12vdc Fridges - Average Power Used?

[wildebus]

I think the potential issue is that the fans might just circulate cold air in and out of the grill without it being pushed up the back of the fridge to the top where the work is done. And the already hot air that is just circulating up by the fridge fan too. I’m pretty sure that’s what happened with my attempt to improve things with the 3way.

A compressor fridge is quite a bit different to an Absorption. The heat is generated by the compressor unit which is at the bottom of the unit. there is no heat generation anywhere else. With my last camper, the (compressor) fridge was not vented externally at all and I fitted a computer fan that pointed directly at the compressor. When it kicked in, the temp drop was notable.

If you were trying to improve cooling/airflow to a larger degree (maybe in a very hot environment?) you could fit fans to both the top and bottom vents, with one set to push and the other to extract.

 

[wildebus]

Do you have the fans in the top sucking hot out or in the bottom blowing cold in.

bottom, blowing outside air in directly at the rear workings of the fridge.

It never gets really hot anyway. The fans were a precaution that I use since fitting a CRX into my T5 conversion which had no airflow at the rear and while it never failed to work, it did hit 50C at the back, and felt that was a bit too warm.
First fan setup in van after T5 was temp on/off controlled computer fan. motorhome setup is the posh Titan kit.

 

[Fazerloz]

A compressor fridge is quite a bit different to an Absorption. The heat is generated by the compressor unit which is at the bottom of the unit. there is no heat generation anywhere else. With my last camper, the (compressor) fridge was not vented externally at all and I fitted a computer fan that pointed directly at the compressor. When it kicked in, the temp drop was notable.

If you were trying to improve cooling/airflow to a larger degree (maybe in a very hot environment?) you could fit fans to both the top and bottom vents, with one set to push and the other to extract.

The comps are mounted at the top on the 65s and 80s with the condenser down the back so get quite hot at the top end.

 

[Canalsman]

bottom, blowing outside air in directly at the rear workings of the fridge.

It never gets really hot anyway. The fans were a precaution that I use since fitting a CRX into my T5 conversion which had no airflow at the rear and while it never failed to work, it did hit 50C at the back, and felt that was a bit too warm.
First fan setup in van after T5 was temp on/off controlled computer fan. motorhome setup is the posh Titan kit.

I had assumed that the fans were at the top drawing air out. That's why I suggested blanking the areas to the side of the fans.

In that scenario, which is my installation, not blanking it will bleed air from the sides into the fans. That is the line of least resistance to the air flow. I remember picking up this tip from instructions for fitting a bathroom extractor fan. It advised explicitly not to site the fan near the door but as far away as possible to ensure that air was drawn through the room rather than drawing air through the doorway and straight out through the fan.

I think the description was 'short circuiting' the air flow.

I suspect that pushing air from the bottom it will be less of an issue though I'd still be inclined to do it.

 

[wildebus]

I had assumed that the fans were at the top drawing air out. That's why I suggested blanking the areas to the side of the fans.

In that scenario, which is my installation, not blanking it will bleed air from the sides into the fans. That is the line of least resistance to the air flow. I remember picking up this tip from instructions for fitting a bathroom extractor fan. It advised explicitly not to site the fan near the door but as far away as possible to ensure that air was drawn through the room rather than drawing air through the doorway and straight out through the fan.

I think the description was 'short circuiting' the air flow.

I suspect that pushing air from the bottom it will be less of an issue though I'd still be inclined to do it.

Yup, I can see if you are pushing air out, you would want to do that.
I suppose sucking the air in it could go straight out on the sides but the distance between fans and 'target' it is unlikely.

Right now, the vents are actually blocked off currently top and bottom to stop the fridge getting too cold from the natural venting. About time to remove those now.

 

[wildebus]

The comps are mounted at the top on the 65s and 80s with the condenser down the back so get quite hot at the top end.

interesting. and unusual

 

[MrRob]

How come there is no cooling piping on the back of my we fridge, its all closed in and you can hardly hear it run, I did put vents above just to keep air around it and to stop any damp or smellsView attachment 108636View attachment 108637

Where does the extracted heat go?

CRE venting in manual is

Mine is sealed from the inside of the van and vents high and low in side of van. The fridge fan and elements could be enclosed with only vents for incoming cool and out going warm air. Might be more efficient as per the vent fan discussion

 

[MrRob]

interesting. and unusual

Good packaging? at the top It robs freezer not fridge space.

 

[wildebus]

Good packaging? at the top It robs freezer not fridge space.

Maybe it depends where the freezer section is? On mine it is at the bottom. Same as in the house fridge/freezer.

 

[Nabsim]

Mine is the older MDC110, it has the compressor at the top where the freezer compartment is but has cooling tubes(?) all over the back of the unit. There are big fridge vents behind it from where the van originally had a tall 3-way fitted and gets a lot of ventilation, so much so I have blanked off the top a couple of years ago. Top vent is probably three or four feet above top of fridge though and it does have vents into hab area above it.

 

[wildebus]

Mine is the older MDC110, it has the compressor at the top where the freezer compartment is but has cooling tubes(?) all over the back of the unit. There are big fridge vents behind it from where the van originally had a tall 3-way fitted and gets a lot of ventilation, so much so I have blanked off the top a couple of years ago. Top vent is probably three or four feet above top of fridge though and it does have vents into hab area above it.

I replaced pretty well like for like, however the new fridge was around 2" shorter and 2" narrower. those gaps on the side in the winter allowed cold drafts from the exterior vents to come in to the van interior through the (neccessary for hinge action) gaps at the front, so I blocked the top half with insulation to eliminate. The discussion has reminded me it is time to remove the insulation from the lower vent.

PS. if temperature is an issue, it should be noted that the walls on the sunny side of a van can get very hot and that heat can pass over to the fridge workings. A compressor fridge won't care much, but it can affect the absorption fridge. I was thinking of putting silver foil on the inner side of the van wall to reflect the heat but never got round to it before fitting the fridge, but still think it could be a good idea.

 

[MrRob]

The CRE80 Is usefully smaller that the 3way it replaced so we have somewhere to store some of our “curtains” and an extra kitchen / junk draw. I did think about extra insulation for the new fridge as some boat installations have seen it reduced consumption. But I like the extra space.

My top vent is mat black so heats up in direct sunlight… I have wondered if that interferes with the draw the vents achieve. Hence trying the vent fan.

 

[MrRob]

The fans are in … I can’t find anywhere convenient to mount the control panel so it’s stuck to the back of the fridge

It’s been warm and windy here today and fridge is on the shaded side and I haven’t seen/heard them kick in so that’s good.

Bought a cheap Bluetooth thermometer to monitor temperature and it seems additional insulation would indeed be a good thing as temperature rises as fast as fridge cools. Even without the door opening where temp jumps up.

 

[wildebus]

Where I fitted mine was handy for access, but in reality it is not something you need to access really, so fitting where you have will work well

I found fridge internal temps vary much more than you would expect between the compressor turning on and off. And this was true of both normal 240V domestic fridges and a 12V Weaco motorhome fridge.
I no longer use the fridges own thermostat to control when it goes on, but just set it to max and use an temp sensor that goes to the Cerbo and then goes to a relay that activates when the freezer goes above -11.5C and off again (cutting power) when it goes below -12.5C. A very tight range, but even then the range varies more than that as the effect of the compressor running is delayed, but still is a significant improvement on leaving the fridge to its own devices. Also allows you to set the temp appropriate to the use e.g. I have it set so it operates as a 2* Freezer rather than a 4*, which is fine for my needs as well as using a little less power overall.
Relay State is Fridge power control - Fridge has power when closed, no power when open;
Temperature is the Freezer (can monitor better on Freezer section than Fridge I found).

 

[1 Cup]

Just fill the fridge with beer and freezer with ice packs to hold the cold in, an empty fridge runs more.
Mine is ok but always full with beer and when I run low I restock quickly.

 

[trevskoda]

Just fill the fridge with beer and freezer with ice packs to hold the cold in, an empty fridge runs more.
Mine is ok but always full with beer and when I run low I restock quickly.

Other way round, many fridge makers tell you not to overfill it as less effective.

 

[1 Cup]

Yer its like a washing machine ram it in it don't work well
But cans and plastice ice packs have room for air , you can help fridge by puttin the stuff in fridge at home first befor you leave. I used to put my freezer packs in freezer with 3 in1 now have the domestic 70ltr freezes them from fluid. I've not turned fridge off since Christmas.
I turned it up to half way about a month ago to go to hereford and 200w solar wont fully charge battery its at about 80%so ill have to use b2b to fully charge
The pics have dates and watts used with fridge only apart fom time away.

 

[mistericeman]

As a Airconditioning/ refrigeration engineer....

2 identical fridges
One loaded and one empty
And open/closed the same
Etc

Will run the same amount of time.
..

The fridge space is a static load (food in the fridge isn't exothermic (generating heat)
So like for like loaded/unloaded and left alone
Once down to temp.... That's it game over...

All acedemic as IF the beer/food/wine is in there...

I'm in and out like a fiddlers elbow

 

[MrRob]

Luckily I like warm beer most of the time so I don’t have to go in there every few minutes Unless it’s it’s above 20 deg then to heck with battery consumption I’m opening the door and stacking it with warm beer to chill.

Question/Thread was just to check that I’m within normal range for my type of fridge. But thanks again for all the help.

 

[mistericeman]

Luckily I like warm beer most of the time so I don’t have to go in there every few minutes Unless it’s it’s above 20 deg then to heck with battery consumption I’m opening the door and stacking it with warm beer to chill.

Question/Thread was just to check that I’m within normal range for my type of fridge. But thanks again for all the help.

I'm sure life was simpler when 'cold milk' was kept in a bucket of water in the shade lol