refrigerator hook up

[colinhulse]

My new unit runs off 12v or 24v. I have a double pole double throw switch, so that I can run it off the batteries (12 volt) or throw the switch and operate off a 120 volt AC /24 volt DC converter. When I flip to 'battery' the unit functions fine- but in dock and with shore power hooked up I want to use the converter. I flip to it and the unit doesn't function. I tested the voltage at the unit. It is 12.5 DC on battery power and 24 volts when I flip to the converter. The wire runs are short and I used 10G wire. I know the unit cuts out if it senses a low battery at 11.8volts. I wonder if it thinks the converter source is low? Baffled

 

[Benny17441]

I would imagine the unit has an automatic voltage sensor for the input. Make sure that the converter is rated to supply the amps required by the unit and that you use a proper table for sizing the wires.

 

[colinhulse]

Check!

Did all that! The amp rating on the 24 volt DC converter is higher than required and the marine grade wiring is all oversize and soldered at connections. As I said, if I meter the output for the 12V batteries and flip over to the 24V source at the compressor everything is Jake. The unit just will not run at 24 volts. My only thought is that the unit wants a slightly higher voltage. Believing that 24 volts indicates the batteries are running low (But no such condition exists) I can't think of a way to check it.

 

[Benny17441]

Take two 12V batteries and hook them up in series to get 24V and connect them to the unit. If the unit still does not run then the voltage sensor is likely out of whack; but should it run on the batteries then the fault would be in the converter. The batteries fully charged should put out around 25.4V.

 

[bawlmer]

You may have an inverter issue. Take your voltmeter and set it on the AC setting and measure again. If you are measuring over 0.25 volts AC then too much AC is sneaking through. The Fridge will not like that.

 

[Ken Cross]

I'd give the manufacturer a call. You may have a bad unit.
Ken

 

[Ron20324]

I do not see this in your post, but to clarify: you use the same wire input for 12 as for 24- and it internally switches to work via the supplied voltage? I don't think I'd like that, but if it's supposed to work....

 

[capta]

Many times start amperage is considerably higher than run amperage on these units. Perhaps the rated amps of the converter do not meet the start amps need of your refer system.
My inverter has more than enough power to run our refer system, but it cannot start the unit, even though it should, though marginally.

 

[wufibugs]

I have an ac only fridge. Ran a dedicated fused line to a plug near the fridge for shore power with a selector switch in the unlikely event I want to run the thing off the inverter.

 

[colinhulse]

reply to all

The switch is an industrial DPDT that completely disconnects the battery both + and - and switches them with the converter. It is rated at 25 amps. The idea of connecting the house and starter battery in series to get ??25 volts?? crossed my mind but GOD what a hassle. The converter is rated as follows...120 volts AC to 24 volts DC at 9 amps. The reefer runs at 2.5/ 3 amps. It can't be either. I tested the voltage at the compressor and all was well. 12.5V and 24V when I flipped the DPDT switch. I will check the AC bleeding through. Thanks for the thoughts.

 

[Benny17441]

At this point I concur with Ken about giving the manufacturer a call. Your converter specs seem to be fine and the fact that it works well at 12V seems to eliminate a number of other possibilities. It seems the unit may be faulty and unable to operate at 24V.

 

[colinhulse]

Call me!

I called and I wrote two emails to tech support. NOVA KOOL if your interested they ain't home and the E mail must be down.

 

[twalker H260]

Model no?

What are the model numbers of your fridge and inverter? Perhaps we can find something in the manufacturers documentation to help?

For instance it looks like the Danfoss BD35F / BD50F / BD80F all are set to require 24.2v for cut in.

(http://www.novakool.com/support/documents/R134a_12-24V_DC_11-01_Cn46c702.pdf)

It looks like the cut in/ cut out settings on these models would be adjustable to give you a cut in voltage less than 24v.

 

[seadaddler]

Nova Cool

I have a front load ref on my 2007 H-36 and from the factory it worked off
12- volt's only and the first 2 years I was in a marina with shore power
and so I got a converter that is added to the ref down in the bottom part where it fitted nicely and it always worked fine but years later I was the hard in Fl for
a bottom job and while at the marina I was plugged into 110 GFI outlet and most times when i went to the boat no 110 at the outlet that the boat was plugged into.
During the summer we get many storm's here and any way the 110 power kept
getting popped off and on I think and so my inverter/charge blew a relay inside
of it and my Nova cool ref relay blew and the converter also was damaged.
Nova Cool was very helpful finding the problem and any way I decided to only replace the relay and run off 12 volt's and not replace the converter.
I have 2-195 Solar Panels that run my Nova Cool and my Engel ref all the time and also all my 12 volt equipment and only use the shore power for AC/dehumidifier.
Nick

 

[Richard Kollmann]

Troubleshooting Swing compressors.

Swing compressor systems like Norcold when equipped to run on either AC/DC power are difficult to repair because electronic are all in a common component box. When unit runs on DC but not AC failure is normally a shorted main large transformer that decreases 115 volts to 60 cycle 22 or 26 volts AC needed to power compressor. For 12 volts to operate compressor there is a second set of transformer coils or a second transformer that increases 12 volts to 22 or 26 volts needed to operate compressor depending on model Swing compressor used. Direct Current will not cause compressor to pump refrigerant when operated on 12 volts. To produce the 60 of ON OFF cycle pulse needed to vibrate pump piston there are voltage interrupter circuits in main electronic box.

Inside Nova Cold some twenty different electronic control boxes over the years there is an automatic change over circuit and relay designed to always connect to DC power in the absents of AC power. These units are not designed to be switched manually. There are two separate power sources to electronic box protected by proper sized circuit breakers. Some boxes have separate small breakers on thermostats. When refrigerator is to be operated generally both AC and DC breakers are in the ON position. If there is a generator on board or boat is connected to shore-power refrigerator will transfer to AC sparing battery power extending battery life.

My advise is:
If, AC side of a Swing compressor fails Run unit on DC until you are ready to buy a new replacement system.
If, DC side of Swing compressor fails Run unit on AC provided by a 12v to 110-120 volt inverter.

At one time Electricboat refrigeration did repair Norcord units and control boxes. You might also contact RV industry suppliers for a repair company recommendation.

 

[Benny17441]

Does the unit have any LED lights that may help with the diagnostics of a problem? When switching voltages there could be a delay of around a minute for the unit to start the compressor; I'm sure you have allowed for this but just trying to cover all the bases.

 

[Benny17441]

One last thing, voltage drop cannot be measured without a load. If the compressor is not running there is not a load and the voltage reading of 24V could be inconclusive. Even though specs on the converter are good it remains untested.

 

[Richard Kollmann]

Benny, Swing compressors do not have a built in troubleshooting microprocessor like the newer designed Danfoss BD compressors. Swing compressors have been around for over 25 years but getting their control box problems solved is difficult.

 

[Gunni]

Run it exclusively from your 12VDC system (via the batteries). If you have shore power, use it to charge your batteries (120VAC charger). If your battery charger is properly sized it will be able to charge your batteries and supply your house loads as well. That is how electric marine refrigeration works and it is simpler. Simple is good.

 

[colinhulse]

Thank you.

Lots to think about. I did let it sit at 24 volts for 5 minutes. Nothing! This isn't a SWING unit. That style simply hook up to both a 12 V source and 120 AC and flip to shore power automatically. I have to use a DTDP switch to change it over. Still no response from NovaKool support after three E Mails. I think the voltage is the next thing I'll try. hook something up and feed it 25 volts DC. I have been told that you can shut off the circuit that shuts the unit down when it detects low voltage. Looking into that. I am running the fridge off the house battery and it is working very well. Problem is my smart charger thinks the battery is low and is feeding a full charge to it when the compressor operates. I wanted to get away from that and use shore power at the dock so the battery could charge / rest properly. Thanks all.