450: Just signed on a new 450s!

[davedindubai]

OK. It's project time!
This should be a good one. We need air conditioning. I've read all the 'you don't need it, you want it' comments in other threads but the fact is, Hayley is in Miami, in May, in a marina and pregnant. The last 10 months we have lived off anchor and despite a couple of nights where it was slightly too warm, on the whole, as long as it's not raining then the breeze is plently cool enough.

Next year however, we will spend much more time in marinas. Partly due to the bubba on the way but also because I will be working more often (the last 9 months off work has left us nearly bankrupt) so single parent, dinghy runs with baby just isn't happening. Like I said: we need AC.

The beauty of not having it installed by Lagoon is I can now install exactly what we want (need). So what do I want?

AC in the 3 cabins plus saloon. Do, I need it in the saloon or will the cool air from each hull provide sufficient cooling upstairs?

My thinking is to fit 2 separate units. (I had thru huils put in prior to launch).
Unit 1 can chill master cabin and saloon.
Unit 2 can chill the 2x port side cabins.
I'll fit separate pumps and controls so that they are completely independant. Often we won't need the port side unit running.
The under seat storage in the corner is hardest to access so this will be home for 1 unit. Can i fit both in there?

Today I've been reading up on air con unit power requirements because I'm thinking that once we're all used to sleeping in AC in a marina we are going to want it out on anchor. Obviously I'm no expert (yet) but here's a few calculations I've done with an eye on running it on inverter. These are approx and I've rounded up or down for ease:
6,000btu = 5a
8,000btu = 6a
10,000btu = 7a
12,000btu = 9a

I read today that there's a 10x rule for AC / DC. Basically, the 6 amps that the 8k unit draws will use 6 x 10 = 60 amp hours from my batteries. I'll use 10 hours run time for simplicity which is obviously 600ah. (a lot!) But, the compressor doesn't run flat out all the time so you can assume 80%. 600 x 0.8 = 480ah

Here's the calculations for all the units:
6,000btu. 5 x10 = 50ah x 10hours = 500ah x80% = 400ah
8,000btu. 6 x10 = 60ah x 10hours = 600ah x80% = 480ah
10,000btu. 7 x10 = 70ah x 10hours = 700ah x80% = 560ah
12,000btu. 9 x10 = 90ah x 10hours = 900ah x80% = 720ah

This is all a very simplified version of reality but it gives an idea of what is feasible. I've not gone into only being able to use 50% of your banks amp hours as some have huge lead acid banks and others are on lithium and using 80% DOD. We are currently on the standard Lagoon LA's with 840ah so at present it's not possible but this has highlighted the sweet spot and I think the 8,000btu unit is a go!

In a years time I could be installing a lithium bank or I might have even bought someones 6 LA's who's swapping out their bank for lithium. I could probably get another 6x 140ah batteries for £500 and put them under our port side bed. My point is the 8,000btu unit should be cool enough for us? and should be future proof.

To run off inverter you also need a soft start to reduce the current spike on starting the compressor. I've been researching the Dometic Turbo self contained units which have an optional Smart Start that takes care of the spike.

Of course we can simply run it all off generator but I'd rather not. I've found our solar has our current bank fully charged by lunchtime so if we double our bank we would need more solar, however, we do tend to run the genset most evenings 5-6pm for an hour to make water so this ensures our bank is at 100% and of course there's time spent motoring too. All things considered, I think it will work for us most of the time.

I've waffled more than usual there so what do you guys think? Please correct me if there are any huge glaring errors there?

[c-reel]

First : congratulations !!!

2nd: shoot, i was so hoping your next project would be on dive compressor installation - of course, a real membrane for nitrox with booster and He option - :-(

3nd: was more thinking of the smallest units for owner cabin only (5/6kBTU) so it is easier on batteries bank and can run overnight. And then when really hot and with guest(s), a larger unit (8/10kBTU) for both salon and SB hull. On shore power or through generator mostly.
But the description you made on your situation makes sense.

Originally Posted by davedindubai

OK. It's project time!

Here's the calculations for all the units:
6,000btu. 5 x10 = 50ah x 10hours = 500ah x80% = 400ah
8,000btu. 6 x10 = 60ah x 10hours = 600ah x80% = 480ah
10,000btu. 7 x10 = 70ah x 10hours = 700ah x80% = 560ah
12,000btu. 9 x10 = 90ah x 10hours = 900ah x80% = 720ah

This is all a very simplified version of reality but it gives an idea of what is feasible. I've not gone into only being able to use 50% of your banks amp hours as some have huge lead acid banks and others are on lithium and using 80% DOD. We are currently on the standard Lagoon LA's with 840ah so at present it's not possible but this has highlighted the sweet spot and I think the 8,000btu unit is a go!

In a years time I could be installing a lithium bank or I might have even bought someones 6 LA's who's swapping out their bank for lithium. I could probably get another 6x 140ah batteries for £500 and put them under our port side bed. My point is the 8,000btu unit should be cool enough for us? and should be future proof.

To run off inverter you also need a soft start to reduce the current spike on starting the compressor. I've been researching the Dometic Turbo self contained units which have an optional Smart Start that takes care of the spike.

Of course we can simply run it all off generator but I'd rather not. I've found our solar has our current bank fully charged by lunchtime so if we double our bank we would need more solar, however, we do tend to run the genset most evenings 5-6pm for an hour to make water so this ensures our bank is at 100% and of course there's time spent motoring too. All things considered, I think it will work for us most of the time.

I've waffled more than usual there so what do you guys think? Please correct me if there are any huge glaring errors there?

[Steve_C]

I like your plan for the two units. I think I would also include the ability to direct the output to starboard owners hull only or to the saloon only. This would allow you to reduce the compressor run time for long nights on battery only. It would also allow you to cool (or heat) just the salon if its really hot during the day. Its nice to have options and it should not increase the cost much at all.

[Pascals Wager]

The saloon will not cool via cabin cooled air, the expelled hot air from the cabins will rise into the saloon. Also the saloon is exposed to more direct light and heats further when the oven or stove is on. As an example I run 36kBtu in the Saloon and with both port cabins closed still have not turned on the owners cabin Aircon. Temp outside right now is 36C, so cold air will flow down not the other way. As for units, I would recommend a chilled water system, each unit can be mounted in the engine bays and then run the chilled water pipes to where you need the cooling. Under cabin bunks there is room for the air handlers and Lagoon have already cut in holes for ducting as well as semi pre cut vent holes. In the saloon an airhandler will fit under the seating. Condensate needs to be pumped overboard also and not into the bilge imho. Less water sloshing around means way less humidity.

As for power requirements, I suggest calculating the Aircon power you need not what elec power you can provide. If you under spec the Aircon it will be a waste of money, there are rough formulas to calculate this based on room volume, sea water temp and airtemp.
Chilled water systems are more expensive than stand alone units, but are more efficient, convenient to install and some units are based on inverter technology which greatly lowers their power requirements.

[davedindubai]

Originally Posted by Pascals Wager

As for power requirements, I suggest calculating the Aircon power you need not what elec power you can provide. If you under spec the Aircon it will be a waste of money, there are rough formulas to calculate this based on room volume, sea water temp and airtemp.
Chilled water systems are more expensive than stand alone units, but are more efficient, convenient to install and some units are based on inverter technology which greatly lowers their power requirements.

I've ruled out chiller units due to cost and space. A: we ran out of money ages ago and B: when you're sailing around the world you need every cubic mm of space you can get. I know you've seen Hayley's show collection so you know what I mean!

Regarding BTU requirements, what I'm really after is real world results and feedback from anyone running say a 6k btu or a 8k btu unit in a similar space as our owners cabin?

[mr336]

Hi Dave
theres this company in Fort Lauderdale Florida called Mabru Power Systems. I visited their factory and they showed me a small unit that had a a 2 speed compressor that was made to run off batteries.

Just another option to check out. they were very helpful and friendly. FYI

Cheers

Mike

[davedindubai]

Interesting, I actually posted some incorrect figures, sorry. The Dometic Turbo units are more efficient than I thought. Here are the actual full load amps for 220v / 50hz units:

DTU6 = 2.2a
DTU8 = 3.2a
DTU10 = 3.3a
DTU12 = 3.3a

They seem to be very efficient little units. Pascals Wager is right, the chiller units are more efficient still but bang for buck, this is the way I'm going. After a little more research I think 2x 12btu units is the way to go and as suggested a diverter / selector for each cabin. The port aft cabin being the most difficult to run 6" ducting from the unit in the saloon but i'm not on the boat at the mo to properly work this out.

[Steve_C]

Many years ago, I was on a friends Monohull and he had a diverter and a large valve in the bulkhead to the engine compartment so that if he needed to work in there when its REALLY HOT he could cool it down. Not a bad idea.

[davedindubai]

Has anyone any experience with running AC ducting from the saloon too the aft cabins?

Ideally I would like 2 units in the saloon to run 4 zones but I’m having trouble getting my head around chilling the port aft cabin from a unit under the salon sofa. Any ideas?

[Sand crab]

Originally Posted by davedindubai

Interesting, I actually posted some incorrect figures, sorry. The Dometic Turbo units are more efficient than I thought. Here are the actual full load amps for 220v / 50hz units:

DTU6 = 2.2a
DTU8 = 3.2a
DTU10 = 3.3a
DTU12 = 3.3a

Dave I didn't read the entire thread but if you are stateside then you probably want something that will run on 60 hz so you can plug in at the marina.

[davedindubai]

Originally Posted by Sand crab

Dave I didn't read the entire thread but if you are stateside then you probably want something that will run on 60 hz so you can plug in at the marina.

Nope, I’m keeping everything 220v/50hz so it will run off my inverter

[davedindubai]

Another issue, the height of the Dometic DTU12 is: 318mm and with the sound cover: 356mm and the height under the saloon sofa is 316mm from wood floor level and 335mm from fibre glass floor level.

The corner of the saloon sofa has a recess into the floor which adds another couple of cms of depth but is only large enough for one unit!

So that leaves me with space for 1x 12btu and 1x 8btu.

[Pascals Wager]

With two units, what is your planned distribution to each port cabin, saloon and stb cabin?

[davedindubai]

That was my plan but now I’m on the boat I just don’t think it’s possible (or efficient) to run the 6” ducting from saloon to the port aft cabin. Even tho that’s what I’d really like to do.

Going to revisit your chiller unit idea...

[davedindubai]

Originally Posted by mr336

Hi Dave

theres this company in Fort Lauderdale Florida called Mabru Power Systems. I visited their factory and they showed me a small unit that had a a 2 speed compressor that was made to run off batteries.



Just another option to check out. they were very helpful and friendly. FYI



Cheers



Mike

Hey Mike,

Just been into Mabru. Really liked the guys, thanks for the tip!