Thermostat

Olden

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Feb 16, 2021, 3:55:18 PM2/16/21

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Best to ask here or ?

My gas furnace is a Holly.
It has an old mercury two wire thermostat.

I want to change the thermostat so that I can set the same two
temperature ranges, day / night, for every day.

I do not understand thermostats.

The local store does not know how to advise me.

Thermostat suggestions please and maybe a little tutorial.

Sjouke Burry

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Feb 16, 2021, 6:41:24 PM2/16/21

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It would be nice to know the open voltage and the switch current when
closed.
Around 24 volts any ordinary programmable thermostat unit might do.

amdx

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Feb 16, 2021, 7:03:04 PM2/16/21

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The easy way is to have two thermostat and a switch. Have one adjusted
for day and the other for night and

day/night switch to go between them. It gets more complicated if you
have an air conditioner to deal with.

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danny burstein

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Feb 16, 2021, 9:20:02 PM2/16/21

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In <602c5820$0$27446$e4fe...@textnews.kpn.nl> Sjouke Burry <burrynu...@ppllaanneett.nnll> writes:

>On 16.02.21 21:55, Olden wrote:
>> Best to ask here or ?
>>
>> My gas furnace is a Holly.
>> It has an old mercury two wire thermostat.
>>
>> I want to change the thermostat so that I can set the same two
>> temperature ranges, day / night, for every day.
>>
>> I do not understand thermostats.
>>
>> The local store does not know how to advise me.

There are (or at least were...) plenty of thermostats
with multiple settings that followed the time of
day and used a battery to operate the clock, hence
could be hooked up to a basic two-wire control system
and not worry about wiring for power.

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Evgeniy

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Feb 16, 2021, 11:12:39 PM2/16/21

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Hello, Olden!

On Tue, 16 Feb 2021 12:55:07 -0800
Olden <Ol...@Olden.com> wrote:

> Best to ask here or ?
>
> My gas furnace is a Holly.
> It has an old mercury two wire thermostat.
>
> I want to change the thermostat so that I can set the same two
> temperature ranges, day / night, for every day.
>

Just an idea: you can use two thermostats and mechanical 24 hour timer to switch them. Something like that: https://www.theben.de/en/syn-161-d-1610011 Timers can be different, with different outputs (output relay type/voltage/current, etc), this is just an example. If you do not need precision time keeping on power loss, it's preferable to use a timer without battery (no potential battery leaking out). I do not know your schematics and may be any safety limits, so it's just an idea.

------
With Best Regards,
Evgeniy

Olden

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Feb 18, 2021, 7:19:01 PM2/18/21

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I need to buy on-line.
Any model numbers ?
What terminology do I look for ?

Please help.

whit3rd

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Feb 19, 2021, 1:43:19 AM2/19/21

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On Thursday, February 18, 2021 at 4:19:01 PM UTC-8, Olden wrote:
> I need to buy on-line.
> Any model numbers ?
> What terminology do I look for ?

Almost any 'smart' thermostat can do a daily fallback, but this
does mean it's a display-and-buttons-and-clock elaborate item.
Honeywell is a big manufacturer, their web site should give you
some ideas
<https://honeywellstore.com/store/products/wi-fi-7-day-programmable-thermostat-honeywell-rth6580wf.htm>

Look at a few, and maybe check out the manuals online.

Dan Purgert

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Feb 19, 2021, 7:58:43 AM2/19/21

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The major thing you need to know is the control voltage - that SHOULD be
stamped / molded into your existing thermostat. After that, it's a
quick wire-for-wire swap -- check the existing, it's probably labeled as
"W" / "R" (for "White" and "Red" wire, respectively). Connect those
wires coming out of the wall to the same terminals of the new thermostat
(ignore Y/B/etc, as those connections are for cooling / multi-stage
heat / etc.).

Then program the thing for whatever temperatures you want.
>

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