Pressurising/cooling canopy

Submitted: Saturday, Dec 30, 2017 at 19:29
ThreadID: 136036 Views:18692 Replies:15 FollowUps:19
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I am about to have a canopy made up. It will be fully sealed and have a 12v fridge within. Wanting to allow hot air to escape and also keep dust out, I have read the archived posts, having searched, but I am still unsure.

If I want to allow hot air out, I will need to vent (I have thought of one of the solar vents used in yachts). However this outlet will need an inlet, which can be filtered.

Do I need to do anything differently, as the common opinion has it that the unit should have positive pressure, to reduce dust ingress. I have read some used a movement initiated inlet and close this when vehicles approach on a dirt road. Sounds rather inefficient and clumsy to me.

Any suggestions on the best options you have seen/used?

Cheers,

Mark.
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Reply By: IvanTheTerrible - Saturday, Dec 30, 2017 at 19:39

Saturday, Dec 30, 2017 at 19:39
A lot of canvas canopies have two flaps on the front that, when open positive pressure the canopy while the vehicle is in motion. Have a few mates that swear by this system, I have a rigid canopy and I purchased a secondhand heater fan that I use drawing through a Holden V6 flat panel air filter. It's can be a bit heavy on power though.
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Reply By: noggins - Saturday, Dec 30, 2017 at 19:44

Saturday, Dec 30, 2017 at 19:44
On the canopy of my ranger I used a home made version of a ship's scupper vent where the air is forced in and has to go slightly forward to go down into the canopy
The white bit you can see in the roof is a cut off plastic plumbing fitting that has the rear of it ( can't see here ) cut down so there is only a ridge facing forward.

As you can see the air has to go down into the canopy and at the back of the scupper I cut about a 5mm hole for any water collected to be blown out the rear.
This pressurised air then goes out all the little air gaps etc that usually the suction at the canopy brings all the dust in through.
It was a bit of a ''trial and see'' but we've just done 30.000 K trip around Aus and dust in the canopy ?
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Reply By: Hoyks - Saturday, Dec 30, 2017 at 19:58

Saturday, Dec 30, 2017 at 19:58
Mine is a white painted ally box with no vents. I thought about them, but was in a hurry to finish it and was going to see how it went and fit them later, but then decided not to bother. Some guys I know fitted solar powered ventilators, but for the amount of air they shift I don't know if it would make that much difference.

Mine does have a roof top tent on top, so that works for shade/tropical roof and stops it getting too hot. Some foam insulation bonded into the roof would probably be of more benefit than a fan, better to keep the worst of the heat out in the first place.

During the day when driving the fridge copes no worries as it has the extra Amps from the alternator, when stopped the side doors are generally open or the sun is going down,so it doesn't get hot then either.

If you do go with some vents, look at how they do it on cars. Inlet high at the front (You can get clever with air filters on the inlet if you want) and outlets on the sides towards the rear. Thin rubber flaps are enough of a seal, provided you have fresh air coming in the front. Don't put them on the back as then they will be more likely to suck in the dust that swirls in the vortex behind the vehicle..
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Reply By: Frank P (NSW) - Saturday, Dec 30, 2017 at 20:08

Saturday, Dec 30, 2017 at 20:08
I presume you're getting an alloy or steel tradie type canopy.

I have a fully sealed tradie canopy with no airflow at all to ensure dustproofness. I run my compressor fridge as a freezer. It does not suffer unduly in the closed canopy - my frozen stuff remains frozen. If I were to use it as a normal fridge I would expect a similar result.

When the canopy is sealed up when driving I presume the compressor runs more, but that doesn't matter because then it is powered by the alternator system.
When camped and the fridge is running off the second battery the canopy is usually open or partly open for ventilation.

To get positive pressure you need an air inlet but no outlet, so there would be little or no air circulation and therefore little or no practical ventilation benefit for your fridge.

If the door seals are done right I don't think you need positive pressure, and in my experience the lack of incoming air makes no difference to the fridge's performance.

The subsequent lack of dust is the huge benefit.
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Follow Up By: Gronk - Saturday, Dec 30, 2017 at 20:27

Saturday, Dec 30, 2017 at 20:27
As said above, if the canopy is sealed, the fridge will cope.
As opposed to a van that can't be sealed, a positive air pressure fan does wonders ( we have a fan that pressurizes the van )....for dust, and in either case, when you stop, for camping, you open either.
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Follow Up By: IvanTheTerrible - Saturday, Dec 30, 2017 at 20:44

Saturday, Dec 30, 2017 at 20:44
I'll also add to this that the fridge was not my reason to positive pressure my canopy. It's was in an attempt to eliminate dust 100%. No matter how much I've tried the really fine dust got past the seals.
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Reply By: Member - silkwood - Saturday, Dec 30, 2017 at 20:49

Saturday, Dec 30, 2017 at 20:49
Thanks for the prompt replies. So it appears that a sealed alloy canopy will be better off remaining sealed and minimising heat via coverage on top (will do) and insulating, rather than bothering about a fan?

Certainly makes life easier (I'm going to insulate anyway, and really can't see myself stopping regularly to open or close a vent).

Cheers,

Mark
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Follow Up By: Frank P (NSW) - Saturday, Dec 30, 2017 at 21:22

Saturday, Dec 30, 2017 at 21:22
Mark,
Just one caveat on what I said in my reply... You need an exceptionally well made canopy for the doors to be dustproof.

You said you're getting your canopy made. I have presumed it will be custom made-to-order. Without casting aspersions on your canopy builder, most made-to-order canopies leak dust around the doors. Therefore a pressure vent may be wise.

I'm lucky enought to have a pretty high quality factory-made canopy (from CSM in Qld) with very rigid doors and very effective seals. Even the rear door is dust-tight. Not all are as good as the CSM, so take care.

Maybe stress to your builder what you want to achieve in terms of sealing, and if he says it can't be done for your price consider a pressure vent.

Cheers
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Follow Up By: Member - Phil G (SA) - Saturday, Dec 30, 2017 at 22:18

Saturday, Dec 30, 2017 at 22:18
I agree with Frank - keep it sealed.

Also, a white canopy will be cooler than any other colour.
Don't bother with insulation - it just keeps the heat in.

Cheers
Phil
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Follow Up By: Member - silkwood - Saturday, Dec 30, 2017 at 23:11

Saturday, Dec 30, 2017 at 23:11
"Don't bother with insulation - it just keeps the heat in."

Phil, you are partly correct there. Insulation will mean the interior will be slower to reach ambient. However, once it does it will be slower to cool in a lower ambient temperature (keeps the heat in). This can be overcome to a large degree by simply opening the doors occasionally.

Of course, if we're being picky, you also have the heat generated by the fridge being maintained , but this is splitting hairs. The biggest killer is the dramatic increase in internal temperature by direct radiation (from the sun).

White is not an option (sadly aesthetics has some degree of sway over the senior partner!). Pity.

Cheers,
Mark.
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Follow Up By: Member - Phil G (SA) - Sunday, Dec 31, 2017 at 23:43

Sunday, Dec 31, 2017 at 23:43
Hi Mark,
I had a white aluminium canopy on the back of a 79series for 8 years. Had a digital temperature gauge inside the canopy. Travelled in some pretty hot weather - on a 48 degree day, the inside of the canopy wasn't a lot hotter.
The white reflects the heat best and aluminium transmits the heat readily - if you insulate it, you lose that benefit.
The only additional way I can suggest to reduce heat is to add a second layer to the roof - a "tropical roof". Used to have them on LandRovers and many years ago I had one on a 47series Troopie.
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Follow Up By: AlbyNSW - Monday, Jan 01, 2018 at 10:01

Monday, Jan 01, 2018 at 10:01
My experience is similar to Phil's
Surprisingly there is minimal heat buildup in the canopy
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Follow Up By: Allan B (Sunshine Coast) - Monday, Jan 01, 2018 at 12:06

Monday, Jan 01, 2018 at 12:06
.
There are techniques useful in insulating spaces.
In the situation of a vehicle canopy being insulated from sunshine yet having internally-generated heat (a fridge), it can be a benefit to insulate the surfaces which are heated from sun radiation but allow shaded surfaces (e.g. floor) to remain uninsulated and conduct internally generated heat away from the interior to the external atmosphere.

Incidentally, white surfaces have a very similar heat reflectivity to polished aluminium. Either will serve as a canopy shell.
Cheers
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Reply By: Member -Pinko (NSW) - Saturday, Dec 30, 2017 at 23:04

Saturday, Dec 30, 2017 at 23:04
I have a 2007 build 79 series single cab 100,000k.on dirt roads has a 40lt engel inside no dust at all.
Will have a dog shortly so have to have a rethink.
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Follow Up By: IvanTheTerrible - Saturday, Dec 30, 2017 at 23:11

Saturday, Dec 30, 2017 at 23:11
Same here. The bugger migrated from the canopy to the back seat since my oldest daughter doesn't come with us much now
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Reply By: Parafan - Sunday, Dec 31, 2017 at 08:44

Sunday, Dec 31, 2017 at 08:44
I have a Concept Canopy made in Brisbane. They have a vent on either side. One at the front and one at the back on the opposite side. On dirt roads I simply open the front and close the back vent which pressurises the canopy and no dust. Otherwise I leave both vents open which allows airflow through the canopy. The airflow helps a little when I carry fuel for the outboard/chainsaw etc. If sealing completely be careful of carrying gas bottles. I am not an expert but if these leak in a sealed unit ????
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Follow Up By: Frank P (NSW) - Sunday, Dec 31, 2017 at 09:50

Sunday, Dec 31, 2017 at 09:50
Not just "be careful"!!

You should NEVER EVER store or carry a gas bottle in a sealed environment.

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Follow Up By: Dean K3 - Sunday, Dec 31, 2017 at 11:29

Sunday, Dec 31, 2017 at 11:29
Illegal to carry bottles in a unvented condition need to be where gas escape.
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Reply By: Member - shane r1 - Sunday, Dec 31, 2017 at 09:21

Sunday, Dec 31, 2017 at 09:21
G’day all,
My experience is,
A few years ago I had a 40 litre Engel in the back of a freestyle cab. I found when closed up and hot, the fridge wasn’t cooling and was running the aux. battery down. Fridges do need cooling air to work.
Now I have a aluminium canopy and I am going to vent/duct air to the fridge, as I have the fridge running all the time , weather travelling or parked while working. Am going to try a thermostatically controlled fan .
Probably ok to not have ventilation when travelling as others have stated , charging while moving and doors open when stopped.
Cheers
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Follow Up By: Member - silkwood - Sunday, Dec 31, 2017 at 10:07

Sunday, Dec 31, 2017 at 10:07
Shane, you reflect my thoughts. I am happy (after seeing these responses) to have the canopy (aluminium- should have stated that in the first place, sorry) sealed and insulated- no need for air movement whilst travelling.

It's when I'm holed up for four or five days in the north, I don't want to have to have the canopy doors open constantly. That's why I'm thinking of a solar powered fan (used on boats to minimise mould).

Cheers,

Mark
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Follow Up By: 2517. - Sunday, Dec 31, 2017 at 10:14

Sunday, Dec 31, 2017 at 10:14
I have a similar set up with a 140 watt solar panel on top so the battery is charged all the time, generally a few hrs in the morning is enough.I found it better then a portable panel.
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Reply By: Batt's - Sunday, Dec 31, 2017 at 10:12

Sunday, Dec 31, 2017 at 10:12
Insulation is one of the best things you can do for any metal canopy it will greatly reduce the radiant heat. I have only done the roof on mine so far, it has made a big difference but haven't done the front wall or any of the 3 doors yet.. My neighbour has done his roof and walls with rubber insulation from Clarke Rubber before that you could only hold your hand on the inside wall or roof for a very short time before it got to hot now you hardly feel any heat coming in. Yes it will slowly heat up during the day everything does but it is much better than getting the radiant heat blasting into the canopy.

I have a solar vent on top of my roof and an intake vent in the front wall I put some thin foam in it to reduce the dust and it works well The fully enclosed alloy canopy on my ute can be up to 7 deg cooler inside compared to the cab of my patrol.

When I first put the canopy on a couple of yrs ago, before I insulated the roof and fitted the vent and solar exhaust fan I was travelling on holidays during summer and my Evakool wouldn't get below 5 deg in the fridge section till later in the day. I had it dialed up to 9 which is flat out where as I usually only needed to run it at 4 to 5 around half way. It was incredible hot inside the canopy because there was no air flow or insulation and all of heat trapped inside the canopy I'm surprised the fridge survived.
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Reply By: Les - PK Ranger - Sunday, Dec 31, 2017 at 10:34

Sunday, Dec 31, 2017 at 10:34
ARB canopy on tub.
ARB rear mounted pressurising vent.

150k, much on SA and NT back roads and deserts, never get more than a cm of dust in the jamb.

I leave it open all the time.
Only in very heavy rain and highway driving does it need to be shut, or a very small amount can be blown in over time, but then dust is not an issue :)

Never an issue with dust from oncoming (passing) traffic, it is brief.
If behind a vehicle, or in convoy and the dust is bad, I stay back far enough to avoid dust plumes, if wanting to overtake I'm patient, and / or call on the 2 way to arrange the process in a good manner, or just sit back and enjoy the small differential in speed.

Dust just blows over, the very minimal amount that may go into the open vent, goes straight out through the open tailgate jambs.





AnswerID: 615821

Reply By: Harry C - Sunday, Dec 31, 2017 at 10:44

Sunday, Dec 31, 2017 at 10:44
I have a aluminum fully sealed canopy by Metalink it is gunmetal grey but we painted the roof and the inside off white and we also have two solar panels on the roof it is dust proof and reasonable cool inside with the panels keeping the direct sunlight of the canopy plus the white roof.
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Reply By: Bob Y. - Qld - Sunday, Dec 31, 2017 at 10:49

Sunday, Dec 31, 2017 at 10:49
We've got 2 canopies Mark. One is sealed and the other, which we use in the desert, has had 2 forward facing vents fitted. These are the ones sold by ARB, about 75 x 200mm and cost around $70.





Being bare alloy it gets very warm, but don't seem to have had any dramas with the fridges. I often leave the sliding window open, depending on wind direction. The amount of dust that gets in is minimal, but might be different on heavy bull dust tracks. You might be able to swing your CEO to getting a white roof, to help with cooling?

Very easy to go overboard with accessories for these canopies, making them ultra heavy and threatening the vehicle's GVM. Couple of things I've done to restrict weigh gain is an upright fridge, and Oates plastic drawers, from Bunnings. The 80L upright is only 5kg heavier than a 40L Engel, and saves using a heavy dropslide. Plastic drawers are okay, but heaps lighter than a pair of Titan drawers at 60kgs empty.

Good luck with your build, it's fun............and expensive!

Bob

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Reply By: Les - PK Ranger - Sunday, Dec 31, 2017 at 13:38

Sunday, Dec 31, 2017 at 13:38
I am sure one thing not touched on here in this thread, or the numerous past similar threads, is . . . if you are pressurising to keep dust out, you NEED an opening for escape like tailgate jambs, or some may feel general loose canopy doors on theirs is enough.

All you need is slightly more air coming in, than can escape, and this seems to work at speeds over say 20ks or so in my experience.

The vent at top is also good for allowing hot air rising to escape when parked, in camp, etc, a little more bearable at least.
AnswerID: 615836

Follow Up By: Frank P (NSW) - Sunday, Dec 31, 2017 at 13:55

Sunday, Dec 31, 2017 at 13:55
You've got me there, Les :-)

If you're just pressurising, why do you need an escape vent?

For sure if you're trying for ventilation and circulation, but simple pressurising?

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Follow Up By: Gronk - Sunday, Dec 31, 2017 at 14:32

Sunday, Dec 31, 2017 at 14:32
Yep, my little offroad van has a pressurizing fan....draws in fresh air via a vent and filter, and blows it out inside the van.....idea is to pressurize the inside and any excess air will escape thru any means possible.....like anywhere that isn't 100% sealed. If you had an escape vent, it wouldn't pressurize !!
I've had 2 KK campers and while they are very good for dust, still not 100% sealed.
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Follow Up By: Les - PK Ranger - Sunday, Dec 31, 2017 at 15:31

Sunday, Dec 31, 2017 at 15:31
Frank, where did I post escape vent ??

What I posted was you NEED an opening for escape like tailgate jambs, etc.

It's fortunate for ute owners this is up the back, where any fine minuscule amounts of dust through the vent coming from other road users in general can escape fast.
Canopy slide ons etc could vary more where dust comes in.

If you didn't have these gaps, you wouldn't have a dust issue, and wouldn't need to pressurise.

Gronks example is a perfect one for his camper, which have ample gaps usually . . . the filter also helps his to keep dust going into the interior, and excess pressure isn't anything to be concerned with.
Campers have far more places to trap dust so the filter is a good idea, but this isn't as important with utes and canopies.
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Follow Up By: Frank P (NSW) - Sunday, Dec 31, 2017 at 16:11

Sunday, Dec 31, 2017 at 16:11
Sorry, Les, I paraphrased "opening for escape" into "escape vent".

It's a given that many canopies and ute tubs have air leaks that allow pressure air to escape.

But I still don't understand why you NEED such an escape.

I would have thought that to maximise the pressure to keep the dust out, the fewer the opportunities for pressure air to escape, the better.

But as my sealed box doesn't have a dust issue I'm just theorising. You have found a working solution for your situation, so I will defer to your experience.

Cheers mate
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Follow Up By: Les - PK Ranger - Sunday, Dec 31, 2017 at 16:20

Sunday, Dec 31, 2017 at 16:20
I can see that chain of thought easily Frank.
Think of it in an extreme example . . . if you had a 2' x 2' hole up front, and very little room for all that pressure coming in to escape, air will be forced into the area, and dust with it at those times discussed previously.
If too much air pressure, and dust brought with it, the dust will stay to a certain extent.

I guess tailor enough air in, but not too much.
You wouldn't put a home made right angle PVC pipe 100mm dia in, if one of those small boat scupper vents (as above in one post) would do the job.

Have seen people seal their tailgate jambs with special rubber sealing kits, they are happy that this has kept dust out, so yes, if people have their solution and happy, then all good.
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Follow Up By: IvanTheTerrible - Sunday, Dec 31, 2017 at 17:15

Sunday, Dec 31, 2017 at 17:15
John Deere run two fans in a lot of their equipment. One multi speed is for the HVAC and the other is a positive pressure fan. There is no outlet vent. The second fan is to maintain the cabin pressure higher than the ambient pressure outside. That way if there is a pressure leak the higher internal pressure stops dust entering the cabin. Having a outlet vent would defeat the purpose on the fan in the first place
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Reply By: Matthew G3 - Sunday, Dec 31, 2017 at 16:41

Sunday, Dec 31, 2017 at 16:41
Just wandering if anybody has put in vents in there canopy head board, like in the fridge box of a T-VAN [fluted vents outside with air filter held in place on inside] with Muller vents down the back of the roof. Muller vents will suck filtered air through front vents on move, and then Muller vents will let hot air escape went parked, this is what I am thinking in next build.

Matt
AnswerID: 615839

Reply By: Baz - The Landy - Sunday, Dec 31, 2017 at 17:29

Sunday, Dec 31, 2017 at 17:29
Hi Mark

I have an aluminium canopy with no vents and no dust or water ingress. It has 2x120 watt solar panels on top and an Engel 60-litre fridge that runs constantly.

This current one has done circa 120,000 kilometres of outback travel, and a previous vehicle had the same set-up (different canopy) and was the same construction.

My experience has been a well manufactured canopy appears to remove the need to have vents or be pressurised for dust. And while on a hot day the canopy temperature does increase with the ambient temperature the Engel never misses a beat even after 12 years of constant running.

Both of my canopies have been manufactured by Dave Vella, Dave's Metal Products in Sydney.

Good luck with your research...

Cheers, Baz - The Landy

AnswerID: 615840

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