Adding a new DC Fridge during a LA Heatwave

[themexicandoctor]

Originally Posted by themexicandoctor

Okay my fridge is now down to a very respectable 36.6°F without any cooling.

It was probably the Sensorpush falling off its velcro mount at midnight as I was driving & then falling onto a warm ledge (?) and or maybe by clicking it off the way down to 2.75 on the 1-7 knob & having it reset the compressor.

I certainly have no external fans blowing on it now.

Now I am really confused, the unit dropped all the way down to 36.6°F with no extra personal fan blowing on the condenser.

I buy some groceries, turn the generator on for the batteries tomorrow & then an hour later as the graph shows, it races to 48°F in the space of an hour.

I put the extra personal fan on the co denser coils right now, hoping for this to work.

[themexicandoctor]

Here is the data;

[themexicandoctor]

49.9°F from 36.6 in 2 hours.

Just bought a bunch of groceries which I am probably going to have to throw out.

[booster]

Originally Posted by themexicandoctor

49.9°F from 36.6 in 2 hours.

Just bought a bunch of groceries which I am probably going to have to throw out.

I keep going back to the 2.2 amp draw, which is likely because the frig is set to run at minimum speed on the compressor to look good in the specs.


That speed is probably too low for over 100* continuous temps so likely needs to be turned up or made adjustable.


This is done by puting resistors in the thermostat connections, as has been mentioned by several poster earlier.


Talk to your installer about doing the speed up, it is very possible it can be done at the thermostat control in the frig itself without pulling it out.


on edit: I figured I would refer back to this thread


https://www.classbforum.com/forums/f...pecs-9459.html


which was put up to show that running amps are absolutely no good for predicting energy use per day, but the chart shown in the first post also allows you to see what the actual cooling capacity is at various compressor speeds and evaporator temps. Cooling capacity is the issue if you can't maintain temp like the good Dr can't in the high temps.


As can be seen, over the range of compressor speeds at any particular evaporator temp, there is approaching a 50% increase in cooling capacity between slowest and fast compressor speeds.


Letting the evaporator run warmer at any particular speed also can increase cooling capacity a lot. You can increase the evaporator temp by letting more of the cold air escaped from the freezer to the frig area.


Both of these changes reduce efficiency a bit, per the same chart, but if you food is getting spoiled, that is a small downside.


It probably would be useful to get an evaporator temperature and combined with the running amps, get a look at about where the unit is running on the chart. It won't be exact, though, as the condenser temp also affects capacity and very high like is being seen will reduce the capacity quite a bit.


The resistor values to get the speeds are also shown in the chart document. Note they need not be exact the same resistance, as it is a progressive setting so being in between the listed resistances just put you at between the listed speeds.

[themexicandoctor]

6 hours later its back down to 37.8°F - going to talk with Novakool later today about resistors, etc.

As you can see, because I ran the Generator I got the usage down so it's easier to recover in the am

Which is more effective, the Potentiometer or the Reaistors?

[booster]

Originally Posted by themexicandoctor

6 hours later its back down to 37.8°F - going to talk with Novakool later today about resistors, etc.

As you can see, because I ran the Generator I got the usage down so it's easier to recover in the am

Which is more effective, the Potentiometer or the Reaistors?

IIRC when I was looking at doing ours, I couldn't find a rheostat with the right range, not too much or too little, and also had the mounting style I wanted for the limited space I had for it. I think either would work as long as you stay in the correct range limits.

[themexicandoctor]

Originally Posted by booster

IIRC when I was looking at doing ours, I couldn't find a rheostat with the right range, not too much or too little, and also had the mounting style I wanted for the limited space I had for it. I think either would work as long as you stay in the correct range limits.

I must say Novakool have been excellent thus far.

Today the suggested adding*;

1. The Resistors from 495 to a maximum of 1500ohms but of course then my unit would be using a much higher amp draw

2. Adding Reflectix to the rear skin of the Chevrolet fridge area &

3. And blocking off some of the lower venting area

4. Putting the existing fan, in the middle & having it blow up] against the condenser

5. And possibly adding ducting at the top & a switch controlled extractor fan (computer type), mounted to the upper grill.

As for the ambient temperature design the answer* was 120° but of course after 100° outside the rig, more accurately 115° coming off that hot road or parking surface performance does dip a little but my unit should normally handle this easily.

*I may have this wrong (will send an email asking for confirmation), 0ait seems my unit is the only new install with these unusual performance characteristics this far - the compressor is running nonstop.

Going to a bigger compressor & fridge ie; the R4500 with a BD50 versus the BD35 Compressor is not the solution.

[GeorgeRa]

Originally Posted by themexicandoctor

I must say Novakool have been excellent thus far.

Today the suggested adding*;

1. The Resistors from 495 to a maximum of 1500ohms but of course then my unit would be using a much higher amp draw

2. Adding Reflectix to the rear skin of the Chevrolet fridge area &

3. And blocking off some of the lower venting area

4. Putting the existing fan, in the middle & having it blow up] against the condenser

5. And possibly adding ducting at the top & a switch controlled extractor fan (computer type), mounted to the upper grill.

As for the ambient temperature design the answer* was 120° but of course after 100° outside the rig, more accurately 115° coming off that hot road or parking surface performance does dip a little but my unit should normally handle this easily.

*I may have this wrong (will send an email asking for confirmation), 0ait seems my unit is the only new install with these unusual performance characteristics this far - the compressor is running nonstop.

Going to a bigger compressor & fridge ie; the R4500 with a BD50 versus the BD35 Compressor is not the solution.

Adding Reflectix to the rear skin of the Chevrolet wall in the fridge area will reflect IR / heat back to the condenser. Adding Reflectix on the external wall will deflect Sun's IR back to nature. Adding a second external wall with 1/2-1" gap will form a "double roof". Or, just add a layer of styrofoam in lieu of proposed inner Reflectix.

[themexicandoctor]

This is where I am now.

My RV Guy, 60 years experience, climbed under my rig while planning how to configure the new battery position & said;

"Well here is your first problem you have a bad connection. The two batteries that sit on the rear passenger side of the truck & connect to underneath where the 2005 190 Versatile meets the bottom of the electrical box (?) ...."

I didn't bother to check, I trust him 100%.

He said "We don't have time to do this today (he has a backlog), & that it will have to be next week but just that small change we did should make a big difference, maybe not in relation to the fridge performance but very much so with relation to charging ..."

A little frustrated we couldn't do it this week but the fact he was under there for 30 minutes & found that was valuable.

He said to wait & what happens now with thr charging & the fridge performance.

For Booster, I did ask him if the batteries are connected directly to the shunt so the meter can read the power & he said "Yes it is ..."

I cannot emphasize how supportive Novakool & this Forum has been.

As it is, I left the power off for 2 hours while we doijg this work & I am now waiting for the fridge to catch up, it as 40.7°F & fallinh whereas the Front Cab 10 feet away is reading over 102°F & the couch from where I am writing this in the back is 97.6.

[themexicandoctor]

For thr first time ever, it does not seem like the Novakool is pulling power - WOW!

[avanti]

Originally Posted by themexicandoctor

My RV Guy, 60 years experience, climbed under my rig

So, you are making an 80 year old guy crawl around under your rig?!



[Just teasing...]

[themexicandoctor]

He is 70.

He knows his stuff.

And he gets paid for it.

[themexicandoctor]

I think perhaps he was right about the charging at least.

Although I ran my generator until 1.30am or so & the fridge was turned off for two hours while they worked on my truck between other jobs, I have been in Float for a few hours

[themexicandoctor]

Originally Posted by themexicandoctor

I think perhaps he, my RV Guy who found the loose connection was right about the charging improvements at least.

Although I ran my generator until 1.30am or so & the fridge was turned off for two hours while they worked on my truck between other jobs, I have been in Float for a few hours

Here are four screenshots of the MTTP in present time, the history, the METER in present time, the history

As it is the fridge is stuck at 40.7°F but I just turned the knob up.

[themexicandoctor]

Hats off to Mariam, the Head Engineer at Novakool who said "Perhaps you have an issue with the negative side of your dc charging ..."

If he was correct, fantastic!

Cannot wait for the fridge to cool down from 40.7 as it is now 43°F, broke open a small tray of ice into one of storage trays in the fridge, this should help to bring down the temperature much quicker along with turning up the knob.

[themexicandoctor]

I cannot work out what is wrong now its skyrocketing to 45.7!!!!!!

I slowly turn the knob back & then adjusted it slightly (I don't really know what that does but its been mentioned a few times).

[themexicandoctor]

Now its 46.8°F!

I am completely dumbfounded.

Have parked under the shade of a big tree & hoping this, the ice & the increase can catch up.

[booster]

Originally Posted by themexicandoctor

Now its 46.8°F!

I am completely dumbfounded.

Have parked under the shade of a big tree & hoping this, the ice & the increase can catch up.

The guess has to be the the unit has gone into a thermal overheat type shut down or power reduction to save itself. A call the Novakool may be able to answer for certain.

[hbn7hj]

Here is the pot for it.

https://www.amazon.com/Taiss-Potenti.../dp/B07DKCBVTP

[themexicandoctor]

Just called my RV Guy & he said "just crank that knob up", it cannot use any more power than it