Dometic 3 way fridge

[mikerezny]

Hello @mikerezny , found some interesting data on inverters for you to think about. Quoted direct from Australian Direct - Batteries and Charging Guide
"Probably one of the most battery hungry devices you can run from a battery is an inverter. When calculating the loads for a 700 watt inverter, use a multiplier of 1.2 in the following formula;
Wattage X 1.2 divided by voltage. So our 700 watt load would look like this:
700 X 1.2 divided by 12 = 70 Amps.
A small inverter can pull some serious loads off a battery........." A compressor fridge is nowhere near this amount!
Whilst a compressor fridge is more efficient, it comes at a cost in battery power. Even a small one would be dragging out nearly 40 amps daily working on a 40% running cycle. You would need to have a lot more battery storage as well as at least 200 watts of solar to be able to continue running the fridge. If the sun God was not kind to you, say 3 or 4 days of cloudy or rainy weather, you would have to seek another source of power - eg generator or connect to tug and run engine for long periods. This can be done and is quite reasonable too. To change, you would have to swap your gas bottle/s for batteries and solar panels. But if it comes down to the wire both heat absorption and compressor fridges (with transformer) can run on 240 volts and that is where the compressor fridge is superior. The whole trouble with that for me is that I go where there is NO 240 volt power, so I will stick with my gas operation. !4 days continuous operation on one 8.5 kg gas bottle will do me and no need for more outlay of money. That's why I do everything possible to increase the efficiency of my inferior (to compressor type) heat absorption type!!!

Hi @Boots in Action,
thanks for the interesting feedback.

What tickled my interest in inverter fridges was their claimed efficiency over compressor fridges. One manufacturer claimed up to almost 50%. Then I looked at prices of domestic fridges from Samsung and LG and it is not impossible to get a 200l domestic fridge for less than $500. Rough calculation, is that this is $1,000 cheaper than compressor fridges for specifically caravans. $1,000 buys a lot of battery and solar.

There is quite a lot of discussion on this topic on other caravan forums. Quite a few people have installed them in their vans.

That was the upside. The downside is that domestic fridges are not designed to be mounted in a caravan. A domestic fridge would have to be run through an inverter, so the efficiency is reduced by the 240V inverter losses. The last is that I could not find an inverter fridge for caravans or a domestic fridge with a capacity of 90l that would fit in the Penguin.

We love our Penguin, so I am not going to buy an Expanda so I can fit a large 200l inverter fridge and 500W of solar and 3 batteries and a generator and a new vehicle to tow it all just to avoid using a gas fridge. At the moment, we get 20-21 days from a 9kg bottle and we have used two in six months at about $15 per refill or $20 per swap'n'go.

In the future, if we happen to be heading into the tropics, my preferred option at the moment would be to get the Waeco-type fridge that Aldi sell to use if we get into a situation where the Dometic absorption fridge isn't able to cope. But that won't be happening soon, so I have plenty of time to think about it, read about how other people cope, and change my mind numerous times.

We mostly free camp and even in caravan parks would always use unpowered sites.

Also, sometime over the weekend I will take a picture of our LED strip light bedhead light.

cheers
Mike

 

[mikerezny]

Hi @Boots in Action,
your comment on air compression inside the fridge is something I never considered. As you have said, assuming the fridge has a good seal, hot air will be drawn in from arguably the hottest part of the fridge and van. That is obviously not good.

Clearly, your idea of avoiding using the tray and putting the outlet / inlet through the floor would help. I am going to implement this.

However, my thought is to reduce the amount of hot air getting into the fridge when the door is opened. So, I have more confidence in what I am currently doing:
1: Put plastic containers on all shelves to reduce the cold air getting out. If the containers have nothing in them, we put the lid on them to stop the cold air getting out.
2: Keep the fridge as full as possible and reduce the amount of cold air in the fridge that can be lost when the door is opened.

Keeping the fridge full also has the benefit of:
1: having more thermal momentum. i.e A large solid mass that is cooled overnight to keep the fridge cooler in the hotter parts of the day.
2: A large cold mass, so that when the door is opened, the recovery time to cool down the (reduced amount of) hot air will be quicker.
3: Less space for air in the fridge means less water-laden hot air getting in to condense as ice around the cooling fins.

The bung I have put in the drip tray was really simple. I used about 1" of three core flex and removed only the copper wire. So there are only three tiny holes. The piece of cable is a loose fit in the hole and I used a cable tie around the top to stop it falling through and to let me lift it up to clear any water build up. Have never had any water build up.

cheers
Mike

 

[Boots in Action]

Hi @Boots in Action,
your comment on air compression inside the fridge is something I never considered. As you have said, assuming the fridge has a good seal, hot air will be drawn in from arguably the hottest part of the fridge and van. That is obviously not good.

Clearly, your idea of avoiding using the tray and putting the outlet / inlet through the floor would help. I am going to implement this.

However, my thought is to reduce the amount of hot air getting into the fridge when the door is opened. So, I have more confidence in what I am currently doing:
1: Put plastic containers on all shelves to reduce the cold air getting out. If the containers have nothing in them, we put the lid on them to stop the cold air getting out.
2: Keep the fridge as full as possible and reduce the amount of cold air in the fridge that can be lost when the door is opened.

Keeping the fridge full also has the benefit of:
1: having more thermal momentum. i.e A large solid mass that is cooled overnight to keep the fridge cooler in the hotter parts of the day.
2: A large cold mass, so that when the door is opened, the recovery time to cool down the (reduced amount of) hot air will be quicker.
3: Less space for air in the fridge means less water-laded hot air getting in to condense as ice around the cooling fins.

The bung I have put in the drip tray was really simple. I used about 1" of three core flex and removed only the copper wire. So there are only three tiny holes. The piece of cable is a loose fit in the hole and I used a cable tie around the top to stop it falling through and to let me lift it up to clear any water build up. Have never had any water build up.

cheers
Mike

All good in theory, but it looks like you are on the ball pretty well. The only problem is if you stack your fridge too much, there is no room for any airflow to circulate even with fans!!! See previous thread by our knowledgeable @Drover. Clever use of wire for bung in water outlet though, and would definitely be a good restriction on the air flow of air yet lets water out very slowly too. Keep up the good work!!

 

[Boots in Action]

Hi @Boots in Action,
thanks for the nteresting feedback.

What tickled my interest in inverter fridges was their claimed efficiency over compressor fridges. One manufacturer claimed up to almost 50%. Then I looked at prices of domestic fridges from Samsung and LG and it is not impossible to get a 200l domestic fridge for less than $500. Rough calculation, is that this is $1,000 cheaper than compressor fridges for specifically caravans. $1,000 buys a lot of battery and solar.

There is quite a lot of discussion on this topic on other caravan sites. Quite a few people have installed them in their vans.

That was the upside. The downside is that domestic fridges are not designed to be mounted in a caravan. A domestic fridge would have to be run through an inverter, so the efficiency is reduced by the 240V inverter losses. The last is that I could not find an inverter fridge for caravans or a domestic fridge with a capacity of 90l that would fit in the Penguin.

We love our Penguin, so I am not going to buy an Expanda so I can fit an inverter fridge and 500W of solar and 3 batteries and a generator and a new vehicle to tow it all just to avoid using a gas fridge. At the moment, we get 20-21 days from a 9kg bottle and we have used two in six months at about $15 per refill or $20 per swap'n'go.

In the future, if we happen to be heading into the tropics, my preferred option at the moment would be to get the Waeco-type fridge that Aldi sell to use if we get into a situation where the Dometic absorption fridge isn't able to cope. But that won't be happening soon, so I have plenty of time to think about it, read abou how other people cope, and change my mind numerous times.

We mostly free camp and even in caravan parks would always use unpowered sites.

Also, sometime over the weekend I will take a picture of our LED strip light bedhead light.

cheers
Mike

Hi @mikerezny , I guess with inverter fridges, they are like air- conditioners. Those with inverter technology are far more efficient than the old compressor type wheezing away as it stops and starts. Our a/c unit at home uses an inverter.
If you are doing all you say on improving the efficiency of your fridge in your Penguin, you will not have any problems at all. We travelled to Cairns and the Daintree last April and the only small problem was the build up of ice on evaporator fins. That is no longer a problem with the upper fan now blowing air across the face of the evaporater, whilst the bottom fan was already in operation so no frozen lettuce etc. Cheers

 

[mikerezny]

All good in theory, but it looks like you are on the ball pretty well. The only problem is if you stack your fridge too much, there is no room for any airflow to circulate even with fans!!! See previous thread by our knowledgeable @Drover. Clever use of wire for bung in water outlet though, and would definitely be a good restriction on the air flow of air yet lets water out very slowly too. Keep up the good work!!

Hi @Boots in Action,
yes, I agree, completely filling the fridge would not be good, neither would having almost nothing in it. So there should be a sweet spot somewhere between those two extremes. Good thermal mass 'momentum' and enough space for cold air from the cooling fins to circulate around the contents. If I had to guess, I would start at a 80/20 rule: 80% contents and 20% air. This reduces the amount of air that MAY be replaced when the door is opened by a factor of five over an empty fridge.

Enjoy your weekend.

Tomorrow morning, we are off to Walhalla for 3 days.

cheers
Mike

 

[Drover]

But then a Pengiun only has a medium sized Esky passing as a fridge doesn't it..............room for a bag of ice and a can of coke..????

 

[mikerezny]

But then a Pengiun only has a medium sized Esky passing as a fridge doesn't it..............room for a bag of ice and a can of coke..????

Oh @Drover, sometimes you can be so cruel!

 

[chartrock]

Oh @Drover, sometimes you can be so cruel!

And with very little effort.

 

[Boots in Action]

But then a Pengiun only has a medium sized Esky passing as a fridge doesn't it..............room for a bag of ice and a can of coke..????

A bit tough @Drover !! Not all of us are able to "Expand" because I for one do not have such a need. The fridge in the Penguin, although much smaller than your Expanda, can keep all the important things cold - the next nights dinner in the freezer a bit of butter, some milk for coffee and several cans of "drink" too. Don't need a bag of ice, only enough to put into my Jim Beam and coke!!
I cannot tell a lie on this forum. @Drover might find out!! I also run a separate gas fridge outside the van to keep the other necessities for camping - more drinks etc. Another proud Penguin owner among all you big Expandas. Good to have some "big" friends around though.

 

[Boots in Action]

Hi @Boots in Action,
yes, I agree, completely filling the fridge would not be good, neither would having almost nothing in it. So there should be a sweet spot somewhere between those two extremes. Good thermal mass 'momentum' and enough space for cold air from the cooling fins to circulate around the contents. If I had to guess, I would start at a 80/20 rule: 80% contents and 20% air. This reduces the amount of air that MAY be replaced when the door is opened by a factor of five over an empty fridge.

Enjoy your weekend.

Tomorrow morning, we are off to Walhalla for 3 days.

cheers
Mike

Take your winter woollies when you go into them thar hills. Safe journey.

 

[mikerezny]

Take your winter woollies when you go into them thar hills. Safe journey.

Hi @Boots in Action,
thanks.

We will certainly have warm clothes and bedding. We have hiked and camped numerous times along parts of the Alpine Trail in April and November. One night we slept in our small hiking tent at Mount St. Guinear. Thermorests, down sleeping bags, thermal under wear, thick hiking socks, woollen gloves, beanie, long-sleeved t-shirt, long pants, warm hiking jacket. and we were barley warm. The only clothing we had left were our gortex rain coats which we were using for pillows. Next morning there was frozen dew on the tent and inch long icicles in the water puddles.

Our nostalgic day hike on Saturday will be to walk from Walhalla to the iron bridge and back. Should take a little under 2 1/2 hours to get there.

Take care
Mike

 

[Drover]

Oh @Drover, sometimes you can be so cruel!

Just a bit of humour to keep morale up.................

 

[Crusty181]

and likewise can crap on a bit too much I'm afraid.........................

My new mantra @Dobbie "I'm not going off topic, I'm not going off topic............"

Locked and loaded. Or should I say saved, cut and pasted. Like feeding the monkeys at the zoo; these two gems will no doubt get a regular airing as a constant (and I do mean constant) reminder