12V Refrigerator issue

 

Temperature of Refrigerator (freezer) on 120VAC 

I'm checking out the systems of the 210P.  The refrigerator has been "OFF" and so prior to a trip I powered up the 3-way Dometic refrigerator.  It worked fine on AC. The sensor I put in the freezer registered minus 15F and then I switched to DC.

As you can see in the graph above, the cooling stopped on DC.  I've done some trouble-shooting and I ordered a part.  After installation I'll try again and post the results.

 Original material http://roadtrek210.blogspot.com/

Keeping cool in summer heat

Well, it is that time of year again, and the sun is beating down on some of us. One challenge is to keep cool, and keep that refrigerator running. A couple of years ago we were trekking in TX and hit 103F heat. We really weren't prepared.

We've done a few things to help us. Some are the same things others have done and based on my observation, some are not.  Of course, one thing is to park in the shade if possible. However that may be easier said than done. So if we have to park in full sun, then what? How to keep our Roadtrek from becoming a sauna?  The Duo-Therm Cool Cat heat pump works really well, but it does need some help when the sun is bearing down upon the front of the RT.

Here's a few things we have done to aid us in keeping cool in our RVs.

Reflectix
A bubble wrap reflective foil in windows has been a big aid, particularly in the Roadtrek, our class B. That has a large front window which simply seems to pull the heat into the vehicle. Reflectix has been very helpful. We use it in all windows except the side entry in summer and fall/winter trekking. Glass has a R-value of about 0.1 which means almost no insulating value. I understand that Reflectix has an R-value of 1.0. I understand the Roadtrek has an R-value in the walls of about 4.5. Anything we can to to improve the insulation is a good thing.

Screens
The Roadtrek came with side entry and rear entry screens. When the outside temperature is acceptable, if we can get better airflow that is an aid. However, we prefer to close the side door. I fabricated a magnetic held screen for the front side window. These can be purchased, if one prefers. The goal is to get the interior temperature down to the exterior without the use of air conditioning. We open the side window a couple of inches and use the Fantastic Fan, or open the rear door which has a full interior screen.

Fans
Our RVs have roof fans. These include Fantastic Fans. That's helpful for pulling warmer interior air out, and drawing in cooler outside air, when it is available. Or, after a shower, these fans can move moisture laden air to the outside, reducing interior humidity.

However, we also use a 12V DC fan in the Roadtrek, We found one that sits on the shelf above the side door. It has side air inlets and variable speed. Very helpful to move air around in the front of the RV, particularly if the vehicle is facing the sun.

A small 120VAC fan is also useful. This we use in the travel trailer to move the air around. Got a small 8 inch diameter Vornado which is also variable speed.

Create Shade
If one can't park in the shade, the next best thing is to create it. Many rigs have an awning, and if possible one might be able to orient the position of their RV so they get some benefit. Creating partial shade is easier than it may seem. We use several sun screens to aid us. One we fabricated from a roll of Coolaroo material. We hung that one the side of the TT which gets a lot of afternoon sun. It made quite a difference. We purchased a triangular piece and we position it as necessary with the Roadtrek. Usually to the front. I use a couple of expandable metal tent poles and 1/8 inch green nylon rope with tent stakes to get it into place. A 36 inch wooden dowel holds the front up to keep it off of the vehicle. I use aluminum carabiners to attach the sail to the tops of the poles. This allows me to quickly drop the sail if the wind comes up, or when evening approaches. The lines are strung to stay in place and hold the poles up with the sail dropped.

Here's the Roadtrek with awning extended, reflectix in the front window and the coolaroo sun sail up.

When not in use the sun sail folds conveniently and with the tent poles goes easily into the side storage compartment of the Roadtrek.

The travel trailer gets a lot of side sun in the dining/living slide. We hung a piece of coolaroo fabric. I used the coolaroo lacing kit to clean up the cut fabric ends. A custom wooden clamp the full length of the top keeps it in place. I fabricated a spacer to keep the upper area of the shade off of the side of the trailer. The spacer is made from a chromed shower rod and foam pipe insulators. That space is important to keep an air gap along the entire length of the shade. 

I use a couple of clamps designed for that purpose on the bottom with a bungees at a slight tension to hold the bottom out from the RV.  I attached the bungees with 1/8 nylon cord to a couple of bricks.

Cover the Roof Vents
A Maxxair vent cover is nice. It keeps the sun from directly striking the lid of the roof vent and it keeps bugs and birds away from an open vent. We added one to the Roadtrek.

However, the previous owner of our TT didn't install these covers and it has three roof vents. While on the roof I noticed that the covers were showing some distress after being in the sun for about 6 years. We also noticed a lot of heat in those areas during hot sunny days. One can install a insulator.  Camco has one which has a bright aluminized surface, which can be pointed up. These aren't very convenient if one wants to open the vent lid frequently. However, in cool weather we use one in the bedroom to keep the heat inside and provide some insulating value.

I decided to cover the vent covers with heavy duty aluminum foil. That reflects the heat away from these covers. It really made a difference in the travel trailer. I used a tube of exterior silicone caulk and after applying a bead on the edges, sides and in a pattern along the top I simply placed the aluminum foil and smoothed it into place. I trimmed the foil and folded the edge under the vent cover lid.  The travel trailer has 10 windows and frosted glass in the doors, so we get ample light even with the vents opaqued.

Camco vent insulator, aluminum side up:

Refrigeration
Our Roadtrek has a Dometic 3-way absorption type refrigerator. When we first encountered 103F we were on a site with the refrigerator side of the RT in full sun. The refrigerator had some difficulties keeping things sufficiently cold.

We had one of those battery operated fans and it was useful. An internal thermometer mounted on the top shelf told us the real condition inside. I did some research and read the Dometic manuals about "Power Ventilator Installation" and concluded that improved ventilation would be helpful. I added two very low power 12V DC fans and a thermostat with an in-line fuse.

Refrigerator interior fan

Ventilation Fans

Refrigerator Thermometer

RV Refrigerator Tweaks

It’s getting warm and I see more and on the social websites about complaints or issues about RV refrigerator performance. There are some things that one can do without voiding warranties or spending serious cash.

What type of refrigerator? Some of the newer rigs have 120VAC compressor refrigerators (residential models) with big batteries and a large inverter (12VDC in/120VAC out) to power the refrigerator when trekking down the road and off of 120VAC shore power. Our 5th wheel (HB#3) has such an arrangement. The TT (HB#2) has a larger absorptive refrigerator with separate freezer and refrigerator compartments. We don’t trek in it so it runs on 120VAC.

Our Roadtrek (RV #1)) also has an absorptive refrigerator. It’s a single door model 5 cu. ft. We do trek in it and so we do run it under a variety of temperature extremes, and on 120VAC as well as propane/12VDC battery. It’s a good size but not as large as the one in the TT. We use the Roadtrek refrigerator to transport initial food to the summer camp (HB#2) and of course when on our treks (longest to date was 110 days). The refrigerator has performed well, but we decided to make some modifications to help it out under high ambient temperature conditions. This post is primarily a consequence of our experiences in the Roadtrek with treks from 2 weeks to 110 days.

There are some things to know about the absorptive type of refrigerator. Adapting to what we’ve learned makes our treks better. ‘Better” as in more successful or easier. I suspect some of our lessons learned would be helpful with any style or model refrigerator.

IMHO having a good time means learning to live within limitations. That might be our financial means, our time constraints, or the limits of the available technology. One can resist or one can adapt. It’s all a matter of choice. I prefer successful treks and so I learn and adapt.

1. The absorptive type of refrigerator is slow to cool. That means turn it on and give it some time to reach 45F. If the refrigerator is 90F when you turn it on, don’t expect instant frost. Sounds simple, but you would be surprised what people expect. It also means put cold things in it to give it a boost. Put warm things in a warm refrigerator and one can expect soured milk. What can we do to avoid this? Start up the refrigerator several hours before first use. How early? The warmer the refrigerator is when you start it up, the longer it will take to chill. Use common sense. As an aid we also put a large, frozen ice pack in the freezer when we pack it for a trek. That works very well. See the photo.

2. On hot days don’t park with the sun striking the side of the RV that the refrigerator is on. The additional heat from the sun is sure to create efficiency problems for absorptive refrigerators. We travel with a triangular sun sail to shield the RT from the hot sun.

3. Do what one can to help the refrigerator. We load it up with fully chilled goods before we trek, and that large ice pack.

4. Once on the road we minimize the bulk addition of warm items, and prefer to add these only in the evening when the ambient temperatures are falling. For example, we only add 2-4 cans of warm soda or sparkling water at a time. When we shop, we put the coldest things in a small cooler, to keep them cold. When we introduce them into the refrigerator there is less “heat shock.”

5. Use an interior fan. There are battery operated ones, and fairly inexpensive wired 12VDC fans. We opted for the battery powered simply because our refrigerator doesn’t have an interior light, or some easy means to get to 12VDC power.

 6. If you are planning on travelling in elevated temperature areas, add exterior, supplemental fans to draw air into the compartment behind the refrigerator. This we decided upon when we experienced the consequences of daytime temperatures consistently above 100F.

Here's the sun sail mounted to shield the front of the vehicle. if the sun was on the refrigerator side, we'd position it to provide shade on that side. 

Adding Refrigerator Exterior Fans

Photo During Construction!

The sun is a beneficial thing in RVs in the winter. Most RVs have a lot of glass, and that surface area loses heat in the winter. So sunshine is a good thing. However, in summer the sun can contribute to discomfort and can interfere with operation of the refrigerator.

When we trek, we sometimes park in full sun and occasionally in partial shade. More often than not we don't get to choose the orientation to the vehicle to the sun or the amount of sun we receive.

On a trek a while back we were in a location where we and a lot of other people were in full or partial sun. The outside temperature in the shade peaked at 103F (39C). To make things worse, the vehicle was oriented so the afternoon sun was full on the side of the vehicle that houses the refrigerator.

Our Class B has a single door Dometic refrigerator. This is the absorptive type, which does not have a compressor. It works well, but is slow to cool from ambient temperatures. It has rear radiators. The radiators are behind the refrigerator and two grills on the side of the RV provide cooling of the radiators via convection. "Cool" air enters the bottom vent, passes through the radiators and the compartment cooling them. It then exits through the upper vents.

On our trek which reached peak temperature of 103F the refrigerator struggled. We weren't alone and a lot of rigs both big and small had similar issues.

We decided to do something about this. Short term, some people put a bucket of ice in their refrigerator. That is not always practical. First, one has to find a source of ice. Second, that bucket takes up interior space, which is precious in a 5 cu. foot refrigerator. Third, the water has to be disposed of. If a covered container is used, as the ice melts it won't slosh around while moving, but otherwise it can get messy.

The other choices we considered included one active and one passive supplemental cooling technique. The passive one was to add a moveable sun shade. However, we usually orient that in such a way as to reduce sun on the front of the vehicle, where most of the glass is. The other was to add electric fans to improve the airflow behind the refrigerator.

Dometic has instruction on how to do this for both single and dual door refrigerators. Here's a link to the single door instruction. Dometic also has instructions on the web for their dual door refrigerators:
Dometic Power Ventilator Instructions

Installing these will vary from model to model and that includes the details of the RV. I chose a location directly behind the upper vent openings. I also installed an simple aluminum strut to bolt the fans to. I used two low power fans and a thermostat mounted on the hot side of the coil. Seems to work well.