Digital Thermostat Quit Working

Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

 

[gregz]

<oldschool@tubes.com> wrote:

Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

I had at least one fancy stat that ran off Line with battery backup. Most
I've seen have a two way mechanical relay of some sort except the one that
ran on line I think. The digital ones have better accuracy with less temp
swing, and some have adjustable swings. I don't like the many that limit
cycles. By the way, I've had a few electronic types go bad. The mechanicals
are fairly reliable.

Greg

 

[Look165]

Mercury is prohibited because of environmental considerations.

Coould you precise the exact failure ?

Are the batteries in the right position ?

Did you check them with a meter ?

oldschool@tubes.com a écrit :

Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

 

On Tue, 7 Feb 2017 10:30:19 +0100, Look165 <look165@numericable.fr>
wrote:

Mercury is prohibited because of environmental considerations.

Yep, but there are lots of them still around. I know I have several of
them in my shop, if I can remember where I put them.

Coould you precise the exact failure ?

Are the batteries in the right position ?

Did you check them with a meter ?

I said it works now, since I replaced the batteries. No need to check
anything more. I am just wondering how this thing is switched.

By the way, I got a surprise. I found a manual for it on the Honeywell
site, and it IS a programmable 'stat. After having it for 4 years, I
found this out.... Not that it matters, I dont live on a schedule and I
dont like it cool when I'm sleeping. I just keep it at 68 deg all the
time. Once and awhile I may raise it a few degrees when I take a bath,
othrsise it stays the same.

When that guy installed it, all he told me was to use the up / down
arrows to set the desired temp, and press the HOLD button to keep it at
that temp. He never told me it was programmable or gave me a manual. But
now that I have the .PDF manual, I know what it does, and I did set the
correct time on it, which I never knew how to do, nor did I really care,
since I got plenty of clocks.

I still might replace it with an analog 'stat. Knowing this could cause
a loss of heat, just because of batteries, makes me uncomfortable.
Normally I am home in the winter, but like when I visited distant
relatives and stayed overnight for Christmas, I could have ended up with
frozen pipes if the battery failed. I dont like that idea....

---

oldschool@tubes.com a écrit :
Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

 

[pfjw@aol.com]

On Tuesday, February 7, 2017 at 12:12:28 PM UTC-5, et...@whidbey.com wrote:

The thermostat on my wall, a modern programmable type, also has
batteries and will not work without them. I don't understand why it
was not made to be powered by the furnace. It has a mechanical relay
inside, a reed relay I think. I can hear it when it switches on and
off. The 3 AAA batteries will power it for about 3 years.
Eric

As it applies to two-wire heat-only stats:

a) Imagine a programmable thermostat that wiped-and-reset at each power failure.
b) Furnace/boiler power can vary from micropile DC up to 24V AC.
c) Imagine an expensive device that could be spiked very easily from many sorts of causes.

Hence the need for batteries. All the on-board relay does is switch the AC to the unit. Furnace/Boiler power is entirely isolated from the thermostat power.

Not to mention the additional complications with 5 and 7 - wire heat-pump systems.

Peter Wieck
Melrose Park, PA

 

[pfjw@aol.com]

On Tuesday, February 7, 2017 at 12:40:26 PM UTC-5, pf...@aol.com wrote:

On Tuesday, February 7, 2017 at 12:12:28 PM UTC-5, et...@whidbey.com wrote:

The thermostat on my wall, a modern programmable type, also has
batteries and will not work without them. I don't understand why it
was not made to be powered by the furnace. It has a mechanical relay
inside, a reed relay I think. I can hear it when it switches on and
off. The 3 AAA batteries will power it for about 3 years.
Eric

As it applies to two-wire heat-only stats:

a) Imagine a programmable thermostat that wiped-and-reset at each power failure.
b) Furnace/boiler power can vary from micropile DC up to 24V AC.
c) Imagine an expensive device that could be spiked very easily from many sorts of causes.

Hence the need for batteries. All the on-board relay does is switch the AC to the unit. Furnace/Boiler power is entirely isolated from the thermostat power.

Not to mention the additional complications with 5 and 7 - wire heat-pump systems.

Peter Wieck
Melrose Park, PA

Small correction/clarification: The *micropile* (thermocouple driven by the pilot light) fires a *millivolt* gas valve. Usually, such devices operate at/around about 0.700 VDC or so. And the typical thermocouple puts out about 0.750 DC - or *just enough*.

 

On Monday, February 6, 2017 at 11:55:35 PM UTC-5, olds...@tubes.com wrote:

Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?
I'm guessing it could be any of those. mechanical relay or SS relay.

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

When my battery wore out years ago I wired in the Mercury relay that was
right next to the new electronic one. (previous home owner had not removed it.)
Like you it was at night and I just wanted heat.
I've never un-wired the Mercury switch. To me it seems like the perfect
technology for controlling a furnace.

George H.

 

[pfjw@aol.com]

On Tuesday, February 7, 2017 at 1:10:53 PM UTC-5, Ralph Mowery wrote:

If designed correctly the thermostat should hold all its memories during
a power giich or fail without depending on the batteries. It should
have some short back up battery or 'super capacitor' to keep the time
for a few hours or more.

I would want it powered by the furanace for the problems stated above.
Dead batteries and none in the house late at night or snowed in.

OK, I'll bite.

a) A micropile/millevolt system will not make enough power to operate an electronic programmable thermostat. Here in this region of very much older houses, many of which had central heat first installed in the 1930s, many of which are gravity-types (both air and radiators), such furnaces are probably 10% of the operating base. There are several on my block alone.
b) So, let's exclude that base and go with standard systems (2 - wire for now). Voltage can be anywhere from 12VAC to 24VAC. Ours is a 24V system (WM Ultra). Our neighbor is at 12V. So, at the very least the stat would have to convert from AC to DC, be smart enough to understand both 12 & 24V, keep a super-cap or rechargeable battery charged and so forth. Adding to the cost.
d) And, of course, we are still left with potential spiking issues - and it is not exactly as if one might unplug a thermostat in the case of nasty weather, storms, or potential power-outages.

These are $40 items unless one wishes to get a "Nest" or some similar device. With all these refinements, probably the cost would double.

As it happens, all this applies even more-so to heat-pump stats as large motors (and associated spiking) are involved, as well as many more variations in voltage and functionality assigned to those 5-7 wire stats - some of which are even proprietary by brand. Those, as it happens, are often mains-powered via the system, due to that complexity.

Writing for myself, our 'annualized battery program' includes smoke/heat/gas detectors, the thermostat, the flashlights (car and house) wireless mice and similar devices. Removed-still-good batteries go into things like my radios that take D or C batteries, remote-controls and other non-critical items until death. As we use only name-brand batteries with good warranties, and within their use-by dates, we have no worries about explosive outcomes, if any. We keep spares in the house for all critical applications (we once went 9 days without power after Sandy, so this is no small thing.

Does it cost us a few bucks per year? Do we contribute some nasty chemicals to the waste stream - Yes and probably. But there is peace-of-mind.

Peter Wieck
Melrose Park, PA

 

[pfjw@aol.com]

On Tuesday, February 7, 2017 at 3:51:44 PM UTC-5, olds...@tubes.com wrote:

On Tue, 7 Feb 2017 09:44:28 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com
wrote:

And the typical thermocouple puts out about 0.750 DC - or *just enough*.

Since tou mentioned thermocouples, I always wondered how they produce a
voltage. I've probably installed/replaced at least 10 of them, but never
understood how they work to create a voltage.....

They convert a small amount of the heat differential (hot end to cold end) into DC electricity. It is, mechanically, a bi-metallic strip inside the probe that converts the heat. They are quite elegant little devices, but, sadly, do not make much voltage (0.750V) at tiny, tiny currents. Just enough to trip a gas-valve. Certainly not enough to drive electronics on a thermostat.

 

[Jerry Peters]

oldschool@tubes.com wrote:

Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

My programmable thermostat has an auxiliary thermoswitch that will
turn on the furnace if the temperature goes below around 50F or so,
even if the battery fails or the thermostat itself fails. It's a
Robertshaw, about 20 or so years old. The thermoswitch is clearly
visible on the baseplate assembly. The thermostat itself is removable
from the baseplate so you don't have to stand at it when setting
the program.

I'd expect most decent battery powered thermostats to have a similiar
feature. Otherwise I could see lawsuits against the manufacterers or
the heating contractors when the battery fails and the pipes freeze
and cause extensive water damage.

 

On Mon, 06 Feb 2017 22:55:31 -0600, oldschool@tubes.com wrote:

Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").

The thermostat on my wall, a moden programmable type, also has
batteries and will not work without them. I don't understand why it
was not made to be powered by the furnace. It has a mechanical relay
inside, a reed relay I think. I can hear it when it switches on and
off. The 3 AAA batteries will power it for about 3 years.
Eric

 

[Ralph Mowery]

In article <386dbce2-9c67-45a1-8c4c-d385ea1a2f8c@googlegroups.com>,
pfjw@aol.com says...

a) Imagine a programmable thermostat that wiped-and-reset at each power failure.
b) Furnace/boiler power can vary from micropile DC up to 24V AC.
c) Imagine an expensive device that could be spiked very easily from many sorts of causes.

Hence the need for batteries. All the on-board relay does is switch the AC to the unit. Furnace/Boiler power is entirely isolated from the thermostat power.

Not to mention the additional complications with 5 and 7 - wire heat-pump systems.

Peter Wieck
Melrose Park, PA

If designed correctly the thermostat should hold all its memories during
a power giich or fail without depending on the batteries. It should
have some short back up battery or 'super capacitor' to keep the time
for a few hours or more.

I would want it powered by the furanace for the problems stated above.
Dead batteries and none in the house late at night or snowed in.

 

[Jeff Liebermann]

On Tue, 7 Feb 2017 09:40:24 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com>
wrote:

>As it applies to two-wire heat-only stats:

If a digital thermostat only had to run a furnace, life would be easy.
However, it's also used for heat pumps, staged HVAC, solar, radiant
(pump with pipes in the floors and walls), exhaust fans, etc. Note
the maze of wires and functions.
<https://xtronics.com/wiki/Thermostat_signals_and_wiring.html>
However, I think the real reason they run on battery is that batteries
are cheaper and smaller than a regulated, protected, and approved
power supply.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

On Tue, 7 Feb 2017 09:40:24 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com>
wrote:

On Tuesday, February 7, 2017 at 12:12:28 PM UTC-5, et...@whidbey.com wrote:

The thermostat on my wall, a modern programmable type, also has
batteries and will not work without them. I don't understand why it
was not made to be powered by the furnace. It has a mechanical relay
inside, a reed relay I think. I can hear it when it switches on and
off. The 3 AAA batteries will power it for about 3 years.
Eric

As it applies to two-wire heat-only stats:

a) Imagine a programmable thermostat that wiped-and-reset at each power failure.
b) Furnace/boiler power can vary from micropile DC up to 24V AC.
c) Imagine an expensive device that could be spiked very easily from many sorts of causes.

Hence the need for batteries. All the on-board relay does is switch the AC to the unit. Furnace/Boiler power is entirely isolated from the thermostat power.

Not to mention the additional complications with 5 and 7 - wire heat-pump systems.

Peter Wieck
Melrose Park, PA

If the thermostat only turned the furnace on and off I could see
battery power because there would be only two wires. But my thermostst
will and does control much more and there are several wires connected
to it. Not only that, my house is only 8 years old so the furnace is a
modern one. A memory backup battery I can understand but my thermostat
uses the barreries to power the complete thermostat, even powering
the mechanical relay. And anyway, either the memory is non-volatile or
there is a super capacitor on board because the memory is not lost
when the batteries are replaced.
Eric

 

On Tue, 07 Feb 2017 11:11:17 -0800, etpm@whidbey.com wrote:

If the thermostat only turned the furnace on and off I could see
battery power because there would be only two wires. But my thermostst
will and does control much more and there are several wires connected
to it. Not only that, my house is only 8 years old so the furnace is a
modern one. A memory backup battery I can understand but my thermostat
uses the barreries to power the complete thermostat, even powering
the mechanical relay. And anyway, either the memory is non-volatile or
there is a super capacitor on board because the memory is not lost
when the batteries are replaced.
Eric

When I changed the batteries for a second time yesterday, the digital
numbers were still there after I removed the batteries, but by the time
I opened the batt package they faded away.

I just have 2 wires. I had a new furnace installed this last Novemnber.
It still only has 2 wires. The guy never even touched the thermostat.

 

On Tue, 07 Feb 2017 09:12:34 -0800, etpm@whidbey.com wrote:

The thermostat on my wall, a moden programmable type, also has
batteries and will not work without them. I don't understand why it
was not made to be powered by the furnace. It has a mechanical relay
inside, a reed relay I think. I can hear it when it switches on and
off. The 3 AAA batteries will power it for about 3 years.
Eric

My two AAA batteries lasted 4 years and 3 months. I checked my paperwork
for when that 'stat was installed. Like I said, I never knew it even had
batteries or I would have changed them long ago.

 

On Tue, 7 Feb 2017 09:44:28 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com>
wrote:

>And the typical thermocouple puts out about 0.750 DC - or *just enough*.

Since tou mentioned thermocouples, I always wondered how they produce a
voltage. I've probably installed/replaced at least 10 of them, but never
understood how they work to create a voltage.....

 

[Michael Black]

On Tue, 7 Feb 2017, Jeff Liebermann wrote:

On Tue, 7 Feb 2017 09:40:24 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com
wrote:

As it applies to two-wire heat-only stats:

If a digital thermostat only had to run a furnace, life would be easy.
However, it's also used for heat pumps, staged HVAC, solar, radiant
(pump with pipes in the floors and walls), exhaust fans, etc. Note
the maze of wires and functions.
https://xtronics.com/wiki/Thermostat_signals_and_wiring.html
However, I think the real reason they run on battery is that batteries
are cheaper and smaller than a regulated, protected, and approved
power supply.

And unless they can get power from the control line to the furnace, it may
not be convenient to have a power supply. There are suggestions on where
to place the thermostat, and there may not be a convenient outlet just
below.

Michael

 

[Wayne Chirnside]

On Tue, 07 Feb 2017 03:58:36 -0600, oldschool wrote:

On Tue, 7 Feb 2017 10:30:19 +0100, Look165 <look165@numericable.fr
wrote:

Mercury is prohibited because of environmental considerations.

Yep, but there are lots of them still around. I know I have several of
them in my shop, if I can remember where I put them.

Coould you precise the exact failure ?

Are the batteries in the right position ?

Did you check them with a meter ?

I said it works now, since I replaced the batteries. No need to check
anything more. I am just wondering how this thing is switched.

By the way, I got a surprise. I found a manual for it on the Honeywell
site, and it IS a programmable 'stat. After having it for 4 years, I
found this out.... Not that it matters, I dont live on a schedule and I
dont like it cool when I'm sleeping. I just keep it at 68 deg all the
time. Once and awhile I may raise it a few degrees when I take a bath,
othrsise it stays the same.

When that guy installed it, all he told me was to use the up / down
arrows to set the desired temp, and press the HOLD button to keep it at
that temp. He never told me it was programmable or gave me a manual. But
now that I have the .PDF manual, I know what it does, and I did set the
correct time on it, which I never knew how to do, nor did I really care,
since I got plenty of clocks.

I still might replace it with an analog 'stat. Knowing this could cause
a loss of heat, just because of batteries, makes me uncomfortable.
Normally I am home in the winter, but like when I visited distant
relatives and stayed overnight for Christmas, I could have ended up with
frozen pipes if the battery failed. I dont like that idea....

---

oldschool@tubes.com a ĂŠcrit :
Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button
and the furnace did not turn on. I popped it off the wall and found
two AAA batteries. Of course this is 3am and there are no stores open
closer than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had
some furnace work done. I never knew it even had batteries, thinking
it was powered from the transformer on the furnace. It's NOT a
programmable t-stat, so aside from the digital readout, it's nothing
more than a plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I
hardly ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round
Honeywell ones with the mercury switch. They lasted decades and never
needed any repairs. So much for so called "improved technology").

Have the same here.
24 volt transformer on the AC -furnace and the units either pass the 24
volt current or not to switch the relay on the furnace _ Ac depending on
whether it's set on heat or cool.
Relay on the AC - Furnace has a evaporator fan sequencer to keep the fan
running for some minutes after heat or cool and prevent the AC compressor
from restarting so soon as to damage the compressor.

 

On Tue, 7 Feb 2017 21:29:16 -0000 (UTC), Jerry Peters
<jerry@example.invalid> wrote:

oldschool@tubes.com wrote:
Last night it began getting cold in my house. I went to the thermostat
and found out the Digital readout was blank. I pushed the UP button and
the furnace did not turn on. I popped it off the wall and found two AAA
batteries. Of course this is 3am and there are no stores open closer
than a 25 mile drive (I live in a rural area).

Then I remembred that my small LED flashlite has AAA batteries, so I
used those. The thermostat had alkaline batts, but the ones in the
flashlite were carbon-zinc, but they worked fine and I had heat again.

That thermostat was installed in here about 4 years ago, when I had some
furnace work done. I never knew it even had batteries, thinking it was
powered from the transformer on the furnace. It's NOT a programmable
t-stat, so aside from the digital readout, it's nothing more than a
plain thermostat.

I never knew those thermostats would completely fail to start the
furnace when the batteries went dead. Apparently so.

Now that I know it has batteries, I will replace them yearly, but I'm
actually thinking about replacing that t-stat with a standard analog
one. The last thing I need is for the pipes to freeze because the
batteries failed, when I was not at home. (Even new batteries can be
bad). There is no advantage to having a digital readout for me. I hardly
ever change the temperture anyhow.

My question is how does this sort of thermostat switch the furnace on
and off? Is it a semiconductor type of switch or what?

Yea, I did buy some new alkaline batteries today and put those in this
thermostat.

(I still think the best Thermostats made were those old round Honeywell
ones with the mercury switch. They lasted decades and never needed any
repairs. So much for so called "improved technology").


My programmable thermostat has an auxiliary thermoswitch that will
turn on the furnace if the temperature goes below around 50F or so,
even if the battery fails or the thermostat itself fails. It's a
Robertshaw, about 20 or so years old. The thermoswitch is clearly
visible on the baseplate assembly. The thermostat itself is removable
from the baseplate so you don't have to stand at it when setting
the program.

I'd expect most decent battery powered thermostats to have a similiar
feature. Otherwise I could see lawsuits against the manufacterers or
the heating contractors when the battery fails and the pipes freeze
and cause extensive water damage.

I'm gonna check mine and see if it has the extra thermoswitch. If not
I should wire one in. It is a great idea. A friend of mine had his
house freeze while he was gone due to some sort of malfunction and a
pipe burst inside the house. Water ran for over a week before the
problem was discovered. The leak was quite small and still damaged a
lot of stuff.
Eric