Dick all understood. When next aboard I will, for completeness, dig out the make and specification of our dehumidifier. Being built in I have no idea what brand etc it is.
Simon
edited by simoncurrin on 1/16/2019

Hi Simon,
Thanks for the info: I do not believe I know of any other cruiser with a built-in de-humidifier.
To be clear, I have no knowledge of built in de-humidifiers such as you have aboard Shimshal. I was using your comments to respond generally to de-humidifiers that much more commonly find themselves aboard cruising boats. The ones I was referring to are the household type de-humidifiers that are about suitcase size. I know of no significantly sized portable de-humidifier built with the marine environment/being-on-a boat in its design parameters.
I am unable to cite sources, but I remember at least 2 articles/notices in the UK slicks (probably able to be found) when I was cruising those waters and, of course, there is the first-hand observation I mentioned in my previous posting. I would not bring it up, but I do believe the portable household de-humidifiers are an unnecessary risk and that a sweet boat unaffected by mold etc. can usually be achieved with-out this risk, small as it may be.
My best, Dick

Dick

I, of course, agree ventilation is important and we have dorades too.

In damp, cold climates such as Scotland and Iceland then dehumidifying makes a great difference to comfort when on board. It’s something to do with the latent heat of evaporation if my school boy physics is correct. That is primarily why we had a permanently installed dehumidifier specified when we built our current boat. It sucks in moist air from the saloon and pumps dry air fore and aft to ensure good air circulation. The condensate is pumped directly overboard and does not accumulate in the bilges. It is a 240 volt AC device which has a very stable power supply through our isolating transformer. It has it’s own RCD breaker and thermal protection circuits. I believe the risk of fire is miniscule. Famous last words!

We always leave all cupboards open and cushions away from the hull but have no reservations about leaving the dehumidifier on when left unattended and when there is a reliable power supply.

I accept that there is no need to do this in very cold climates but I would prefer my boat to over winter at a lower humidity than the ambient humidity present in Scotland and Iceland during winter.

We spent two winters afloat in Reykjavik with free electricity and advise anyone doing likewise to leave their dehumidifiers set to 80% or less for entire winter.

In Newfoundland and in Greenland we left the dehumidifier on for the autumn when there would be freeze / thaw cycles. We know that the power will be disconnected through the depths of winter but the hope is that the boat will be by then frozen.

I would be interested to hear about the incidence of fires caused by these devices. It is not something I had considered.

Simon

Hi Simon,
Even if the AGM batteries were above 12.0 rather than 12.7, I believe that is charge enough to protect them from most freezing temperatures likely encountered and that capacity to hold a charge over 9 months is impressive. Dick

Hi Simon and all,
I apologize in advance, Simon, for using your comment to kick off from and write about the wider issue of unattended de-humidifiers and storage. And I do know yours is a built-in unit: I am speaking of the suitcase size household units that many skippers, I noticed, in cooler/colder climes use 24/7 when not aboard. Sometimes this is a full winter storage and sometimes this is from weekend to weekend when not aboard and the boat is waiting for its next outing.
The argument in favor of doing this is that the boat remains sweat and mold free and onboard equipment is likely to be freer of problems. The latter may be true, but with high quality equipment, I doubt it, but the former is definitely true for many boats. Some dehumidifiers also impart a bit of warmth, which I am sure the boat appreciates as well.
I am perfectly clear that when living aboard in cool/cold climates, a dehumidifier is an absolute must (at least for Ginger and I who prize comfort and in no way want our cruising lives to approach camping). Some very stalwart souls can live in boats that they keep open in all but the coldest weather, but we like a warm cozy cabin and, without a dehumidifier, we would soon have condensation covering the inside of the boat and start mold everywhere.
I would want to make the case that the proliferation of de-humidifying devices one sees in the marine market (gels, electric etc.) is directly related (at least to some extent) to how poorly ventilated modern boats are nowadays. Manufacturers are saving money by not ensuring that their boats can be well ventilated. Good ventilation when rain is falling, when salt water is flying costs money, but is never a deciding factor in purchasing.*
So, I believe that de-humidifiers are a great boon to comfort (and the ship’s well-being) when living aboard, but I think it is fairly easy to make the case that leaving dehumidifiers going un-attended is playing a bit of Russian roulette with the chance of a fire. I know of numerous reports of this occurring and have seen first hand the melting insulation, smoke and char of a de-humidifier about the go to the next stage of a live-aboard neighbor in London.
This worry about de-humidifiers and their potential for fire, I would guess, just escalates in those locations where the cleanliness of the power feed may not be so well regulated (voltage spikes and drops, varying hertz). As well, it should be noted, that de-humidifiers are built to a price and designed with the expectation that they will be used in a home with good power, in a secure location and not moved around all the time (a typical life of a d-h on a boat).
I would want to suggest that the safest way to leave a boat, whether for a winter or for a week or two between sails, is for the vessel to be well ventilated and “allowed” to equalize with the ambient air, temperature and humidity. If your vessels ventilation can’t ventilate well enough to mirror the outside conditions, then I would suggest doing something about it: if only because when offshore, life below will be a misery at times. An added benefit is that you do not have to leave your boat plugged in when un-attended: a practice which, while likely to generally work out, but when it goes awry can lead to problems, especially when no one is around to catch problems in the making.
But my position does not lead inexorably to a moldy un-sweet boat when skipper and crew return to it. For example: Alchemy has adequate ventilation (two dorades in a 40-foot hull) which, when we are gone, we augment with the shower portlight being left open and a portable solar fan in an access hole to the engine area. Usually this is enough. The next level is to ensure cushions are “ajar” and the cabinets etc. are open, done to ensure air gets into the nooks and crannies. I suspect this might not suffice in some locations (The Rio Dulce in Guatemala for ex.), but this has worked for us in over-wintering spots from southern Turkey to London to Lerwick, the Shetland Islands. In these weather-disparate weather locations we have returned to a boat that was sweet and habitable.
All is not lost if your boat is not adequately ventilated, augmenting can usually be done. Best might be to add dorades (or dorade equivalent scoops as that will help underway as well). This is often more easily accomplished than initially supposed. In storage portlights can be left open such as the shower portlight. Where rain might get in where one does not want it, there are commercial “hoods” or one could cobble together portlight covers for the winter. If the boat is covered for the winter, worries are over: leave lots open and the boat will equalize with the outside. Some skippers effectively and permanently install solar fans, but location would be important as I am not sure how water-tight they are when flooded with green water.
Please come back with thoughts/comments.
My best, Dick Stevenson, s/v Alchemy
*Ventilation is also a huge issue at sea. A poorly ventilated vessel makes for unhappy, seasick, uncomfortable crew at sea and borders on a safety issue in certain conditions. Many purchase their boats with little consideration of this important factor. (Alchemy, with its 2 dorades, when underway and closed up in rain or wild conditions can get stuffy down below. This is especially the case downwind when the dorades do little to contribute to ventilation. Multiple interior fans help a great deal as even stuffy air is made more acceptable by movement.)

Hi Simon,
I know you have built in de-humidifying. Can you say more about it? The equipment, how it works, dissicant? , power draw etc. Thanks, Dick

Hi Phil,
That sounds good.
It would be nice to have those who have thoughts on these subjects and who enjoy sharing and comparing on the Forum. That way the ongoing search for an approximation of “best practices” can be archived.
My best, Dick Stevenson, s/v Alchemy

Dick the Facebook post asks folks specifically to come to the Forum to share their knowledge and experience rather than post on Facebook. Frances Rennie has also made the post on Facebook "sticky" so that it stays at the top of the OCC page for a while. We will see what happens. Cheers Phil

Dick,
You have made me doubt my memory which can play tricks at times! I am though certain it was >12 volts.

Ivan is keeping an eye but I gather the yard has a policy of switching off all power during that period - I think for insurance reasons. We left the sacrificial two batteries connected to SHOREPOWER with our dehumidifier on in order to cope with the periods before and after the winter freeze.

I will certainly report back on the voltages of all circuits in June. As ever we are keeping our fingers crossed!

Simon

Simon

Hi Simon,
That is a very impressive stat: 6 yo AGM battery bank left for winter on its own and reads 12.7 after 9 months: even for lightly used batteries. Part of me wants to argue with you that it is not possible while the other half intends to go out and buy AGMs for Alchemy. It would have been interesting to know what the “in line” battery v was after a winter of parasitic draw as well as the bilge pump.
Is Ivan watching over Shimshal in Lewisporte? If so, I bet he could get an extension cord to the boat for a charge. In any case, it sounds like it is un-necessary with the AGMs lasting so long and it sounds like you may have disconnected them.
I doubt you will have an unpleasant shock and need new batteries. My gels always gave me a year or two warning.
My best, Dick