Should you turn your fridge off at night?

[pearley]

Modern fridges seem to use about 30AH per day. Taking overnight to be an 8 hour period (1/3 day) that is about 10AH. But probably less than that due to being cooler than average in the galley and not opening the door, so lets say 8 AH overnight. That would be 3% of capacity even if you only had 2 x 110AH. If your electrical system can't stand 8AH over night there is something horribly wrong with the batteries and/or setup. In our setup (4 x 100AH) I don't notice a difference between the SoC on going to bed, vs on waking up. Once we hit the bats with the electric kettle and toaster, that is a different matter!

Interesting figures.

 

Our Shoreline Fridge/freezer seemed to have problems lately, everytime I woke in the night it seemed to be running and it ran the 5 x 135AHr batteries from 100% to 87%. We found it was pushed back too far, probably because everytime you shut the door it seemed to move back a little. When I get off this flooding river I'm going to fit a batten across the rear of the enclosure to stop it happening again and mount a couple of small fans to drag more air from the bilges to cool the condenser. It will be interesting to see what difference this makes. What is noticeable is how long it seems to take to get back down to temperature after the door has been opened for any length of time although this doesn't have any effect on the batteries.

 

Now it has a decent air gap behind it the temperature runs between 6 and 3 overnight and it takes about 7% of battery capacity, or rather SOC reduces by 7%.

 

Being gas free with a generator that's not a problem as the batteries soon charge back to 100%

 

To answer the original OP, there is no way my wife would allow me to switch it off. She would tell me to sort the batteries.

 

Regards

Pete

[by'eck]

When this topic came up before someone suggested turning fridge up to maximum (coldest setting) when engine running and batteries charging or fully charged and turn to a lower setting for when engine stopped. Didn't work for me on account of bad memory. Fridge left on high overnight from 4pm until 10:30am had extremely detrimental effect on batteries over only a couple of days. But, if you get into a routine it could work.

 

That's the principle the Isotherm ASU models use in conjunction with a cold (storage) plate. When the supply voltage exceeds 13 volts the compressor runs on steroids taking the plate down to and maintaining -10°C. When supply drops below 13 volts, compressor remains off until the plate rises to -2°C when it maintains this higher temp with compressor on tickover.

 

FWIW my Shoreline has a fair sized freezer compartment usually kept full so it never gets turned off.

[mrsmelly]

We have a 12v Shoreline fridge. My chap insists on turning it off every night saying it will flatten the batteries.

 

Is that what you're meant to do, and will it indeed flatten the batteries?

 

Apologies if I'm being a simpleton.

Never turn it off never have. The reason is quite simple in that during the night the door is never opened so once down to temperature the fridge consumes little power anyway so leave it on. Never flattened the batteries in my 2o odd liveaboard years mostly off grid.

 

Tim

 

Three words...

Gas, fridge, simples

That is all!

Completely agree. they are way better than leccy ones.

 

Tim

[nicknorman]

I don't get the point about water vapour given any kettle will do this anyway, not sure at all how much will be produced by the hob.

Of course a hot kettle full of water will result in some water evaporating off. But burning gas produces lots more of the stuff, from the moment its lit and not just towards the end when the water is getting hot. Anyway, the one thing you will never find on our boat is teabags, we always make a full pot with loose leaf tea (50% Assam, 50% Earl Grey, yummee) so with pot-warming as well, we need to start with a full kettle.

[gazza]

Throw the tea out and get some decent coffee on board, you will have the added bonus of the water vapour wafting about smelling wonderful. Much better than that wishy washy tea waste of a boiled kettle...

Edited May 29, 2013 by gazza

[nicknorman]

Throw the tea out and get some decent coffee on board, you will have the added bonus of the water vapour wafting about smelling wonderful. Much better than that wishy washy tea waste of a boiled kettle...

Unfortunately coffee and my stomach don't agree after more than 1 cup per day.

[Biggles]

We have a 240v fridge freezer. I did a test one night. The freezer went from - 18 to - 8. I concluded it's best left on. Not sure a fridge would be less lossy. Obviously don't want frozen food changing like that. Its an A+ rated ff and took ages to get back down although it was then daylight and the solar system took over.

[Guest]

Of course a hot kettle full of water will result in some water evaporating off. But burning gas produces lots more of the stuff, from the moment its lit and not just towards the end when the water is getting hot. Anyway, the one thing you will never find on our boat is teabags, we always make a full pot with loose leaf tea (50% Assam, 50% Earl Grey, yummee) so with pot-warming as well, we need to start with a full kettle.

So over the whole process of boiling a gas kettle you are saying more water vapour would be put into the air by the combustion process than that produced by the water coming to temp and then boiling, sounds dodgy to me, but could be convinced if there was some evidence.

[alan_fincher]

Never flattened the batteries in my 2o odd liveaboard years mostly off grid.

I bet you used to say "Never run out of diesel in all my 20 odd live-aboard years!".........................

[nicknorman]

So over the whole process of boiling a gas kettle you are saying more water vapour would be put into the air by the combustion process than that produced by the water coming to temp and then boiling, sounds dodgy to me, but could be convinced if there was some evidence.

It is of course quite possile to boil water without releasing any of its volume into the air as vapour, eg by using a pressure cooker. In reality it will of course depend on many factors such as the time taken to boil the water, the exposed surface area of the water, the degree to which the kettle restricts loss of water vapour from it etc. Meanwhile there is of course a fixed amount of water vapour produced by burning propane into carbon dioxide and water, for a given amount of released heat. If I was clever I could work it out!

[Guest]

Who the heck boils water in a pressure cooker to make tea?

 

We were talking tea making and gas kettles none of which are sealed to prevent vapour escaping.

 

(And so are none of the pressure cookers we have ever had BTW.)

[nicknorman]

Who the heck boils water in a pressure cooker to make tea?

We were talking tea making and gas kettles none of which are sealed to prevent vapour escaping.

(And so are none of the pressure cookers we have ever had BTW.)

I am just pointing out that the amount of water lost to vapour when heating to boil is very variable - potentially zero though as you say, that would not be normal. But in your average kettle with a lid and small spout, not much vapour comes out until the water is boiling, whereas the hob is chucking it out all the time. Edited May 29, 2013 by nicknorman

[gazza]

Unfortunately coffee and my stomach don't agree after more than 1 cup per day.

Bummer.

That would wreck my day, I run on coffee and bacon butties at work, the norm is a minimum of a mug an hour. Caffeine was invented to keep us hard pressed engineers going.

[BudgetBus]

What about a one cup kettle...those instant ones.

[nicknorman]

Bummer.

That would wreck my day, I run on coffee and bacon butties at work, the norm is a minimum of a mug an hour. Caffeine was invented to keep us hard pressed engineers going.

 

...whereas us pilots just have a little snooze if we get tired at work.

 

What about a one cup kettle...those instant ones.

 

That would require the use of that invention of the devil, tea dust wrapped in a paper bag resembling disposable underpant material (aka tea bag). Someone has to maintain standards!

Edited May 29, 2013 by nicknorman

[BudgetBus]

...whereas us pilots just have a little snooze if we get tired at work.

 

 

That would require the use of that invention of the devil, tea dust wrapped in a paper bag resembling disposable underpant material (aka tea bag). Someone has to maintain standards!

Small tea pot or dispense more than one cups worth?

[Grace and Favour]

Small tea pot or dispense more than one cups worth?

Proper tea leaves in a small Bodum type cafetiere

[BudgetBus]

I dont like tea so its lost on me.