Heater Thermostat upgrade

[mkosina]

Just a note on a good cabin thermostat find - dropped in the ICM controls SC1600L to replace the original equipment (?) Honeywell (second pic) which was starting to physically fall apart (loose battery cover, etc)

Actually turned out to be a bit of a challenge to find battery operated unit that is heat-only by design (I.e. no unused fan or a/c mode controls to fumble with accidentally in the dark).This one is dead simple, three buttons with big numbers and a backlight. Also couple settings for the temp swing and minimum duty cycle, haven't tried adjusting yet. There is also a vertical form factor version, the SC1600VL, both advertised as USA-made.

Any other good ones out there?

[N147JK]

I went through the exact same thing - wanted a simple, heat-only thermostat. I ended up with an Emerson 1E78-140. Works alright.. only thing is the buttons are too soft and a little finicky. The backlight is great, but sometimes the backlight seems to "deprogram" itself - have to go back into the menus and turn it back on. But, it is better than the original and it was cheap (like me!). And, almost forgot, the size and shape was the right fit.

[posplayr]

Originally Posted by N147JK

I went through the exact same thing - wanted a simple, heat-only thermostat. I ended up with an Emerson 1E78-140. Works alright.. only thing is the buttons are too soft and a little finicky. The backlight is great, but sometimes the backlight seems to "deprogram" itself - have to go back into the menus and turn it back on. But, it is better than the original and it was cheap (like me!). And, almost forgot, the size and shape was the right fit.

So in reading the specs for both of these thermostats, they both (IIRC) control 24VAC using battery power but I presume the heaters you are controlling are 12V. So that implies there is a DC mechanical relay. Is that correct?


Emerson 1E78-140

• ELECTRICAL DATA Electrical Rating
• 0 to 30 VAC 50/60 Hz. or D.C.
• 0.05 to 1.0 Amps (Load per terminal)
• 1.5 Amps Maximum Total Load (All terminals combined)

https://thermostat.guide/emerson/eme...specifications

SC1600L
NON PROGRAMMABLE THERMOSTATS, THERMOSTATS
Electrical rating: • Millivolt to 30 VAC/VDC
• DC Power: 3.0 VDC (2 “AA” alkaline batteries included)
• 1 amp maximum per terminal
• 2 amp maximum total load
https://www.icmcontrols.com/wp-conte...eLIAF005-2.pdf

I'm an EE but the manuals are not very specific on this.

[N147JK]

Originally Posted by posplayr

So in reading the specs for both of these thermostats, they both (IIRC) control 24VAC using battery power but I presume the heaters you are controlling are 12V. So that implies there is a DC mechanical relay. Is that correct?

The entire heating system is 12V - gas solenoids, blower, thermostat. The documentation includes this as an appropriate use case. Works perfectly in our van.

[posplayr]

Originally Posted by N147JK

The entire heating system is 12V - gas solenoids, blower, thermostat. The documentation includes this as an appropriate use case. Works perfectly in our van.

Thanks, I just wanted to confirm it was 12V which I will assume means there is a mechanical relay.

[N147JK]

Originally Posted by posplayr

Thanks, I just wanted to confirm it was 12V which I will assume means there is a mechanical relay.

Hmmmm I'm not following you. A mechanical relay where? For what purpose?

[posplayr]

Originally Posted by N147JK

Hmmmm I'm not following you. A mechanical relay where? For what purpose?

When you see the spec for the load rating 30 VAC/DC it implies that a mechanical relay is used to control the load.

In the picture below the solenoid uses a DC voltage to generate enough current in the coil to close the contacts (i.e. electromagnet). However, the load circuit can be completely independent of the solenoid control and can be higher or lower voltage and AC or DC. The mechanical contacts don't care.

I had found an HVAC website where someone was looking for recommendations for a thermostat. The locals were giving him a bit of a tough time. They told him to buy a relay with a mechanical relay (one that clicks). Well, this is not easy buying online and the thread went on and on with how to tell if the thermostat had a mechanical relay.

There are also solid state relays and this site does a comparison.

https://www.ia.omron.com/support/gui...roduction.html


Not wanting to make this a science project I just wanted to confirm that the van application was for a 12VDC load despite the thermostats being typically used for 24 VAC loads.

It sometimes confuses engineers when you specify a voltage but not if it is AC or DC (i.e. VAC or VDC)


You will notice in your table some of the use cases are for 24 volts and the one you pointed out is 12VDC. So what is the 24V? VAC or VDC? It is kind of a guessing game.

[mkosina]

Both the OEM Honeywell RTH110B (I assume - datasheet was embedded in the 2008 Fresno SMB owners manual) ) and the SC1600L I replaced it with certainly mechanically "click" on and off.

[posplayr]

Originally Posted by mkosina

Both the OEM Honeywell RTH110B (I assume - datasheet was embedded in the 2008 Fresno SMB owners manual) ) and the SC1600L I replaced it with certainly mechanically "click" on and off.

Thanks .........

[porschedpm]

This is what I went with. I only needed one to operate the furnace but liked the modern look of it. Runs on AA batteries

https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1