RE: Fan cooled trailblazer

Submitted: Saturday, Mar 12, 2005 at 23:27
ThreadID: 21177 Views:2866 Replies:6 FollowUps:8
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Experiments have been completed in my objective of fitting a fan to my 60l Trailblazer. Would like to thank all those who put there 2 bobs worth in - especially stephen (WA) for finding correct wiring points, and put to rest those who did not beleive or think it was worthwhile.

Re : Post 20811 - I tested the fridge without fan amb. temp. outside 32 fridge 28, -2 hrs and 55mins later - fridge 0. With fan, amb. temp. 33 fridge 29, - 1hr and 27mins later - fridge 0.

Given that the fridge would draw approx. 4 amphr and fan approx. 1/2 amphr. - the maths looks good for me when drawing of battery power, when it halfs the power consumption!!! This test wasnt about getting the fridge colder, - it does that great by itself being a Trailblazer and all, it was about making it run more efficent when camping on limited battery power without starting the geny a night earlier!!

Enough said.....milo...
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Reply By: Wok - Sunday, Mar 13, 2005 at 07:17

Sunday, Mar 13, 2005 at 07:17

May I suggest that you carry out a diffent test?

After the unit settles down[preferably with prechilled load, I used 12l of water - , coke bottles] check the ON and OFF times over a day. IMHO This would more closely simulate a camping scenerio.

I went through the same exercise last year[3bdf comp in my TB?]

Good to see interest in test results & not surfing specs.

cheers.....................waiting with interest
AnswerID: 102212

Follow Up By: ozi explorer - Sunday, Mar 13, 2005 at 08:49

Sunday, Mar 13, 2005 at 08:49
Yeah, I will actually do that sort of test, as in a matter of a week or 2 will be back on the road camping full time for the next 6 - 8 months, which I will able to afford to have more time to do the more intensive testing. Problem is, dont have the internet while travelling to post results, so will try to get results online asap.

I would assume tho, if it takes half the time to get to 0 deg. ,the cycles of the fridge would have to be the around the same time as before, but only running half the time in that cycle. Sound right???

Sounds like it will be a really hard test as there are a lot of variables (besides fishing, drinking, sleeping etc.) as it will be over 24 hrs, battery voltage at beginning, amb. tempertures etc. - oh well see how I go.

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Follow Up By: Wok - Sunday, Mar 13, 2005 at 09:26

Sunday, Mar 13, 2005 at 09:26
The ratio doesn't crossover like that, my rough figures I gave before. My ON cycle is about half hour[ doesn't seem to change much regardless of ambient] the OFF time shortens > 30oC. From my measurements I found the 25% dutycycle TB quotes is about 25oC over 24hrs.

If you have time, build a sock for the lid.......helped me a lot[25mm CSF Clarks - blue grade or Armaflex = $$$]

Have a great trip and please post when you get back.

FollowupID: 360006

Reply By: DINGO - Sunday, Mar 13, 2005 at 11:30

Sunday, Mar 13, 2005 at 11:30
i agree with what you are saying, but if it is true why do fridge makers not do this?????
i have a 60lt engle that would struggle in >40C until i got my fridgy to put a small computor fan blowing over coil, which made it heaps better although i never took much notice of power comsumption i am sure it used heaps less, now i see engle put a fan on some models.
then i tried a liemack which used heaps of power, but when i did a heap of tests on amps draw and voltage drop etc i found that when the fan started, about 1/2 a min after the compressor starts, then power use of the fan was stuff all.
so when i got an evacool i asked " if i were to pay extra is there anything they could do to make it even more power efficient?" they said no, but i told them what i thought about the fans power use and how much better the fridge cools when blowing away hot air, they said they have a bigger fan they use on bigger fridges and they could fit that if i wish, so we did and i am very impressed with this fridge and a 80watt solar panel will keep this fridge running indefinatly as long as you do not get too much cloud cover.
so i now wounder if putting an even bigger fan or perhaps 2 fans would improve??? too much for me to get around to but it would be interesting.
i also have been going to cut the shade mesh type venting in the engel insulation bag as this i feel also stops air flow, although it now only gets used as a 240V freezer on coastal fishing trips
i look forward to hearing how it goes on your camp trip,
i am so jealous of a 8 month trip
Regards Dingo
AnswerID: 102216

Follow Up By: Wok - Sunday, Mar 13, 2005 at 18:01

Sunday, Mar 13, 2005 at 18:01
The TB has its condenser fitted to the large rectangular sides. The fan fitted to the compressor cavity would help to cool the compressor. As the Engel condenser is within the compressor cavity, I expect the fan would help as you have proven.

FollowupID: 360024

Reply By: Member - Jimbo (VIC) - Sunday, Mar 13, 2005 at 15:40

Sunday, Mar 13, 2005 at 15:40
Good results Milo,

I reckon the "science" you have applied is sound ie the numbers stack up.


AnswerID: 102234

Reply By: Robsoff - Sunday, Mar 13, 2005 at 16:49

Sunday, Mar 13, 2005 at 16:49
How about some details and a photo or diagram. I got the old girl out the other day and it gets very hot when cooling things down so i;d like to fit one to mine.

AnswerID: 102238

Follow Up By: Wok - Sunday, Mar 13, 2005 at 18:02

Sunday, Mar 13, 2005 at 18:02

Are you talking to Milo or me?

FollowupID: 360026

Follow Up By: Robsoff - Monday, Mar 14, 2005 at 09:55

Monday, Mar 14, 2005 at 09:55
Sorry, Milo it is.
I want to fit a fan to my trailblazer so any info would be great.

FollowupID: 360083

Follow Up By: ozi explorer - Monday, Mar 14, 2005 at 13:33

Monday, Mar 14, 2005 at 13:33
G'day Rob,

I bought the computer fan from Jaycar $15 ish, about 100mm dia or so, about 20mm thick square casing 12V.

Mounted it btween the casing and compressor (just fits!), drilled series of 20mm holes around where the blades are, than bolted on.

The wiring was more tricky as it sounds there slightly different in different models. But mine was (early 90's mod) to the black box which is mounted on the wall of fridge, which along the bottom has left to right, C , T , # , F , # , + , -.

Where the '#' are, is where I hooked mine into, being neg or pos, - cant remember, but by hooking to those ppoints allow the fan to only activate when the compressor is on (obviously the only time it needs blowing on).

The only other thing that I did different was mount in a switch (standard 240V architrave elec. switch), beside my similar freezer on/off, to be able to turn it off/on as my desire. As I found the fan to be not the quietest out there (not that I experimented with different fans), and with the wind sucking thru the holes made, was noisier than expected, thus when sitting around the campfire in the cool of the night with hearing nothing but the fire crackling, did not want to here a fan kick in, also not needing it if weather is cooler like at nite or down south.

Hope this helps...

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Reply By: Member - Stephen (WA) - Sunday, Mar 13, 2005 at 22:32

Sunday, Mar 13, 2005 at 22:32

Good work. I reckon I'll leave my bigger fan in place now esp. after your little test.

Did you have fun in mounting the fan? I used about 3 biggish cable ties - but I found that if I pulled them too tight the fan went "out of round" and would protest on startup (blades hitting casing).

Cheers fellow.

Stephen J.
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AnswerID: 102298

Reply By: Wok - Monday, Mar 14, 2005 at 09:14

Monday, Mar 14, 2005 at 09:14
My mods
[ View Image]
AnswerID: 102335

Follow Up By: ozi explorer - Monday, Mar 14, 2005 at 09:54

Monday, Mar 14, 2005 at 09:54
Wok, do you not have freezing capacity with you TB? As looking at the pictures you only have the one thermostat control?....

I was also wondering why you had so much extra room in your motor compartment, - is it only 12V? Mine has a 240V conversion box down in that right hand corner, as there was no chance to do what you have done!!

Still dont quite follow what your doing with the lid tho?
FollowupID: 360082

Follow Up By: Wok - Monday, Mar 14, 2005 at 10:44

Monday, Mar 14, 2005 at 10:44
Milo, my TB is 'no frills' , I built an external power supply from bits I had. In the rare time I am at caravan park I can charge the aux battery as well as power the TB via the Andersons.
Yes, only 1 thermostat.I built a spacer board that fits a third up from bottom so I can freeze the bottom[sort of works] The pickup is at the top with the thermometer pickup at the same level[where it is the warmest]

I used a blower because its directional and can 'compress' the cavity. It could be positioned in other locations.It is mounted with 2 bolts.Checkout the smaller blower from Jaycar..could run direct from the controller & heaps quieter than the one I used [hindsight] there is enough air flow from the baby.

My tests showed the lid was the weakest part of the TB[w.r.t heat gain].I set out to remove [a]metal-metal paths [b]metal-cavity path
For [a] : the hinges were repositioned to the back, I fitted a strengthing bar across the back; the screws holding the inner shell were removed[no longer needed]
For [b] : the Al inner shell was removed

The sock is the blue bit; I used sprayon glue to make it. I found that it was not performing to my satisfaction[after settling down the surface of the sock was still significantly cooler then ambient]...hence the other mods.

Note: my lid is removable, ie slide-on. In hindsight I should have welded the corners when the outer shell was naked.......duh...duh

My conclusion: The lid mods were more effective in improving the TB then the fan [ in agreement with Nudenut on this point]The hassle with fridge tests is the time factor, I found it took up to 6hrs before the thermal gradients were established and I could get repeatable measurements.

Talking too much!

FollowupID: 360087

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