120vac Refrigeration Questions

[btrayfors]

Exactly right, Rick. And, to add to your add, the "hard start" can be much harder than normal even with start and run capacitors in place whenever:
(1) the capacitor(s) go bad; and/or (2) the compressor motor goes bad. Then, it's Nellie-Bar-the-Door in terms of amp draw :-)

But, what most of this discussion has failed to address is the REAL costs of AC refrigeration, not just the lower acquisition costs.

Nigel Calder has an excellent article in the Aug/Sep issue of Professional Boat Builder, in which he takes a crack at estimating the real costs of generating electricity aboard -- from alternators, generators, solar panels, wind generators, water generators, etc.

Bottom line is that it costs a lot. Much, much more than shore-based power. Shore-based power (at dockside) might cost, e.g., $0.15 per kilowatt hour, while generator or motor/alternator-based power while you're cruising or on the hook might cost, e.g., between $2.75 and $4.42 per kilowatt hour. That's somewhere between 18 and 28 times as much!!

This includes the real costs of amortization of equipment, inefficiencies in battery storage, charging, heat loss, cost of POL and maintenance on engines, etc., etc.

No matter how you cut it, unless you live aboard in a marina plugged into shorepower most of the time, 120V refrigeration is going to cost much more on a smallish cruising boat than would the much more efficient 12V refrigeration and -- like it or not -- you're going to pay those extra costs along the way.

Don't be lulled into believing that because you paid $150 for a 120-volt refrigeration system you're better off than paying $1,150 for a 12-volt system.

BTW, Nigel didn't try to attribute costs to your mental health, layover time in port awaiting parts, etc., etc.

Bill

[cantxsailor]

Yes the Engel requires some space, but then they all need some air flow. Where mine is mounted I have about 8" all around 3 sides and have never had warm beer even when the cabin temp was in the 90s. I don't have 110v unless I'm at the dock so I am happy to be able to have cold beer powered by my solar and wind setup. Unless you stay at the dock a small boat(we are talking 27/30ft) probably won't have the space required for all the batteries required to run a 110v from an inverter. You will have to run a generator of some sort to keep it in power.

They(Engel) are expensive(mine was with some extras about $900) to buy but in my case the function and the usability of the Engel trumped anything else I could find and as I mentioned the machine is very tough.

Most(not all) of the specialized marine fridge/freezers that will fit in a boat of the size "nine" is talking about are mostly about the same size as the Engel I have. They are no where near as efficient(12v/amp wise) as the Engel and require a lot of extra space and/or know how to keep them functioning. This may be just my personal experience with them though. I can if I want to use mine as a freezer but mostly its just my fridge.

The small 110v fridges are not very good at keeping things cold as my kid in school will attest. If you open them they take a long time to get back to cold again.

I hauled the Engel out of the boat yesterday for the party today. The little thermometer I use was showing 84.2f at 12:40 when I plugged it in(empty) and set it to freeze. At 14:20 when I checked it it showed 9.6f.

I am not a fridge tech or an electrician but I do like my beer cold. I have a very small boat and a limited amount of space for a fridge and the power source for it. This is what I use and it works for me.

You mileage may vary..........m

P.S. There is no "hard start" with a Sterling engine which is what I think the Engel uses and only one moving part........m

[motion30]

A questions fo4 the experts...... After viewing the avaliable 12 v units I don;t any that fit my cutout so can I convert my 110 v box with a 12 v kit? Can I use the existing evapator? Can a regular havac tech pump down abd charge the result What is a good systen to buy?
thanks

[endurance]

Hi Motion30 -

Sorry but I am not sure what you mean by 'hard start'... I suppose what context it is used. A system may start hard due to old age, low voltage, bad/weak starter capacity, Start to Run switching system, too high of system pressure, break down of refrigerant, ... to name some possible causes.

I guess if an A/C is shore powered, conventional A/C design would work and not too many people would care about the efficiencies. But, if an A/C system is getting the power from an inverter or generator - I would look at the not only the capacity but also the line voltage and frequency. Again, I am not an expert on inverters and have not seen many boat A/C units ... maybe someone can enlight me on this.

If I were to install an A/C, I would go with a water cooled system as appose to air cooled; more efficient and smaller in size.

Another information might be of interst to some, starting 2010 in the USA, all A/C has to be at least SEER 13 - this means much larger system, and very common refrigerant 22 will not be manufactured. Also, the new refrigerants (blends) run at much higher pressures.

Rick

[motion30]

[quote=endurance;312142]Hi Motion30 -

Sorry but I am not sure what you mean by 'hard start'... I suppose what context it is used. A system may start hard due to old age, low voltage, bad/weak starter capacity, Start to Run switching system, too high of system pressure, break down of refrigerant, ... to name some possible causes.

I guess if an A/C is shore powered, conventional A/C design would work and not too many people would care about the efficiencies. But, if an A/C system is getting the power from an inverter or generator - I would look at the not only the capacity but also the line voltage and frequency. Again, I am not an expert on inverters and have not seen many boat A/C units ... maybe someone can enlight me on this.

If I were to install an A/C, I would go with a water cooled system as appose to air cooled; more efficient and smaller in size.

Another information might be of interst to some, starting 2010 in the USA, all A/C has to be at least SEER 13 - this means much larger system, and very common refrigerant 22 will not be manufactured. Also, the new refrigerants (blends) run at much higher pressures

I am talking about refrigerator not an ac system , I guess they may be simiular. ANY ideas? My box is 3.5 or 4 cf

[hellosailor]

Lorenzo-
"If ... 110v unit uses 9 amp @ 12v off an inverter and a comparable 12v unit uses 3 amps, that's a hugh difference. It just doesn't make sense to me. "

Sure it does, you just have to open your eyes. I've been using flourescent bulbs for 35 years now and it wasn't so long ago that one of them cost $10 to replace a 50-cent tungsten bulb. Folks told me I was crazy to spend 20-x more money for a light bulb. Folks still won't buy a CFL for $3 when a tungsten bulb costs 75 cents today.

So what makes sense? To save 80% of my power bills every month, or to save 80% of the price when I buy a light bulb?

To most folks the cheap bulb makes sense, that's why they are being banned form the general US market around 2012. Because folks don't open their eyes and see the "other" math.

120V refrigerators are built to use CHEAP MAINS POWER and it doesn't really matter how much of that cheap endless power they use. 12V fridges are built more expensively because 12v power usually comes with a much higher cost attached to it.

Need more proof? Go buy a vacuum cleaner. The most expensive ones are sold on the basis that they CONSUMER MORE WATTS and therefore are more powerful. Except, that just ain't so. A more powerful motor won't consume more watts than a more efficient motor will, it will just cost more to operate. Nevertheless, that's how the entire vacuum cleaner industry works. Consumes more watts, so it must be more powerful!

[chala]

Originally Posted by hellosailor

Sure it does, you just have to open your eyes. I've been using flourescent bulbs for 35 years now and it wasn't so long ago that one of them cost $10 to replace a 50-cent tungsten bulb. Folks told me I was crazy to spend 20-x more money for a light bulb. Folks still won't buy a CFL for $3 when a tungsten bulb costs 75 cents today.

So what makes sense? To save 80% of my power bills every month, or to save 80% of the price when I buy a light bulb?

I do not share your enthusiasm for CFL.
If TL and PL where a success, I doubt of CFL.
CFL have a power factor of around .42 this make them ½ as efficient than claimed.
Cannot be dimmed so their consumption of electricity cannot be reduced.
A lot of light fittings will become unsuitable and will require replacement.
The light produced is not as good than an incandescent bulb.
They contain mercury and are not environmentally friendly.
Their electronic does not withstand hot climate and do not last much longer than an incandescent bulb.
In consequence the price of electricity will raise and the cost of disposing of them will make them no more economically efficient than an incandescent bulb.
DDT used to be great stuff to.
For people who like nice light they better stock on incandescent bulbs before 2012. In Oz they already have been banned.
CFL are just a way of increasing consumerism.
Some people will make money but I doubt that the planet will be better off.

[hellosailor]

Chala, I'm not stuck on CFL I just find them handy for conversions. I have 8' and 4' and 22" tubes in various locations, and my version of "dimmable" is just to turn off the bigger lights. I like BRIGHT light when I'm reading, or looking for something on the floor. My first pair of 8' tubes replaced 750 watts of tungsten bulbs, even with ballast inefficiencies that's a huge savings.

And there's really a big difference between "Oh, I have to change a light bulb" and "Gee, didn't I change that one ten years ago?"

Only two tungsten bulbs left. One in the fridge, one in the bathroom. Both places where a short on-off cycle will kill any type of phosphor bulb.

[Cheechako]

I believe by hard start they mean the surge in amp draw typical of electrical motors at start up, usually about 3 times the running amps...

[btrayfors]

Originally Posted by chala

I do not share your enthusiasm for CFL.
If TL and PL where a success, I doubt of CFL.
CFL have a power factor of around .42 this make them ½ as efficient than claimed. etc.

Most CFLs these days have a power factor around 0.5. However, this does NOT necessarily mean that they use more power (watts), merely that voltage and current are out-of-phase and VA readings will be almost double what they would be with a purely resistive load.

However, the power isn't lost. It's stored, used elsewhere, or returned to the grid. A 25-watt rated CFL will, indeed, use 25 watts of real power.

Thus, they are indeed as important in saving power consumed off the grid as they are billed to be.

FWIW, IMO the other negatives mentioned are really straw men. My house has been nearly 100% CFLs for over a year now, and we love 'em. The "soft white" variety creates light which is virtually indistinguishable in color from the much less efficient incandescent lights-of-old. Also, unlike normal fluorescent lights with long tubes, ballasts, etc., they don't create RFI which interferes with radio reception.

Bill

[mesquaukee]

Found a website which lists the energy use of refrigerators and chest freezers. Energy Labelling - Selecting an efficient appliance


A 2-3 cubic ft chest freezer uses depending on brand, etc. from 210 to 250 kwattHrs a year in a house. That is from 58 to 73 AmpHrs a day as drawn by an inverter at 85F . Any hotter and the unit may/will run continuously unless you turn the box temperature up.


If you were to run it as a fridge, you may need to change the thermostat, a simple task. Your amphrs/day would likely be 35 to 40.


I am sure this is more than the Engel but given the cost difference you can buy a lot of beer.

How many amphrs/day does an Engel use and at what temperature for the box and the surrounding air. Without knowing that we are comparing apples and oranges.

I have run a number of small 110 volt compressors on inverters (up to ¼ hp).


The increase in current draw through an inverter I have found to be less than 10%, ie. for a current into the compressor of 0.96 amps at 110 volts it is 10.7 amps at 12 volts. The starting current only lasts for a second or so and Ranges from 75 amps down to 35 amps. A 1500 watt inverter easily starts a compressor with a run amperage of 1 amp (1/8 hp). A 1000 watt inverter sometimes will, sometimes won’t but then the locked rotor amps is 16.4 amps at 110 volts.

[chala]

Bill
A 25W CF light bulb at 0.5 pf require as you say 50VA from the grid but you are only billed for 25W.
A 50W incandescent light bulb at 1 pf require also 50VA from the grid but the owner of the bulb is billed for 50W.
This means that when incandescent bulbs are phased out the cost of electricity will have to rise to provide the same income to the suppliers.

Originally Posted by btrayfors

However, the power isn't lost. It's stored, used elsewhere, or returned to the grid. A 25-watt rated CFL will, indeed, use 25 watts of real power.

“stored” where?
“used elsewhere” where?
“returned to the grid” how?
In the past the power used to be corrected to 0.85 pf, which in a sens could be seen as a waste of energy. I do not know what will happen in the future.

[cantxsailor]

Hey mesquaukee,

According to the book the Engel(mine is a mod35) uses 3.7amps(12vdc) at maximum cold setting.
On my unit that is -9.4F in my cabin at 88.7f ambient. How much it takes to keep it there once attained I can't tell you. It doesn't drain my batteries and I can have the very real treat of ice cream if I plan around it. 2 Engels(one each for fridge/freeze) would be nice but ain't in the picture because of space as much as money.

An Engel is NOT one of those little car boxes that keep the contents at 40F less than ambient.

90f-40f=50f beer. YECH.

My fridge has run on the power provided by an 85w solar panel and a 400w Airx marine wind turbine for 2 years. I have 2 160Ahr 4D agm batteries for house power and they never seem to be behind in volage even when the temp in the cabin is in the 90s and 29f inside the box. I keep it set so that the inside temp is 29f because I like my beer cold. There is a little thermometer that shows both inside and ambient temp and I'm pretty sure it's right.

I'm not sure what else I can tell you about the system other than I know how well it works in my boat. I tried a small 110vdc fridge for a while and as it was plugged into the dock I didn't care how much electricity it used. It didn't keep the beer as cold as the Engel probably because it just wasn't designed to opperate efficiently in a room that is 90f and everytime I opened the door my feet got a nice blast of cool air.

Front opening fridges, although the standard of every kitchen I've ever been in, are not the way to go for REAL cold keeping efficiency. Top opening fridges while not nearly as conveinient for rooting through ARE better at keeping things cold simply because all the cold doesn't fall out everytime you open the door, making the motor run all the time. Good insulation helps, mine has the available extra thermal cover.

By the way, apples and oranges stay cold in it to even though it does cost a bunch more............m

[Cheechako]

Yea, the Engel seems a perfect solution for smaller boats with limited space. Wish I'd have had one in '85 on my 30 footer! Start up amps really arent relevent as they are only for a second or so.

[mesquaukee]

Cantxsailer, thanks for the info.
I have heard they are good. I just would love to know the Amphrs/day

I must agree those front opening fridges are terrible. There is also a point due to a design problem when the air temperature gets to high over a certain amount and they run continuously chewing up amphrs.
I just started thinking that someone could take a small 2 or 3 cubic foot chest freezer and run it as a fridge. This would solve the problem of the weakness of the design of the capillary tube, it would cycle properly and be cold!