TAMING The power hog.

[jungpeter]

Hi FF,

The install can be easy , just stick in a self draining cockpit or if above the WL build a well that can drain overboard and vent it.

Well, on my Tolly 48, the "self draining cockpit" is aft of the aft cabin, a loooonnnnggg way from the galley. So, exit the galley, hike down the side deck into the cockpit, just to pull out the ingredients for a sandwich, only to lug them back to the galley? Nah. Not so easy.

And, I believe that even if your galley is above the waterline, "...a well that can drain overboard" does NOT satisfy ABYC standards. If I recall, the words are something like "...A propane refrigerator must be placed DIRECTLY against an exterior bulkhead." And thus highly unlikely to pass scrutiny from any competent marine surveyor, and thus equally unlikely to survive an insurance claim. Not to mention being stupid silly to save a few $$ in search of efficiency with disregard to safety.

There's a reason you've had 100% negative pushback from those of us that haven't' used propane refrigeration aboard. There are few (any?) that choose to compromise simple and affordable (and safe!) marine refrigeration units in a search for those self-same few $$ in a custom build.

Censorship? Nope, a viable, knowledgeable, difference of opinion. Your boat, your choice. Ditto mine.

Regards,

Pete

 

[markbarendt]

In physics there are no "free lunches".

What I'm getting at is that there is no real energy savings available in turning the fridge off for a few hours overnight and then back on when you wake up, none.

Even if the doors haven't been opened the fridge and everything inside will have warmed up some overnight, the insulation isn't perfect. Anything 'saved' during the off time, gets 'spent' when you turn it back on bringing everything back down to the normal thermostatically controlled temp.

The only real 'gain' I see in turning off the fridge, is with regard to noise reduction, not energy savings.

 

[psneeld]

Turning off may not be a "total"energy savings if sitting still for a few days, but it may keep up battery power for other things till you get underway the next day or the solar starts up again.

 

[rslifkin]

I physics there are no "free lunches".

What I'm getting at is that there is no real energy savings available in turning the fridge off for a few hours overnight and then back on when you wake up, none.

Even if the doors haven't been opened the fridge and everything inside will have warmed up a some overnight, the insulation isn't perfect. Anything 'saved' during the off time, gets 'spent' when you turn it back on bringing everything back down to the normal thermostatically controlled temp.

The only real 'gain' I see in turning off the fridge, is with regard to noise reduction, not energy savings.

Yup. Any gain from turning it off is due to the warmer average temperature inside the fridge over that time period. Which means you could have gotten that by setting it slightly warmer. Or it's getting warm enough to be a food safety concern.

 

[psneeld]

Food in a cooler gradually warms too...till you go and buy the next bag of ice...


Do I really care if overnight my freezer warms to 25 degrees and the fridge up to 40? I don't knowing that if it doesn't get any warmer till I turn it on and start the engine...no big deal.



But long term, I agree no energy savings.

 

[rslifkin]

Food in a cooler gradually warms too...till you go and buy the next bag of ice...


Do I really care if overnight my freezer warms to 25 degrees and the fridge up to 40? I don't knowing that if it doesn't get any warmer till I turn it on and start the engine...no big deal.

And that's why we don't use coolers for long term storage generally. A fridge getting to 40 is no big deal. But if I don't have temperature monitoring on it, how do I know it didn't get up to 45 or 48?

 

[psneeld]

Good point, some form of "monitoring" is necessary.


Not recommending it as a "usual" practice, but a way of conserving battery if critical.

 

[markbarendt]

Good point, some form of "monitoring" is necessary.


Not recommending it as a "usual" practice, but a way of conserving battery if critical.

If I ever willingly flatten all three of my battery banks down to that point I need my boat taken away.

 

[psneeld]

If I ever willingly flatten all three of my battery banks down to that point I need my boat taken away.

Guess you have mammoth battery banks and charging capabilities....not all boats or setups have that luxury..... back at ya.......

 

[rslifkin]

Guess you have mammoth battery banks and charging capabilities....not all boats or setups have that luxury..... back at ya.......

No mammoth batteries here (house bank is 400ah at 12v), but I'm in that same boat of "if I can't keep the fridge powered, something is very wrong". Assuming no shore power available, I've got 2 engines, a generator, and soon to be solar panels, all of which can charge the house batteries. And house loads are incapable of draining my engine start batteries. So if I can't produce the 50 - 80 ah / day my fridge needs, something is very wrong and I've also probably lost the ability to power an anchor light or other important functions.

 

[markbarendt]

The only thing that I am getting out is that in the real world the only risk is pulling the house battery bank down too far. That’s a problem for the longevity of the house batteries but it doesn’t impact me starting the engines in the morning.

 

[Simi 60]

240v ac all the way.
Far cheaper and easier than 12v and fridges can be replaced almost anywhere for less than the cost of a DC fridge tech callout.

Solar and inverter runs the lot

I have had gas and 12v on several previous boats
Never again.
Aside from being small and hot the Gas fridge failed the first time I got a refill in another country - not all gas is the same apparently.
12 v as stated above, far to expensive /cubic ft of space.

 

[Simi 60]

The only thing that I am getting out is that in the real world the only risk is pulling the house battery bank down too far. That’s a problem for the longevity of the house batteries but it doesn’t impact me starting the engines in the morning.

Not an issue if you have an adequate battery bank
We run a 2 door 550 litre
A 100 litre freezer
2 x 150 litre bar fridges
Total 330 cubic feet - All 240v

Battery bank is never lower than 80% soc in the morning.

Even the smallest boat on these pages could carry sufficient battery to adequately power a small 240v fridge with no fear of flat batteries.

 

[rsn48]

Very expensive thermometer for the fridge:

https://www.amazon.ca/Refrigerator-...ocphy=9001446&hvtargid=pla-945462890537&psc=1

 

[boatpoker]

Good point, some form of "monitoring" is necessary.


Not recommending it as a "usual" practice, but a way of conserving battery if critical.

Digital controller (+- 1 degree}. $14.00ea on Amazon

This one for the freezer is kept at -17.0C because we like hard ice cream. The one for our fridge/freezer is kept at 4.0C.

Both run from two 315W solar panels supplying four golf cart batteries, Never had a problem getting enough juice from the panels to run these even this winter in Ontario. We've barely seen sun for the last two weeks and I have not had the battery charger on for about a week.

 

[catalinajack]

Yes, of course, but no one suggested that there would be an overall savings of energy. The point was that batteries would not be drawn down as much overnight so that the following day, if it were a travel day, the alternators would do the job of bringing the fridge back down to its set temperature or solar would do so if staying multiple days away from shore power. As to whether the difference in amp-hours consumed is enough with which to be concerned, only a real-world test on your boat in warm weather would be determinative. I suspect that turning off our 110VAC seven cubic foot chest freezer overnight may be worthwhile but the two 4.2 cf 12-volt fridges not so much.

In physics there are no "free lunches".

What I'm getting at is that there is no real energy savings available in turning the fridge off for a few hours overnight and then back on when you wake up, none.

Even if the doors haven't been opened the fridge and everything inside will have warmed up some overnight, the insulation isn't perfect. Anything 'saved' during the off time, gets 'spent' when you turn it back on bringing everything back down to the normal thermostatically controlled temp.

The only real 'gain' I see in turning off the fridge, is with regard to noise reduction, not energy savings.

 

[catalinajack]

Sure keeping one fridge powered with a 400ah battery bank is no problem. How about two fridges and a seven cf chest freezer? Would that work for you? I rather doubt it. As always, every boat and user profile is different. For those with small battery banks relative to demand profiles, then perhaps shutting down appliances overnight may be worthwhile albeit with no OVERALL energy savings.

No mammoth batteries here (house bank is 400ah at 12v), but I'm in that same boat of "if I can't keep the fridge powered, something is very wrong". Assuming no shore power available, I've got 2 engines, a generator, and soon to be solar panels, all of which can charge the house batteries. And house loads are incapable of draining my engine start batteries. So if I can't produce the 50 - 80 ah / day my fridge needs, something is very wrong and I've also probably lost the ability to power an anchor light or other important functions.

 

[catalinajack]

Simi 60, your boat is an anomaly to most boaters on this forum. Two hundred volt AC is seen on very few boats so your setup has no relevance to most who ply this forum.

240v ac all the way.
Far cheaper and easier than 12v and fridges can be replaced almost anywhere for less than the cost of a DC fridge tech callout.

Solar and inverter runs the lot

I have had gas and 12v on several previous boats
Never again.
Aside from being small and hot the Gas fridge failed the first time I got a refill in another country - not all gas is the same apparently.
12 v as stated above, far to expensive /cubic ft of space.

 

[markbarendt]

Yes, of course, but no one suggested that there would be an overall savings of energy. The point was that batteries would not be drawn down as much overnight so that the following day, if it were a travel day, the alternators would do the job of bringing the fridge back down to its set temperature or solar would do so if staying multiple days away from shore power. As to whether the difference in amp-hours consumed is enough with which to be concerned, only a real-world test on your boat in warm weather would be determinative. I suspect that turning off our 110VAC seven cubic foot chest freezer overnight may be worthwhile but the two 4.2 cf 12-volt fridges not so much.

My point is that, the net math still doesn't change.

If you run the fridge all night then the house batteries are lower in the morning.

If you turn off the fridge for the night the fridge and it's contents are warmer in the morning.

For either scenario the alternator or solar or generator has to replace the same number of amps in the end.

Now, if you've been on anchor for 4 days and the house bank is getting really really low on juice, and you don't want to fire up a power source until tomorrow by all means, turn off the fridge for the night.

In that case you are protecting your batteries and most of the fresh food is probably gone anyway.

On night 1 or 2 or ... though with a nearly full house bank I see no point, even if you are traveling the next day.

 

[markbarendt]

Simi 60, your boat is an anomaly to most boaters on this forum. Two hundred volt AC is seen on very few boats so your setup has no relevance to most who ply this forum.

Sure it does, just substitute 120 for 240. Anybody with a properly sized inverter and battery bank can do what Simi 60 does.

 

[psneeld]

Yes, of course, but no one suggested that there would be an overall savings of energy. The point was that batteries would not be drawn down as much overnight so that the following day, if it were a travel day, the alternators would do the job of bringing the fridge back down to its set temperature or solar would do so if staying multiple days away from shore power. As to whether the difference in amp-hours consumed is enough with which to be concerned, only a real-world test on your boat in warm weather would be determinative. I suspect that turning off our 110VAC seven cubic foot chest freezer overnight may be worthwhile but the two 4.2 cf 12-volt fridges not so much.

I did back in post 33....

 

[FF]

"We don't use the freezer compartment for anything because of the chance of repeated and undetected partial defrosts."

If you put ice cubes in a bowl or plastic bag , they are a simple test to decide if the freezer got above 32F.

Use salted water to make cubes to check a lower melting temperature.

 

[FF]

Another old method to enjoy a reefer is the Eutetic system.

Here "cold plates", boxes filled with salt water are frozen with a large , frequently belt driven , compressor that melt silently .

Depending on the size of the fridge/freezer and the quality of the insulation the holdover period can be 3 or 4 days, between engine runs.

Yes, the plates take up room in the compartments , but they never need servicing , or replacing,as aging batts will.

We have such a system in our 90/90 and it holds at 5F for 4 days , so we coastal cruise changing anchorages every 3 days.

2 hours of engine time are sufficient to drag the freezer to -15F which freezes a 0F plate and eutetic solution to solid.

I know custom built reefers are expensive for assemblers who much prefer to toss in a factory fridge , but its a one time expense amortized over the next few decades.

Silent nights with ice cream and cold beverages does have a value.

 

[Iggy]

What a thread!! Most boats in the 30 to 45 foot range are mainly 120V. Not all marinas have 240V and if they do there limited on how many towers have it.

To me and who am I? You need to do the math between load, time and amp hours. Than come up with a plan.

Myself, I just install a 330 watt solar system to keep the house batteries up when on the hook. If nothing else, it extends the time that I need to start the genset. Also, if I go on shore for the day, I don't have to worry coming back to dead or almost dead batteries. I am hoping to get at least 20 amps from the panels anyways.

As to propane, it depends on how you use your boat. Myself, I would rather not have it. We don't cook that often and if I had to run the genset to cook, I could recharge the batteries at the same time.

 

[catalinajack]

I stand corrected!

Sure it does, just substitute 120 for 240. Anybody with a properly sized inverter and battery bank can do what Simi 60 does.

 

[rslifkin]

Sure keeping one fridge powered with a 400ah battery bank is no problem. How about two fridges and a seven cf chest freezer? Would that work for you? I rather doubt it. As always, every boat and user profile is different. For those with small battery banks relative to demand profiles, then perhaps shutting down appliances overnight may be worthwhile albeit with no OVERALL energy savings.

That might be pushing it, depending on what my other overnight draws were and how much power I could put back into the batteries during the day. However, if I had room for that much more fridge, I could probably find room to add a bit more battery. I am curious to see if keeping my ice maker powered from the inverter I'm putting in this weekend will be viable or not. I won't know until spring though, as I don't have solid power draw numbers for the unit.

 

[catalinajack]

My boat has eight golf car batteries. In addition to the two fridges and a fairly large chest freezer, we also have a large commercial icemaker on the aft deck. Now this beast runs constantly when it is making ice. It gets shut off when we are not on shore power or generator or under way as it is way too much of a power draw to run off the inverter. But, the bin will keep an adequate reserve of ice for three or four days without the unit being turned on.

My user profile: in addition to the fridges and freezer, we keep two sat tv receivers powered up, one televsion, use the microwave (no more than a few minutes), a television, the coffeemaker in the morning, and general lighting. Pretty much we do not angst over useage as I care not trying to squeeze an extra year out of a set of batteries. Still, if we anchor at 3pm and shove off at 9am (18 hours) we generally will have consumed about 450ah's or so, 50% to 60% depletion. I am not averse to sometimes depleting down to 30%. Our house bank is also our start battery. Even down to 30%, the Lehmans spin as fast and start as fast as if the batteries were 100% charged.

That might be pushing it, depending on what my other overnight draws were and how much power I could put back into the batteries during the day. However, if I had room for that much more fridge, I could probably find room to add a bit more battery. I am curious to see if keeping my ice maker powered from the inverter I'm putting in this weekend will be viable or not. I won't know until spring though, as I don't have solid power draw numbers for the unit.

 

[rslifkin]

My boat has eight golf car batteries. In addition to the two fridges and a fairly large chest freezer, we also have a large commercial icemaker on the aft deck. Now this beast runs constantly when it is making ice. It gets shut off when we are not on shore power or generator or under way as it is way too much of a power draw to run off the inverter. But, the bin will keep an adequate reserve of ice for three or four days without the unit being turned on.

My user profile: in addition to the fridges and freezer, we keep two sat tv receivers powered up, one televsion, use the microwave (no more than a few minutes), a television, the coffeemaker in the morning, and general lighting. Pretty much we do not angst over useage as I care not trying to squeeze an extra year out of a set of batteries. Still, if we anchor at 3pm and shove off at 9am (18 hours) we generally will have consumed about 450ah's or so, 50% to 60% depletion. I am not averse to sometimes depleting down to 30%. Our house bank is also our start battery. Even down to 30%, the Lehmans spin as fast and start as fast as if the batteries were 100% charged.

It sounds like your usage is a whole lot higher than mine. Without the inverter and solar that I'm adding, I've more than once stayed in one spot for 48 hours with maybe 3 hours of generator runtime (split across 3 or 4 short runs). And we've still been at or above 60% battery at the end of that. So including power put back by the generator, that would mean somewhere around 220 - 240 ah in 48 hours.

Considering I'll be adding 800w of solar, even if my power consumption doubles once we've got the inverter installed, it won't be an issue.

 

[Shrew]

I see a few potential issues.

1) propane fridges work very inefficiently when not level.

2) leaks in a propane fridge dump out the bottom of the RV (outside), while leaks in a boat go into the bilge.

3) To my knowledge it's not ABYC.

 

[Tator]

Not an issue if you have an adequate battery bank
We run a 2 door 550 litre
A 100 litre freezer
2 x 150 litre bar fridges
Total 330 cubic feet - All 240v

Battery bank is never lower than 80% soc in the morning.

Even the smallest boat on these pages could carry sufficient battery to adequately power a small 240v fridge with no fear of flat batteries.

I remember you giving these figures in a previous post and being amazed at your amp hr usage. Please remind me what size your battery bank is and the actual amphrs. used in a 12 hour period. We typically use 225 amphrs. in a 12 hr. overnite, in a cool 60deg environment, to mainly power our 120v 10cu.ft (225 liter) fridge and 120v 5cu.ft. chest freezer. I did discover that our fridge seems to always be on defrost-I can constantly feel heat around the freezer door opening. I attribute this to the defrost timer not playing well with the modified sine wave inverter and being one of the reasons I am switching this year to a pure sine wave inverter. I tried disconnecting the timer, but this played havoc with the air circulation system becoming clogged with frost in just one day.

Thanks, Tator