Isotherm AC, DC or AC/DC

fwunder

Trying to get a handle of wiring logic - 2023 TAB 400 BD.

I assume the Isotherm Cruise 130 Elegance is always running on 12v DC?

So what feeds it in these different configurations:

CONVERTER 15 amp breaker OFF, REFRIGERATOR 20 amp breaker ON

CONVERTER 15 amp breaker ON, REFRIGERATOR 20 amp breaker OFF

With both breakers off seems obvious it's running off battery. I just don't understand what the 15 amp REFRIGERATOR breaker is doing?

Thanks!

elbolillo

Here is what the Tab manual says: The refrigerator is wired to 12V DC only. When you are connected to shore power, the power center will convert the 120V current to 12V DC to provide power to the refrigerator.

Grumpy_G

The Isotherm fridges can run on 12/24V DC or 120V AC. In a RV the 120V mode seems redundant because RVs typically have a converter that can supply 12V when plugged into shore power. There may be other applications where running 12V is not always available, the fridges are marketed for marine applications but I'm not familiar with how boats deal with shore power vs. out on the water. 

AnOldUR

Grumpy_G said:

The Isotherm fridges can run on 12/24V DC or 120V AC.

Is it a 12V or 120V compressor? Is there a converter built into the fridge that converts the 120V to 12V if the source is 120V?

fwunder

elbolillo said:

Here is what the Tab manual says: The refrigerator is wired to 12V DC only. When you are connected to shore power, the power center will convert the 120V current to 12V DC to provide power to the refrigerator.

I believe this is correct. I did some tests today and what I can tell by watching Victron Smart Shunt, the breaker labeled REFRIGERATOR makes no difference. I think it is just a leftover label from three-way fridges. So, it's either 12 volt from battery or 12 volt from converter. Makes sense.

Grumpy_G

AnOldUR said:

Grumpy_G said:

The Isotherm fridges can run on 12/24V DC or 120V AC.

Is it a 12V or 120V compressor? Is there a converter built into the fridge that converts the 120V to 12V if the source is 120V?

Turns out the manufacturer makes two versions, one is DC only and the other is AC and DC operation. The latter ones contain a simple power supply to convert AC to 12V dc. Why that one exists I have no idea. 

I retract my previous post, apparently the labeling also covers three-way fridges  which were (and maybe still are) an option on 400s. 

Mickerly

The breaker in question is marked ALDE/Refrigerator. Probably using up old stock stickers. I'm betting the refrigerator is wired 12v DC as the Norcold AC/DC was. The Isotherm and the Norcold NR751 have the same 12v Danfoss compressor. The 110v AC input on the Norcold is designed for different installations, not switching. There is an internal inverter, changing 110v AC to 12v DC. In either installation, the refrigerator is 12v DC. Wiring it directly to 12v uses less power. This also allows changing power supplies without issue. No matter how the power enters the trailer, the refrigerator is always 12v.

elbolillo

This is our distribution panel. Our’s reads a bit differently.

fwunder

That makes more sense. Thanks.

otr_320

Our '23 320 came from the factory with an Isotherm 65.  According to the data tag on the interior of the unit it is capable of running on 12/24vdc or 100-240vac, 50/60Hz.  However, there's only 12vdc power connected to a terminal board on the rear of the unit---the frig has no other electrical connections.  The pos side is fused via a 15a ATO fuse located on the back of the frig itself.  It is fused again with a 20a ATO fuse at the WFCO DC power center.  There's an unused, recessed male plug (labeled 100-240vac 50-60Hz) located on the top rear of the unit.