[PUP] Refrigeration revisited (PPM)

[hannu venermo]

This is also applicable to the PPM thead

Trawlerguy ...
You may wish to do some research re: sub-zero.
Sub-zero has proven to be less than optimal (maybe the worst) 
refrigerator you can own on a boat.
Its hugely inefficient, and many in the Nordhavn crowd are throwing 
theirs out ... and de-activating the de-icing circuit has often been 
talked and asked about and desirable.
Their reliability has been fair to poor.

In general- any de-icing model is a Very Bad Idea.
Your total consumption is often 4-8 times higher for a model that does 
this, than a std refrigerator model !

De-icing actually heats the inside of the refrigerator with a fairly 
high current. Inefficient.
You then need to re-cool the surface and contents. Very inefficient.

In my opinion, the best option is the most energy-efficient consumer 
model you can find.
Bog std, big box store stuff. Look at consumer reviews, and measure 
actual used current if you can locate someone with the same model. Power 
companys often give or rent metres to measure used power in an 
appliance, maybe a 1$/day or free...
Due to economies of scale, you will probably get a cheaper,more 
reliable, more efficient system than any custom solution at 20x the cost.

A compressor in a refrigerator is the cheapest, best way to make that 
piece of equipment known to man, due to the nr of millions that are 
produced, and the fact that manufacturers are required to give a 2 year 
guarantee for and in consumer use. Over 40 years of commercial 
competition, manufacturers know how to build them efficiently, and 
tooling costs are by now under 1$/unit.
If you want a better way, you need instrument- grade stuff, that is 
available from some industrial suppliers, and is very, very expensive.

So-called marine stuff in DC is usually extremely inefficient 
(electrically) and unreliable (mechanically), although pretty to look 
at, imo.

Inverters are about 90% efficient - your cabling losses in DC systems 
are similar !

If you want to make it look nice, a custom cabinetry/stainless 
chassis/shelf/cupboard with removable (hinge) pins is the way to go, 
imho. It will allow you to change/dismantle/replace it whenever, 
wherever, with 5 minutes work.

One very important note;
The hot-air outlets on refrigerators, be they cold/plate or whatever, 
are often to almost always not vented or have constricted airflow. The 
energy consumption of the system is 3-4 times ! higher on such systems. 
Do not think that You are heating the inside (often desirable) - you are 
mostly heating the sea  through your hull, and you are unlikely going to 
enjoy the results !

Some have put a small 2W (computer fan) 12 V fan on the hot air outlet 
and or removed grilles and report 1/3 of the previous power draw due to 
not having restricted airflow.
This is, in my experience, a typical design failure very common to all 
manufacturers.
Its also, in my somewhat cynical option, due to us, the consumers, 
normally not knowing or caring about such issues, nor demanding that 
they be properly built in the first place.
When buyers want to know -
Whats the energy use of the top 5 appliances ?
Whats the MTBF of same and cost (in $ and hours) to replace same ?
Manufacturers will happily give us good reliable solutions at a fair 
price related to their capacities and manufacturing costs.