Visit our Popular Forums

CookiesnTequila · 02-12-2018, 03:00

Quote:

Originally Posted by john61ct

No, 600AH of a properly installed LFP system is exactly the kind of "very difficult & expensive" electrickery I was talking about.

Just be aware actual AH/hr draw will vary a lot with conditions.

> Big question here that I still have: is 20000btu enough?

Besides cubic volume area,

how well insulated / sealed up the living space will be is critical.

After those, varying ambient temps, as opposed to your wife's comfort zone temps will answer both questions.

Hence my idea of a smaller unit dedicated to a smaller better insulated space. . .

With one big system, you need to design for a worst case scenario that maybe only applies for a very small number of days per year.

Maybe you missed that our 600ah Li batteries are @24v (so 1200ah @12v equivalent)? No trickery at all!!

The Wabasto air con is rated at maximum 8A @ 230v, so <2000W (our inverter is 5000W). Our 600ah batteries could theoretically run that 20000btu unit for 7+ hours constant, without any cycling!

It uses less energy than our watermaker!!

valhalla360 · 02-12-2018, 03:07

Quote:

Originally Posted by CookiesnTequila

Maybe you missed that our 600ah Li batteries are @24v (so 1200ah @12v equivalent)? No trickery at all!!

The Wabasto air con is rated at maximum 8A @ 230v, so <2000W (our inverter is 5000W). Our 600ah batteries could theoretically run that 20000btu unit for 7+ hours constant, without any cycling!

It uses less energy than our watermaker!!

Unless you are limiting cooling to a small part of the boat, 20k BTU is pretty marginal for most 50' cats.

Also what kind of horrible water maker do you have that it's using more power than the air/con (or are you misdirecting because you have a very high output model but it only runs for a very short period of time so instantaneous power needs (wattage) is high but total power consumed (watt-hr) is much lower).

CookiesnTequila · 02-12-2018, 03:25

Quote:

Originally Posted by valhalla360

Unless you are limiting cooling to a small part of the boat, 20k BTU is pretty marginal for most 50' cats.

Also what kind of horrible water maker do you have that it's using more power than the air/con (or are you misdirecting because you have a very high output model but it only runs for a very short period of time so instantaneous power needs (wattage) is high but total power consumed (watt-hr) is much lower).

I only want to take humidity out and drop the temp a few degrees, and only at night so we can sleep, or I suppose possibly on very hot very wet days in the tropics. We would not install one for the Med!

Our watermaker makes about 130L/hr. A 1.5kw hp pump and 700w low pressure. I can run it either off the generator or batteries, so can use as much water as we like.

CatNewBee · 02-12-2018, 03:43

That is what we have done, we have run the A/C unit in the owners hull only and just to chill down a few degrees in the evening to fall asleap comfortably..

Cold air stays down below.

we did not cool down / dehumidify the whole vessel. During the day there is plenty of ventillation by open doors and hatches, so dehumidifying is worthless anyway.

**noelex 77** · 02-12-2018, 04:24

Quote:

Originally Posted by CookiesnTequila

We want air con prinarily for dehumidification (my wife is allergic to mold, and sneezes uncontrollably if there's any around)

Large cats are ideal for mounting solar. With 2000w and 600Ahrs (@24v) of lithium batteries I dont think you will have any problems running an A/C with the modest aim of reducing humidity rather than producing a large drop in temperature.

It needs a more detailed energy analysis, but suspect your prediction of 4.5 hours of generator run time (if not motoring) will prove to be a little pessimistic. I suspect in practice you will have less than this.

My only caution for anyone following a similar route is that a boat with multiple air conditioning units, generator, large alternators, two engines, watermaker, large solar array etc in addition to the other required equipment, is becoming immensely complicated.

When using this equipment full time, the required repairs, replacements and maintenance can significantly reduce the time available for doing the things that draw us to cruising in the first place.

With your specific requirements such as the mould allergy I can understand the reason behind the decisions, but for most cruisers a simpler boat may prove to be more luxurious, because one of the greatest luxuries is time to do just what you want.

valhalla360 · 02-12-2018, 05:42

Quote:

Originally Posted by CookiesnTequila

I only want to take humidity out and drop the temp a few degrees, and only at night so we can sleep, or I suppose possibly on very hot very wet days in the tropics. We would not install one for the Med!

Our watermaker makes about 130L/hr. A 1.5kw hp pump and 700w low pressure. I can run it either off the generator or batteries, so can use as much water as we like.

That makes more sense and is more viable if that is the desired usage.

But someone looking to keep it 20-22C when it's 42C outside will be disappointed if they saw your original comment and assumed it would work fine.

CookiesnTequila · 02-12-2018, 10:01

Quote:

Originally Posted by noelex 77

Large cats are ideal for mounting solar. With 2000w and 600Ahrs (@24v) of lithium batteries I dont think you will have any problems running an A/C with the modest aim of reducing humidity rather than producing a large drop in temperature.

It needs a more detailed energy analysis, but suspect your prediction of 4.5 hours of generator run time (if not motoring) will prove to be a little pessimistic. I suspect in practice you will have less than this.

My only caution for anyone following a similar route is that a boat with multiple air conditioning units, generator, large alternators, two engines, watermaker, large solar array etc in addition to the other required equipment, is becoming immensely complicated.

When using this equipment full time, the required repairs, replacements and maintenance can significantly reduce the time available for doing the things that draw us to cruising in the first place.

With your specific requirements such as the mould allergy I can understand the reason behind the decisions, but for most cruisers a simpler boat may prove to be more luxurious, because one of the greatest luxuries is time to do just what you want.

Lol - very well and diplomatically said!!!The only thing I might have done different, is put your 2nd, 3rd and 4th paragraphs in all caps and underline them!! And, I would add that it also requires a pile of money!!

CookiesnTequila · 02-12-2018, 10:06

Quote:

Originally Posted by valhalla360

That makes more sense and is more viable if that is the desired usage.

But someone looking to keep it 20-22C when it's 42C outside will be disappointed if they saw your original comment and assumed it would work fine.

If you go back and read all my posts, I had already clarified that previously!

"We want air con prinarily for dehumidification (my wife is allergic to mold, and sneezes uncontrollably if there's any around) and for sleeping on those nights when it's too hot and humid, or raining. Not looking to cool below 28c (82f)."