Small Digital Thermostat

[N147JK]

Looking to replace my original 20+ year old Suburban thermostat with a digital one. All I've found are thermostats also meant for home use, some of which will work on 12V, or a few that do too much and/or are very costly. Most are also too large in size for the limited wall space in my tiny camper van.

Does anyone know of a simple (heat-only) inexpensive digital thermostat for RV use that is also very small in size?

Thank You in advance.

[ks@yvr]

This one should work.
https://www.globalindustrial.ca/p/no...hoCzkMQAvD_BwE

Or this one.

https://www.amazon.com/Emerson-1E78-...11&s=hi&sr=1-2

[N147JK]

Originally Posted by ks@yvr

This one should work.
https://www.globalindustrial.ca/p/no...hoCzkMQAvD_BwE

Or this one.

https://www.amazon.com/Emerson-1E78-...11&s=hi&sr=1-2

Thank you for these suggestions. The first one is an excellent compact size, but says it's for 24V systems. I wonder if these will work in our 12V vans? I'm assuming they will not.

[avanti]

Originally Posted by N147JK

Thank you for these suggestions. The first one is an excellent compact size, but says it's for 24V systems. I wonder if these will work in our 12V vans? I'm assuming they will not.

As long as the logic is battery-powered, it should work fine.

[ks@yvr]

They will work fine with 12V just maximum they can handle is 24V. Just a thermostatic on/off switch basically.

[hbn7hj]

Home Depot and Lowes have them. They are battery powered. Honeywell is one brand.

[revcon372]

Had an older Xplorer with cheap original that was replaced with a battery powered thermostat looked great and worked like a charm It was mounted with its face looking forward An emergency stop caused the batteries to launch themselves and the cover forward Easy fix with a screw but not something I anticipated

[bertible]

Most but not all home thermostats have a 24 V AC adapter (not DC) at the furnace, that sends 24V to the thermostat. RV systems can use either a microvolt system with a simple tilting mercury switch thermostat, or a 12V DC connection to drive the digital display and electronics. While you need to confirm if your RV has a microvolt system, I would tend to search for a 12V DC, or a AA battery powered thermostat, rather than 24 AC. You can't mix DC with AC, or you'll fry the unit so if you want to use a 24AC thermostat you would probably need to power it through two devices, a 12V to 110VAC inverter, then a from 110V to 24AC adapter available at any big box building store.

I suspect since your unit is an older one it does not have an electronic ignition furnace, so it has a standing pilot light (the little flame you have to start when you want to use the furnace)? For your background, a millivolt system will usually have standing pilot light the heat from the flame heats up a little metal cylinder called a thermopile that produces a low voltage (around 1 volt or less) when heated. That small voltage drives the gas on/off valve that operates your furnace, and a mercury thermostat, but not enough to drive a thermostat with electronics.

[markoch]

Analog is better. Just get a new suburban tstat for $15 on Amazon.

[avanti]

Originally Posted by bertible

Most but not all home thermostats have a 24 V AC adapter (not DC) at the furnace, that sends 24V to the thermostat.

As stated above, a great many low-cost electronic residential t-stats have their internal logic powered via internal, replaceable batteries, with a dry-contact relay as the interface to the furnace. The relay doesn't care whether it is switching 12vdc or 24vdc. It will work fine in an RV.

This is not a complicated issue. If the t-stat has such a battery (and many do), it will very likely work fine, and it will likely be more robust than a mechanical unit.

[GallenH]

I just replaced my original thermostat with a Honeywell. It uses the same 2-wire connection as the original. Power comes from 2 batteries in the unit. Worked great in Utah at 22 degree nights. No issues. I use rechargeable batteries and plan to charge them before trips....or carry some spares. Would recommend. Easy install. Only a slight size difference.

[ChicagoTom]

Why replace it? If it's broke, replace it with the same. This is a very small space, and believe it or not, "too accurate" can cause issues, like the furnace shutting off too soon. (Meaning on off way more than it needs to be). JMO, ex HVAC Tech You don't need a fancy T-Stat in a Class B RV... KISS!

[jakegw2]

I replaced my Suburban thermostat with this one:

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

I wired the two wires from the original thermostat to the "RC" and "W" connections on the Emerson. When the thermostat triggers heat these two connections go from open to close (e.g. there is continuity between them when the thermostat turns the heat on, and no continuity when it is off). The thermostat is voltage agnostic, since all it does is close the circuit it could be used for anything up to 24V.

The thermostat itself is powered by AA batteries.

This was an easy and very worthwhile upgrade. It handily resolved pretty much all arguments about the temperature setting and made for a more peaceful camper. It also works very well and is super-simple.

[GallenH]

Although many might think this unimportant....A digital thermostat does give you an good readout of both the current temp in the RV and the setpoint for the furnace to kick in. Some also allow an adjustment of the number of cycles/hr. I don't consider any of these features to be overkill but that's just my opinion.

[avanti]

Originally Posted by ChicagoTom

Why replace it? If it's broke, replace it with the same. This is a very small space, and believe it or not, "too accurate" can cause issues, like the furnace shutting off too soon. (Meaning on off way more than it needs to be). JMO, ex HVAC Tech You don't need a fancy T-Stat in a Class B RV... KISS!

Nobody has advocated for a "fancy" T-Stat. The digital stats that have been recommended are all very basic.

It is incorrect that a "too accurate" (actually "too precise") stat will affect running time. All stats have hysteresis built into them, which is what determines minimum run time. This is important, and is rather tricky to do with a mechanical stat, so it sometimes doesn't work very well. In a digital stat, it is very easy to do properly. Sometimes it is even programmable.

Mechanical stats meant for home use are not designed for the constant vibration found in a vehicle. Companies like Atwood make RV-specific stats which are more robust. The problem is that many of them make a loud "ping" every time they go on or off. This used to wake up DW every time the stat went on or off. This was the proximal reason I upgraded to a simple (and silent) electronic stat. It was a very worthwhile upgrade.

[booster]

Originally Posted by avanti

Nobody has advocated for a "fancy" T-Stat. The digital stats that have been recommended are all very basic.

It is incorrect that a "too accurate" (actually "too precise") stat will affect running time. All stats have hysteresis built into them, which is what determines minimum run time. This is important, and is rather tricky to do with a mechanical stat, so it sometimes doesn't work very well. In a digital stat, it is very easy to do properly. Sometimes it is even programmable.

Mechanical stats meant for home use are not designed for the constant vibration found in a vehicle. Companies like Atwood make RV-specific stats which are more robust. The problem is that many of them make a loud "ping" every time they go on or off. This used to wake up DW every time the stat went on or off. This was the proximal reason I upgraded to a simple (and silent) electronic stat. It was a very worthwhile upgrade.

I have gone over the thermostat questions in structures quite a few times the most recent about a year ago when I replaced the house heating and cooling system myself, and would tend, in general, with previous post about unwanted, energy wasting, frequent cycling.
Frequent cycling in many or our RV furnaces wastes a lot of electricity power and some propane power in the start/proofing/run process. The hot water systems are probably a bit better, but I don't know that.

AFAIK, the only benefit of frequent cycling is to maintain a more uniform room temperature, and the public has tended to wanting that feature. This is also one of the reasons for the multistage furnaces and AC, I think.
I have not found moderately priced, or cheap, thermostats that have adjustable hysteresis, or whatever name the call it like range, variation, whatever. You get what you get and most don't tell you what it is.
The higher end stuff used to, for the most part, have a settable two or three point hysteresis, but when I did ours this time many did not, including the top end Honeywell units that are very popular. The Honeywells were at +/-.5*F IIRC which makes for very fast cycling. I searched for a long time to find one with settable hysteresis and with the other things I wanted like intelligent recovery logic. I wound up getting an Emerson (which is really the old White Rodgers) commercial unit that had all I wanted. It also used manual switches which are much more intuitive, and hopefully reliable, than the small touchpad ones. DW hates touch pads so that is a plus. Her hate got reinforced big time with new HRV we put in with the new furnace and AC, as it had a horrible touch screen that required a bunch of scrolling to make simple changes, and we had multiple failures due to lockup that required 4 replacements in 18 months before I finally ripped all the electronics out of the unit and made a mechanical relay setup for it. Two switches, 4 LED indicators, mechanical humidistat plus a small thermostat for defrost function. We got more control with ours than than the touchscreen gave and it has run a full year without issue so far.
I think most of the settable thermostats have +/- .5/.75/1.0 degree or so settings of which we use .75* and get a 1.5* variation in room temp. Of the ones I could find out for, most of the digital, newer, version were on the tight side of .5*. We have the furnace and AC sized as low as we can and still cover the loads needed for the house in very hot or very cold weather, so we naturally have longer, more efficient, runs besides.
In our van the furnace is very large for the volume of the space so inherently runs less time, plus as soon as the fan goes off the airflow in the space changes so colder air can easily gravitate to the thermostat and retrigger it early. The original mechanical thermostat does seem to have a wide hysteresis and does a pretty good job of balancing comfort with run time. I haven't even looked to see if it has one of the old school "anticipaters" in it to make it adjustable hysteresis.
I am not sure what we will wind up with if our stat dies, but I will certainly want one with wide hysteresis.

[avanti]

There are plenty of electronic stats with adjustable hysteresis. Here's a random one:

https://www.amazon.com/LuxPRO-PSP511...2989732&sr=8-3

The problem is that they are hard to find since marketing people are afraid of the term "hysteresis", so they are often described via terms like "temperature differential", or "swing" or some such.

[booster]

Originally Posted by avanti

There are plenty of electronic stats with adjustable hysteresis. Here's a random one:

https://www.amazon.com/LuxPRO-PSP511...2989732&sr=8-3

The problem is that they are hard to find since marketing people are afraid of the term "hysteresis", so they are often described via terms like "temperature differential", or "swing" or some such.

I think LUX has a lot of early stuff still for sale, which certainly isn't a bad thing sometimes. I have had a couple of them in the shop that worked OK, but didn't hold up more than a few years. They also make the loud relay quick you don't like, as do many of the thermostats, including our new Emerson/White Rodgers.


I like the very first of the questions section of the link, complaining about the non adjustable ones and particularly, Honeywell.


We have one of the original Honeywell "automatic intelligent recovery" programmable stats, which was one of the very first available that way. It is probably over 20 years old and was still working fine, but was single stage and new furnace is two stage. It also was battery only, not furnace powered with backup batteries so we needed to keep up with remembering to change the batteries on time or it was no heat.


I don't think the furnace powered ones would work in an RV because the controls are normally 24v AC and 5v DC.