Electrical Fridge fans
- Thread starter JamesW
- Start date
Well, I can't take my money with me to hell so I have purchased a KlevaCool external fan kit and remote switch. The attention to detail and finish is awesome and I am pretty hard to please due to my work background. The DIY posters might well say it should be perfect for the price. I'll post some photos of the install as it proceeds.
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I'll be spending big on diesel too later in the year. A trip to WA and back from rural NSW.
Certainly covers the whole vent, since my fans run above a certain temperature they are not running all the time and no need to do so, having a clear area of unrestricted air flow allows heat to vent unaided.
While it looks like the fan kit covers the vent completely there are quite a few gaps. Heat build up behind the fridge is an end result of many factors. The ambient temp of the day or even night, what side of the van the fridge is on and if any shade is available. A open vent with a few fans attached may well be an inefficient way of extracting heat, possibly not much better than no fans at all. On the other hand the kit I am fitting or it's competitor may not be the most cost efficient way of extracting heat. The variables are many and without side by side testing in a controlled environment a conclusion as the what is better would be difficult to arrive at. So we all do what we think is best for our own situation and hope it works. The fan kit is not the only modification I am making, as the natural rise of heated air would have better laminar flow if the path was smoother so I am working on that. It's a simple and cheap thing to.
Whilst the actual product appears to be high quality, the actual design leaves a lot to be desired.
The main area to have airflow is over the condenser fins on th LHS of the fridge.
The best position for fans is thus on the LHS. Further, the fan on the RHS is going to be drawing HOT air from the boiler.
This has the added problem of actually COOLING the boiler. Not particularly efficient.
Then to top it off they have blocked the LHS of vent where the circuit board is mounted. Why?
Lastly, the fans are thermostatically controlled. This is obviously good. But ask yourself this question. What happens when the fans are not activated? Well, because of the lack of ventilation, heat will more quickly build up over the condenser fins making the fridge work less efficiently until the fans have to be activated.
The design would be better if both fans were mounted on the LHS of the external vent, the circuit board mounted away from the vent, and leaving as much open area for air to flow naturally through the external vent.
Note that if you have a power problem or the fans aren't working, you will have to remove this assembly ASAP to allow your fridge to vent normally.
The main area to have airflow is over the condenser fins on th LHS of the fridge.
The best position for fans is thus on the LHS. Further, the fan on the RHS is going to be drawing HOT air from the boiler.
This has the added problem of actually COOLING the boiler. Not particularly efficient.
Then to top it off they have blocked the LHS of vent where the circuit board is mounted. Why?
Lastly, the fans are thermostatically controlled. This is obviously good. But ask yourself this question. What happens when the fans are not activated? Well, because of the lack of ventilation, heat will more quickly build up over the condenser fins making the fridge work less efficiently until the fans have to be activated.
The design would be better if both fans were mounted on the LHS of the external vent, the circuit board mounted away from the vent, and leaving as much open area for air to flow naturally through the external vent.
Note that if you have a power problem or the fans aren't working, you will have to remove this assembly ASAP to allow your fridge to vent normally.
All good theoretical scenarios. I will put them all to the designer and manufacturer to see what he thinks.Whilst the actual product appears to be high quality, the actual design leaves a lot to be desired.
The main area to have airflow is over the condenser fins on th LHS of the fridge.
The best position for fans is thus on the LHS. Further, the fan on the RHS is going to be drawing HOT air from the boiler.
This has the added problem of actually COOLING the boiler. Not particularly efficient.
Then to top it off they have blocked the LHS of vent where the circuit board is mounted. Why?
Lastly, the fans are thermostatically controlled. This is obviously good. But ask yourself this question. What happens when the fans are not activated? Well, because of the lack of ventilation, heat will more quickly build up over the condenser fins making the fridge work less efficiently until the fans have to be activated.
The design would be better if both fans were mounted on the LHS of the external vent, the circuit board mounted away from the vent, and leaving as much open area for air to flow naturally through the external vent.
Note that if you have a power problem or the fans aren't working, you will have to remove this assembly ASAP to allow your fridge to vent normally.
They are not all that theoretical. The ideas come from the experience gained operating a three-way fridge over the past 6-7 years, having adequate academic qualifications, and many years experience as a tradesman. Oh, and wanting to exercise the brain when we are out camping.All good theoretical scenarios. I will put them all to the designer and manufacturer to see what he thinks.
I have a Jayco Penguin Windup camper. This is the worst type of van for operating a three-way fridge. Due to the design it is impossible to mount the top external vent above the condenser fins as per the instalation instructions. Thus, there is little chance to get the desired Venturi effect to ensure efficient natural airflow over the condenser fins. Further, the small 95l fridge has the disadvantage of having to cram the boiler assembly close to the condenser fins. Thus one has a hot boiler mounted right next to condenser cooling fins! I have put more insulation around the boiler to improve its efficiency and to reduce the amount of heat reaching the fridge walls and hot air finding its way up to the condenser fins.
Our fridge will survive in ambient temperatures up to 40C. But it takes a bit of effort to achieve that.
I have ONE 120mm fan mounted on the far LHS of the top external vent.
I tried two and am of the opinion that too much airflow can be a problem if some of that air is hot air being sucked up past the boiler. After quite a bit of testing, I believe I can achieve better results with just one fan optimally placed. That is the way it has been for over 5 years.
The choice of fan is also important. I search through many fan specs (good fans are made for use in high performance gaming computers)
My first choice was ok, but, I found a better fan.
I use a Pure Wings 2 120mm fan. It is quiet (19.2 dB(A)), pushes a reasonable amount of air (51.4cfm), and is efficient (90mA). This fan pays particular attention to efficient and quiet blade design). Total energy draw is 2.16Ah over 24 hours at 100% duty cycle. It also has a long service life.
The fan is controlled by a 50C thermostat mounted on the pipe from the boiler to the condenser fins on the top LHS of the fridge. I want the fan to come on as soon as possible after the gas flame is on full.
There are a couple of ideas that I should get off my but to do:
1: Put a baffle in between the condenser fins and the boiler to ensure as little as possible hot boiler air gets up to the condenser fins.
2: Put a short square shroud around the fan to favour drawing air from around the condenser fins and to reduce the chance of the fan recirculating its own air from front to back.
It's not gonna happen in this lifetime.
Mike
The positioning of fans has little to do with the operation of fridge and the exhausting of hot air if installation is poor and not in accordance with the manufacturer's installation instructions. I came across a case just recently involving a 2017 Jayco Starcraft. This 21ft van was much bigger than my little Penguin and even had a slide-out for bedroom and a AES 180L 2 door fridge with electronic thermostat control!! While my little 93L single door Thetford was easily operating in the 28 to 31C ambient temperatures (my thermostat setting of 3 and a half on 5 scale) whilst connected to 240v power and holding MINUS 22 to MINUS 24C in the freezer section and 2 to 4C in the fridge section most of the time, after 3 or 4 days the big Starcraft was in trouble- unable to make any ice at MINUS 2 to MINUS 3C IN FREEZER and fridge temperature at 8 to 10C. Something was drastically wrong!!!
We checked for levelness firstly - all good. Removed the top and lower vents (large ones too) and had a look in the bottom section. All wiring and gas lines appeared okay. But a look upwards from the bottom vent towards the top revealed nothing but clear light. The cavity behind fridge was approx 620mm wide and 150mm deep. THERE WAS NO BAFFLE WHATSOEVER TO DIRECT ANY ANY AIR THROUGH THE CONDENSER COILS. Two small fans were running in the open space well below the condenser fins, (ineffectively) just circulating the air and not directing the air towards the condenser fins at all. The fridge condenser fins extended approx 70mm into the gap leaving over 80mm clear from edge of condenser fins to inside of external wall. No noticeable airflow was detected coming out of the top vent, nor was any perceivable warmth felt. Obviously with a gaping 620mm X 150mm gap, any airflow would be difficult to notice.
Now quoting directly from my Thetford installation manual:
"If there is more than 25mm of clearance between the rear of refrigerator and the enclosure, add two baffles to the rear of enclosure.
Put one baffle at the top edge of the lower intake vent. ( to direct air over the heat exchanger parts)
Put the other baffle at the lower edge of the condenser of the refrigerator. (to direct air through the condenser fins)
Make sure the baffles are LESS THAN 6 MM FROM THE COILS AND CONDENSER OF THE REFRIGERATOR.
Make sure the baffles are the FULL WIDTH of the inside of the enclosure".
The fridge in this Starcraft was certainly NOT installed in accordance with Manufacturer's installation instructions!! We cut down a swimming "noodle" which just happened to be approx 80mm in diameter and pushed it into the 570mm X 80 mm space between bottom of condenser fins and internal wall to block off the excess space so ALL air from below was forced to pass THROUGH the condenser fins and not go around or just past it. An immediate difference was noted. There was a definite flow of air through the condenser fins and some warmth was also felt. An hour later, freezer temp had moved to MINUS 6C and fridge dropped to 7C. Next morning, fridge was down to 0 to 1C and freezer had reached MINUS 10C, freezer still not low enough but improving, with fridge/freezer thermostat still set for maximum cooling. Freezer temp should be MINUS 18C minimum and MINUS 14C maximum.
Summing up, there is a definite need to direct the maximum amount of air THROUGH the condenser fins just like the shroud around the radiator housing in front of car engine fan. That means that there is an important need for a baffle/s to ensure minimum gap between baffle/s and condenser fins/coils. Also, if using fans at the top to draw the hot air out, make sure there are no gaps around top of fridge - there were several 6 to 10mm gaps in Starcraft exit area which would have reduced the amount of air from below being drawn through the condenser fins. If using a fan in the lower vent, be sure to shield the boiler area from the fan draft. I used a piece of aluminum roof flashing between the heat exchanger coils and the burner/heating area. I have two 120mm fans - one in bottom vent and one in top vent, both thermostatically controlled with a 50C thermostat. My success is obvious!!
So there you have it!! Have a good look at the installation of your fridge. It will be of little adding mods use if the basic installation is poor and airflow ineffective, even if you fit fans. Remember, this 2017 Starcraft had fans that did nothing at all.,
I am far from being inexperienced myself due to my own working background, prior to retiring. My situation and fridge installation is different. I have a different caravan. And what I am doing is to achieve the best outcome for my situation. Differing ideas on how to achieve an optimal outcome is just part of the learning process. Life is like that and education should never stop I reckon. Laminar flow and thermodynamics is an interesting subject and can be applied to the workings of a 3 way fridge and the best outcome to remove heat buildup behind them. Lets just agree to disagree, try to apply what we believe best to our own situations and live life to the fullest.
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Well mike @mikerezny , I accept that you have had some success with your 3 way Dometic fridge. However, there are some things that I am not fully in agreement with. But I do agree with your findings not being theoretical but based on factual field experience.
I do not agree with your statement that your Penguin (and Mine) is the worst type of van for operating a 3-way fridge. The top fins on the condenser of my 93L Thetford fridge is just 50mm from the bottom of the top vent and unfortunately, because of wall height, cannot be any bigger. However, I have streamlined the outflow off condenser fins with a piece of thin aluminum roof flashing carefully rounded to fit from rear of condenser fins to bottom of top vent. Fits perfectly and works well in providing a smooth clear path for exiting air. Easy done and you are more than capable of doing the same thing...and cheap too. I have also fitted the same 35mm wide (shiny) flashing alongside and between the the boiler/heating area and the other plumbing in that area, all the way to the top of burner stack and exhaust piping, so NO heat is directly upon the heat exchanger coils and the condenser fins fins too. I still like the idea of two fans (120mm type) - one at the top and one at the bottom - as long as the boiler/heater area is properly shielded. As the Thetford installation instructions seem to indicate that there is a need for airflow over that area, with a second baffle, I believe there is only an advantage in having air blowing over heat exchanger areas.. Your fans are much more expensive than mine are certainly quieter, but my fans, being ball bearing type, move 93cfm each. Yes, they make a bit of a whirr on start up, but rarely run more than 40 seconds before turning off and have never had them obtrusive as they only run for very short periods, and have never run at night when cooler than 25C ambient. Been running now for more than 6 years without failure, drawing around 250ma each when running. Agree that a shroud on top fan to prevent outside air being sucked back into top area is a possibility, but I have never felt any air flow that way as 93cfm creates a considerable airflow that can be easily felt when running. Look forward to seeing you when you get up here.
I have a few decades fiddling with RV fridge set ups, certainly only real world expeience no techo certificates, 3 ways are 3 ways no matter what brand of van and if they don't fit and insulate properly no matter what you do with fans will achieve very little and having modded a few set ups that were done wrong, right from the factory I don't hold van builders QC in much regard.......... Even condensor fridges need good venting and insulation ........... I have experimented with fans to extract the air from behind the fridge and my current set up is most efficient but my fridge is not a small unit and so has large vents where 2 fans allow a large area open to free venting and my flue is a different affair compared to the smaller units in that it exhausts well below the vent.... In all 3 ways the hot air at the rear must flow at a reasonable pace to allow cooling at the condenser fins if its allowed to accumulate it means hot beer ......................
On my old 14.44 it had the small fridge and my first set of fans was encased in a similar mounting which I made but then ended up discarding and just mounted the fans direct to the vent to improve flow when fans not needed to operate..... it was also fitted by just shoving into the cabinet and hooking up, no insulation or baffles what so ever including the cable runs thru the wall either side, it was a food warmer which I pulled out and redid better than the manufacturer instructed and worked better than others, a run from Winton to Julia Crk, 36 deg and no 12v turned on, dropped 2 deg ..............
My latest fridge comes with fans one mounted at the bottom and one half way up, set up to operate when ambient is 32 deg a bit too high I think but a boffin deemed it so............................ be interesting to see this summer.
Look forward to hearing how your set up runs, good or bad its all good info..............@JamesW
On my old 14.44 it had the small fridge and my first set of fans was encased in a similar mounting which I made but then ended up discarding and just mounted the fans direct to the vent to improve flow when fans not needed to operate..... it was also fitted by just shoving into the cabinet and hooking up, no insulation or baffles what so ever including the cable runs thru the wall either side, it was a food warmer which I pulled out and redid better than the manufacturer instructed and worked better than others, a run from Winton to Julia Crk, 36 deg and no 12v turned on, dropped 2 deg ..............
My latest fridge comes with fans one mounted at the bottom and one half way up, set up to operate when ambient is 32 deg a bit too high I think but a boffin deemed it so............................ be interesting to see this summer.
Look forward to hearing how your set up runs, good or bad its all good info..............@JamesW
Hi @Boots in Action,
I should clarify that my statements refer to a Dometic RM2350 as fitted to my Penguin.
It might be best to download a copy before reading on. I have attached a copy for your viewing pleasure.
Refer to Fig 3A on Page 5.
This shows the requirements for the placement of the two external vents. Note that the top vent must be placed above the height of the fridge.
This is important. It also states in the Ventilation Heights table on page 6 that the minimum distance between the bottom of the lower external vent and the top of the upper external vents is to be a MINIMUM of 864mm. This is impossible to achieve in a Jayco windup. The solid wall is only 800mm high. The distance between vents on my Penguin is only 700mm.
So, I stand by my statement that windups are the worst type of van for operating a three-way fridge as it is not possible (at least on a Dometic RM2350) to install the fridge according to the manufacturer's instructions.
Older Jayco wind-ups were able to get around this by cutting a vent in the bench above the condenser fins. But this is now illegal.
The flashing you added to redirect airflow through the condenser fins was a standard feature on my 2016 penguin. So I didn't have to do that.
I needed to add insulation on the bottom of the benchtop above the fins to reduce heat getting into the top of the fridge from convection and conduction.
I also sealed all around the top and sides with insulation to reduce the heat from the back of the fridge from getting along the sides of the cabinet.
I looked at putting a baffle between the boiler and the rest of the fridge but decided that putting an extra layer of insulation completely around the boiler was a better option since it reduced the heat coming off the boiler AND made the boiler more efficient by reducing heat loss.
Also, as stated, I found that putting a single fan on the far LHS of the external vent reduced hot air being drawn up from the boiler and through the condenser fins.
There is always more than one way to skin a cat and no one way is necessarily any better than another.
We have both done a lot of analysis, made a lot of observations, found exactly the same problems but solved them in different ways.
On another note, I have been doing some testing on gas usage by my fridge in Winter. I am now using at least 50% less gas. On our last camping trip, it was between 0.2 and 9C overnight and usually below 20C during the day. My rough estimate is that I needed to run the fridge for no more than around 6 hours a day. The saving is that for 18 hours a day there is no heat being generated by the gas flame burning in pilot mode. Which leads me to believe that a three-way fridge with electronic ignition that only lit up when colling was needed would be vastly more efficient.
See you in Queensland.
I should clarify that my statements refer to a Dometic RM2350 as fitted to my Penguin.
It might be best to download a copy before reading on. I have attached a copy for your viewing pleasure.
Refer to Fig 3A on Page 5.
This shows the requirements for the placement of the two external vents. Note that the top vent must be placed above the height of the fridge.
This is important. It also states in the Ventilation Heights table on page 6 that the minimum distance between the bottom of the lower external vent and the top of the upper external vents is to be a MINIMUM of 864mm. This is impossible to achieve in a Jayco windup. The solid wall is only 800mm high. The distance between vents on my Penguin is only 700mm.
So, I stand by my statement that windups are the worst type of van for operating a three-way fridge as it is not possible (at least on a Dometic RM2350) to install the fridge according to the manufacturer's instructions.
Older Jayco wind-ups were able to get around this by cutting a vent in the bench above the condenser fins. But this is now illegal.
The flashing you added to redirect airflow through the condenser fins was a standard feature on my 2016 penguin. So I didn't have to do that.
I needed to add insulation on the bottom of the benchtop above the fins to reduce heat getting into the top of the fridge from convection and conduction.
I also sealed all around the top and sides with insulation to reduce the heat from the back of the fridge from getting along the sides of the cabinet.
I looked at putting a baffle between the boiler and the rest of the fridge but decided that putting an extra layer of insulation completely around the boiler was a better option since it reduced the heat coming off the boiler AND made the boiler more efficient by reducing heat loss.
Also, as stated, I found that putting a single fan on the far LHS of the external vent reduced hot air being drawn up from the boiler and through the condenser fins.
There is always more than one way to skin a cat and no one way is necessarily any better than another.
We have both done a lot of analysis, made a lot of observations, found exactly the same problems but solved them in different ways.
On another note, I have been doing some testing on gas usage by my fridge in Winter. I am now using at least 50% less gas. On our last camping trip, it was between 0.2 and 9C overnight and usually below 20C during the day. My rough estimate is that I needed to run the fridge for no more than around 6 hours a day. The saving is that for 18 hours a day there is no heat being generated by the gas flame burning in pilot mode. Which leads me to believe that a three-way fridge with electronic ignition that only lit up when colling was needed would be vastly more efficient.
See you in Queensland.
I am relieved to see a bit of bromance going on between long time members. I was beginning to think that romance was dead in forums. Good luck with it all you blokes. Your posts going back a few years make for interesting comparison reading. 
Good luck with it all you blokes. Your posts going back a few years make for interesting comparison reading. Thought I'd add my 2c to this thread. I've got a roof-mount vent on a full height van and the fridge did struggle a bit on all 3 sources in heat. I added 2 x smallish PC fans to the bottom vent pointing up on the LHS, with an ambient temp controller set at 30deg. Sourced power from the solar controller on the top of the fridge, which I ran to the back of the fridge (also pushed it into the fridge itself to provide circulation fan and light with door activation switch). Helped a bit.
Finally got around to opening to roof vent only to find 2 pieces of thin plywood lying on top of the fins, clearly left there when the roof hole was originally cut. Blocked probably 30% of the fins. Fished them off, then added a single big fan to suck from the LHS of the fridge. Added a switch at the lower vent so this top fan can be independently turned off. Fridge runs like a dream now.
Finally got around to opening to roof vent only to find 2 pieces of thin plywood lying on top of the fins, clearly left there when the roof hole was originally cut. Blocked probably 30% of the fins. Fished them off, then added a single big fan to suck from the LHS of the fridge. Added a switch at the lower vent so this top fan can be independently turned off. Fridge runs like a dream now.
If your fridge has a roof vent and is having problems thats the first place most mention to have a look at, baffles not fitted properly or fallen to cover the hole, either way the vent is blocked up, another case of poor QC and not just by Jayco either.........
You have rectified it the best way, fix the vent and add a fan, only one would be needed in that case.....
@Fallen, probably did not need the fans at all!! Once you get a good flow of air THROUGH the condenser fins, you are well on the way to proper efficiency. However, fitting the fan/s will accelerate the flow of air and improve efficiency especially in very hot weather. You are only one of many that has found that the installation of their 3 way fridge has been far from optimum. Just very poor workmanship!!!!! Glad you have solved that problem anyway.