Community Forums

GSGracie · 01-24-2012, 02:15 AM

Hi all. I have read a lot of threads here about converting the usual RV fridge to a domestic one. However there is very little on what the number crunches actually come out to be. I have a Dometic, really basic (no temperature control) that freezes everything in the top of the fridge. I want to replace it with a domestic fridge but I need to know what current it will draw and how many Amp-hours a day it will use. I have five AGM 100 hour batteries and 350 watts of solar. In the middle of summer I can get over 120 AH from the solar but on a cloudy day I may only get 70 AH. Do I have enough storage to run a domestic fridge or will I need more solar and storage as well? I really want numbers here folks. If it draws 10 amps at the start, for how long? How often? I cannot afford to use all of my storage on the refer if I have heaps of gas on board that I hardly use at all. Hope someone here can help. BTW I have a 3000W inverter that has a 400A fuse so that part is covered I think. I eagerly await your replies! Graham

GSGracie · 01-24-2012, 02:26 AM

Sorry should have added - I want to free camp as much as possible, or boondock as you guys call it. I have a big LPG tank that is only used for cooking and heating. I have never come close to running out of gas, but I do seem to run low on power occasionally. I have an ONAN 7000 generator that is only used to charge the batteries, it is not connected to any other circuit as it is 110 V - the rest of the RV is 240

SarahW · 01-24-2012, 10:51 AM

Hi Graham. I know lots of people have made that conversion, so hopefully someone will be along soon to answer your questions.

I was just going to ask if you have tried one of those small fans inside your Dometic to help circulate the air? That might solve your "freezing on the top" issue and is a cheap solution. Good luck.

jspande · 01-24-2012, 05:56 PM

You may also want to take a look at a 12 volt compressor refer, commonly used in marine applications. Do a Google search for "Vitrifrigo DP2600". The is an 8 cu. ft., double door unit that's practically a drop-in replacement for a similar volume RV unit. It'll use about 60 amp-hr a day and you won't need to run your inverter 24/7. Another advantage is positive door latches so you don't have to come up with straps or something to keep the door from opening while traveling. Mine cost about $1400. Since you already have an inverter, the cost obviously would be less for the domestic type.

RV Wizard · 01-25-2012, 03:06 AM

Coming up with any accurate numbers will depend on the ambient air temperature, how dense the inside of refrigerator is with food products, how often the doors are opened, relative humidity and if you will be installing a frost free refrigerator or one you will manually defrost.

paz · 01-25-2012, 05:30 AM

As RV Wizard says, much depends on the conditions under which the refrigerator is operating along with the size and efficiency of the refrigerator itself.

One way to get a rough idea of energy usage is to look at the Energy Guide for the particular make and model you're looking at. These are frequently available online on the Lowe's, Home Depot and manufacturers' web sites.

The energy Guide will tell you the estimated annual energy usage. Divide by 365 days to get estimated daily energy usage.

For example, the residential refrigerator we just ordered uses an estimated 445 KW-hr a year. That equals roughly 1200 watt-hrs a day. At 12 volts, that is equivalent to about 100 amp-hrs.

Once we get the new fridge up and running, I will put the Kill-a-Watt meter on it and get some actual readings over several days.

GSGracie · 01-25-2012, 10:57 AM

Thanks Paz. It was actual readings I was looking for. I realize that there will be fluctuations and variances but a ball park figure like your calculation of 100 AH per day is very useful. I had done the same calculation and it seemed quite high for bpondocking so I wanted some actual data to check it against. Since 100 AH is 20% of my total daily storage I think I would have to get more storage and more solar for it to be a viable option for me. I would welcome your actual readings verifying the calculations though. As they say "in theory, there is no difference between theory and practice, but in practice, there is".

jlyon69 · 01-25-2012, 11:39 AM

Quote:

Originally Posted by SarahW

I was just going to ask if you have tried one of those small fans inside your Dometic to help circulate the air? That might solve your "freezing on the top" issue and is a cheap solution. Good luck.

I just added one of these, but haven't had the chance to try it out yet. For $15 I'll try anything

So how is it working for you?

Quote:

Originally Posted by GSGracie

Sorry should have added - I want to free camp as much as possible, or boondock as you guys call it. I have a big LPG tank that is only used for cooking and heating. I have never come close to running out of gas, but I do seem to run low on power occasionally. I have an ONAN 7000 generator that is only used to charge the batteries, it is not connected to any other circuit as it is 110 V - the rest of the RV is 240

Graham,

In my opinion, as log as the Dometic is running fine, I would keep it as I can run mine for weeks on propane. You do have more solar and storage, but I think you can still run into some trouble. We like to free camp as much as possible and being tied down to only one source of power for the frig is a frightening thought for me

It seems to me my Onan in my old MH was easily converted to 240v, have you checked that out?

SarahW · 01-25-2012, 10:09 PM

Quote:

Originally Posted by jlyon69

I just added one of these, but haven't had the chance to try it out yet. For $15 I'll try anything

So how is it working for you?

Honestly, our moho is only 3 months old and the new Dometic fridge works great so far (we even have hard ice cream!!)

I bought one of those small fans but we haven't had occasion to use it yet...though I know several people who swear by them.

Mr_D · 01-25-2012, 10:26 PM

Quote:

Originally Posted by GSGracie

Sorry should have added - I want to free camp as much as possible, or boondock as you guys call it. I have a big LPG tank that is only used for cooking and heating. I have never come close to running out of gas, but I do seem to run low on power occasionally. I have an ONAN 7000 generator that is only used to charge the batteries, it is not connected to any other circuit as it is 110 V - the rest of the RV is 240

Who rewired your rig so it was only 240 volt? Most of them of that vintage are 30 amp and a 50 amp RV is still a 120 volt service even though it looks like a 240. There are actually two 120 volt legs feeding it. Only a few of the high end (Prevost, Newell etc.) actually use 240 volts and then usually only for the dryer.

GSGracie · 01-26-2012, 01:50 AM

Hi Mr_D.
The bus has been completely rewired for New Zealand electrical standards, the only thing still standard USA is the thick feeder cable from the cg to the bus itself. Even that may need to be replaced but it seems OK at present. All new NZ wiring has been laid using trunking where necessary within the bus, but mostly in conduit underneath the bus. I have not yet changed the AC units to 240 V but they will need to be rewired from the switch board when I do so, as well as changing the compressor and heating unit in the AC to 240V as well. I have a current NZ Electrical Certificate of Fitness so I assume that everything of concern has been changed. I appreciate your concern as it has been a major worry making sure that I comply with all of the NZ regulations. I was not able to use ANY of the original American wiring even though the current used for 120V would twice that for 240V, as apparently the original insulation is not up to the standard required here. Go figure!

GSGracie · 01-26-2012, 01:53 AM

Jlyon69 - I agree totally that a well running gas fridge is my best option in terms of versatility, but a new gas refer (Dometic) is nearly $4500 here! I may just have to bite the bullet and go for the top of the line refer and hope that the NZ agents stand behind their product.

GSGracie · 01-26-2012, 01:55 AM

I tried to convert the Onan as my first choice, but the NZ agent said it was not possible.

paz · 02-01-2012, 05:01 AM

Quote:

Originally Posted by GSGracie

Thanks Paz. It was actual readings I was looking for. I realize that there will be fluctuations and variances but a ball park figure like your calculation of 100 AH per day is very useful. I had done the same calculation and it seemed quite high for bpondocking so I wanted some actual data to check it against. Since 100 AH is 20% of my total daily storage I think I would have to get more storage and more solar for it to be a viable option for me. I would welcome your actual readings verifying the calculations though. As they say "in theory, there is no difference between theory and practice, but in practice, there is".

Getting back to your original question, we have now had our new residential refrigerator sitting in the middle of the floor of our motorhome while I modify the cabinet where it goes.

I have been running the new fridge through the Kill-a-Watt meter since we first got it. After discounting the first few days for the initial cool-down and for transferring food from our old Norcold, the new residential refrigerator has been drawing about 1.4 to 1.5KWHr a day. In theory, it should only draw about 1KWHr a day; but as you said, "in theory, there is no difference between theory and practice, but in practice, there is." We are located in Florida where it has been warm, but not been excessively hot. Daytime temperatures have been in the 60s and 70s, and nights have been 40s and 50s for the past few days.

It looks like the estimated energy usage on the energy guide for appliances is about as reliable as fuel mileage on the window stickers of new automobiles.

BTW, the refrigerator we purchased is a Samsung RF197. One reason we chose it is it is said to be capable of running on a modified sine wave inverter. The Samsung starts and runs just fine on our 1000W inverter, even when the inverter is also powering the TV, satellite DVR box and laptop at the same time.