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07-12-2022, 11:49 PM
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#1
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New Member
2022 27' Globetrotter
Napa
, California
Join Date: Jul 2022
Posts: 3
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Solar for electric refrigerator
We traded in our 2018 25RBQ Flying Cloud for a 2021 27' Globetrotter. I wish I could have traded out the refrigerator and hot water heater 😟
My question: Is there any amount of solar that will run the refrigerator (electric) and hot water heater (on demand/instant water hog) for boondocking? I have a feeling if we want to boondock it will be with ice chests, heating water on the gas stove and child showers 😔
We have Honda e2000 generator with companion but I don't want to run them all day and sometimes the noise is an issue. Any input on solar we should get is greatly appreciated.
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07-13-2022, 07:43 AM
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#2
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Rivet Master 
2023 28' International
Mercer County
, New Jersey
Join Date: Oct 2021
Posts: 793
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The on-demand hot water heaters only run on propane so that is not an issue - it may have a minimal draw for ignition and the control panel - in the grand scheme of things.
With factory-level solar and batteries, you could probably run the refrigerator indefinitely, assuming minimal other usage (lights, radio, TV, etc...) if you had sufficient sunlight everyday to replenish. To extend the usage to cover non-sunny days, you need either more batteries (and more solar to replenish them when the sun returns) or to use a generator to charge the batteries.
I have 270W on the roof, 2 100Ah Lithium batteries (double the effective capacity of the "factory" batteries), and a 200W portable panel to account for shaded parking or to add extra capacity after low-charging days. I also carry a generator but rarely need it and when I do, I only need to run for a short while to replenish the batteries.
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07-13-2022, 08:12 AM
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#3
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Rivet Master 

2024 25' Trade Wind
Seattle
, Washington
Join Date: Mar 2022
Posts: 1,199
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Quote:
Originally Posted by jeffb831
The on-demand hot water heaters only run on propane so that is not an issue - it may have a minimal draw for ignition and the control panel - in the grand scheme of things.
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The on demand hot water draws power every time you turn on the faucet (I believe even when you are just using cold) when the hot water heater is on. You can save power by turning the hot water off when not needed. If you use the taps often, that can be a significant extra draw. We don’t generally do that when boondocking anyway because we are trying to preserve water.
Quote:
Originally Posted by jeffb831
I have 270W on the roof, 2 100Ah Lithium batteries (double the effective capacity of the "factory" batteries), and a 200W portable panel to account for shaded parking or to add extra capacity after low-charging days. I also carry a generator but rarely need it and when I do, I only need to run for a short while to replenish the batteries.
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We have about the same (300 watts on the roof and a more portable 100W panel for more regular use, and a 200W hard framed panel that we can bring if we are boondocking for a longer period.
I don’t have enough experience with the Airstream to judge yet how well we’ll do in the often gray Pacific Northwest. Our old trailer had much lighter power draws, we had 480 watts solar on the roof, but 2 - 100Ah AGMs, so tradeoff there. And tanked hot water (which we left off often). We basically never had to worry about plugging in. We’ll see how this new setup works for us.
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07-13-2022, 08:36 AM
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#4
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Rivet Master 
2019 22' Sport
High River
, Alberta
Join Date: Aug 2006
Posts: 1,357
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Quote:
Originally Posted by Sagamore
We traded in our 2018 25RBQ Flying Cloud for a 2021 27' Globetrotter. I wish I could have traded out the refrigerator and hot water heater [emoji45]
My question: Is there any amount of solar that will run the refrigerator (electric) and hot water heater (on demand/instant water hog) for boondocking? I have a feeling if we want to boondock it will be with ice chests, heating water on the gas stove and child showers [emoji17]
We have Honda e2000 generator with companion but I don't want to run them all day and sometimes the noise is an issue. Any input on solar we should get is greatly appreciated.
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The answer is, “it depends.” The compressor refrigerator probably uses 30 to 50 amp hours per day. For this, a 200 watt solar panel will probably suffice. Then you need to add your other requirements. These vary widely, depending on what you and your family deem to be essential.
At least 100 amp hours of usable battery capacity should be installed.
The on demand water heater shouldn’t use a lot of electricity. However, you will want a Showermiser because on demand heaters save energy but waste water. This should be standard equipment with an on-demand water heater. My sister in law’s new r-Pod has one, even with a conventional hot water tank.
These new systems can be made to work if they are augmented with the right equipment.
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07-13-2022, 12:16 PM
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#5
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 16,742
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Hi
Ok, here's the math:
Your 27' has a fairly large fridge. Figure it pulls 5 to 10A when running and runs 30% of the time. You could look up the exact specs. 5A at 30% gets you 1.5A average and 36 AH a day.
If you have the "stock" AGM batteries you have 100AH of usable capacity. If you have no solar then the stock flooded cells get you about 80AH of usable capacity.
Running nothing but the fridge, you get roughly 3 days out of the batteries.
At 13V, the same 36 AH equates to about 500 WH. A "typical" solar setup gets you about 30% of it's rated power for some number of hours a day. If that is 5 hours things are different than if the time is 22 hours. Yes, there is a lot more to it than that really quick snapshot.
As noted, the water heater doesn't pull much. The fan on the boiler pulls a bit. The water pump pulls something. If that adds more than 20% to the above budget, you are using a *lot* of hot water.
Most folks also use lights and charge computers. This very much gets into a "that depends" sort of thing. You can easily double the budget doing this kind of thing.
Fans are also a common item. Running on low, the typical Fantastic Fan pulls about an amp. Set it to high and it could be as high as 4 amps. Leave the bathroom vent fan running overnight and you used a lot of power  . Obviously duty cycle matters a lot here. In some locations we run the fans quite a bit.
This is just a very quick run through. It already has all sorts of options and questions. The real answer is to install something like a Victron Smart Shunt. That will let you do a couple of things:
1) You can see what the real state of your batteries is at any point in time. Doing this with a voltage readout is almost impossible.
2) You can see what you are pulling from the batteries in real time. Turn on this or that and you *know* how much power it pulls.
3) You have a history readout that shows you how you did. For things like fridges that turn on and off, that is very helpful.
A final twist to all of this: Lead acid batteries (AGM or flooded) take way longer than you might think to fully charge up. Everything above assumes you start with a full battery. You can get to 80% or so pretty fast ( so half way between the 50% "stop using" and 100% "full" points). Getting all the way up to a full battery can then take several hours after that. Judging when it is full by a voltage reading is nearly impossible.
Fun !!
Bob
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07-13-2022, 01:55 PM
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#6
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Rivet Master 
2021 30' Globetrotter
Oviedo
, Florida
Join Date: Jun 2021
Posts: 1,415
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A bit off topic, but I recently bought a 26 quart compressor fridge (wins on 110 or 12vdc, a Bluetti 300w power station and a 120 watt portable solar panel. I’ve been running that combo continuously for 2 weeks on the porch of my house just for grins. Maybe a back up, back up for the next hurricane power outage.
Of course this all depends a lot of factors to work. I get a 100% charge on the battery in the mornings (5 hours or so of solid sun). It’s been pretty hot lately, but the fridge is hiding between 38 and 40 degrees during the day
https://www.amazon.com/your-orders/p...sin=B09WW3CTF4
https://www.amazon.com/gp/aw/d/B091G...b_b_asin_title
https://www.amazon.com/gp/aw/d/B08MW...b_b_asin_title
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07-14-2022, 11:20 AM
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#7
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 16,742
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Quote:
Originally Posted by jondrew55
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Hi
.... first link has a problem. It goes to the "your orders" page.
We have a couple of the Dometic CFX3 "powered ice chests". As far as I can see, they are king of the hill right now in terms of low power consumption. We've been running a pair of 100 liter units for the last three months. They have done very well both as a fridge and as a freezer.
Bob
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07-14-2022, 11:30 AM
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#8
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Moderator

2017 26' Flying Cloud
Alamo Heights
, Texas
Join Date: Aug 2006
Posts: 8,722
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Quote:
Originally Posted by uncle_bob
Hi
.... first link has a problem. It goes to the "your orders" page.
We have a couple of the Dometic CFX3 "powered ice chests". As far as I can see, they are king of the hill right now in terms of low power consumption. We've been running a pair of 100 liter units for the last three months. They have done very well both as a fridge and as a freezer.
Bob
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All other things being equal, the "ice chest" form factor has a natural advantage since they have less air exchange when you open the door to access the contents. Unfortunately they're less convenient for viewing/access the contents, but there ain't no such thing as a free lunch...
__________________
— David
Zero Gravitas — 2017 Flying Cloud 26U | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill
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07-14-2022, 02:11 PM
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#9
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 16,742
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Quote:
Originally Posted by DKB_SATX
All other things being equal, the "ice chest" form factor has a natural advantage since they have less air exchange when you open the door to access the contents. Unfortunately they're less convenient for viewing/access the contents, but there ain't no such thing as a free lunch...
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Hi
Very true. Same idea as a chest freezer at home.
If you look at the various versions of the Dometic "ice chests" they have made significant progress in terms of power used over the last few years. That improvement has not (yet) shown up in their more conventional RV fridges. I suspect the market for the "ice chests" is way larger ( and a bit more competitive).
Bob
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07-14-2022, 02:47 PM
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#10
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Rivet Master 
2022 27' Globetrotter
DALLAS
, TX
Join Date: Apr 2022
Posts: 1,674
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Sharing the thoughts below via a cut-n-paste from another fridge thread I recently replied to. Might help here, or it might just be additional noise
Start of copied post:
The "normal" current consumption of the fridge will be pretty consistent (within normal manufacturing tolerances).
What causes the variation in actual usage conditions is the duty cycle along with other key environmental and usage conditions such as:
1. Installation issues: ensuring adequate airflow to the fridge coils (convection, fan forced, etc), including making sure there is sufficient vent area below the fridge, behind the fridge where the coils are and above the fridge where the hot air from the coils need to go.
2. Ambient air temperature profile throughout the day and night.
3. Relative humidity (less important)
4. Trailer location and shade concerns: is the trailer in full sun, part sun/shade, variation in sun/shade throughout the day (how many hours the trailer is in full sun), etc. Are awnings deployed around the trailer.
5. How many times the fridge is opened and closed during the day and how long the fridge stays open each time.
etc., etc.
We can expect a wide variation in total amp-hour consumption for the same fridge placed in different trailer models and used in different situations by real human beings, based on the above variables. Easily 2-3x variation. Someone in a poorly ventilated airstream in Texas, not using A/C on a 105F day might burn 100ah keeping the fridge cool while someone camping at 6000 ft up in the Rocky Mountains during the summer in the same trailer might burn 30ah.
There isn't a single correct answer here unfortunately.
But, we can look at this from a worst case perspective. Worst cast 24 hour amp-our consumption for a 12v fridge from 12v battery bank is probably in the 80-100amp-hour range. As long as you have at least that much in terms of charging capability on a daily basis from solar, the tow vehicle connection, generators, etc, your power budget for the fridge will work out ok and most of the time you will have power left over for other things like fans, etc.
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