Fridge - works on AC but is 'weak'

So you guys nailed it. I noticed the fridge temps creeping up again today. Low 90's, full campground. So I checked it and what do you know... the voltage is down to 110v.

So it's good to know the fridge is in fine shape... and even better - the heat is supposed to break tonight, so I can move on.

NEVER replace a 120 element with a higher wattage element. It is NOT safe and is not needed. Nobody remembers that one cause of the Dometic cooling units failures was because Dometic installed a higher wattage Heat Element. Instead of the 325 watt they installed a 350 watt. I disagree with Chris LP versus 120. We have pretty hot temps in Texas from June to October(90 to 105). I NEVER have a problem with running and/or checking the performance of a RV refer running on 120 only. LINE voltage will make a big difference on 120 operation just as LOW LP pressure will cause poor performance on LP. The refers are designed to run equally on 120 and LP. Thgis is why it is critical for every RV'er to have and understand how to use a voltage multimeter. Always check your line voltage inside the RV. IF it is below 112 to 115, then your refer may not perform as well in 85 plus temps. Switch to LP when your line voltage drops. Doug

Yes, looks like it's 300W - the kill-a-watt is displaying that exactly right now. It's also 121V right now - but the campground cleared out a bit and it's only mid 80's right now. Plus, I don't have my own A/C on yet. I didn't test at the element directly, but right at the dedicated outlet in the fridge bay. Should be good enough to test line loss or campground drop for now.

I just made lunch and was liberal in my fridge use, and it seems to be holding fine in mid 30's.

I'll check again when things warm up and I put my own AC on.

Thanks for the heads up @joe417 - I know what to do and not to do. Always test it with your tongue first to be safe :)

Wow, those EMS units are expensive. I'll look into it more though. Nice to no the fridge has a safety built in. I'm dry camping 90% of the time, but the times I'm on hookups are the times there's likely to be problems (A/C weather).

I've always had a theory about units cooling better on LP- in addition to typically low power, LP acts a bit like a venturi- the rising combustion bases will tend to create more air flow in the back.

Note that the Norcold N series will switch from ac to lp if the voltage drops enough- it does sense the voltage, and on the N621 the voltage is readable in the diagnostic mode on the control panel.

Chilly81,

You may understand electricity but be safe, it's 120v, if you don't, ask someone who does to help you.

If you measure, or have it measured, the voltage and current directly at the heating element you will know whether the voltage or the heating element is adequate.

I'm running on memory here, but I believe the N621 has a 300 watt AC element. You can look it up to make sure.

Watts = Voltage * Current.

Ah, I hadn't thought of a voltage drop - that makes a lot of sense, especially with the squared. I just plugged the fridge into a "Kill-a-watt" and put it back on AC. It will give me the line voltage as well as the power draw. I'll take a look when things heat up this afternoon and everyone's got their A/C's on and report back.

@sch911, I had read about the different fans and I may do that as well. Just wanted to understand why propane is working better than AC first.

chilly81 wrote:

-Or could the AC element just be degraded - not working as well as it once did, and would be worth replacing that element?

Most likely this, but not as in being defective.

The problem is more than likely due to low voltage, as mentioned above which is a very common problem in campgrounds, esp. in the summertime with a lot of folks running AC units. The Norcold electric heating element is rated 300 watts at 120 volts. 120 volts is the standard nominal voltage of electric appliances and devices in NA (with a few exceptions) and is the voltage listed by Norcold.

The output of any electric heater with a resistive element in it varies as the square of the voltage. At 108 volts, the output of the heater would be (108/120) x (108/120) x 300 = 243 watts (down by 19%). If the voltage got down to 105 volts (not unusual), the heater output would be (105/120) x (105/120) x 300 = 230 watts (down by 23%).

When the CG voltage gets really low (around 105), you can see it will take quite a bit of capacity away from the heating element and thus cooling capacity when the outdoor temps are getting high. Unless you invest in an autoformer, running on propane is the solution. It would help to have a power line voltage monitor plugged into a receptacle inside so you can always see what is going on.

As an aside, when voltage gets down below 105 volts, it leads to damaging AC units. An EMS unit like a Progressive Industries (highly recommended) or a Surge Guard will automatically shut your incoming power supply off and protect AC units and anything else that can be damaged by low volts. If you encounter low voltage frequently, getting an EMS is very cheap insurance.

Low voltage is an RV-ers nemesis. We're at a CG in Wa. that has been as low as 105 volts and I get lukewarm coffee out of our coffee maker. Pffft...

Generally propane will always out perform the 120v heating element
What is the line voltage
My guess is you have a big drop in line voltage because the A/C is running
At example 108v the A/C compressor will still work, but the fridge element has lost 12% heating capacity..losing that much in 90+ weather is a big handicap, a new heating element won't help, if the voltage is low

Now is the time to burn propane in the fridge, so you can keep the fridge and the RV cool

Replace the electric heater with one that draws more watts.

To get maximum performance many of us add 12v fans in the refrigerator flue to assist the condensing side. You may need to do this also...