Extra heat

[roberth]

I have installed a dehumidifier to keep the interior of Karsha fresh during the cold winter months.
I was also going to buy a small heater (greenhouse type with thermostat) to run in tandem, to boost the efficiency of the dehumidifier which has been frosting up during cold weather.
I have since been told this is wrong, as the heater will increase the moisture-carrying capacity of the air which will exacerbate the frosting problem.
Can't see that myself - surely warmer air will prevent frosting while allowing more moisture removal? If a heater is recommended, would a small (c500W) machine be sufficient?
Any advice would be greatly appreciated.
Robert

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[Evadne]

Warm air will hold more moisture than cold air - the air in the arctic and antarctic is noticably drier than in temperate zones. Warming up the air on a continent will therefore allow it to hold more moisture, cooling it will allow less. If air cools, it deposits its moisture content out as condensation. If the boat itself is generally warm, then the air will hold more moisture and you'll get the same or more moisture, but less condensation. Either heat the boat and seal it, preferably with a dehumidifier, or heat the air then blow it out drawing in cold air, which has been filtered to remove the water content.
Or do as most of us do, and remove all components susceptible to damp then de-mildew the boat in the spring when this part of the planet warms back up again. That's the cheapest option.


P.S. Don't use a gas heater, this converts hydrocarbons to water and CO2 and makes the air wetter.

<hr width=100% size=1> <P ID="edit"><FONT SIZE=-1>Edited by Dave_White on 12/11/2004 15:29 (server time).</FONT></P>

 

[dralex]

My combination of 700w oil filled heater and a B& Q dehumidifier works a treat- the boat, bedding, bilges, in fact everything is lovely and dry. It also feels lovely to go down to the boat as opposed to that cold to the bone chill. I don't think about the physics too much, just what it feels like.

<hr width=100% size=1>Just enjoy it.

 

[roberth]

Thanks very much to you both - got the B&Q dehumidifier - now to track down that oil-filled heater....after the run from Newhaven to Eastbourne and back tomorrow. Looks like a good breeze up this end of the Channel.

Robert



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[Anthony]

I can testify to the B&Q dehumidifiers, I put one on Olli this morning, produced a frightening amount of water in te short time I was there. Dissapointed that they were not mentioned in PBO recent review alongside the expensive swindalry ones.

Have you any idea how much it costs in electricity to leave a duhumidifier and oil type heater on? Just hesitant to add a heater for fear of the number of zeros on next quarters elec bill!

Anthony

<hr width=100% size=1>The difference between men and boys, is just the price of their toys...

 

[roberth]

Helps to have a fixed tariff, as we do at Newhaven - or perhaps I'd better check the small print again!

Robert

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[geoffatstanpit]

My "domestic" dehumidifier uses 200 watts and pulls about 2 litres of water a day out of my Parker 21. It always feels nice and warm and dry inside.

Geoff

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[Phoenix of Hamble]

Anthony,

If its only one of the low wattage heaters (typically circa 200W), then they are pretty cheap to run... perhaps 1 to 2 p per hour, or around £2.50-£3.00 per week.... looking at the PBO article, the dehumidifers are about the same, so no more than £25 per month if run full time... put 'em on a timer, especially the dehumidifier, and much less could be acheived.... I would guess with a bit of common sense, and a timer you could cover the entire off season for no more than £60.... worth it for a clean dry boat in the spring....

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[steve_cronin]

But his de-humidifier will keep on working to dry the air. If it is icing up then he needs to resolve that.

That the air is holding more moisture isn't really the issue. It's how much of that moisture is allowed to settle on and be absorbed by panels that you can't get at and therefore get mildewed that really matters. Unless it's completely open to the outside, the boat will act as a sealed space and once dry, will remain so with the help of the two electrical devices.

In my experience "Most of us.." actually use de-hums. these days and often augmented by a small fan heater. The de-hum itself in less severe conditions will provide quite a bit of heat. What's going on behind the headlinings of a cold boat?

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[steve_cronin]

Electricity (unless you want 415 three phase) is free at our marina.

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[dralex]

I total 900W, which is 0.9KwH ( unit)- I'm also on a fixed tarif. The dehumidifier is only 200w and if there was an issue, I would run this primarily and just set the heater thermostat to tkae the chill off on really cold days.

<hr width=100% size=1>Just enjoy it.

 

[capricorn]

I have the 80 quid B&Q dehumidifier also, it's been running for the last month and I agree that it extracts quite remarkable amounts of water. No numbers to support how less humid the boat is but it feels much dryer.

Some dehumidifiers (including this one although I didn't know when I bought it) have an auto-defrost feature which should prevent the icing up issue. Not sure how effective this will be when it gets really cold though although I think these things ice up more as a result of the function of the evapouration cycle than from the ambient temperature. Might be wrong about this though.

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[Trevethan]

The warmer air will hold more moisture taking it from inside the boat, which can be sucked out by the dehumidfier instead of letting spend the winter woring on ruining your fabric wood etc,



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[steve_cronin]

Dew point.....

...that's what it's all about.

The heater will prevent the air dropping to dew point, which is the temperature at which, given a certain atmospheric pressure, the water falls out of the air all over your interior (both visible and hidden) Whilst it's temperature is being artificially held up, the de-hum. will rob it of it's moisture.

Steve cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion