Nova Kool Fridge - low voltage cut-out

[Sno' Dog]

We noticed recently - now that we're down in the Bahamas and anchoring out a lot - that our fridge was misbehaving. Only 6-8 hours after stopping our engines, our fridge would start cycling on and off. (You have to listen carefully to hear the compressor starting and stopping.) The bottom line was, it wasn't staying cool. According to my calculations, we should have plenty of battery capacity to run for at least 24 hours without charging. And, sure enough, our battery voltage - at the panel - was still showing a healthy 12.4 V.

The problem turned out to be the fridge's built-in low voltage cut-off. (They do this to help save your battery.) But it was shutting off the compressor when our batteries were still half charged. I suspect that the voltage at the fridge was much lower that at the panel, although I never checked it.

What we did do, after a call to Nova Kool (who was very helpful!) was to add a jumper wire on the fridge control panel between terminals "C" and "P". (This did involve pulling out the fridge, but it wasn't as hard as I thought.)

Remarkbly, this has solved the problem. The fridge now runs happilly for at least 24 hours on battery power without complaint.

I thought I'd post this in case others might have a similar problem. It's not something you would notice unless you spend a lot of time at anchor. Previously, although we anchored (or stayed off shore power), we always got underway the next day. It's not untill recently that we have remained off-grid for long periods while living aboard - that this problem became apparent. I suspect that PDQ skimped a bit on the wire size running to the fridge - considering the long length of the run. But adding the jumper is a lot easier than running a whole new wire to the fridge.

Henry
aboard Sno' Dog - in White Sound, Abaco BAHAMAS
latest web page: www.snodoglog.com/08Winter-Pg5-Bahamas.html

[Rhumbline]

Thanks so much for the tip on the low-voltage problem with Nova-kool. This had plagued us for years (inc. many conversations with Nova-kool). This am it took us 20 min. to jump "c" to "p" and we are happy cruisers here in Georgetown, Exumas.
Stan and Jean Ozimek
O/B Rhumbline

[Bob]

I wonder if this is true for the compressor units with the black box and evaporator plate. I noticed a few days with no hard ice and then it started working again.

[S Slater]

Hi Henry
Once again the analysis is correct. The basic problem is the wiring size. This is only a 4.5 amp draw. We new that it needed big wiring so I think we put 10 gauge in the loom. I can't quite remember but believe that they wanted 8 gauge wire instead, we really felt that this was a little bit crazy. it seems that there was something else going on and that there EC was probably a little to sensitive to low voltage.
simon

[duetto]

"our fridge would start cycling on and off. (You have to listen carefully to hear the compressor starting and stopping.) The bottom line was, it wasn't staying cool."

hi henry,

when you say "wasn't staying cool", do you know the temp it got up to? i've never really listened to the fridge.

[Sno' Dog]

Hello J & D,

The first sign of something amiss was some dripping from the cooling plates, normally they stay solidly frozen (both freezer and cooler) until defrosted. When I checked our little fridge thermometer, it was up above the "normal" zone - up close to 50°, I think. When working normally, our fridge stays about 36-38° with the thermostat set to about "3".

duetto wrote on Wed Apr 16, 2008 11:16 am...

when you say "wasn't staying cool", do you know the temp it got up to? i've never really listened to the fridge.

[duetto]

hi henry,

we have the telltale dripping. i thought it was just a by product of the 85o temp. soooo...what magic screws do i need to undo to get at the control unit....when i get back to ct.

[Sno' Dog]

John,
It's not as bad as you think!

To remove the fridge, you just have to remove the four screws around the outside frame - they're hidden under little plastic caps that must be popped off. Then, the whole fridge should slide right out. We put some towels on the counters and rested it there. (See photo below.) Once out, you'll see the "control module" box on top and, on close inspection, you'll see the lettered terminals. Putting a jumper between terminals "C" and "P" reduces the low-voltage cut-out by 1.7 volts - enough to overcome the voltage drop in the long wire and make the the fridge continue running normally until your battery voltage drops below 12 V.

If your fridge is the same as ours (model RFS7500), terminal "P" is empty, but there's a wire connected to terminal "C". I cut this wire and inserted it into a new spade connector along with a short piece of wire (jumper) which I then conected to "P" with another female crimp-on spade connector.

If you wanted the option of being able to run the fridge either way, you could use a longer jumper and bring the wire out front and put a toggle switch in the line, but I didn't feel the need for this. So far, I haven't run the batteries down low enough to test our new set point, but I doubt that it would do any harm to our batteries.

We were a bit daunted by the thought of removing the fridge, but the whole operation took less than an hour and really wasn't too difficult. Having read Simon's comments (above), I suspect every PDQ might benefit from this small "fix".

Henry
http://www.snodoglog.com

[duetto]

done!

took about an hour. we have the older galley layout which is a lot narrower and therefore made getting at the control unit a little more difficult.

thanks to you henry and the others who convinced me that this was a doable "field" project.

i will report back if i see any radical change in battery consumption.

thanks again.

[Lady of the Lake]

I wish I had a fridge like that in my 36