thermostat wire

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My old house has a 3-wire thermostat, and I can either use a mechanical thermostat, or one that uses AA batteries.
I want to put in a smarter thermostat that requires power supplied by the furnace. This requires more wires. I'm thinking of pulling out the old wire and put in new thermostat wire. I think the maximum I can get is 8-wire. Is it advisable to do this or is 5-wire sufficient? The 8-wire will be harder to pull/fish.
What kind of furnace uses 8-wires anyway?
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bob wrote:

Hi, You'll have spare wires then. If you don't use a/c, 4 wire is needed. Or forget the wire all together and go wireless. I did that and we can move thermostat to any spot in the house.
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Wireless may be fine for now, but if you switch to a high end system like Carrier's top-of-the-line Infinity, you have to use their wired thermostat that goes with the system.
The communication between units is computerized. It does not use a lot of wires. Five will be enough. Shielded could be a bonus in an electrically noisy environment.
Don. www.donwiss.com (e-mail link at home page bottom).
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Don Wiss wrote:

Hi, That's what I got Carrier IAQ system. (Infinity) I made it work. When they installed the system, control part, I did.
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wrote:

That's good to know. I'll avoid Carrier like the plague.

A shield is superfluous. Five may not be enough, depending on the system. I believe mine has 8 (not all are used, currently).
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snipped-for-privacy@attt.bizz wrote:

Hi, If number of wire is not enough you can use multiplexer(s) which make one wire acts like two for an example. Different signals time sharing one wire. Advantage of digital circuitry.
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wrote:

If I'm designing the HVAC unit and thermostat, sure. If I'm buying one off the shelf (infinitely more likely), not so much.
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On Tue, 10 Sep 2013 16:38:03 -0400, snipped-for-privacy@attt.bizz wrote:

There are definite advantages to a high end Cariier system. Like variable speed and precise humidity control.
Don. www.donwiss.com (e-mail link at home page bottom).
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wrote:

There are other fish in the pond. Ones that don't lock you into their system.
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On Wed, 11 Sep 2013 22:25:23 -0400, snipped-for-privacy@attt.bizz wrote:

An example please. One with variable speed and humidity control. And lets you use any thermostat to get these features.
Don. www.donwiss.com (e-mail link at home page bottom).
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wrote:

Nest will control humidity, assuming the HVAC system will do a reasonable job. It should be a big stretch to go from there to whatever it is that the "high end carrier" does. Again, I'm certainly not in the habit of locking myself into one solution.
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On Thu, 12 Sep 2013 00:05:13 -0400, snipped-for-privacy@attt.bizz wrote:

Nest will control it only when heating. Carrier's Infinity will also control humidity for air conditioning. For that you need a variable speed fan and compressor.
Most a/c units simply have a set point and they turn the unit on and off as it crosses that point. One with variable speed will always run. The speed will be what is necessary to keep the temperature right at the set point. None of this up and down temperature you get with regular air conditioning. I know I can very much tell the temperature change. On a relatively cool, but very humid day, a regular air conditioner will not get the humidity out. A variable speed one will.
It is a matter of comfort. But I guess for some people comfort isn't that important.
Don. www.donwiss.com (e-mail link at home page bottom).
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On Thursday, September 12, 2013 10:12:51 AM UTC-4, Don Wiss wrote:

I've lived in a lot of houses and haven't had up and down AC problems with a basic thermostat. Set it for 75 and it stays at 75. If you've got ups and downs, it's because you have a poorly installed system.
I know I can very much tell the temperature change. On a relatively cool,

If it's cool outside, it's never humid inside my house here in NJ. If it is a bit humid on the couple days a year when the AC isn't running, I can just turn it on for 30 mins and the humidity is gone. Hard to justify spending a lot of $$$ for a problem that is almost non-existent.

I'm comfortable. There is no question that an advanced super duper Carrier, with multi stages, humidity control, etc can do a better job. But when I went out for quotes two years ago, the Carrier guy was $6K more than the $8K quotes for systems that were perfectly fine. The cost/benefit equation just isn't there. And then, you're stuck with Carrier's thermostat? I'll bet my Honeywell VisionPro is easier to program.
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snipped-for-privacy@optonline.net wrote:

Hi, Still Infinity IAQ full set up needs tweaking to suit the local situation. I had to interface it with my wireless 'stat and first year I had to spend some time in summer/winter to make everything satisfactory to our R2000 spec. house. Yesterday our new house cleaning lady mentioned "Your house has very little dust build up", Of course IAQ also maintains clean fresh indoor air.
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. > > If it's cool outside, it's never humid inside my house here > in NJ. If it is a bit humid on the couple days a year > when the AC isn't running, I can just turn it on for 30 mins > and the humidity is gone. Hard to just ify spending a lot of $$$ > for a problem that is almost non-existent. > >

ort isn't that >> >> important. >> >> >> >>
I will be curious to see how comfortable you feel when the variable speed d rive motor fails and you see the bill for the repair.
Mark
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On Fri, 13 Sep 2013 09:28:22 -0700 (PDT), snipped-for-privacy@yahoo.com wrote:

I have a annual maintenance contract. So far what has broken has been covered under the warranty. For many parts it is 10 years.
Don. www.donwiss.com (e-mail link at home page bottom).
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Don Wiss wrote:

Hi, Maybe I am one of lucky one. Never, ever had trouble with Carrier system which is my favorite. My BIL is chief designer/estimator for a large commercial contractor. He always point me to a good I mean real good service techs.
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wrote:

OK, maybe I missed something but this is relevant, how?
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On Monday, September 9, 2013 9:14:34 PM UTC-5, bob wrote:

hermostat, or one that uses AA batteries. I want to put in a smarter thermo stat that requires power supplied by the furnace. This requires more wires. I'm thinking of pulling out the old wire and put in new thermostat wire. I think the maximum I can get is 8-wire. Is it advisable to do this or is 5- wire sufficient? The 8-wire will be harder to pull/fish. What kind of furna ce uses 8-wires anyway?
5-wire should be ok, but I like the wireless idea even better.
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On Monday, September 9, 2013 10:14:34 PM UTC-4, bob wrote:

Another option is just get one of the thermostats that will operate off of batteries and change them once a year. Most of the programmable ones work like that. I have a Honeywell VisionPro, which is a really nice one that I recommend. It will work with either battery or furnace power. The advantage to furnace power is:
1 - You can set it so the display is backlight all the time. With battery it only lights when you touch it to use it.
2 - You don't have to worry about changing batteries, or having dead batteries in winter when you're not there, etc. Some thermostats have a backup mechanical that closes at 40F or so to prevent freezing.
This requires more wires. I'm thinking of pulling out the old wire

Typical is:
heat cool fan common
That's 4.
Add in your additional power wire for the thermostat, and you're at 5.
next level of complexity is two stage heat and/or cool which would add one more wire for each stage. So two stage heat, two stage cool, which is common, would be 7 wires.
Then some thermostats can control a humidifier, which I presume adds an additional wire. That would give you 8.
If you're re-wiring, I don't see pulling 8 wire being much different than 5, either in cost or difficulty.
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