A ball peen hammer is OK, just*align a large flat blade screwdriver between it and the evaporator.Bendit wrote:I also discovered that the freezer (the real one) doesn't enjoy being defrosted with a ball-peen hammer.
I have the manual for my Nova Cool here on the desk.* The only difference between the 12V model and the 120V / 12V models according to the wiring Schematic is in the dual voltage unit it has*a*power supply box*that is in the system that the 12V from the battery goes into and 120V from the shore power goes into*then 12V exits to the compressor control module.** All test procedures refer to 12V only at the control module.Marin wrote:
Perhaps there are different kinds of AC/DC units. I have always been told that the AC/DC units are all AC, but they have inverter circuitry in them so they can run "on" DC. That's one of the things the repair shops who work on Norcold units--- or used to--- in the Seattle area told me they don't like about them. They apparently use a bizarro (their word) 20-volt or 24-volt AC motor.
Nearly all the modern units use the Danfoss BD brushless DC compressors. These are variable speed permanent magnet rotor machines that use a fairly sophisticated commutation system that is in many ways identical to the power controls on diesel electric propulsion.Marin wrote:Perhaps there are different kinds of AC/DC units. I have always been told that the AC/DC units are all AC, but they have inverter circuitry in them so they can run "on" DC. That's one of the things the repair shops who work on Norcold units--- or used to--- in the Seattle area told me they don't like about them. They apparently use a bizarro (their word) 20-volt or 24-volt AC motor.
Would this basic description apply to the Norcold AC/DC units too, or at least Norcolds from the late 90s?* It was the Norcold specifically that the service shops in this area didn't like because (among other reasons) of what they considered to be a very odd motor setup.RickB wrote:
The motors are DC, the voltage into the motor on the Danfoss units varies from 27 to 45 VDC to control speed. There are three wires going into the motor so that might be why some people think it is an AC motor. That and the fact that that little box on the side of the compressor contains both a converter to turn AC into DC, and an inverter to*generate the DC pulses that drive the motor.
RickB wrote:The motors are DC, the voltage into the motor on the Danfoss units varies from 27 to 45 VDC to control speed. There are three wires going into the motor so that might be why some people think it is an AC motor. That and the fact that that little box on the side of the compressor contains both a converter to turn AC into DC, and an inverter to*generate the DC pulses that drive the motor.
Marin wrote: Would this basic description apply to the Norcold AC/DC units too, or at least Norcolds from the late 90s?*
JD wrote:Is the control module where the 12V gets to 27V?
ARoss wrote:
When I "inherited" my MT34, a previous owner had installed an apartment-sized 120v Haier fridge.* Admiral loves having all that space, and since we are marina cruisers, it runs on shore power at home and at marina stops, and with a* dedicated 2000w inverter under way.* It's at least 9 years old, and shows no signs of rust or other deterioration from a marine environment.
We also carry a Honda 1000 genset for times when we do raft-ups, etc. and want to keep it cold.
You other MT34 owners will note that the port side of the salon was also modified to remove the upright cupboard and* settee, replacing with the fridge and a nav desk.
It's about 10 cu.ft. draws 11 amps. and probably cost $250-$300.* A look at Defender shows a 7 cu.ft. Norcold for $1280.* What am I missing?
-- Edited by ARoss on Sunday 13th of February 2011 09:30:16 AM
You are missing efficiency (less insulation, less efficient components) and the ability to just "set it and forget it".
I don't have to carry and run a gasoline powered portable generator with its CO and fuel risks, and I don't have to switch power sources frome shore power to inverter to generator.
All I have to do with my Nova Kool AC/DC refrigerator is turn it on and fill it up.**A caveman could do it.*