Dometic dust reduction for vans

Submitted: Friday, Sep 17, 2021 at 20:22
ThreadID: 142583 Views:2010 Replies:8 FollowUps:32
Hi All. Just wondering if anyone has fitted the Dometic dust reduction system to your van or camper, and if you have, how has it worked for you?
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Reply By: RMD - Friday, Sep 17, 2021 at 20:54

Friday, Sep 17, 2021 at 20:54
RI.
I had a look and read of the site. Just an obstructing frontal area to catch air and a $50 filter AND you have to cut a whacking great hole in the roof to do the fitment. All for a meagre $650 initial cost. Surely there are other ways. Yes, it might work but no moving parts or technical bits just a filter. I presume by it's design the faster you drive the more air gets filtered.
Unless travelling in someone's dust where it may be of benefit, is it possible to modify the shower vent area of a van or high up air vents to make it pressurize clean air flowing past/over the van?
I would be happy with a small fan to create pressure internally and use it when dust conditions are present and it will work at low forward speed and not depend on frontal wind direction.
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Follow Up By: Rusty Iron - Friday, Sep 17, 2021 at 21:00

Friday, Sep 17, 2021 at 21:00
First of all, a genuine thanks for responding, I do appreciate it. But please trust me, due to the cost I have done an awful lot of homework on this problem. There are any number of home made options on Youtube and elsewhere and I have no doubt they work. As to how good, that you can't know for sure until you actually do it to your van. I know this is very expensive for what it is but 1) If it's installed by my van dealer it becomes part of the van warranty 2) It does look a whole lot better than any home made thing and 3) It has a much bigger scoop area than any home made one I've see so I think it will work much better at low speeds.
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Follow Up By: Gronk - Friday, Sep 17, 2021 at 22:52

Friday, Sep 17, 2021 at 22:52
This relies on air speed to pressurise the van. A fan will pressurise at any speed.
On my last hybrid, I could have had one installed ( $600), but I made my own ( $150 ).
A bilge blower, a box housing it and a filter, some ducting and a vent for the inlet air.
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Follow Up By: RMD - Saturday, Sep 18, 2021 at 09:40

Saturday, Sep 18, 2021 at 09:40
RI.
It sounds like you are sold on the idea when defending the Dometic option.
No matter how much homework you do the fact remains the Dometic unit, while it may work due to huge frontal area isn't high tech or almost any tech. Having it fitted by by a dealer for warranty? apart from water leaks leaks what can go wrong. It is costly as you mentioned but more than $600 for almost nothing! + fitting.
I would be concerned about it catching on overhead trees, if so, then you have an instant problem which can only be rectified by another $600 or so.
Gronk's idea of a blower fan, I have similar for various uses, and they draw 2.2 amps and shift far more air and can pressurize at any speed. Returning to a hot van in summer the unit can be used to displace the hot air inside van with door or other end window open.
Usually on dusty roads you aren't going fast and so less pressurization. Tractors cabs which use a forced air fan and filter extract dust they must work in, is effective. It has to work on a fairly sealed caravan.

"Dust REDUCTION" or elimination?
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Reply By: Member - McLaren3030 - Saturday, Sep 18, 2021 at 09:02

Saturday, Sep 18, 2021 at 09:02
Hi Rusty Iron,

There are a number of better options for dust ingress prevention out there. The most efficient use a fan through a filter to pressurise the van. Dometic do make one, Carafan is another. From what I have read, you can replace one of the existing “skylight” vents in the van with a pressurising fan. Not sure on price, but would be far more efficient as they do not rely on driving speed to provide sufficient air volume/pressure to work.

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Reply By: Peter_n_Margaret - Saturday, Sep 18, 2021 at 09:14

Saturday, Sep 18, 2021 at 09:14
The system in our OKA is very simple.
1. Seal up every crack you can find. Bright lights inside at night help.
2. Add a ram air vent up high. It is always open and has a torturous path to stop the ingress of water.

Fact is, if the holes are all sealed, the air flow into the vehicle to pressurise it is extremely low.
If there is no forward speed, there is also no dust coming in either.
It has no filter.., just some s/s flywire to keep the bugs out.
It doubles as the vent required for the gas installation.
We get almost zero dust inside. It works.

Cheers,
Peter
OKA196 motorhome
AnswerID: 637969

Follow Up By: pmk03 - Saturday, Sep 18, 2021 at 19:04

Saturday, Sep 18, 2021 at 19:04
Hi Peter,
Def agree with your comment on the proper sealing. I had done mine when we got our van over 5 years ago. We spend a lot of time on the dirt & to date don't have a dust problem.
We do 1000s of dirt kms when on out trips.
When travelling on dirt we cover door vent, rangehood/ kitchen vent & lower fridge vent.
We don't use any form of pressure vent.
I doubt the van is completely sealed. Might just be lucky & sealed in the right places.
Cheers
Paul
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Follow Up By: Keir & Marg - Sunday, Sep 19, 2021 at 15:09

Sunday, Sep 19, 2021 at 15:09
With regard to a roof vent satisfying the requirement for a gas vent, LPG is heavier than air and will drop to the lowest point of the van. The roof vent will not vent gas to the outside until the whole van is full of gas!!
Gas vents are usually fitted to the bottom of the entrance door, which is almost always the lowest point in a van.
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Follow Up By: Peter_n_Margaret - Sunday, Sep 19, 2021 at 15:14

Sunday, Sep 19, 2021 at 15:14
Gas legislation requires 2 vents. One at high level and another at low level.
My ram air vent satisfies the requirements of the high level one.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: Member - McLaren3030 - Sunday, Sep 19, 2021 at 16:17

Sunday, Sep 19, 2021 at 16:17
If you look at the door, there is a low vent at the bottom of the door.

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Follow Up By: Peter_n_Margaret - Sunday, Sep 19, 2021 at 16:32

Sunday, Sep 19, 2021 at 16:32
Yes???? And???
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Peter
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Follow Up By: Member - McLaren3030 - Sunday, Sep 19, 2021 at 18:50

Sunday, Sep 19, 2021 at 18:50
Just pointing out to Kier that you do have two vents, one high and one low in the door.

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Follow Up By: Peter_n_Margaret - Sunday, Sep 19, 2021 at 18:53

Sunday, Sep 19, 2021 at 18:53
So has every RV with gas installed.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: Keir & Marg - Monday, Sep 20, 2021 at 09:28

Monday, Sep 20, 2021 at 09:28
Thanks for the reply about a second vent. Buggered if I can find one in our Jayco Freedom pop-top when the roof is down, except the exhaust fan above the stove. There are two tiny vents in the canvas of the pop-top, but I think they just help raising or lowering the roof when the door is shut.
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Follow Up By: Peter_n_Margaret - Monday, Sep 20, 2021 at 10:19

Monday, Sep 20, 2021 at 10:19
That may be them?
The size of the vents is specified according to the size of the van.
This document is old, but I don't think there have been changes.

Cheers,
Peter
OKA196 motorhome
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Follow Up By: Keir & Marg - Monday, Sep 20, 2021 at 13:38

Monday, Sep 20, 2021 at 13:38
Thanks Peter,
The Freedom pop-top also has a vent at the back of the microwave compartment. Next time I take the cover off the van (possibly a couple of months given lockdown), I'll measure the cross-sectional area of this vent and the one for the exhaust fan above the stove to see if they total the requirement of 150cm2 for the upper vent.
Cheers, Keir
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Follow Up By: Peter_n_Margaret - Monday, Sep 20, 2021 at 17:00

Monday, Sep 20, 2021 at 17:00
Note that the lower one is to be within 150mm of the floor.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: Allan B (Sunshine Coast) - Monday, Sep 20, 2021 at 18:17

Monday, Sep 20, 2021 at 18:17
.
Peter and others,
Perhaps we should be referring to AS/NZS 5601.2:2020 "LP Gas Installations in Caravans and Boats" for valid regulations.
I have access to the current version of this Standard.
In respect to ventilation it states...... "7.2 Ventilation Systems: In order to flow of air for ventilation, high level and low level ventilation shall be provided. .... 7.3.1 Minimum Free Area. The free area of the total permanent ventilation.... shall be at least 4 000 sq mm or the value obtained from the formula below, whichever is the greater: v = (610 x u) + (650 x P) where v = minimum free area in mm2, u = input rating in Mj/h, P = number of sleeping spaces (persons)"

A stovetop burner is typically 6 Mj/hr so a 3 burner stove would represent 18 Mj/hr and running that through the formula for 2 persons produces a requirement for 12,280 sq mm area for each (upper & lower) vents which would need to be approx 110mm square.
These vents must be permanently open and positioned on opposite sides of the enclosure and within 150mm of the floor and ceiling. Close-able roof vents or windows do not meet the requirement for ventilation.

I can consult the Standard and provide more information if needed.
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Allan

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Follow Up By: Allan B (Sunshine Coast) - Tuesday, Sep 21, 2021 at 10:06

Tuesday, Sep 21, 2021 at 10:06
.
Further to what I have quoted above, Clause 7.4.2 of the Standard states that "Permanently open ventilation .... shall be provided" etc. Note the words "Permanently open".

I should think it difficult to pressurise a van against dust ingress if you have the required open ventilators specified by this Standard.
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Allan

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Follow Up By: Member - Dick L - Tuesday, Sep 21, 2021 at 12:04

Tuesday, Sep 21, 2021 at 12:04
Allan B
What if while moving?
1. The Gas is turned of at the bottle
2. Disconnected at the botle.
Then under the standards is the ventilation still needed ?
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Follow Up By: Allan B (Sunshine Coast) - Tuesday, Sep 21, 2021 at 13:19

Tuesday, Sep 21, 2021 at 13:19
.
Dick, it is not for me to authoritatively interpret the Rules or Standards. But from my experience with the "Australian Standards" I can usually understand their intent. In this case I would believe that the vents are required to be "permanently open" in order to eliminate the possibility of them failing to be opened when required. By the same reasoning, I would not expect exemption to be approved to close vents if the gas is "turned off" because again, it may be forgotten to do so.
The 'rules' do not offer an option to being "permanently open".

An objective of safety regulations is to avoid the possibility of 'human error' causing an unsafe situation.
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Allan

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Reply By: Noel L2 - Saturday, Sep 18, 2021 at 18:51

Saturday, Sep 18, 2021 at 18:51
I have read a number of posts (van facebook threads) by people who have fitted them and they seem to happy.... and they seem to work. There really isn't much about that looks ok at this price point... you jump to a bit over $2k for the powered units.
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Follow Up By: Gronk - Saturday, Sep 18, 2021 at 22:09

Saturday, Sep 18, 2021 at 22:09
$150 for the one I made and installed !
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Follow Up By: RMD - Saturday, Sep 18, 2021 at 22:26

Saturday, Sep 18, 2021 at 22:26
Noel L2
Around 2K for a fan and a bit of ducting eh? makes a van hot water service cost of unit sound very cheap and they are complex technology.
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Reply By: Rusty Iron - Sunday, Sep 19, 2021 at 09:40

Sunday, Sep 19, 2021 at 09:40
Ok, after more thought, I've decided the Dometic unit won't work for me. Neither will the passive, snorkel type. We do a lot of remote touring around WA, and other places when the borders are open. We spend almost as much time on gravel as we do bitumen, more on dirt on some trips. A lot of it is at low speeds, 10 ~ 15 kmh or less because the tracks are often rough. I've had a number of occasions where we've had a tail wind and the dust overtakes us. So I figure there's no point having a system that will only work with forward motion to scoop air, if we are travelling too slow for it to work properly or the wind is coming from the wrong direction.

I'm going for a DIY option with a Donaldson type air filter, with a bilge fan behind that to draw air through it, and then an elbow, to tubing through the roof of the pop top. Use a speaker grill or similar on the inside. This is going onto a new van and talking to the dealer yesterday, the roof looks like the only suitable place due to the construction of the van. Although, once I get the van and I can have a good long look and think, I might look at the front boot as an option for the air cleaner body and run a pipe up to the roof line with a snorkel on top of that for the intake. The outlet could then be ducted under the bed, exiting at the end of it similar to the caravan heaters.

I think there's a couple of advantages to this. It will work no matter how slow we go. And I've seen some people say that it can help to cool the van down, if you've been out for the day and the weather is warm. Turn the system on and help to expel the hot air. The bilge fans draw around 2.5 to 4.5 amps depending on the type, but with 2 x 120 lithium batteries in the van that won't be an issue.

It looks like the bits would add up to around the 300 ~ 350 mark, so less than half the price of the Dometic installed. It will be a bit fiddly to install it all but I reckon it will work a lot better for our situation. And there is no way in the world I'll pay up to $2.5k to have a Carafan fitted. As nice as that would be...

Thanks all for the responses and I'll report back once I've got it done. Pick the van up 1st October.
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Follow Up By: RMD - Sunday, Sep 19, 2021 at 11:20

Sunday, Sep 19, 2021 at 11:20
Rusty,
Now you are talking and seem to have a really good idea how to achieve the result you want. The satisfaction of "I made that" and it works means a lot.
Interesting you mentioned the overtaking dust cloud with wind from behind the vehicle. Your system will still work because it is positive flow. unlike the tail wind taking the flow from radiator cooling on vehicles and they then tend to overheat. Be good to see what you create!

If using a Donaldson filter somewhere, maybe the fan can be included inside the case of it, all depending on physical sizes of course.
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Follow Up By: Rusty Iron - Sunday, Sep 19, 2021 at 11:30

Sunday, Sep 19, 2021 at 11:30
Thanks RMD. The fan won't go in the filter body because the element fills it completely. I'll put the fan directly behind the filter so it draws air through it. Easier to get to as well if it needs replacing. And the fans are fairly cheap ($40 to $50 will get a good one) so I'll probably carry a spare one. The Donaldson can be had with either 75mm or 100mm outlet / inlet, and so can the bilge fans. And it's not hard to source the same sized flexible hosing.

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Follow Up By: Peter_n_Margaret - Sunday, Sep 19, 2021 at 15:01

Sunday, Sep 19, 2021 at 15:01
Make sure you choose a centrifugal (squirrel) fan, not an axial (propeller) blade fan. The latter will not provide airflow at pressure against significant resistance.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: Rusty Iron - Sunday, Sep 19, 2021 at 15:43

Sunday, Sep 19, 2021 at 15:43
Thanks Peter. Can you advise what sort of air flow I should look for? The van is a 16 ft pop top.
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Follow Up By: Peter_n_Margaret - Sunday, Sep 19, 2021 at 16:50

Sunday, Sep 19, 2021 at 16:50
No idea. It has to first provide enough air flow to exceed the "leaks" then enough grunt to add some pressure to ensure that all the leaks are OUT, not IN.
I would position the inlet so there is a ram air effect too. That will reduce the fan's job and you don't want to be fighting that. As I have said, mine works well with no fan, just ram effect.
That is why sealing as many of the leaks as possible first is important. Less leaks, smaller fan and lower air flow required. If there are ZERO leaks, you don't need a fan, or anything else at all :) ... :) ...
Small leaks from the windows and doors can be difficult to seal.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: RMD - Sunday, Sep 19, 2021 at 19:07

Sunday, Sep 19, 2021 at 19:07
Rusty
The size of the van is not really important as it is the slight positive pressure which is going to do the job. The same fan will cause the same pressure for the same number of escape points. A fan which creates a positive pressure with a reasonable flow. If the flow is huge but no more pressure, then the fan is effectively overkill.
To be sure you are achieving something you can do similar to below.
For some air filter flow restriction testing, I made a box to test airflow of filters using a vacuum source and a water filled manometer tube of plastic tube. The reverse could be done to test positive pressure ability of the fan you choose. ie, restrict the ducting size to equate approximate to leaks of van and test/see the difference on the home made water manometer tube.
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Reply By: Daniel G3 - Sunday, Sep 19, 2021 at 17:22

Sunday, Sep 19, 2021 at 17:22
Hey Rusty

I have just installed a 75mm bilge blower (continual) in my 17.6 full caravan.
It is yet to be tested on road.
I have a microwave vent high on the right hand side of my van so no new hole was required.
I used 90mm storm water pipe to connect to the blower and then the flexible hose to a heater outlet.
I intend to fit a filter where the air comes out as it is too difficult to remove the microwave just to service a filter.
I wired in a cigarette plug as it only draws 2.5 amps and it plugs into the wall where my 12 volt television is connected to .
I may be wrong with the filter bur time will tell
AnswerID: 637977

Follow Up By: Rusty Iron - Sunday, Sep 19, 2021 at 17:25

Sunday, Sep 19, 2021 at 17:25
Thanks Daniel. Actually, you've made me think a bit further - do I really need a full on Donaldson type air cleaner? Maybe just some filtering material at the inlet, and some more at the outlet in the van. Maybe some of that air con filter material at Bunnings is all that's really needed...
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Follow Up By: RMD - Sunday, Sep 19, 2021 at 18:42

Sunday, Sep 19, 2021 at 18:42
Unless you are actually travelling in constant clouds of dust, ie following too close to someone else, and the air intake is high up anyway, is a filter really needed? Is it going to be sucking in dirty air at all? The idea is for pressurization to exclude ingress at lower levels, and the fan forced aspect will do the job. Any filter begins to negate the fans force of air.
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Follow Up By: Rusty Iron - Sunday, Sep 19, 2021 at 18:51

Sunday, Sep 19, 2021 at 18:51
Some filtration is absolutely needed. On many of our trips our current camper trailer has been completely enveloped in dust. I've been through many bulldust holes where the dust literally runs like water. It's just like talcum powder. It will get in anywhere it can.
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Follow Up By: RMD - Sunday, Sep 19, 2021 at 19:12

Sunday, Sep 19, 2021 at 19:12
In that case I would be absolutely thoroughly checking the sealing of the engines airbox. You will be stunned at how some leak dust into engines. I use a Unifilter. ie, pre oiled foam as it removes far more fine dust than OE filters do. I noticed the intake to my turbo on previous HJ 61 LC and changed to something which worked. OE filter not so good. Sorry to change to engine filtering.
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Follow Up By: Daniel G3 - Monday, Sep 20, 2021 at 05:42

Monday, Sep 20, 2021 at 05:42
Just my thoughts on the requirement of a pre- filter.
Lots of people use a scupper vent with no filtration at all, none mention the ingress of dust.
I have put very fine insect screen on the vent but no filtration as where it is situated is just too hard to get to for servicing. The vent (existing)is situated about 2500mm on the right hand side approximately in the middle of the van.
I do use a stone stomper and find it tends to keep the dust down.
I think a piece of filtration on the outlet side is good enough to stop any dust from entering the caravan and it is easily accessible to service or clean if necessary.
The filtration at this end does not affect the bilge blower performance.
This has cost me about $100 and if it fails I have not drilled any additional holes other than the outlet inside the van which does not look out of place.
Good luck with your project
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Reply By: Member - Rick T4 - Tuesday, Sep 21, 2021 at 09:02

Tuesday, Sep 21, 2021 at 09:02

This setup incorporates a pre filter to spin out larger dust particles then balance of air flow is sucked through a Donaldson filter by a centripetal fan. I have it set up to turn on by turning on my clearance lights.
These units are available from Lyons WA and are commonly used in vehicles in the mining earth moving industries.
I think you will need good positive pressure in extreme bulldust I certainly did.
Expensive to buy or DIY
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Follow Up By: Daniel G3 - Tuesday, Sep 21, 2021 at 17:14

Tuesday, Sep 21, 2021 at 17:14
Rick

Well done that system looks really good.
I think it is critical to seal up as much as possible in the van/camper so the positive pressure has the best chance at keeping the dust out.
As Peter has said previously windows will always have some air escape but if all other vents are sealed than the positive pressure will keep most of the dust out.
Certainly a lot less money than a carafan.
Perhaps in a few years I may consider a carafan on a new van, time will tell.
I think at the moment it is just a matter of when travel can happen
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Reply By: Brenton B2 - Tuesday, Sep 21, 2021 at 12:11

Tuesday, Sep 21, 2021 at 12:11
I've gone the KISS route in regards dust ingress, still use the basic roof dust hatch but with a cowling over the top so when the hatch is open it seals the back end & makes for a larger Air-ram effect, when the hatch is closed air & bugs just flow straight thru. Inside I have a removable (washable) filter. As stated in previous posts all gaps have been resealed & larger vents have clip on/off covers. Its not "open" when its raining & dosen't use any power, and it "works" extremely well even in bulldust situations
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