Fridge using lots of amps in the hot weather

[Mark26]

The fridge can’t use any more than it’s rated consumption.

One should set-up the electrical system, i.e. battery capacity, based on the fridges rated power consumption, as the fridge is normally the biggest user, and then add on the consumption of all other equipment.

The problem occurs when users assume a 50% duty cycle for the fridges consumption when working out battery capacity. Although it may not happen very often in the UK, there will be times when your fridge is running at 100%. With sufficient battery capacity that should not be a problem.

It’s also worth noting that some fridges when working 100% may only be capable of reducing the ambient temperature by 20C, others may say they will cool to a certain temperature.

 

[GHA]

Really not that relevant but.... Fridges (mine anyway) draw a little more current at the start of an on cycle, then the current it draws tapers off just a bit as the fridge cools down. Fiddling today with an Esp32 based replacement thermostat which will record lots of lovely data

 

[PaulRainbow]

Sorry Paul I didn't realise that I had to run my suggestions past you to ensure you consider them sensible.

I didn't say you had to run anything by me, you're off on one of your childish threads again. I'm just pointing out that suggestions need to be realistic to the person asking the questions, not what you think is a great idea because you sail off South Africa in a large steel boat. Try looking at the needs of posters for a change, rather than suggesting everyone does what you did on your boat.

If we're just throwing in random garbage to answer the question "Is there anything else, other than insulation, that I should be looking at? ", how about:

1) Stop buying things that need refrigerating, get rid of the fridge.

2) Move the boat to Iceland, put the fridge in the cockpit.

 

[sailorman]

The OP owns a Westerly Centaur, 26 foot bilge keel boat. He weekend sails on the East Coast of the UK. The last few days have been abnormally hot for here, the hottest few days since the 1960s.

I'd suspect the OP wants a viable and not ruinously expensive solution to his "problem". Are solutions for live-aboard Caribbean cruising, cruising in South African waters, solutions applicable to 40--50ft yachts really the best answer here ?

I got "Paul the Fridge " to check mine after issues 3 w/e ago, fridge compressor working full chat, on batteries.
He said fridge ok, get new batteries. Those o/b (domestic bank ) are 7 yrs old, 4 new batteries arriving tomorrow

 

[PaulRainbow]

I got "Paul the Fridge " to check mine after issues 3 w/e ago, fridge compressor working full chat, on batteries.
He said fridge ok, get new batteries. Those o/b (domestic bank ) are 7 yrs old, 4 new batteries arriving tomorrow

Paul is the man for fridges around here

 

[rogerthebodger]

I didn't say you had to run anything by me, you're off on one of your childish threads again. I'm just pointing out that suggestions need to be realistic to the person asking the questions, not what you think is a great idea because you sail off South Africa in a large steel boat. Try looking at the needs of posters for a change, rather than suggesting everyone does what you did on your boat.

If we're just throwing in random garbage to answer the question "Is there anything else, other than insulation, that I should be looking at? ", how about:

1) Stop buying things that need refrigerating, get rid of the fridge.

2) Move the boat to Iceland, put the fridge in the cockpit.

Clearly what I consider as sensible and what you consider as sensible are different things so just leave it at that.

I personally think your two suggestions above are sensible but again it up to the OP to decide.

By the way I had a small boat when I lived in the UK 19ft to be propose with an inboard engine which I fitted in myself which some may not consider sensible either but it was what I wanted and was much more reliable that my old outboard.

 

[RupertW]

50 litres of air, changing ever few seconds, that might be a mol per second at 29 J/mol/K. Maybe 25k difference? That's 700W for the time the door is open, just for the air.
The condensation, let's guess it's 30degC i nthe cabin, air holds 4% water so maybe thats up to around a gram per second coming in at around 2420 J per gram latent heat. So with air flowing while the door is open, we can be looking at 3kW

It might not chage the temperature of the coke very quickly, but it takes the fridge a long time to get back to how it was after the door has been open a little while.
It will be exaggerated by the efficiency / COP of the fridge going to ratshit as the condenser temperature rises in hot weather. People may have notied that the fridge's duty cycle increases rapidly as the ambient gets above a certain point.
A boat fridge is what? 50W DC in? COP about 3 in good conditions, falling below 1 as the condenser gets too hot.

Your initial assumption is so crazy it makes the rest pointless. For the 50 litres of air to be changing every few seconds you would need to have the door permanently open and with a fan running to circulate the air. And even then as 50 litres of warm air contains such a tiny fraction of the cold maintained by the single coke can it would be many minutes before that warmed up.

Once again I would ask you to consider the weight of water in 50 litres of warm air compared to a single cold can of coke. None of the rest of what you say has any meaning unless that water vapour weight is a noticeable fraction of the 330g.

 

[JumbleDuck]

50 litres of air, changing ever few seconds, that might be a mol per second at 29 J/mol/K. Maybe 25k difference? That's 700W for the time the door is open, just for the air.
The condensation, let's guess it's 30degC i nthe cabin, air holds 4% water so maybe thats up to around a gram per second coming in at around 2420 J per gram latent heat. So with air flowing while the door is open, we can be looking at 3kW

You are making the numbers artificially and nonsensically high by looking at power rather than energy. It's the total heat transferred to the fridge which matters. Nobody would expect the refrigeration system to keep a constant temperature over timescales of a second or so.

50 litres of saturated air at 30C holds 1.5g of water vapour which at 2430 J/g = 3645 J, which in turn is only enough heat to raise the temperature of a pint of milk by 1.5C. Or, to put it another way, if it's an hour before you open the fridge again, that's just over 1J/s heat transfer required. Trivial.

 

[ashtead]

What sort of fan in the cooling tube running from the condenser locker might assist the OP ? We have a plastic tube but no fan ( tube looks just like the stuff used in bathrooms to vent shower steam So say 3in diameter) so might this be a cheap solution . I’m guessing the fridge sits where the old cold box did in front of forward bulkhead on port side ?

 

[vyv_cox]

No reason why it cannot be converted, technically.

Other than, you'd have to dissect the the fridge, re-locate the condenser (or whatever you were replacing it with) pay to have it all silver soldered or brazed together, pay to have it re-gassed etc etc. You also need to find space to fit it, not the easiest task on a 26 foot bilge keel Westerly Centaur.

A little bit of overkill perhaps for an East Coast UK boat, where we get enough hot weather to cause the OPs "issue" for about a week, once every three years.

That's how mine was done, a lot of work. Fortunately in my case I had a son who was more than capable of doing it!

 

[vyv_cox]

Friends have sailed from France to the Pacific and back to France without a fridge.

I met a man in Greece who had taken the fridge out of his boat. It is possible to live without one but considerably more convenient to have one

 

[vyv_cox]

This usually requires an electric pump to circulate seawater, so additional electricity consumption.

My pump is the smallest Jabsco, a Par Max 1. It runs at 6 volts using an Isotherm voltage converter to reduce its speed. Because it is not developing pressure its consumption is quite low, 0.4 amps. The compressor draws 4.0 amps at start of cycle, 3.0 at end.

 

[TernVI]

You are making the numbers artificially and nonsensically high by looking at power rather than energy. It's the total heat transferred to the fridge which matters. Nobody would expect the refrigeration system to keep a constant temperature over timescales of a second or so.

50 litres of saturated air at 30C holds 1.5g of water vapour which at 2430 J/g = 3645 J, which in turn is only enough heat to raise the temperature of a pint of milk by 1.5C. Or, to put it another way, if it's an hour before you open the fridge again, that's just over 1J/s heat transfer required. Trivial.

If you want a side opening fridge, feel free.
The reality is that people find they tend to use more electricity.
Many people have observed this.

 

[LittleSister]

I detect a certain froideur in parts of this thread!

 

[pvb]

My pump is the smallest Jabsco, a Par Max 1. It runs at 6 volts using an Isotherm voltage converter to reduce its speed. Because it is not developing pressure its consumption is quite low, 0.4 amps. The compressor draws 4.0 amps at start of cycle, 3.0 at end.

But it's still an extra half an amp.

 

[vyv_cox]

But it's still an extra half an amp.

Yes it is but it's the difference between running 30% of the time and more than 50%.

 

[pvb]

Yes it is but it's the difference between running 30% of the time and more than 50%.

I wonder why the published specs for air-cooled and water-cooled compressors don't reflect this?

 

[Daverw]

Keel cooled ok unless your on a drying out berth and want to use the fridge then

 

[JumbleDuck]

If you want a side opening fridge, feel free.
The reality is that people find they tend to use more electricity.
Many people have observed this.

It's entire possible, but probably because the best place to put the worst heat leak - the seal round the opening - is at the warmest part of the inside. At the top.

 

[peter gibbs]

I have a Dometic/Waeco CRX 50, up until the weekend I thought it was fairly frugal with amps. But the weekend was hotter than usual, and the fridge compressor seemed to be on most of the time, even when turned down to the minimum setting.

View attachment 96923

Would adding insulation to the sides, back and top help?

Is there anything else, other than insulation, that I should be looking at?

Would a top loader with plenty of insulation perform better?

TIA

Yup, a few degs and their limitations become glaring. Top loader is better I find but you can lay in extra foam insulation with yours and save the not inconsiderable cost of replacement. Also the usual - a bag of ice will help things in hot weather as well as stocking the frg with as much as possible

Cheers PWG