HVAC - "Sick boat syndrome"

It has been determined that microbial growth in HVAC systems is linked to poor maintenance of ducting associated with this system. There is also a growing awareness of "sick boat syndrome" coined from the same phenomena experienced in ill ventilated buildings.

I would like to ask this forum therefore: How might maintenance of the HVAC system be improved and how might "sick boat syndrome" be avoided?

 

Are you talking about huge ships with monster physical plants, or fifty footers?

 

Chris,

I would look very closely at best practices in the building industry. Things like more frequent air exchanges, UC lights in the Hvac system, more frequent cleaning of the ducting, ect. There has been a lot of research done in this regard in the last few years, and I doubt that there is anything specific to the marine industry that prevents the use of many of those solutions.

Of course there may be some limitations imposed by the specific boat.

 

HVAC stands for Heating, Ventilation and Air Conditioning.

 

HVAC about sums it up.

Three other words come to mind:

Ventilate, ventilate and ventilate.

Very good for cabins, not good for props.

 

there is a disinfectant spray good for smaller systems, one brand is called "frigi-fresh" or something similar for use in automobiles and RVs. I have used Lysol brand for similar purposes. I would expect it would work in smaller boats system as well.

It is difficult to keep mold from forming inside of anything that is in a marine environment. keep all fabric and other porous materials (cushions, bedding, curtains, etc) or you have to keep the inside heated during colder months, there are also electric devices that are supposed to prevent mold and keep moisture levels down. and regularly use disinfectants both inside any system, and inside any closed-in space.

good luck.

 

My thoughts exactly ! new boats have window and door that seal air tight . same with houses all sealled so it creats a artificial climate inside the boat or house . with natuaral ventilation the musty smells and dampness all go away .
I used to lay wooden floors in my sparetime when fireglassing became a hassle and got bored . and asian houses were the one had the most problems with because of the cooking habits they neve open window the boil rice and more tha 2 cuts of water goes into the air each time they shower with doors clsed then open and 200% moisture spills straight into the same air thats locked inside the house . so floors used to do all kinds of not nice things , and wet cloths left laying about for days
Boats are the same theres a artificial climate locked inside the boat from end to end and no fresh air gets in or goes out How many vents do you see on any new boat ?? apart fron the forward opening hatch wheres the air going to come from ?? apart from the openi g companion way where and how does fresh air get into the main cabin . side windows are sealed !! Aircons just move the same stale air round and round and warm it and make it smell even worse ,so who do you going to call ?? "Ghost busters "
(Couldnt resist that one ) do you blame the designer (i would ) do you blame the builder ( i would ) do you blame them both (deffinitly and all there friends ) just 2 small words to say "FIX IT" !! they designed they built so make it right !!

 

The critter most closely associated with sick building syndrome lives in the evaporator towers outside or on the roof, or in fountains (particularly ones with lights in them that create a warm zone), or potable water systems. It is a common critter that you have probably been exposed to all you life. Under the right circumstances, it can bloom. And if the mist from the evaporators gets pulled into the building, some people can get sick. It takes a massive bacterial load to make a healthy person sick. The solution is to not draw the mist into the building (and interior fountains are a particular hazard). There are several ways to control it in the evaporators. Most try to use various free resources such as waste heat from a boiler or some such. Setting the hot water heater back up to where you had it before they told you to turn it down is an effective precaution for potable water systems. The only problems with ships that I can think of is the swampy conditions of the cold water tanks. Potable H2O should be kept below 68 degrees, or above 150. Good luck with that if you load a miilion gallons at Key West. The hot pipes need to be exposed to 160 intermittantly.

As for other things that get balled up into this sick building syndrome, it helps to know what you are talking about. The HVAC system is not what is making you sick. It is distributing what is making you sick. The colorful, plentiful fauna living in your ducts and indoor coils won't make you sick unless things have gone very badly out of whack.

http://en.wikipedia.org/wiki/Dipslide

Major irritants includes -

Ants- formic acid
Mold- irritating spores. (the poisons that some molds produce don't really enter the airsteam, that is a widespread misconception.)
Pollen
VOCs- in particular formaldahyde and similar stuffs used in glues which tend to dissociate in moist environments. Citrus based cleaners are another major problem item used in large amounts as floor cleaners and wax strippers in commercial buildings.



My personal take on the matter is that one of the biggest problems is the routine use of antibacterial agents which kill off the stuff we are accustommed to and create niches for the weird stuff. That and the fact that we are not as healthy as a population compared to fifty years ago.
Time to throw a few carp into those cruise ship tanks.

 

I remembered one other proven problem regarding the hotwater distribution systems. On big systems such as a hotel, you use a reverse flow circulator pump. The main hot pipe distributes to several floors and back to back rooms down the wing of the building. In order for the tail end room to get hot water promptly, a small pipe is run out to the end and a tiny circuator pump keeps the main pipe warm. This way, it doesn't take twenty minutes to get warm water at three in the morning. These things can create the perfect environment for legionaire bacteria. A dripping showerhead can sicken the entire hotel.

 

On the yachts side its proper maintenance.....

Each season .... filtration system and routine cleaning of fan coils , blower assemblies , extractor fans in heads and galley and appliances like clothes driers .
After that a pro contractor is brought every few years to physically clean the ductwork with various brush vacume tools then sterilize the system by applying an anti microbial coating to the ductwork.

 

For a new small (under 65 ft) boat I would consider a modern "Mini Split" house style unit.

These are very efficient and can operate as heaters , down to well below Zero F.

Air cooled no underwater connections , pumps etc .

The compressor is external and the room , cabin only has an evaporator with a scroll fan. This should be easy to maintain.

For larger boats the water chiller style uses evaporators fed with cold or hot water (as required) in each cabin.

Cleaning is a snap, and every cabin is zone controlled.

 

The recommendations for maintenance of ventilation and A/C systems on small vessels is similar to those valid for cars.

A regular cleaning of your A/C air filters is the single most important thing to do, followed by occasional cleaning of the ventilation ducts (how many people do we know who actually do this?). Since the A/C systems on board the small vessels mostly recirculate the ambient air, it means that keeping the cabin clean from dust on a regular basis also plays a role.

I have always asked myself if varnishes and gel-coats used for the finishing of boat interiors can have some bad effects on human health, because their odor in cabins is very noticeable - especially in the first few years of boat's life.

Check, for example, this description of the effects of exposure to styrene, which is omnipresent in fiberglass boats (and in plastics in general):
http://apps.sepa.org.uk/spripa/Pages/SubstanceInformation.aspx?pid=86

Cheers

 

I presume you are referring to UV lights here. The jury is still out on whether these things do any good within the ducts themselves, as most of the bad things are flying by the light source too fast for the light to kill them. However, a UV light shining on the AC coil is probably a good idea, especially if there are reflective coatings or mirrors inside the coil housing.

The UV light does have to be replaced annually to maintain effectiveness. They do wear out, even though they are still putting out plenty of visible purple light.

 

Talking about buildings and cruise ships - the described problem exists, but there are ways to resolve it. The Legionella bacteria is effectively killed or sterilized by high temperatures (75+ °C), so a very diffused strategy is the so-called "thermal-shock" method. A by-pass motorized valve is installed between the heater and the main hot-water distribution line, so that a sterilization cycle can be programmed for around 30 minutes during night, for several nights in a row. At some time the heater kicks in and the by-pass valve opens, sending high-temperature water to the hot-water distribution system. The water recirculates for around 30 minutes through the return pipe you have described, sterilizing the system.

Another efficient method is the hyperchlorination of the system, which is performed in a manner similar to the above. Instead of high-temperature hot water, a mass of highly chlorinated water is sent through the hot water piping.

The hot-water tank is a bigger problem, because of stagnating water - which is what bacteria just love. The best precaution against Legionella is to not over-size the tank (thus helping a more frequent renewal of the mass of water) and to keep the water storage temperature above 55-60 °C. At that temperature, the bacterial growth is inhibited. And, of course, a frequent cleaning of the tank with chloride products.

Cheers

 

Hi all!

Thank you very much for your posts. Its very interesting to hear your viewpoints. It seems that the cause of microbial growth is not just dependant on the air conditioning system, but rather it is facilitated by it. The very nature of the cabin environment seems to facilitate this as well. It is true to also think that bad maintenance can increase the effects of microbial growth. But like "daiquiri" states .... who really does this? I have managed to arrange a private interview with several crew members of private and commercial yachts to see if the maintenance procedure of HVAC systems is properly executed and to enquire as to how might this issue be resolved through simply... better design.

Current observations of HVAC systems have also indicated that although maintenance has been considered in both systems, it is not easy or intuitive and may require the instruction manual.

As a designer however I wish to minimize the risk of microbial growth and wondered if there were any more suggestions on how I might design GA or cabin, such that stale air doesn't pursue and microbial growth is stemmed or is there any way in which I can help the crew maintaining such a system.

Thank you for your comments!