tonyg3nwl Posted December 19, 2015 Share Posted December 19, 2015 Hi folks, having had damp problems, allegedly fixed by marquis before purchase, and second attempt this year by them again sadly disputed under warranty(long sad tale), I have now and for last 2 weeks put a dehydrator in the van permanently running. Each day checked how much water in tank, and nearly always the little tank was close to full. It holds about 1 litre. today, I have plumbed in a short hose and run it down into and through the fresh water tank to drain away continually. This is because when the little tank is full, the dehydrator stops and waits for it to be emptied. all cupboards etc are left open in the van, and soft furnishings are stored in house I hope that this will help prevent any further problems.. according to marquis, the wet was getting in through the cable entry through the floor front nearside just behind front wheel. And possibly through the nearside locker fixings. they say that it has all been resealed in relevant places.. I hope they have repaired it properly this time. tonyg3nwl Link to comment Share on other sites More sharing options...
colin Posted December 19, 2015 Share Posted December 19, 2015 It may be that you are just removing the natural moisture from the air, Link to comment Share on other sites More sharing options...
colin Posted December 19, 2015 Share Posted December 19, 2015 It may be that you are just removing the natural moisture from the air, Link to comment Share on other sites More sharing options...
George Collings Posted December 19, 2015 Share Posted December 19, 2015 To comply with the gas regulations 'vans have more than ample ventilation to ensure the air changes regularly to avoid gas concentration to dangerous levels . As fast as you dry one lot of air in the high humidity UK its replaced more.. Adding a little heat so condensation does not form is far more effective than a dehydrator. Drying out flooded premises is totally different as ventilation can be more controlled. Link to comment Share on other sites More sharing options...
Rayjsj Posted December 19, 2015 Share Posted December 19, 2015 George Collings - 2015-12-19 12:08 PM To comply with the gas regulations 'vans have more than ample ventilation to ensure the air changes regularly to avoid gas concentration to dangerous levels . As fast as you dry one lot of air in the high humidity UK its replaced more.. Adding a little heat so condensation does not form is far more effective than a dehydrator. Drying out flooded premises is totally different as ventilation can be more controlled. Thanks George you are confirming what I already thought, I live in very rainy (at the moment,and most of the Winter) and damp Pembrokeshire, I aways keep a small convector heater on a timer switch, in my van. This seems to work at stopping mould from forming on the soft furnishings. A dehumidifier would have its work cut out, trying to keep the whole of Pembrokeshire dry. And the cost of using the heater is far less than replacing ruined furnishings. Done that, with an unheated Caravan,in the past. Ray Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 19, 2015 Share Posted December 19, 2015 I think the problem is much less to do with temperature, or humidity, in isolation, and all to do with the way they keep fluctuating. Our climate is, shall we say, fickle. We have (or at least we used to!) cold spells, when it is often quite sunny and the air is relatively dry. We then have mild spells, often with rain. Between, we may get misty spells, when the humidity is around 100%. So when it is cold, in the absence of any heat in the van, the whole structure cools right down. If the cold spell is followed by a mild, humid, period, moist air will permeate into the van via all those vents, and condense as moisture on the cold surfaces inside. It will not then re-evaporate until the van itself warms up sufficiently, which may not be for some time since the now generally warm moist air will be reluctant to take up further moisture, and the condensate needs extra heat energy to change from water into vapour. So, it hangs damp. The damp then creates the conditions for mould spores, which are always in the air, to grow. This cycle of cooling and warming, with attendant dry and then humid air, persists on and off from late autumn to early spring, sometimes more, sometimes less. De-humidifying, as George says, is a bit of a waste because of all those permanent vents. On the other hand, a little gentle heat in the van to counter the periods of extreme cold will keep the internal surfaces generally above the dew point of the air, and prevent condensation forming. Ideally, it needs a thermostatically controlled heater rather than a time switch, as the problem is temperature related and not time related. Somewhere around 5C should be about right, but a bit of experimentation will be needed to adjust for the characteristics of the van and the heater. We use a very simple electric greenhouse heater, which has a low temperature range 'stat. Quite cheap if you can find one. Link to comment Share on other sites More sharing options...
maggyd Posted December 19, 2015 Share Posted December 19, 2015 We use a couple of the silicon moister traps lift all cushions away from the walls , stand them vertical if you can, leave all cupboards open , we have never had a problem over the many years with motor homes or caravans. The trouble with dehumidifies draw in the damp from outside I always think. Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 20, 2015 Share Posted December 20, 2015 Those moisture traps are just chemical dehumidifiers, Maggy, and suffer the same problem of humidity endlessly being replaced via the permanent vents. Both will have a marginal affect on humidity in the van, but only marginal. Link to comment Share on other sites More sharing options...
Silicongyro Posted December 20, 2015 Share Posted December 20, 2015 George makes the case that warming a motorhome in winter is preferable. This view has also been promoted by others on this forum in the past and is, I believe, a fallacy. So I would like to challenge this on behalf of the humble dehumidifier ! I accept that a motorhome's ventilators (and other unintentional leakage points) allow for a fairly significant flow of air to be exchanged between the interior and exterior. Both from air movement and even in still air times, air diffusion. However, to a first order, the volumes lost to the outside are just the same whether the air is warmed, dried, or indeed left alone. You will lose some of the dried air and the warmed air equally! We need to lower the interior humidity levels - both to minimise condensation and to discourage moulds, bacteria etc setting up home on the interior soft furnishings. To this end, air circulation is also desirable. Now both heating the air, and drying it will achieve these aims. To my mind, the choice is whether you wish to pay to heat the air or dry it. I believe drying it is significantly cheaper - in the end, the electrical power you pay for ultimately ends up as heat. A dehumidifier located inside a motorhome will nett heat up the interior far less than a heater. Further to this the warmer a motorhome interior is the more energy is lost through the walls, windows etc. Long live the Humidifier - and the quarts of water I empty out every few days at the moment ! Link to comment Share on other sites More sharing options...
EJB Posted December 20, 2015 Share Posted December 20, 2015 A dehumidifier in a caravan or motorhome cannot dehumidify the world! I assume that people who use them check the humidity inside and out to realise that they don't actually make any difference? As for heating the inside in cold weather!!!!!!!!!!! Link to comment Share on other sites More sharing options...
Muswell Posted December 20, 2015 Share Posted December 20, 2015 Exactly. What you need is more air circulation. Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 20, 2015 Share Posted December 20, 2015 Silicongyro - 2015-12-20 11:46 AM......................Long live the Humidifier - and the quarts of water I empty out every few days at the moment ! Which, to me, seems to make its own point. If humidity doesn't enter the van that readily, where do those quarts keep coming from? :-D But, what we are dealing with is not net humidity, but relative humidity. Relative humidity changes with air temperature, and is the measure of the degree to which the air is saturated at that temperature. Air with the same net amount of moisture has a different relative humidity at say 10C, than it does at, say, 20C. If the air is 100% RH at 10C (saturated), it will be about 58%RH at 20C. If 100% at 0C it will be about 50% at 5C. So, by just warming the air that bit, say to about 5C, it will continue to retain its moisture, and will also raise the internal surface temperatures slightly as well so, with the right balance, it will keep the interior above the dew point of the air to prevent condensation forming. Temperatures generally fluctuate over any 24 hour period, so at some point the external temperature will rise above 5C and the heater will switch off. The humidifier, assuming it is humidistat controlled, will continue running until RH falls below its set point. Yer pays yer money..............! :-) Link to comment Share on other sites More sharing options...
Muswell Posted December 20, 2015 Share Posted December 20, 2015 So does anyone keep a dehydrator or heater running in their car while it is parked overnight? Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 20, 2015 Share Posted December 20, 2015 Probably not - but I'd guess most cars don't get parked for several weeks at a time during winter! :-) Link to comment Share on other sites More sharing options...
Silicongyro Posted December 20, 2015 Share Posted December 20, 2015 Muswell - no I guess they do not ! However a car's inside is virtually sealed unlike a motorhome. Brian - yes I appreciate the issue you make wrt relative and absolute humidity. What we need is to maintain a low relative humidity. As I stated this can be achieved by heating the air as you suggest to maintain the same absolute humidity but lessen the relative humidity - or - take out some of the moisture with a dehumidifier to reduce both the absolute and relative humidity but at the original (cooler) temperature. The point re emptying water from the dehumidifier - this illustrates the degree of air exchange which happens whether we like it or not ! Either we heat a volume of air to be lost to the outside (your proposal) or we take out some of the moisture entered via the exchange of the same volume of air - which I contend is cheaper to achieve the same resultant RH. Doing nothing is not an option for me - I have tried this and the interior starts to smell "manky" and patches of "staining" ocour here and there all over the place - roof covering , fixed soft furnishings. Mind you that was in North Cornwall which is the very definition of dampness in Winter. Link to comment Share on other sites More sharing options...
Rayjsj Posted December 21, 2015 Share Posted December 21, 2015 Bet our Damp is wetter than North Cornwall 's Damp ! Link to comment Share on other sites More sharing options...
Brian Kirby Posted December 21, 2015 Share Posted December 21, 2015 Ah, but Colin's damp has travelled from America, while yours has only come from Ireland. Atlantic damp is renowned for being much wetter then Irish Sea damp! :-D Link to comment Share on other sites More sharing options...
Will H Posted December 21, 2015 Share Posted December 21, 2015 'Tis the size of one's droplets. Link to comment Share on other sites More sharing options...
tonyg3nwl Posted December 21, 2015 Author Share Posted December 21, 2015 Hi folks, whatever the arguments are , for or against, dehumidifier or some form of heating, etc, I carried out a series of damp meter readings yesterday inside the van, at various locations, top of walls, below windows, and floor levels, near vent points etc.. best obtained figure was 10 %, worst 11.5%, .. Since this set of readings are typical in any van, of similar construction, and in Marquis testing they state no action required at that level, I cant pursue any further complaints. what figures do you expect to get in your van. tonyg3nwl. Link to comment Share on other sites More sharing options...
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