how long should programmable thermostat batteries last?

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A white-rodgers generic cheapie that came with the new furnace 3-4 years ago, specifically. Takes AA x2. New duracells (with use-by dates several years in future) seem to go flat in 3-4 months, and the thing loses all the settings. Doesn't seem like there should be a lot of juice used driving a couple chips and that tiny LCD.
Given that power is available from the furnace, why do these things need more than a button cell for memory backup, anyway?
-- aem sends, adding another item to the shopping list for tomorrow...
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What do you expect from a POS?
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wrote:

POS? I thought White - Rogers was one of the better brands.
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I was going by your description "generic cheapie". There really is no such thing as a "better brand" in today's day and age unless you spend a thousand bucks. It's all chinese crap. I've seen sony (reputation earned in the 70's, but not since and now made mostly in the asian rim ) do crap that would embarass a fly by night walmart brand.
I have a luxtx1500 that is is also a POS. It hasn't had any trouble running a year on it's 9v battery.
There are many ways a poorly designed thermostat can run the batteries down in short order. Junk output design with current wasted going through pull down resistors on the transtor bases -- use of cheap bipolar output transistors instead of higher quality MOSFETs.
ESD sensative chips partially damaged during assembly.
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aemeijers wrote:

My UPM Thermostat seems to go several years on fresh batteries. I don't seem to remember it loosing settings when the batteries are changed... but I could be wrong its been quite a while since I changed them.
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Ned Flanders wrote:

I just read the manual for my thermostat - it suggest you should replace the batteries once a year but it will let you know when the battery is getting low. If the batteries are replaced within 20 seconds the thermostat will not loose the programing.
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aemeijers wrote:

If there is a blue wire in your cable, assuming it's a 5 conductor thermostat cable, the blue wire would normally be hooked up at the furnace and the thermostat so it would have 24vac power. The normal color code would be for the red and blue wires to be the 24 volt supply. I always install digital thermostats so they are powered from the air handler and have batteries for backup. The inexpensive thermostats may be battery only but most of them I come across have the option to also use 24 volt power. The reason for AA batteries is that a relay/relays inside the thermostat needs to be activated to operate the HVAC system.
TDD
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The Daring Dufas wrote:

Wire colors are not standardized, but you are correct, without both the "R" (24V) and "C" (common) connections being wired to the thermostat, it has to run entirely off of the batteries and while an LCD display takes little power, a backlight and most importantly the fan and stage relays do take a fair amount of power relatively speaking. If the "R" and "C" are wired to the thermostat it's powered by the AC and the batteries are only used for setting backup during power failures and last a lot longer.
Pop the thermostat off the sub-base and see how it is wired. The most common reason for not having the complete "R" and "C" connections is not having enough wires in the existing cable.
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Pete C. wrote:

Nope, all 5 in place. Next time I run across my VOM, I'll put it across the R and C leads, and see if there is juice. Brand new batteries in there now, and it seems happy. Now I just have to remember how to program the damn thing. And I did write today's date in pencil on the inside of the lid, since my memory is not so hot any more...
--
aem sends...

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mine has the programming instructions on the inside of the TS cover.
--
Jim Yanik
jyanik
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Jim Yanik wrote:

case, so you keep having to flip it over to remember which one to punch next. Shoulda been on the inside of the fold-down door. I'll figure it out, it is just one of those tedious annoying things that could have been made a lot simpler for a couple more bucks. I might even have the paper instructions Someplace around here, but right now I haven't a clue where.
--
aem sends...

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wrote:

Does the TS have a reset button?
That will set it to factory defaults I think, mine does. (energy star suggested settings for a 5+2 type)
I never made any custom settings, so the default is fine for me.
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Oren wrote:

The whole programmable setback thing is not applicable for a lot of folks since it presumes nobody is home during the day, which is not the case for folks who are retired, work from home, stay at home parents, etc.
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How do you figure that? We used[*] a setback thermostat not only for daytime but nighttime, as well. AAMOF, the nighttime setback was further (59F) than the day (62, IIRC). We set the temperature for morning and evening to 66F and kicked it up if we got cold.
[*] Don't now because heat pump recovery is an oxymoron.
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

Guess age is starting to rear its ugly head for me. I can't sleep well in a 59 degree room any more. Not to mention, those middle-of-the-night walks are hard to get back to sleep from, at that temp.
-- aem sends...
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I like it cold while sleeping (it's just another blanket). We keep it about 64F now that we have a heat pump. I'd rather have it cooler but even 64F is stretching it for the morning shower and as I said, heat pumps don't recover. Heat isn't nearly as expensive as it was, though. Moving from Vermont to Alabama has changed a few things (heat bills, taxes,...). ;-)
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aemeijers wrote:

Yes, and yes. Heat pumps are nice and efficient, but more than a 2 degree change in set point and you're on aux backup heat. Yes also, I don't like a drastic change in night temperatures either and I also find getting back to sleep after the 3am page is difficult if the temps have dropped.
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snipped-for-privacy@att.bizzzzzzzzzzzz wrote:

the AA cells in my lakeside camp needed replacing every few months. Tossed it and went back to old fashion dial.... worried it would 'die' in winter season freezes.
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my cheapo programmable TS works fine without any setback programmed. Plus there's an OVERRIDE switch for when you're home.
It cost me $15 at Home Depot about 15 years ago. having a digital TS is better,as it sets to temp more accurately.
--
Jim Yanik
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Jim Yanik wrote:

Yes, I'm well aware of that. My point is that the idea of the setbacks doesn't work in a lot of cases. Also with a heat pump they are even more problematic. My TS is in hold mode all the time.
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