[mrbee]

Hello, all. I am a newbie here, but I have been reading posts for a year or so. Excellent site, very helpful. I just installed a Bryant Evolution Plus furnace
(80%, 2 stage, VS fan), a Bryant single stage A/C condenser, and a W-R single stage touchscreen t-stat. I'm very happy with the install, good installer (Factory Certified, NATE, etc.). I read on here that a 2 stage furnace should always have a 2 stage t-stat. I spec'd a 2 stage t-stat for this job, but the installer vehemently insisted on a single stage t-stat. He said that the Evolution has its own board that controls the 2 stage logic/algorithms, etc. so there is no need for the t-stat to do that with a 2 stage t-stat, and that if I had a cheaper unit without the board, only then would I need a 2 stage t-stat the run the logic/algorithms, etc. He also mentioned that the condenser was only a single stage. Is the installer correct? If not, was he trying to keep the job within budget (is a 2 stage t-stat much more $ than a single stage t-stat?), or was he trying to avoid pulling new wires (the wire path in my house to the t-stat is a bit convoluted, perhaps the installer recognized this and was trying to avoid more labor cost on the budget? Does a 2 stage t-stat require more wires than what was on the 1960's vintage system that was replaced?) I'm trying to decide if I should go back to the installer now, while the system is very new, and request a swap-out to a 2 stage t-stat. The posts here say that you get better "comfort" with a 2 stage t-stat. My system seems very comfortable so far. "Comfort" is a bit vague. What specifically am I missing without a 2 stage t-stat? Your thoughts, input, and opinions would be most appreciated and thanks for reading!

 

[lra]

I am not familiar with that particular furnace. As a rule though, yes a 2 stage stat would be your better bet. The furnace is manufactured to provide multiple installation variables. It (the furnace board) doesn't know if you have a multiple zoned system, air flow characteristics of the stat location, etc. Unless the literature with the furnace specifically requires a single stage stat, I'd use one. And yes, there needs to be another wire for the 2 stages of heat.

 

[mrbee]

Hi, Ira, thanks for the response. Since the condenser is still only single stage, and if I usually run heating on "Auto" rather than on the "Fan On" setting, would a 2 stage t-stat really be cost-effective in terms of the cost to upgrade to the new t-stat, and the labor cost for pulling the new wire? Or am I really running a "tweener" system that is functioning more like a single stage system, so that a single stage t-stat isn't so bad? Thanks! mrbee

 

[indytech]

A 2 stage t-stat will help with heating will call for 2nd stage quicker than the control board on furnace. you need 2 stage heat 1 stage cool you will save money.

 

[beenthere]

The 2 stage stat will still provide better comfort then the boards logic.

As far as pulling more wires, he can use the Honeywell IAQ, it only needs 3 wires to the stat. It is more expensive, but saves teh labor of pulling new stat wires.


The furnace board will force second stage after the furnace runs for so long.
The stat will keep it in first stage as long as the temp is not dropping.
If it really didn't work better with a 2 stage stat, why would it have terminals for a 2 stage heat stat.

 

[mayguy]

I usually run heating on "Auto" rather than on the "Fan On" setting, would a 2 stage t-stat really be cost-effective in terms of the cost to upgrade to the new t-stat, and the labor cost for pulling the new wire?

Since you got a nice variable speed system, I'd suggest turning on the fan in the winter to move the air. It'll make the house more even in temps.

I'd go and put in the IAQ t-stat, they only need 3 wires, where most other two stage t-stat will need 5 or 6 wires.

 

[mrbee]

Hello, all, and thank you for all of the helpful and informative responses. You are all true professionals. I will study the IAQ unit and post how this issue turns out and resolves itself. A great weekend to all! mrbee

 

[Cmore]

This subject turns up in this group every few days. Why? Do the HVAC professionals have something against the manufacturers who design and build 2 stage furnaces. For me, as a consumer, if the manufacturer recommends a 2 stage thermostat, it should be installed. I had a Trane XV90 installed last month and frankly had to argue with the installer to have a 2 stage T installed. He thinks I'm crazy, spending extra monies for the 2 stage T. For 2 weeks before he installed the 2 stage T, the furnace ran on the timer and it ran often. Ten minutes on low then on high. Since installing the 2 stage thermostat, I find the furnace runs on low the majority of time and the temperature on the 'stat never varies. Simply put, would all you HVAC experts install what the manufacturers call for. I'm sure that most consumers who order a 2 stage furnace, would absorb the extra cost for the 2 stage stat.

 

[mrbee]

Cmore, I went around and around the horn with the installer on this issue while the install was in progress. It started to get a bit ugly and I backed off to the 1 stage t-stat. I couldn't figure out why there was an issue here, I thought maybe it was me being picky or something, it's been bothering me ever since the install, so I decided to post it up here. It looks like I have only 3 wires, previous posts indicated the IAQ only needs 3 wires. I have a W-R now, it's fine (except for 1 stage), does W-R make a 2 stage 3 wire t-stat like the IAQ? Again, thanks to all who responded.

 

[mrbee]

Hello all, again. I've been doing some homework (nothing else to do- home ill for 1 week!!). The current single stage t-stat is a W-R 90 Series #1F97-1271.
The 2 stage W-R t-stat I could switch to (it might be easier for the installer to swap me out to another W-R unit instead of a different brand i.e. Honeywell IAQ) is a W-R 90 Series #1F95-1277. Does this 2 stage W-R require more wire(s) to be pulled, or can it use the same amount of wires as the single stage W-R?? I tried to figure this out on the manufacturer's pdf wiring diagrams, but this is way beyond my expertise, the diagrams look like a foreign language to me and it's not just because I am ill! Your input and thoughts would be most appreciated once again, and many thanks

 

[beenthere]

It will need more wires then the IAQ.
Currently, teh IAQ is the only stat that only needs 3 wires to the wall stat and can still control 2 stage equipment.

 

[mayguy]

White Rodger is going to need 5 or 7 wires.

Power
Heat 1
Heat 2
Cool
Fan
Common (If not used, then battery must be used)
Dehumid (I am not sure if this t-stat has it or not)

IAQ

COM 1
COM 2
COM 3


3 wires goes down to an Equipment Interface Module, then it ties to the furnace.

 

[mrbee]

Thanks for the wiring info, this answers many questions I had!

 

[oloenneker]

has no one ever heard of a "add a wire" kit?

If you have four wires already to your stat, you can use the add a wire" kit to do the function of that fifth wire.

 

[beenthere]

Heard of it, never used one.

Wondering if the cost of the add a wire, and a good programable digital stat, isn't about the same as a IAQ stat.

 

[mrbee]

Good morning, all. While we are on the subject of wiring, add-a-wire, etc., I did some more homework. The Bryant Evolution furnace manual says that this unit has an Adaptive Mode where you can run a single stage t-stat with this 2stage furnace, by setting a DIP switch. I believe I am running in this mode right now with my single stage t-stat. The installer also mentioned this mode during installation. The Adaptive Mode sequences are start in low, switch to high, or start in high. Once in high, Adaptive Mode can't ever bump back down from high to low. The manual also states that with a 2 stage t-stat, the sequences are the same, except that the unit can bump back to low from high. How important is the bump-back capability in terms of gas savings and comfort? How often will the bump back to low sequence typically run? I'm still on the fence with going back to the installer for the IAQ. Knowing now that Adaptive Mode exists, should I just "live with" it as is, or should I still try to go for the IAQ? Again, many many thanks for all of your helpful advice. Regards, mrbee

 

[mayguy]

Heard of it, never used one.

Wondering if the cost of the add a wire, and a good programable digital stat, isn't about the same as a IAQ stat.

I am not a dealer so I have no clue, I am guessing they are going to come out close?

Good morning, all.

The Adaptive Mode sequences are start in low, switch to high, or start in high. Once in high, Adaptive Mode can't ever bump back down from high to low. The manual also states that with a 2 stage t-stat, the sequences are the same, except that the unit can bump back to low from high. How important is the bump-back capability in terms of gas savings and comfort? How often will the bump back to low sequence typically run? I'm still on the fence with going back to the installer for the IAQ. Knowing now that Adaptive Mode exists, should I just "live with" it as is, or should I still try to go for the IAQ? Again, many many thanks for all of your helpful advice. Regards, mrbee

I used to work with a dealer who did Carrier,(Bryant is owned by Carrier). You are right about the Adaptive Mode. I am trying to recall it, and don't hold me to it.. I am sure the other Carrier guys can jump in and correct me.

-The board will see how long it runs till it shuts down. So let's say the furnace ran 20 minutes, and the shuts down. On the next call of heat, the board will keep the furnace in low, and if it runs longer than 20 min, it will then fire off in high fire till it shuts down. I honestly don't recall when it "rests itself" to the shorter run time.. I think it if the furnace ran 10 min and shuts down, it reset itself.???

So you will never see it go back into low stage. It's for pure COMFORT, not savings. For an example, last Feb, we had a cold snap of -15 to -20 below zero, my furnace pretty much fan non-stop for few days, and it cycled in and out of 2nd stage as needed. Everyroom in the house was warm and comfortable! neighbor behind me got the same floor plans is ours, and they have a single stage, and one room was warmer, others was colder... cuz the furance was cycling on and off.

 

[BaldLoonie]

To me, the idea of 2 stage is long run periods on low in bitter weather. That can't happen with any timer. The longest Carrier allows is 16 minutes then it times to high and as you said, stays there until the stat satisfies.

Look at May's post about his 2 stage experience during a cold snap. I bet he was more comfy that way than a timer, adaptive or otherwise, that wouldn't allow long low cycles. Seems to me, shortly after timing to high, it could satisfy the stat. Shortly after the sequence would repeat. Many cycles instead of just purring along on low.

 

[beenthere]

With a 2 stage sat. If you set the temp back at night, you can have a quick recovery in the morning if you want. Or can have adaptive recovery turned on, and not use second stage it it isn't needed. Can't do that with the furnace board.

If you bought a 2 stage furnace to save money on the heating bill, you won't.

Its for comfort.

 

[mayguy]

With a 2 stage sat. If you set the temp back at night, you can have a quick recovery in the morning if you want..

.

Been made a good point there about morning recovery.. I set ours back to 62, and back up to 68, it fires off on 2nd stage right away, then throttle back to 1st stage to slowly warm up the home to comfort.