Ready for a new refrigerator

[capran]

No, you can't just ditch the control module. It handles the thermostat, etc. And the Danfoss compressors don't run on DC, I'm almost positive they run on low voltage 3 phase AC (so the controller is doing power conversion regardless of input).

I'm not sure I am understanding that comment, about the compressor running only on AC. I have a 2008 Helmsman, and had a fridge guy out last year. At that point, my Norcold only seemed to work on DC. Upon checking, he said it was not hooked up for auto AC, but there was a plug inside that we bought a small cord to that allows for use when on shore power, just requires me to plug it in to an outlet nearby.

 

[rslifkin]

I'm not sure I am understanding that comment, about the compressor running only on AC. I have a 2008 Helmsman, and had a fridge guy out last year. At that point, my Norcold only seemed to work on DC. Upon checking, he said it was not hooked up for auto AC, but there was a plug inside that we bought a small cord to that allows for use when on shore power, just requires me to plug it in to an outlet nearby.

The control module takes either 12/24v DC or 120v AC in (optional, some modules are DC only). But the control module contains an inverter that drives the compressor motor with low voltage 3 phase AC regardless of what the input power source is.

 

[capran]

The control module takes either 12/24v DC or 120v AC in (optional, some modules are DC only). But the control module contains an inverter that drives the compressor motor with low voltage 3 phase AC regardless of what the input power source is.

Thanks. So you're saying the control module has an internal inverter so the it operates even on DC? Sure is hard to understand, but I understand very little.

 

[rslifkin]

Thanks. So you're saying the control module has an internal inverter so the it operates even on DC? Sure is hard to understand, but I understand very little.

Yup, that's exactly it. That's how they achieve the variable speed control of the compressor. And 3 phase AC motors are also efficient, so the conversion losses are likely out-weighed by the gains from a more efficient motor and the ability to control compressor speed.