Real world electrical consumption?

[Tellie]

Originally Posted by wingssail

We have a 25 year old Power Survivor 35 (originally a PUR35, now sold by Katydine). It produces 35 gallons per day running full time. So that is about 1.4 gallons per hour. Quite minimal in today's terms, I'm sure you would agree, however it supplies all of our drinking and cooking water, depending on the climate we're in (how much we drink in a day) in about 1-1.5 hours of daily operation. This amount of usage extends our tankage which is 140 gallons. We can go a month without refilling.

The watermaker is running at this moment, it's taking 3-5 amps, average 4amps I guess. That is 48watts. We run it only when the engine is on to ensure it has full voltage available, which preserves the electric motor.

We've replaced the membrane twice in 25 years and have done O'ring rebuilds a couple of times, and some other minor repairs, It's been quite durable and has survived a circumnavigation and 25 years of cruising. We're happy with it's durability.

It's a 12v machine obviously, no frills (no electronics, no pre-filter, no-feed pump), and I can rebuild it in about an hour.

I'd live to have one which makes 5-8 gallons but I don't want to spend the money. When this one fails I think I will build one myself. Others have done so.

You are correct. The PS35 uses 35Wats per gallon made.

[mvweebles]

Originally Posted by Tellie

PS " but that is pure luxury and not something you need." You don't "need" a boat either.

An old salt once told me "the only time you need a boat is when the one you're on is sinking and the one next to it isn't"

[teneicm]

Lots of good info here on managing and estimating electrical loads, so won't bother adding on that topic.

BUT, please rethink going with raw water cooled refrigeration. We started out with 2 raw water cooled units and struggled with them for over 5 years before we converted them (one to a keel cooler, the other runs off the fresh water tank). Much happier now!

[demacsea]

The subject of boat electrics is a complex one, but the bottom line is that the current draw, battery bank capacity and charging regime must all be matched for the 12volt system to function satisfactorily. You can download a daily current calculator and get more relevant info at https://www.sailboat-cruising.com/boat-electrics.html

[chrisr]

i've not read this whole thread, so pardon if this point has been raised before...but for us, diversity of supply is important ie there is no point in having a super-duper solar array...if it's solid overcast and rainy for a week

we have
1) 650w solar...not a lot, but enough most of the time
2) 400w wind...some boats hv 2, but one suits us
3) 6kva diesel generator...for when needed

iow we can always get some current for somewhere. eggs are not all in one basket

cheers,

[tomfl]

Just my two cents. I have 420 wats of solar and 440 amp hours in the battery bank. A big fridge/freezer in the galley and an Engle in the salon. I often only open the big fridge every couple of days and transfer what I will need to the Engle. Have a chip in the big fridge that starts it up at 25%, in five minutes it goes to 50%, five more minutes 75%, and five more minutes 100%; but if the fridge gets to the set temperature it shuts off. I charge two laptops, two smart phones, several camera bodies at odd times. I do use an auto pilot and electric windlass. I seldom use the radar as Florida weather is usually clear.

Bottom line is by 10:30AM the battery bank shows 101% and 13 volts so I start dumping power. This is when I charge stuff or maybe use the InstaPot to cook something. I have also run a grinder off the inverter. My daily energy requirement is in the area of 80 amp hours a day. As a rule when I wake up the battery bank is never below 75% and is often 85%.

I would note my solar array is on the davits and almost never gets a shadow from the mast or boom. I also have a Honda 2000 which I try and run at least once a month for half an hour, hopefully every two weeks just to keep in shape. I usually do this late at night and notice getting the last couple of percent to 100% is not possible in the short time I run the Honda.

Thinking about getting a Rainmaker or similar portable water maker in some part to keep the Honda 2000 in working order but suspect I could run it when I am dumping power.

[noelex 77]

Originally Posted by chrisr

i've not read this whole thread, so pardon if this point has been raised before...but for us, diversity of supply is important ie there is no point in having a super-duper solar array...if it's solid overcast and rainy for a week

we have
1) 650w solar...not a lot, but enough most of the time
2) 400w wind...some boats hv 2, but one suits us
3) 6kva diesel generator...for when needed

iow we can always get some current for somewhere. eggs are not all in one basket

cheers,

Marine generators are the work of the devil .

Living without a generator makes life much easier and simpler. Depending on the boat design and existing equipment, this is not always a practical goal, but in most cases it is achievable without sacrificing any comforts (air conditioning at anchor, if this is important to you, is perhaps the one exception).

If you want to be able to cruise diverse locations, a week (or more) of solid overcast conditions and rain certainly needs to be allowed for, but with a well designed system this is not a difficult goal to achieve without a generator.

An electrical system that includes a marine generator may add to to the diversity of electrical production options, but it detracts, usually significantly, from the reliability.

[mvweebles]

Originally Posted by noelex 77

Marine generators are the work of the devil ........

An electrical system that includes a marine generator may add to to the diversity of electrical production options, but it detracts, usually significantly, from the reliability.

I totally disagree with this statement, though do understand the underlying sentiment. Sailors often prioritize weight, size, cost, and ultimately reliability. Even when sailboats are built, the engines are often after thoughts, sometimes under-sized (better these days) with folding/feathering props, and installed without proper maintenance access.

It doesn't have to be that way. There are marine diesel generators that are quiet, efficient, easy to maintain, and will gleefully purr for many 1000s of hours.

We are in the midst of a refit and decided to install a Northern Lights 6kw. We do not plan to use it often, but given our planned cruising grounds are through the Panama Canal to Caribbean, Bahamas, and eventually home to Florida, we opted for A/C. We remember an awful night on a friend's boat in the Bahamas where the choice was sweltering below decks or serving ourselves up for dinner to famished mosquitoes above deck.

But the previous post (TomFL) is spot-on: It's a system. We have 800W of solar and an energy usage in the 175AH/day range with a well insulated fridge and a small freezer as our big energy draws, both built-in with air-cooled compressor units. With 400 gallons of diesel to offset occasional generator use and a 75hp Perkins' that burns around 1gph @ 6.5kts, limits on off-grid are down to food source and library of books. Except for absence of sails, we self-identify more with sail-cruising than power.

Peter
1970 Willard 36 Ballasted/Displacement Trawler

[noelex 77]

Yes, if you want air conditioning at anchor (at least for anything other than a very small percentage of the time) a marine generator is the only option.

It is a pity because otherwise your electrical demands would be reasonably easily met in your cruising locations with your 800w of solar and of course the alternator, which obviously on a trawler is always producing when underway.

[mvweebles]

Originally Posted by noelex 77

Yes, if you want air conditioning at anchor (at least for anything other than a very small percentage of the time) a marine generator is the only option.

It is a pity because otherwise your electrical demands would be reasonably easily met in your cruising locations with your 800w of solar and of course the alternator, which obviously on a trawler is always producing when underway.

Totally agree we have plenty of solar (plus 7x100a battle born LFP and twin balmar). That's why it was a hard decision. I've added extra ports and hatches, and I enjoy sewing so an awning over the foredeck is planned which would allow hatches open during rain. My wife gets warm when she sleeps so AC makes her life particularly easy. We can afford a splurge here and there. That was one. But I agree with the basic premise of simple is better. I'd only add that if you add complexity, spend the extra money and do it right with best possible equipment. In my opinion, Northern Lights simply cannot be matched let alone beat.

[SY Kelpie]

Air-con is definitely not our list... not that we wouldn't like to have it, but if we made it a 'must have' we would be looking at buying a different boat with a big genset, and in all likelihood we wouldn't ever actually get away at all.
We're much closer to the Annie Hill school of thinking, where even a basic fridge is a luxury (our first boat had nothing at all... second boat I made an insulated locker and we bought frozen foods to put in it... third and current boat has a small 12v fridge and it's amazing...)
I like the idea of putting the water cooling heat exchanger in the freshwater tank- one less hole in the boat. Presumably not quite as efficient as raw water but still better than air-cooled?

[mvweebles]

I've never heard of using a fresh water tank as coolant. I would thing it would heat up substantially, not to mention challenge of physically installing the coils in the tank.

I considered water cooled condenser for my fridge and freezer. The keel cooler style especially. In the end, air cooled ones have come a long way and the technology is proven in millions of refrigerators. I have seen many air cooled compressors in boats run for 15 years and longer. So I simply decided water cooling was a solution to a problem that didn't really exist anymore.

[rslifkin]

I agree, air cooled refrigeration works just fine as long as you can build it with an appropriately sized condenser and good air flow. Water cooling does potentially give you some installation flexibility, but probably not worth it.

A big enough fresh water tank will dissipate enough heat to cool a reasonable size fridge, but definitely nothing more, so don't try it for A/C or anything.

As far as reliability, while it's a slightly quirky old piece of equipment, I'd say historically, my generator is probably the most reliable mechanical item on this boat. Mostly, it just works. And when something isn't right, it's usually very minor, simple as dirt and easy to get it sorted.

I absolutely agree with designing your systems so that you're not a slave to a generator, but having a good one does give flexibility. I've got an all electric galley, so no propane to worry about and 1 less type of fuel to carry. Mind you, if I were willing to carry the weight of a lot bigger house bank than I've currently got, I could definitely run a big enough solar + battery system to power the galley without a genset. But as it is, 1 - 2 hours of generator time in a day does the job (for when I need the stove / microwave and to make hot water).

And on a hot day, I'll sometimes fire up the A/C for a bit while I've already got the generator running at dinnertime, that way the boat is cooled off when I shut things down before bed. Being able to do that can make a big difference when there's only a light breeze and the boat doesn't want to cool down quickly.

[mvweebles]

Originally Posted by rslifkin

I agree, air cooled refrigeration works just fine as long as you can build it with an appropriately sized condenser and good air flow. Water cooling does potentially give you some installation flexibility, but probably not worth it.

A big enough fresh water tank will dissipate enough heat to cool a reasonable size fridge, but definitely nothing more, so don't try it for A/C or anything.

As far as reliability, while it's a slightly quirky old piece of equipment, I'd say historically, my generator is probably the most reliable mechanical item on this boat. Mostly, it just works. And when something isn't right, it's usually very minor, simple as dirt and easy to get it sorted.

I absolutely agree with designing your systems so that you're not a slave to a generator, but having a good one does give flexibility. I've got an all electric galley, so no propane to worry about and 1 less type of fuel to carry. Mind you, if I were willing to carry the weight of a lot bigger house bank than I've currently got, I could definitely run a big enough solar + battery system to power the galley without a genset. But as it is, 1 - 2 hours of generator time in a day does the job (for when I need the stove / microwave and to make hot water).

And on a hot day, I'll sometimes fire up the A/C for a bit while I've already got the generator running at dinnertime, that way the boat is cooled off when I shut things down before bed. Being able to do that can make a big difference when there's only a light breeze and the boat doesn't want to cool down quickly.

I have started using an induction hot plate at home and am hugely impressed, especially for low simmer stuff like a stew or rice. Very low power consumption. I'll carry a hot plate on the boat. I see some sail cruisers with large solar arrays and big LFP battery banks are going induction instead of propane. I totally get it - solar + LFP is a game changer. I would think that power boats with all electric galleys might benefit from changing to induction and sizing their generator more appropriately instead of large generator that is over-sized and under-loaded 85% of the time

But your point of sizing for solar but having generator for flexibility and options is exactly my goal. My solar can easily generate enough to cover my 175AH consumption.

BTW - to your point about battery size/weight - I replaced six 6V Golf Cart Batteries weight almost 600 lbs with seven 100AH LFP batteries weighing under 250 lbs and I was able to install in an out-of-the-way spot as maintenance is more or less zero, so I gained a ton of space in my engine room. I more than doubled my usable capacity, halved the weight, and gained a lot of usable space. Also relieved me of a significant amount of money.

[teneicm]

Originally Posted by mvweebles

I've never heard of using a fresh water tank as coolant. I would thing it would heat up substantially, not to mention challenge of physically installing the coils in the tank.

I considered water cooled condenser for my fridge and freezer. The keel cooler style especially. In the end, air cooled ones have come a long way and the technology is proven in millions of refrigerators. I have seen many air cooled compressors in boats run for 15 years and longer. So I simply decided water cooling was a solution to a problem that didn't really exist anymore.

The coils don't go in the tank. You just T a line off the tank supply as well as the return. The water just circulates from the tank, to the compressor/ coil unit, and back to the tank. We converted our water cooled system to this arrangement and it is working great. 80 gallon water tank, cooling a 7 cubic foot freezer. Works fine as long as we keep the tank above 1/4 full. Will work with as little as 5 gallons, but it starts to lose efficiency at that point. The tank is usually around 90 degrees, which is only 2-3 degrees above the sea water temp. It will work even better out of the tropics. Air cooled is very reliable, but we had issue with where the unit could be installed, but still get good air flow. The water cooled unit can be stuck in a much smaller, less ventilated space (although you still need some fresh air, you don't want the compressor and black box overheating!)