs to be extra relays and terminals to handle the extra stages, thus more expensive.

Dehumidification generally is an added cost because of the addition of a humidity sensor, Use of a thermostat that offers dehumidificaion will result in increased comfort and less noise. Dehumidifying in the cool mode, will cause the blower to run slower.

There are a number of thermostats at Furnace Filters, Air Conditioner Filters, Air Quality - iaqsource. I feel that they have done a super job in presenting the information in both concise and detailed form for what they sell.

Remember, for Honeywell, theit Focus Pro line is "simple consumer". Their vision pro line is considered "Professional". Lots of options, nearly zero support to the consumer directly. Their Prestige line is just that "Prestigeous". e.g. It boats a remote so that the temperature regulated is at the remote.

[mcburton]

Hello again,

I am looking at the LuxPro PSP722E (Buy LuxPro PSP722E Programmable MultiStage Thermostat | LuxPro PSP722E) as it has a separate fan program feature. It supports 2-stage furnaces but the company that installed my 2-stage told me that they wire it up as a single stage so the stat will not control the stages -- the furnace electronics will control when the 2nd stage is engaged and work better this way.

I know very little about these furnaces. Will a Two-Stage stat work with a 2-stage furnace (wired as a single stage) and a single-stage A/C unit?

Thanks!

[KISS]

OK, The information that a furnace would not have when operating this way is what is the difference between the deired temperature an current temperature.

When that temperature difference is large, it's a sure way to fire up the second stage.

Some thermostat's can use outside temperature to give it an edge as to when to use the 2nd stage.

A two stage furnace wired to behave as a 2nd stage has to rely on time. Not much happened when I was on low heat for 20 min, lets tyy the second stage or I used the second stage the last time, lets try it again.

The stat has more variables that it knows about.

The stat I have know the cooling capacity, the heating capacity and the outside temperature which it can use to pick where it wants to operate.

A two stage stat is better. What your installer may have done is said. It'd two difficult to run the extra wires I need, so lets' do it this way.

There are ways around the extra wires.

Changing the behavior may require extra wires and/or DIP switch settings.

Using a two stage stat set such the furnace controls the stages doesn't gain you anything except the ability to change to the correct way in the future.

Not a bad choice. It might be difficult to set up. There is "HOLD until next event", "Hold indefinately" and Vacation hold. It doesn't have hold for specific period.

We do use hold for a specific period a fair bit. Go out, you hold it for when your planning to return. We bump it up for say 15 min to take a shower. On rainy days, we may bump the temperature higher for longer periods.

[mcburton]

What your installer may have done is said. It'd two difficult to run the extra wires I need, so lets' do it this way.

That is probably true! How do you work around the lack of wires (I believe I have 4 (common, fan, heat, and cool) to use the 2-stage ability in the stat?

Thanks KISS!

[KISS]

You throw more money at it or you run more wires:

A method: FAST-STAT

Or you use a stat such as this one: Buy Honeywell VisionPro IAQ Programmable Universal Thermostat with Total Home Comfort Control | Honeywell YTH9421C1002

Or some other kind of communicating stat.

The above only requires 3 wires. An interface box mounts by the furnace.

You go wireless (no specific product handy)

You won't have a common with 4 wires. You will have R. Common is relatively new and it's required for the electronic thermostats unless the stat will operate completely on batteries.

Between Common and R, there will always be 24 VAC.

[mcburton]

Thanks Kiss. Do you happen to know how many wires I need to use a 2-stage furnace with variable speed fan and a single-stage AC unit? I would like to be able to run the fan at a lower speed when the heat/AC is not running to move the air.

Thanks Kiss.

[KISS]

Assuming non-heat pump.

(C) - Common, sometimes optional, If not used the stat runs entirely on batteries.

(R)
(G) - Fan
(Y) Cool
(W or W1) 1st stage heat
(W1 or W2) 2nd stage heat

That's 5 or 6 depending on tstat.

The fan only speed setting MAY be a DIP switch setting on the furnace board.

[mcburton]

Thanks KISS. Yep, non-heat pump -- gas furnace.