MICRO-AIR Artic Air 24 Guía de instalación descargar pdf (Pagina 62)

Box Design Features

One of the most common features to be found in boat cold box design is the box drain.

Drains are usually supplied whether the box was originally equipped with mechanical

refrigeration or whether it was designed as an ice box. They are also one of the more

troublesome features. Often iceboxes are configured so that the drain drains into the bilge. A

stinky bilge is the usual unfortunate result. The drain pipe can also conduct as much as 50

percent of the total daily heat load on the box.

An open drain coupled with leaky hatch seals will cause a continuous air exchange as cold air

sinks through the drain and is replaced by warm outside air. Over time this can introduce a great

deal of additional heat. The drain pipe can be fitted with a stopper or a shut-off valve, which

stops the air loss, but does not fully stop the heat loss by conduction. It can also be a source of

odors inside the box by trapping organic material.

An alternative way to empty the box of water is to bring a plastic tube in from the top of the

box. The tube can be attached to a small electric or manual pump, such as a foot pump, and the

water dumped through the sink through hull.

Hatches

If you are redoing your boxes, you can take a fresh look at hatch locations. For safety

reasons, cold box hatches should have some way of latching, even if they are top opening. This

may be a rules requirement for racers. Side opening hatches may be unusable if, when on the

unfavorable tack, the box contents ends up resting up against the side of the door, ready to fall

out as soon as the door is opened.

It is common advice to avoid side doors and only use top loading hatches. The best approach

is probably to use the type of opening that will provide the most convenient access.

A cubic foot of air at 100ºF contains only about 18 BTUs of heat. Even if all of the cold air in

your box were to spill out when you open a door, it would only take a few seconds of compressor

run time to remove the heat that entered. If you have to remove food and set it on the counter

while you access something at the bottom of a box, it will probably add more heat to the box

when you put it back in than would have been contained in the hot air that could enter through a

side opening door.

It is very important that your hatch gaskets do not leak air, especially with side opening

hatches. Many top hatches are designed with a center hinge in the hatch lid, so that only one

side needs to be opened. These often suffer from a constant leak of air and heat conducted by

the metal hinge. The best thermal solution is to replace this with a one piece design. The next

best thing would be to block the air flow with insulating tape placed between the two sections

under the hinge. You can find more detailed information about Glacier Bay ready made hatch

kits on our web site at www.glacierbay.com.

Condensation issues can arise even with the best materials and construction techniques.

One common complaint is condensation behind a settee cushion adjacent to a cold box. This

happens independently of the quality of the box insulation. The extra insulation provided by the

cushion makes the back side of the cushion colder than the ambient air. If the air temperature

reaches the dew point, condensation will occur. The air cools more with the condensation

process, causing a low pressure area which pulls in more moist air. Remarkable quantities of

water can be generated this way. The solution is to provide ventilation between the cushion and

the cold box wall.

Another condensation trouble spot can be the hatch frames, especially with a side opening

freezer. Two ways to minimize the amount of heat conducted, and thus the chances for

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