Truck Fridge Digital Thermostat

[kourt]

The Isotherm Smart Energy Control thermostat does function in "auto" mode with LiFePO4 batteries. I have experienced it many times.

When the thermostat detects a DC supply voltage is above a certain point (set by a dip switch to either 13.2 or 12.7 VDC) it will go into "cold storing modality" on the assumption that an alternator or shore power is supplying surplus current to allow increased compressor demand.

Cold Storing Modality essentially runs the compressor at a higher speed, "banking cold" in the refrigerator contents, and then once a certain low temperature threshold is achieved (set by a dip switch), it will short-cycle the compressor at high speed to maintain that low temperature. The fridge needs to be relatively full for the greatest effect.

In my LiFePO4 experience, this behavior happens continuously when set to "auto" mode, usually because my 200AH LiFePO4 bank (plus solar) seldom ever drops below 13.2 volts. When it does drop below 13.2v, the fridge behaves like normal.

My wife has commented that she really dislikes the higher speed compressor operation when she is sleeping, and I've noticed it, too. But I've also noticed that the higher compressor speed produces less RF noise, which has been a great boon to my amateur radio operations in the van.

I like having this option to switch between "auto" mode and the conventional numbered settings on the adjusting potentiometer in the fridge cabinet. The Inkbird does not deliver anything quite like this in terms of flexibility or performance.

For this Isotherm to really live up to its "energy conservation" promise with LiFePO4 batteries, it would need a dip switch adjustable threshold that is higher than 13.2 VDC. I think 13.6 VDC would be a better set up, since my alternator throws 13.8 VDC at the house battery system when the engine is running.

This makes me wonder if the Isotherm is adjustable... hmmm. More later!

Summary: the Isotherm does cause the TruckFridge to behave differently, with significant increases in compressor speed, and additional compensation behaviors when thresholds are met, plus the option to get out of "auto" mode and run the fridge as originally configured, on a slower compressor speed.

Nice discussion about fridge details. Thank you all.

kourt

[owokie]

[kourt]

I am not being thorough enough in describing how it works, though I agree that relying on the thermostat to operate in consideration of LiFePO4 voltage in this context is unrealistic. One would have to monitor that manually.

The Isotherm also has a programmable low voltage limiter, so at a certain threshold (9.6 VDC or 10.8 VDC) the thermostat stops the compressor. The OEM truckfridge thermostat and the Inkbird both also do this, so that's nothing new.

If you're curious about the cold storing modality of the Isotherm, read the manual, especially page 3, but here's an excerpt:

[owokie]

[DeLvxe]

Maybe something else is going on with mine, but Auto mode resulted in the fridge cycling on and off repeatedly. Like 1 min on and 1 min off for several cycles. I set the dip switch for the higher VDC but didn't get the results I wanted.

I talked with Webasto when I installed in May pointed me to the Intelligent Control thing for LIFEPO4.

I was bummed at first, but have gotten over it. Recently increased my battery from 50Ah to 120Ah so am less concerned about squeezing out efficiency. I DO think the thermostat is better than the TF and is in a better location.
_________________
1991 manual camper with EJ25

[kourt]

Is this the Isotherm Intelligent Temperature Control (ITC) product you're referring to? Just want to be sure.

https://www.defender.com/product.jsp?id=4161337

kourt

[DeLvxe]

[izzydog]

What requirements does the Isotherm need to allow that ITC to work? My Isotherm is at least 6 years old. That Defender page says you can "retrofit to Cruise Elegance" units and I know mine is older than that series. Is there a wiring board picture or drawing for the units that are compatible with the ITC?

[kourt]

Link


The Isotherm ITC requires Secop version 101N0510 (DC only) or 101N0212 (AC/DC), which is the control board used in the TF49 and others of that size. The version will be printed on the wire termination face on the back of the fridge (see the photo on Page 1 of this thread for an example).

Reading the manual for this thermostat, I can see that the "Full-speed/overcooling threshold" voltage has increased to 13.7 VDC which is great. It will also vary the compressor speed between 2500 and 3500 RPM while in the 12.6 to 13.8 VDC range. It also has the ability to report error conditions for diagnostic purposes--also great.

I like the looks of this thermostat, though I'm in the same boat as DeLvxe--I have so much house battery capacity right now (200aH LiFePO4) that I don't really care that much.

Still, I just camped for five cloudy days on a beach, and on day five my voltage was down to 12.8 VDC, mostly due to the fridge. I'm interested in efficiency in the fridge.

I'll be looking for a bargain purchase of this thermostat soon. Search terms "isotherm SED00036DA".

Here we are! Another purchase for the van!

kourt

[izzydog]

Thanks, Kourt. I'll yank my fridge one of these days and see what I have...

[fxr]

[DigiMatrix]

[kourt]

Yep, I think you're right.

The new Isotherm is on its way. Couldn't resist a new project. And I have to admit that the refrigerator is a big part of why I love my van.

kourt

[Sodo]

[kourt]

From my admittedly light research, the Inkbird is really useful for folks who want to control a crock pot within a certain temperature range. Sous vide type of stuff. It's great for that.

It's also great for brewing beer and controlling mash temp and wort cooling. You use it to modify a refrigerator to get a precise temperature and feedback with a probe. Really nice.

Knowing this, it's not a stretch to see how it would be great for a RV refrigerator. You can install the Inkbird and get the same binary function of any standard refrigerator thermostat, but with the added benefit of an actual temperature range, programmable offsets ("always add 6 degrees to the actual temp to compensate for error"), voltage limits, and other things. It's cheap and has a nice red numerical display panel. Pretty good value.

But compared to the special features of the Isotherm thermostats, it's not even in the same realm. The Isotherm thermostats--the older "Smart Energy Controller" I have installed now or the newer "Intelligent Temperature Control" model I have on order-- do special things. Yes, they can certainly function in the "1 thru 7" arbitrary levels of cooling that the original TruckFridge thermostat did, but they can also be switched to do the special "run the compressor faster based on voltage and temperature feedback" mode. The ability to switch between those two modes is what I find valuable. You probably already know all of this.

I'll followup with this thread once I get my ITC installed.

kourt

[fxr]

I'd love to have the Isotherm - but financial constraints apply, I'm afraid. I use the Inkbird set to keep 41°F with a 2° window for our TF65, no other settings played with. We're vegan, so no dairy or meat to worry about, and the important thing for us is NOT to freeze the leafy greens etc that inhabit the fridge along with that day's beer supplies (which take up quite a bit of room for the two of us...).

We replaced the otherwise OK (apart from space) Dometic just because it proved impossible to stop it freezing (and wrecking) food overnight whenever the thermostat was set for daytime use. It was the discussions of the Inkbird that made us decide the TF was worth stretching the budget to acquire.
_________________
Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300

[kourt]

Coming soon: followups of the Isotherm ITC thermostat install.

Warning! Vanagon "purists" beware! Galley faceplate carnage below!

kourt

Preview of coming attractions:

[dobryan]

_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[kourt]

The Isotherm ITC Digital Display Intelligent Temperature Control refrigerator thermostat is now installed.

See photos above for how I hacked up the galley faceplate to accept the control/display for this item. Why did I do that? Both indicators on that display are relative (instead of absolute) and have been replaced by other meters. I long ago replaced the house battery galley voltmeter with the Blue Sea 8248 meter:

...and don't get me started on the water tank meter. The sensors in the tank lid are finicky. I'm in the process of replacing it with a Blue Sea M2 tank meter that uses an ultrasonic sender.

So the OEM galley sensors, while evocative of the original Westy camper aesthetic, were truly useless. I've lost no sleep since ripping the panel out.

Here's what we have now:

I had some leftover Warm Gray paint and clearcoat from my Truckfridge painting project, so I used that to paint this controller faceplate a matching gray (it was originally white).

There was one catch: I didn't read the ITC thermostat requirements carefully enough. The ITC requires the newest DC compressor controller, model 101N0212. I had model 101N0210 in my van. I found a guy on eBay who sells these for about $140. That was a surprise expense. These newer controllers add the "compressor soft start" feature that is missing from the older 101N0210 version.

The result, expensive as it was, works well. The entire refrigerator circuit is controlled from the control panel now. It displays the sensed temperature in the fridge cabinet and can be adjusted for overcooling (which runs the compressor at a higher RPM) when a surplus of voltage is available--like when the alternator is running, or on shore power, or in sunny solar applications. There's also some temperature compensation settings in case the fridge sensor needs to be offset from a known calibrated temperature.

The Inkbird does almost all these things for a lot less money.

In summary, the Inkbird is a more cost effective way to come near this solution, but it lacks the overcooling/high compressor RPM capacity, and does not have a compressor soft start feature. No surprise.

Aside from the engine, a lot of the infrastructure I've added (solar, LiFePO4 batteries, wiring) is for running the refrigerator, so making a big spend on premium refrigerator function is nothing new for me.

kourt

[Sodo]

OK so here's the INKBIRD method by Samba member letsrig
I like that it accommodates 120VAC operation.
I haven't done this yet.
My system is still (crudely) cutting fridge input power, thus my interior light only lights when the fridge is 'warmer' than the INKBIRD setpoint.
I did this because its simple
I don't have the electrical rig skills that member letsrig has.👍🏽

I made a diagram with letsrig's post - to put on my phone so I can take it out to the van.👍🏽
letsrig can you LMK if I got this correct?
If any mistakes I'll try to delete the error pic and re-post a corrected pic.
If anyone 'repeats' my (preliminary?) pic in their "quote", it prevents me from deleting the wrong pic on TheSamba (please don't quote this preliminary schematic !! ).
So I hope you can validate it ASAP before someone makes it permanent.
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb