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We welcome the chance to tell you more about our Micro HPStm
technology and how to use it to meet your cooling needs.
If the answers below do not address all of your questions please don't
hesitate to call us.
System Operation & Performance Questions -
Q - How does the Micro HPS compare to the
Glacier Bay's older systems in terms of energy efficiency?
A - The systems are very comparable. Independent tests conducted on
our older systems found them to be the most
energy efficient refrigeration available at their time. This was
several years ago and no independent organization has recently conducted a
comprehensive test of either the Micro HPS or the new product
introductions of our competitors. However, based on our own tests
(conducted to established industry guidelines) we are confident that the
Micro HPS will maintain our reputation for superior performance.
Q - I saw an ad in a magazine from one
company claiming their refrigeration system uses less energy than a light
bulb. How much does the Micro HPS use?
A - When you think about it you realize that this claim is saying
nothing at all. To make such a statement requires so many
assumptions about your refrigeration requirements (not to mention the size
of the light bulb and how long it is left on) as to be meaningless.
The fact is that estimates of power consumption must be made on a
individual basis. How big are your boxes and what is the quality of
the insulation? How many people will be on board and where will you
be cruising? Do you have refrigerators and freezers or just
refrigerators? It is only with this information that any reasonably
intelligent power consumption estimate can be made. What we can tell
you is that, whatever your refrigerating needs, the Micro HPS is likely to
consume only about 50% - 70% of the power of lower cost systems based on
the Danfoss compressors.
Q - The small Danfoss based systems you are
referring to only draws about 5 amps. Are you saying that the Micro
HPS only draws 2.5 amps?
A - No. The amount of power a system draws while it running is not a
good indication of how energy efficient it is. Indeed, the least
energy efficient systems on the market are generally those that have the
lowest running current. The most energy efficient system is the one
that requires the least amount of total watt-hours of power per day to cool
your box(es) to their required temperature. The Micro HPS will draw
35 amps (including pump) while it is cooling down a refrigerator or
freezer box. This sounds like a lot because it is 6x the power
consumed by the Danfoss system while it is running. However, if the
Micro HPS is effectively removing 12x as much heat when it runs then, at
the end of the day, it will have required only 1/2 as much power.
Q - The idea of running an air conditioning
blower off of the refrigeration compressor is very appealing but how
realistic is this?
A - Very realistic but you have to understand the power requirement.
When the Micro HPS is operating the Arctic Airtm
blower it will provide 6,000 BTU/Hr. of air conditioning. While it
is doing so it will consume approximately 45 amps of power at 12vdc.
If you are at shore power AND you have a battery charger that will provide
45 amps or more of continuous charging current without overheating (check
with the manufacturer) you will be able to run the air conditioner 24
hours per day without effecting your battery in any way. However,
one of the biggest advantages of the Arctic Air option is that it also
permits you to cool the cabin when you are offshore without running an
engine or generator. Obviously, the length of time the system can be
run depends on the size of your battery bank and the state of charge in
those batteries. For example, a cruising couple has a 43 foot boat
with a fully charged, 800 amp/hr battery bank. They would like
to run the system to cool off and de-humidify their sleeping cabin.
In this case they could run the air conditioning system for nearly nine
hours without taking their batteries below 50% discharge. In the
morning they start the generator to replace the power they used overnight.
Q - Is there a limit to the size of the box I
can cool?
A - The Micro HPS is limited to a maximum of two Trimlinetm evaporators in
any one "zone". The number of evaporators required in a particular box depends on the size, temperature (i.e. refrigerator or freezer)
and insulation. In the event that a single box requires more that
two evaporators, the box is simply treated as two "zones" thereby allowing
more evaporators to be used.
Q - Is there a limit to how many separate
zones I can cool?
A - The theoretical limit would be reached only if the system needed to run more that
24 hours per day to remove the heat in all those boxes. In practice,
we find that a maximum of four zones is easily manageable.
Therefore, the Micro HPS is set up to accommodate up to four zones.
Q - Can individual zones be turned off and
on without effecting the operation of the others?
A - Yes. This can be a very powerful tool to manage your energy use
on-board. For example, some blue water vessels use two freezer zones
and one refrigerator. When they are in a good port they stock up on
food,
filling all the boxes. As the food is consumed they shut down the
boxes one at a time and save the energy that it takes to cool them.
Q - What is the ECM option?
A - The ECM (Eutectic Control Module) option replaces the standard digital
thermostat. The difference between the standard thermostat and the
ECM is that the ECM has the ability to sense the activation of additional
power sources such as a generator or engine. It then uses the extra
power available to "top off" the refrigeration system by making sure the
eutectic solution in all the evaporator plate is fully frozen. The
effect is to maximize the charging capability of the engine/generator and
reduce the amount of energy pulled from the battery bank.
System Layout Questions -
Q - How far can the condensing unit be from
my boxes?
A - From the standpoint of efficiency, operation and performance it can be
any distance. You do need to consider the complexity of the tubing
runs and make sure that these can be routed properly without creating oil
traps (refer to the Installation Manual).
Q - What is a "zone" and how is
it different from just adding another plate?
A - A zone is any evaporator (either plate or A/C blower) whose operation
is controller by a single thermostat. In practice, a refrigerator
box would be one zone, a freezer box another and an Arctic Air blower a
third. Some boats only require one zone (a refrigerator-only
installation for example) but most have two, three or even more. The new zone requires a separate solenoid valve (Control T assembly)
and a separate thermostat. A boat requiring both a refrigerator and
a freezer zone would have (a) the required number of evaporators plates
for each box, (b) a Control T assembly having two solenoid valves, and (c)
two thermostats. In operation, the system would first cool only the
freezer "zone" then automatically switch over an cool the refrigerator
"zone". Only one zone is cooled at a time.
Q - Why can't I just use a "spillover"
arrangement and cool my refrigerator and freezer with one plate?
A - You could, it's just that we do not recommend it. In the first
place it is a fallacy that a spillover system permits you to do more
cooling with fewer evaporator plates. X amount of heat will require
Y amount of surface area on the evaporator - that doesn't change.
Secondly, experience has shown that spillover configurations, no matter
how well laid out, do a poor job of maintaining stable box temperatures.
When the boxes are full the temperature rises too high do to poor air
circulation around the evaporator. If you correct this problem the
boxes get too cold when they are only partially full. Lastly, it is
a fact that a spillover configuration will inevitably be less energy
efficient than separately controlled refrigerator and freezer boxes.
This is because all refrigeration systems are less efficient when cooling
a freezer plate than when cooling a refrigeration plate. In a
spillover configuration, all heat from both the refrigerator and freezer
boxes are remover via the freezer plate at the lower efficiency.
Component Questions -
Q - Is it true that Glacier Bay developed
the Masterflux® compressor?
A - Yes. If you look through our History page you will see that we
have developed a number of highly specialized variable-speed brushless dc
(BLDC) hermetic compressors for military and scientific applications.
Through this work we garnered considerable expertise in brushless DC
motors and drive systems as well as various compressor technologies.
With a growing number of requests from many different fields, we decided
to develop a standard BLDC motor, drive and compressor technology which
could be adapted to a wide range of applications.
Q - Why aren't you making the compressors -
what is Tecumseh's role?
A - Producing high-precision compressors in a reliable and cost-effective
manner requires a huge capital investment and extremely specialized
knowledge possessed by only a handful of companies in the world. Had
Glacier Bay chosen to produce the compressors ourselves, the unit cost
would have been 10x to 20x what it is now. Tecumseh's expertise
makes it possible to supply the world market with a premium quality
product at a very affordable price.
Q - What percentage of the components used
on the Micro HPS are manufactured in-house by Glacier Bay?
A - In terms of the total parts count - about 70%. The compressor, valves, filter-dryer, water pump and sight-glass are made
by outside companies.
Q - Why not use more off-the-shelf parts?
A - Off-the-shelf refrigeration components can be divided into that which
is suitable for either high-end or low-end system construction. At
the high-end are very large commercial systems that consume a huge amount
of power and therefore justify the development and application of very
innovative, sophisticated and expensive components and technologies.
At the low-end are residential and small commercial system where the
initial purchase price needs to be kept as low as possible. Serious
off-shore cruisers actually need something which falls between these to
categories. For cruisers, power is exceptionally expensive and hard
to come by. What is needed is extremely small equipment which is
designed around the principles and technologies normally applied to only
the largest and most expensive commercial systems.
Q - With all these unique parts how do I
get spares when I'm cruising?
A - The Micro HPS is
designed to be every bit as reliable in your boat as your refrigerator is
in your kitchen at home. Therefore, we would not expect there to be
a great need for replacement parts. Nevertheless, the question is
relevant. In over 13 years of selling marine refrigeration systems
all over the world, we have found very few marine refrigeration repairmen
stock even common off-the-shelf components. In the event of a
problem you will most likely be stuck having to ship in parts no matter
what system you have. Having said all this, it is worth noting that
the few "active" components in the Micro HPS (i.e. the valves,
filter/dryer, water pump, etc) are the standard components which are
widely distributed.
Q - Why don't you use a "keel-cooler?
A - Keel-coolers do not permit the same degree of control over the
compressor high-side pressure as does a mechanically pumped
coolant/condenser. For boats voyaging into many different water
temperatures and operating boxes with wide ranging heat loads, the use of
a keel cooler would actually increase average energy consumption and
reduce the overall stability of the system. To understand why this
occurs you need to delve rather deeply into the thermodynamics of
refrigeration. For those interested in learning more about the topic
we will be posting a detailed explanation in our Technical Library.
Q - Does the Micro HPS have a
variable-speed control?
A - No. In the Micro HPS such a control would provide no benefit.
The Masterflux compressor is a variable-speed compressor and we do
manufacture variable-speed controls for use in many other systems that we
build. However, but we do not use them on the Micro HPS. To build the most
energy efficient system possible, you would perfectly match the capacity
of the compressor to the heat load. The function of a variable-speed
compressor control is to change the speed of the compressor to try to
accomplish this "on-the-fly". In other words, if you put a bunch of
warm food into your refrigerator, you significantly (but temporarily)
increase the heat load on the compressor. If the system has a
traditional evaporator and a properly designed variable-speed control it
would respond by temporarily speeding up the compressor to compensate.
Once the food had cooled, the compressor would slow back down again to try
to match the lower heat load.
This approach is better than simply ignoring
the change in load but it is still not optimum. All motors
(including those in refrigeration compressors) have a load and speed
"sweet spot" where they are running at their maximum efficiency. In
an ideal system, the load on the compressor is controlled by other methods
to ensure that the compressor is always operating under these conditions
and at maximum efficiency. This is why Micro HPS does not use a
variable-speed control. In the Micro HPS, the Trimline Hybrid
Plate(s) ensure that the load on the compressor remains very constant
under all normal operating conditions by maintaining a reserve of heat
absorbing capacity in the eutectic solution. Bursts of heat coming
into the box are quickly absorbed by the plates without effecting the load
on the compressor.
Micro HPS, Trimline,
Spider-Coil, and Arctic Air are trademarks of Glacier Bay, Inc
OSSA Powerlite is a registered trademark of Glacier Bay, Inc.
Masterflux is a registered trademark of Tecumseh Products Company
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