Inverter question

[John Orentas]

My boat is purely a toy and used only at weekends and occasional holidays, using a gas fridge, a wood-burning stove and an alternator on my engine charging a couple of extra batteries the system works perfectly in that context.

 

Many members of the forum however have very different requirements, living on their boats twelve months of the year, many too claim to aspire to a more planet friendly lifestyle but in reality how many pay more than lip service to some form of low energy living. Never once in the years I have been a member of this forum have I ever seen a word written about how to genuinely cut back on the use of energy.

 

They live in a home which is built using 15/20 tons of steel and discuss endlessly the merits of Arga cookers and diesel generators of a kind which would easily keep an entire African village going. I don't think many of them want to do more than play at being children of the soil, I have visions of Marie Antoinette busy with her toy farm with the silver milking buckets.

[Alastair]

Oi you, go read some of my posts about living on my barge, without shorepower, generators etc. You really a cynical clod of the earth

[whammy]

Hello Theo, I am a live aboard and cc, my views are only based on my experience, when my boat was built it was fitted with a modern 240v fridge run through a 2.5kw inverter, when we showed the electric set up to a experienced boater his comment was that he really feared for us with electricity consumption due to this 240v fridge set up, we thought we would suck it and see and off we went, we soon found that he was right and found that the 240v fridge was whacking the batteries big time and found ourselves turning the fridge off overnight to save power and stop the inverter kicking in in the middle of the night (inverter was next to our bed head). I know this was maybe a false economy as when the fridge was turned back on the following morning it would take more out the batteries starting up and getting up to normal working level but it seemed the only way to do it. Anyway in the end we bit the bullet and forked out £400 on a Shoreline 12v fridge which we now keep on 24/7 and have no problems with keeping up with supply. We did think of a 3 way fridge but these are even more expensive and we had no gas connection on that side of the boat and we did not want to start messing with the boat to get a gas supply to that side of the boat and then there would have ben the problem of venting a gas fridge.

 

So in summary I think you can guess I am in favour of the 12v set up and would advise against 240v fridge -

 

Hope this helps

[ChrisPy]

we soon found that he was right and found that the 240v fridge was whacking the batteries big time ....

 

 

 

So in summary I think you can guess I am in favour of the 12v set up and would advise against 240v fridge -

any idea why a standard 240V fridge should consume so much power in these days of ultimate energy efficiency? Are they badly designed, or what?

[blackrose]

My boat is purely a toy and used only at weekends and occasional holidays, using a gas fridge, a wood-burning stove and an alternator on my engine charging a couple of extra batteries the system works perfectly in that context.

 

Many members of the forum however have very different requirements, living on their boats twelve months of the year, many too claim to aspire to a more planet friendly lifestyle but in reality how many pay more than lip service to some form of low energy living. Never once in the years I have been a member of this forum have I ever seen a word written about how to genuinely cut back on the use of energy.

 

They live in a home which is built using 15/20 tons of steel and discuss endlessly the merits of Arga cookers and diesel generators of a kind which would easily keep an entire African village going. I don't think many of them want to do more than play at being children of the soil, I have visions of Marie Antoinette busy with her toy farm with the silver milking buckets.

 

So what sort of home do you live in? Personally I have never claimed my lifestyle is any planet friendlier than anyone else's, but since you raise the topic (I'm not quite sure why?), and you love to judge everyone else, how do you justify owning that steel toy and burning all that diesel and gas just as a weekend retreat? That is a waste of resources!

[NB Alnwick]

However Graham reckons his has a thermostat on 12 volts, so he presumably would get a run time somewhere between my number and your number. If he can tell us the fridge model number, I guess it would be possible to look at the exact spec, and give a better prediction of when he might run out of battery ?

 

Sorry, I can't find the exact model spec just now - but it equates to the biggest single compartment model in the new range. As previously mentioned the installation was nicely done by a professional installer with a few helpful mods but no automatic changeover. If I were buying now, based on experience, I think I'd go for something similar because we still have a house as well and do not spend all of our time on the boat which means that it gets left for up to a couple of weeks at a time and we usually leave some food in the fridge. Having said that we spent 10 months on the boat last year!

 

My boat is purely a toy

 

Isn't everything these days?

[bottle]

Quick link to peruse models, no connection just the first one on google.

[NB Alnwick]

Quick link

 

We have a slightly earlier Electrolux version of what is now described as the RM7405L so we have 97 Litres capacity, thermostatic control on ALL energy sources but unfortunately, no AES (automatic energy selection).

 

It seems that the power/fuel consumption is:

Electric = 2.6 kWh/24 h

Gas= approx 260g/24 h

 

Complete gobbledegook to me but we get on really well with the fridge whatever language it speaks!

 

Oops! Is gobbledegook allowed under the by-laws?

Edited January 12, 2007 by NB Alnwick

[alan_fincher]

We have a slightly earlier Electrolux version of what is now described as the RM7405L so we have 97 Litres capacity, thermostatic control on ALL energy sources but unfortunately, no AES (automatic energy selection).

 

It seems that the power/fuel consumption is:

Electric = 2.6 kWh/24 h

Gas= approx 260g/24 h

 

Complete gobbledegook to me but we get on really well with the fridge whatever language it speaks!

Well those figures seem to assume 25 degC ambient temperature, so while your boat is any hotter than that, it may well use more, but if the inside of the boat is cooler, perhaps a bit less.

 

It will also depend on how often you open the door, and for how long, as well as how much food (and "beer beer beer") you cycle through it.

 

But sticking with their numbers, it seems to say a standard 13 Kg propane cylinder might last 50 days if used for this purpose alone (simple calculation here: 13000 grammes in cylinder, divided by 260 grammes per day).

 

But running on 12 volts, if they really mean that as a 24 hour consumption rate, even after allowing for the thermostat meaning it's only drawing current some of the time, then repeating my simplistic calculations of yesterday for this fridge model....

 

You are now using about 2,600 Watt hours in 24 hours, then from a 12volt supply that is 2,600 / 12, or about 216 Amp hours.

 

No doubt Chris can give a more accurate idea than I can as to how long your 360 Ah domestic bank could sustain this, but to me it certainly looks unrealistic to expect more than about a day, if you care about your batteries.

 

It seems that the 97 litre model with a thermostat is more hungry than the 40 lite one without. So the fact it holds more than twice as much seems to more than wipe out any saving from the thermostat.

 

Personally unless if you are having to ever run generators to top up Alnwick's batteries if the engine based "on the move" charging is insufficient, I'd never be running this on 12 volt, and would stick to the gas option.

 

But apologies to original poster, and to get back more ON TOPIC, I remember having seem this link before, but can't immediately find the previous thread on it....

 

Link to 240v with inverter vs dedicated 12v fridge test

 

I'm not sure if it's really current enough to truly give latest situation, but would seem to back up some of the comments made, such as those by "Whammy"

Edited January 12, 2007 by alan_fincher

[NB Alnwick]

But sticking with their numbers, it seems to say a standard 13 Kg propane cylinder might last 50 days if used for this purpose alone (simple calculation here: 13000 grammes in cylinder, divided by 260 grammes per day).

 

That seems to match with our experience and at this time of the year - it uses even less gas when the boat is unattended.

 

But apologies to original poster, and to get back more ON TOPIC, I remember having seem this link before, but can't immediately find the previous thread on it....

 

Link to 240v with inverter vs dedicated 12v fridge test

 

I'm not sure if it's really current enough to truly give latest situation, but would seem to back up some of the comments made, such as those by "Whammy"

 

That research is quite conclusive and it backs up the theory that you don't always save money by buying the cheapest equipment.

 

My initial input into this thread was to say that instead of buying a new 230/240v fridge and a more powerful inverter, it would be worth considering a 3-way (gas/12v/mains) fridge.

Edited January 12, 2007 by NB Alnwick

[Gibbo]

But apologies to original poster, and to get back more ON TOPIC, I remember having seem this link before, but can't immediately find the previous thread on it....

 

Link to 240v with inverter vs dedicated 12v fridge test

 

I'm not sure if it's really current enough to truly give latest situation, but would seem to back up some of the comments made, such as those by "Whammy"

 

Those figures are *very* close to the figures I got in the tests I did last year.

 

Gibbo

[John Orentas]

Nobody should be using these absorption type refrigerators on electrical power, they are obscenely inefficient. Fundamentally designed for operation on gas for which they are well suited, they were fitted with the electrical system for use in caravans when travelling between sites, they did and still do required so much power that they required the fitting of a relay which would ensure that they could only be used when the engine was running and charging the battery.

 

When I first looked inside one of these units many years ago I was amazed to find that that both 12 and 230 volts circuits comprised of nothing more that crude heating elements to take over the role of the gas flame. I cut out every bit of electrical wiring and other bits and have done so with subsequent units ever since.

[chris w]

So I think (depending on model) a small basic Dometic 3-way could well end up drawing 8 amps continuously, rather than 4 or 5 amps only 50% of the time.

 

I don't want to dive into "peukert equivalents", (your speciality, not mine!), but I'm suspecting if you redo your more complex maths for a basic 3-way model, that the answer might well come out very roughly around the one days use I was suggesting.

 

Alan

 

At 8 amps continuous current your battery bank would last (to 50% charge state) about 30 hours so you are absolutely correct on your one day assumption.

 

You are now using about 2,600 Watt hours in 24 hours, then from a 12volt supply that is 2,600 / 12, or about 216 Amp hours.

 

No doubt Chris can give a more accurate idea than I can as to how long your 360 Ah domestic bank could sustain this, but to me it certainly looks unrealistic to expect more than about a day, if you care about your batteries.

 

Yep, correct again. 2.4KWH per 24 hours or about 9 amps continuously would give you about 25 hours.

 

Chris

Edited January 12, 2007 by chris w

[Tommo]

I run a 240-volt fridge freezer that is rated at 90watts, when we are cruising all the 240-volt power comes from a 2.5kw Mastervolt Combi unit supplied from 660Ah of batteries. I can usually last about 3 days without starting the engine, which I’m quite happy with, bearing in mind all the other calls on electricity such as toaster, microwave, TV etc.

 

Ian

[chris w]

I run a 240-volt fridge freezer that is rated at 90watts, when we are cruising all the 240-volt power comes from a 2.5kw Mastervolt Combi unit supplied from 660Ah of batteries. I can usually last about 3 days without starting the engine, which I’m quite happy with, bearing in mind all the other calls on electricity such as toaster, microwave, TV etc.

 

Ian

Just out of interest, that works out at about 7A average continuous draw over the 3 days to get to 50% charge state of which the fridge will be drawing approx 4A average at, say, a 50% duty cycle and around 1A average for the inverter losses. The rest (2A continuous average) will be the balance of the equipment.

 

Chris

[Theo]

A subsidiary question. Can you install an inverter on its end. ie with its side up?

 

Nick

[blackrose]

A subsidiary question. Can you install an inverter on its end. ie with its side up?

 

Nick

 

Have it upside down if you want! On the other hand that might not be the most efficient cooling position...

 

My Boat came with a Sterling 1.8kw semi-sinewave installed vertically but I changed it to a horizontal position - no difference.

[DHutch]

A subsidiary question. Can you install an inverter on its end. ie with its side up?

 

Nick

Cant see why not really, although i would check the manual just incase its a consern in terms of warrentes etc.

- Inverters are all solid-state and transforms as far as im consdered, and they shouldnt even be able to tell which way is up.

- The only thing that could be an issue is the fact that heat rises, but there basicaly all fan-cooled anyway so yeah, urrm!

 

Just make sure the cupboard/space is ventilated, as normal.

 

Daniel

[ChrisPy]

the instructions on my Ki-point specified that it should be mounted vertically, see my gallery. The control panel is at the top, the wiring is at the bottom. And I have a big vent on the side of the cabinet just above and below the inverter.

[Gibbo]

A subsidiary question. Can you install an inverter on its end. ie with its side up?

 

Nick

 

Some of them are in a finned case for cooling. Fins (technically) should always be vertical for best cooling efficiency. But they're nearly all fan cooled anyway and once the fan kicks in the direction the fins point will make next to sod all difference.

 

Install it anyway you like. It won't make the blindest bit of difference (as long as it's fan cooled).

 

At the very worst it will cut out on overheat sooner than usual but it won't damage it.

 

Gibbo