Improving the Trailblazer fridge

The cavity is in direct contact with the aluminium inner lid. The inner lid is seperated from the outer shell by 50mm of polyurethane block and the edges are sealed by silastic.

IMHO the metal-to-cavity contact is the weakness.I have levelled the fibreglass skirting so that there is a positive seal between the lid and body (as Des Lexic pointed out, there is now a vacuum effect)

So far I have,
1. Made a plug for the cavity (ccf 20mm)
2. Made a coat for the lid (ccf 20mm )
3. Installed Sirrocco blower in the compressor cavity - operates when compressor is on
4. Installed a fan in the cold cavity

Any further thoughts?

is the inner liner of lid alloy?
the one i copied mine from was plastic...so have they changed design?

What is this plug for cavity? what cavity are you talking about.

And does this inner liner make contact with the outside world (no metal materials that allow thermal heat transfer between inside and outside)...if not its probably OK.

Why add a fan that uses more amps? These compressors are designed to run hot...its the condensing pressure you want to keep down...keeping the compressor cooler does very little to increase efficiency

ditto above above for inside? why why why

I use a 30mm wide .25 inch thick foam gasket around the lid of mine which works perfectly

Dont worry about vacuum too much unless it gets too hard to open and that is usually immediately after you have closed the lid....a little time lasp between lid openings usually alooows for enough air to get back in and give relief to the pressure differnce

incidently ..to test for lid seal...use a piece of paper and under seal and if you can slide it along then seal is no good

1. Yes the inner lid is alloy..unit was built in 1998.
2. Cavity = cold space plug isolates the cavity fgrom the alloy surface
3. The inner and outer shell is connected by stainless pk screws and the hinges
4. The fan in the compressor cavity is to remove the hot air generated by the compressor etc, indirectly 'improving' the cooling of the condenser ( which is attached to the 2 sides)
5. The internal fan provides even temperature throughout the cavity

IMHO the major thermal path is cavity>alloy>alloy>atmosphere
Interested to hear your copy had a plastic inner shell, I am contemplating a PE or PP replacement. Do you know what year your copy was manufactured?

My 15 month old 70l Trailblaza has the compressor cooling fan mounted as standard.... a friends 6 yr old 60l totalled a compressor recently and another mate who is a fridgie also replaced the compressor and was advised by Norcoast to fit the fan.

Incidently, our 70l survived our recent rollover with no battlescars... is still running nearly four weeks later!!!!

WOK, Mine is a copy...built it myslef some time back

Still dont think the fan will help much...as they do have a generous condenser

The inner liner is in direct contact with the ambient?
this is not good if it is so

Brian, Danfoss do bring out a condensing unit which has a fan as standard....if the fridge has a skin condnser I dont see the need for a fan

The fan is a small unit akin to a cpu fan almost... is mounted above the compressor. Is not a condensor fan at all... is used to cool the compressor only.

Des, It aint a problem unless you get big holes appearing

Boredom..................

I use the unit as a freezer only with a cooler as day-fridge. It does meet its specification ( 25% duty cycle in fridge/freezer mode, thermostat setting #5). When you next use your unit, check the temperature of the top of the lid relative to ambient...maybe I'm being paranoid?

If the end result is less battery drain between charges, its will be a worthwhile excercise

Wok,
Post your findings when all mods completed mate.
2 x 80 watt solar panels to help between charges? (i know, cost brass)
Cheers,
Bros.

Placing a fan in the cold cavity has a downside, the temperature at the top of the cavity is much lower then 'normal' ,hence the rate of thermal losses through the lid is higher.

The voltmeter switch won't save much....couple of mA at best.

I was thinking about putting the fan in where the compressor is, as Norcoast now suggest.

The voltmeter on my fridge, a suppressed zero automotive type, draws 50mA, I've measured it. Quite high, about the same as a small fan draws. In fact, as the fan would only be on when the compressor is, there would be a net saving in energy.

Cheers

50mA! ....is it a particularly accurate unit?
A friend just got an RC unit and had him have a look at the fan setup.Apparently it is 50mm(thereabouts) axial unit sitting above the compressor.

To be honest I am sceptical as to its effectiveness, any overclocker would know to input air into a box. An internal fan just moves the hot air about. The blower I am trialling draws just under 300mA, I am hoping(expecting) to pick up extra current in better duty-cycle( 12% so far).

What is encouraging is the improvement in temperature at the top of the cavity.
@ambient 26c: humidity 50%: setting #5: no internal fan
original lid : 7.8 max 3.1 min
moded lid : 4.9 max -1.9 min

In the next few days I will be replacing the inner shell of the lid with corrugated polycarbonate sheeting ( similar to Danpalon..not sure about the spelling). The way its progressing I could end up with a full freezer operation at #5 and not #7...a real guzzler!

Happy camping!

Wok writes:
50mA! ....is it a particularly accurate unit?

No, not really.... it reads about 0.4V low. It's a VDO gauge, more suited to checking whether your alternator is working or not than determining the condition of your slowly discharging battery.

Topcat, its not a 'problem' par se...no product is 'perfect'. Using your example of 20Ah/day, would it not be 'better' if you could reduce it to 15Ah/day?

With a typical wetcell 80Ah deep-cycle battery one would expect at best 2 days(50% discharge) between recharges, then it would require running the vehicle for about 8hrs ( thats assuming the alternator is capable of fully charging the battery)

Its a lot cheaper to 'improve' the lid then battery system. Taking the logic to the extreme....if the usage could be reduced to 6Ah/day, would one even require an auxiliary battery?

Given the reliability of the Trailblazer I don't expect to replace it anytime soon. I have highlighted what I believe to be its weakpoint, thats all.

Be happy

Hi Mick,
I am trying to reduce the dependance on specialised battery like AGMs.The experiment has cost about $80 (with heaps of wasted ccf & silicon). I expect the 'final' solution would be much less.

My current DC Aux system is,
Exide Extreme
110A alternator
10mmsq welding cable ( paired cable runs - no chassis returns)
Home brew management/distribution system ( similar to Redarc with a twist)
Anderson connectors

I am open to suggestions on improving the system.