Fridge and sailboat:poor bedfellows.

[geem]

Refrigeration efficiency improves if you can reduce the condensing temperature whether you use water cooled or air cooled. In the UK we often have colder sea water temperatures than air temperature. In this location water cooled is the way to go. In the Caribbean where sea temperatures can be around 30degC and air temperature a little more the efficiency of water cooled is less significant. However, in those temperatures where air cooled refrigeration heat rejection is discharged in to the cabin, the rise in cabin temperature can be significant. Water cooled is still the way to go for this reason unless you have an efficient way or extracting the waste heat. The other factor is the water cooled system is quieter since it has no fan noise. You also dont have the energy consumption of a cooling fan. Lots of reasons to go water cooled. The only negative is additional cost of purchase and an extra hole in the boat.

 

[TonyMS]

We have 35l portable lorry fridge that lives in the cockpit. It is powered off the solar panels via an MPPT controller only when the voltage exceeds 3.2. In Greece, this is typically from 10:00 to 18:30. So, we have cold beers, wine and G&T until late evening. In the morning, butter and other stuff that needs to be kept cool is fine. On occasional bad weather days, the fridge still works for a couple of hours.

 

[srm]

Most of the problems probably lie with using air cooled fridges, frequently without sufficient ventilation so heat builds up around the cooling coils.
My answer involved a few days DIY and new kit. A small fridge unit with separate compressor and hull mounted (keel) cooling plate. Fitted the fridge with as much foam board insulation as possible filling all voids around it. Compressor was in a ventilated space, and coolant pipes run through to the cooling plate on the outside of the hull. Hole drilled and cooling plate fitted easily between tides. During the initial test battery monitor showed it used 18 amps in 24 hours, admittedly in Orkney with low sea temperatures. However, even here with warm sea in summer fridge still works without significant power usage. We run the fridge 24/7 when cruising and have 3 x 50 watt solar panels with MPPT regulator plus wind turbine for generating.

 

[temptress]

So IMO it depends. I have cruised and lived aboard a number of boats over the years. What type of cruising are you talking about and where?

Can you live without a fridge. Yes of course you can. I have spent many years living onboard without a fridge but its a great thing to have. A freezer - we have a small one now although we often don't use it.

A modern 12v fridge with the correct insulation should not use more than 3 or 4 amps per hour in the tropics and much less in temperate climates.

Where are you proposing to cruise?
How long do you intend to be onboard in a single spell?

Those are the deciders. Living onboard is different to say a few weeks or a month or two onboard. The former is a lifestyle choice while the latter is camping in style.

 

[RupertW]

So IMO it depends. I have cruised and lived aboard a number of boats over the years. What type of cruising are you talking about and where?

Can you live without a fridge. Yes of course you can. I have spent many years living onboard without a fridge but its a great thing to have. A freezer - we have a small one now although we often don't use it.

A modern 12v fridge with the correct insulation should not use more than 3 or 4 amps per hour in the tropics and much less in temperate climates.

Where are you proposing to cruise?
How long do you intend to be onboard in a single spell?

Those are the deciders. Living onboard is different to say a few weeks or a month or two onboard. The former is a lifestyle choice while the latter is camping in style.

Excellent post but a pedantic plea to keep things unambiguous by using the correct units.

I think you meant either “an average of 3-4 amps” or “3-4 amp hours each hour”.

(and for those who think amp hours per hour means amps, then an an amp hour is 3600 coulombs which is an amount of charge passed, whereas amps can only be an instantaneous measurement of the rate of charge passing so average amps over a time period is the same as amp hours but not amps alone).

 

[nortada]

Excellent post but a pedantic plea to keep things unambiguous by using the correct units.

I think you meant either “an average of 3-4 amps” or “3-4 amp hours each hour”.

(and for those who think amp hours per hour means amps, then an an amp hour is 3600 coulombs which is an amount of charge passed, whereas amps can only be an instantaneous measurement of the rate of charge passing so average amps over a time period is the same as amp hours but not amps alone).

Why not bring in watts, joules and ergs to make it really interesting?

 

[ryanroberts]

Why not bring in watts, joules and ergs to make it really interesting?

One upsmanship on this forum?

 

[nortada]

One upsmanship on this forum?

What else ?

 

[roaringgirl]

The raw water cooled fridge worked fine, but the water pump was incredibly noisy and power-hungry and the intake occasionally got clogged with things.

I swapped the raw water pump for a low power quiet centrifugal one, and plumbed it to draw and return water from the fresh water tank instead. This has halved the power consumption and the pump no longer wakes me up every 15 minutes. We run everything off 350W of PV and have (so far) never run the engine to charge the batteries. I say 'so far' as we've been living aboard for 2 months in Spain and Portugal, but we're heading south so PV should get better, not worse!

 

[RupertW]

The raw water cooled fridge worked fine, but the water pump was incredibly noisy and power-hungry and the intake occasionally got clogged with things.

I swapped the raw water pump for a low power quiet centrifugal one, and plumbed it to draw and return water from the fresh water tank instead. This has halved the power consumption and the pump no longer wakes me up every 15 minutes. We run everything off 350W of PV and have (so far) never run the engine to charge the batteries. I say 'so far' as we've been living aboard for 2 months in Spain and Portugal, but we're heading south so PV should get better, not worse!

As long as you are not heading to the Canaries

 

[Yngmar]

I swapped the raw water pump for a low power quiet centrifugal one, and plumbed it to draw and return water from the fresh water tank instead.

Interesting solution. How many degree above ambient temperature does the water in the tank get from this?

 

[roaringgirl]

I have

Interesting solution. How many degree above ambient temperature does the water in the tank get from this?

I have not noticed any increase in ambient temp of water. We keep a couple of bottles in the fridge for drinking anyway!

 

[dulls]

There have been many threads on fridge/freezer power management. Finding the resources to power a fridge, let alone a freezer is difficult without resorting to running engine or a generator periodically. Does anyone cruise without a fridge? If so, how do they manage? What is their diet and how do they store foodstuffs?
Mike.

Our first boat and this is in Australia with the heat had a very well insulated ice box. Top loader by the way. We froze food for the week at home and bought ice. We could no longer get dry ice and that was early in the naughties. You have to buy ice about every 3 days. No getting round it. Also stack in order of use with boards in between but even that is over the top. Just buy ice and fresh veggies etc. In a yacht we never considered running a freezer. Good fridge yes but running the engine needlessly was just over the top. Freezers are for motorboats. Good tinned food around as well.

 

[roaringgirl]

As long as you are not heading to the Canaries

What makes you say that? Not enough sun? This setup was also fine in Scotland!

 

[geem]

Our first boat and this is in Australia with the heat had a very well insulated ice box. Top loader by the way. We froze food for the week at home and bought ice. We could no longer get dry ice and that was early in the naughties. You have to buy ice about every 3 days. No getting round it. Also stack in order of use with boards in between but even that is over the top. Just buy ice and fresh veggies etc. In a yacht we never considered running a freezer. Good fridge yes but running the engine needlessly was just over the top. Freezers are for motorboats. Good tinned food around as well.

We have a sailing boat with a fridge freezer and a fridge. We never run the engine to charge batteries. We rarely go in to marinas and even if we do we rarely hook up to shore power. These days it can all be done with solar panels cheaply and easily regardless of whether you run air cooled or water cooled refrigeration

 

[RupertW]

What makes you say that? Not enough sun? This setup was also fine in Scotland!

Not as many hours of Sun as the Med and much hazier, but the the real issue is fine sand covering the panels so needs frequent washing in fresh water. But if it worked in Scotland you will have no trouble at all.

 

[Paulg25]

Hydro Generator?

 

[STILL AFLOAT]

I had a strange webasto thing, Travelbox ? It worked off all 3 systems .
Gas, 12 v & 220 v. It was mainly good, but in the summer, in the Canaries, it had to be turned up full, on 220 v , to just cool stuff, since its insulation, was based on degrees, below ambient temp. Ok, on gas or 12v it slowly lost cooling, whereas 220 v did a good job of cooling the box down, until July August, where even the 220 v struggled to keep stuff cool.
Then as we approached autumn, and forgot to dial down the cooling, we suddenly had ice in the milk and partially frozen eggs , which look funny, once cracked into the frying pan.