DC Powered Air Conditioning. The Bucket List Trip.

[SKYCHENEY]

 

[JD5652]

I guess I should explain myself a little more. Those who, like me, may remember "old school" capacitors may not get what I said.

Basically, there is a new generation of capacitors based upon kind of a furry dielectric of carbon surface which can therefore hold *enormous* numbers of electrons thus energy.

But there is a catch (isn't there always?). The max voltage is around 2.7V, so they generally exist in banks. Because they can charge unevenly, some sort of balancing circuit is beneficial as well.

The payback is a group of 5 or 6 will support standard 12V systems (with headroom for charge voltages--not completely necessary if using a well regulated DC-DC like our Newmars).

Nowadays they are appearing as battery replacements for automobile starting (at least one member has such a system) thus capable of hundreds of amps for a brief period.

Without endorsing any one supplier, check eBay for "supercapacitors" for a sample offering.

This came up in the context of supporting some potentially undersized cables for a powerful macerator on a new head installation--easy to eliminate voltage sag this way.

I wonder if Scott has paired any with his numerous Victron installs?

DAN

As I am a super old school EE... seems I have some homework to do..

 

[cww]

My friends 1978 60C has a bank full of capacitors for his ships service that runs all of the air conditioners. I liked that idea as you don't see those spikes when the compressors turn on. Hatteras thought to do that in 1978. I know its not new technology, but I was impressed as I had never seen another boat of that vintage with a bank of capacitors.

Do our 53’s have that, or just the convertibles?

 

[scottinsydney]

Perhaps the idea of supercapacitors may have an application here.

+++

Our issue today is how to wire the 110 volt pumps to operate when any aircon is operating on GEN or INV. Or when the big 25K BTU salon aircon is working on GEN and a bedroom is working on INV. Thus the pumps need to work when any of the aircons are turned on in GEN or INV mode.

Another way of saying this problem is "If the pumps are set to INV, then we cannot operate the GEN powered Salon aircon without an INV bedroom aircon turned on to activate the pump."

A possible Victron solution for when a mix of INV and GEN aircons are operating at the same time is to power the pumps from the 110 volt circuit of the autotransformer/inverter. If the inverter failed, then we could switch back to GEN operation for the pumps and aircons.

The Victron inverter charger will allow additional power through to the INV operating aircons and pumps and charge the battery at the same time. The genset when running will directly power any GEN operating aircons and directly power the pumps (flowing via the inverter). This is the beauty of the Victron product.

Of course the inverter is going to get a "jolt" when the first aircon and pump start together. After that the pump runs continuously.

Thoughts?

 

[SKYCHENEY]

Do our 53’s have that, or just the convertibles?

I think most of the boats with 4 or more compressors in the late 70's had that capacitor box. I don't know how many years they installed it but my 1985 does not have it.

 

[JD5652]

I think most of the boats with 4 or more compressors in the late 70's had that capacitor box. I don't know how many years they installed it but my 1985 does not have it.

I have five compressors and have a start and run capacitor in each AC compressor control box. However, these are STANDARD Start/Run capacitors that you would find on almost any unit and are not necessarily designed for inrush currents on an inverter or DC battery based system design.

I have not done the calculations or researched any detailed designs, but my old school EE gut tells me that the soft start design for this type of system would be different than for a 240 VAC system that's being powered from either a generator or shore power.

In my mind, this still does not address the possibility of simultaneous starting of multiple compressors which can multiply the inrush current by 2X, 3X, 4X or 5X. I would be interested in hearing details about how this design challenge has been successfully addressed.

Perhaps others with more current experience or inverter/battery system design knowledge can chime in with updated information.

 

[scottinsydney]

So today we were able to test several aircons on the inverter.

3 Knob Control: The pumps draw about 180 watts each when running. The 10K and 16K BTU condensers draw about 1000-1100 watts each when compressor is running. Worked beautifully.

SMX Control 1: 25K BTU Salon unit overloaded the 5000 watt inverter.

SMX Control 2: 16K BTU Owners Stateroom ran perfectly well for 30 minutes. Then one of the two 40 year old evaporator fan motors decided to smoke and burn out ... now condenser and pump only run for 10 seconds. Oh well.

Anyway a step forward today.

 

[JD5652]

So today we were able to test several aircons on the inverter.

3 Knob Control: The pumps draw about 180 watts each when running. The 10K and 16K BTU condensers draw about 1000-1100 watts each when compressor is running.

SMX Control 1: 25K BTU Salon unit overloaded the 5000 watt inverter.

SMX Control 2: 16K BTU Owners Stateroom ran perfectly well for 30 minutes. Then one of the two 40 year old evaporator fan motors decided to smoke and burn out ... now condenser and pump only run for 10 seconds. Oh well.

Anyway a step forward today.

Thank you for sharing these details as these are the design challenges as part of this system. Following this with keen interest.

 

[oscarvan]

I think most of the boats with 4 or more compressors in the late 70's had that capacitor box. I don't know how many years they installed it but my 1985 does not have it.

I fit that description...... Going to have to look around port engine room with new eyes.... I do not remember a "wonder what's in here?" moment with that outcome..... Thanks.

 

[SKYCHENEY]

I fit that description...... Going to have to look around port engine room with new eyes.... I do not remember a "wonder what's in here?" moment with that outcome..... Thanks.

I'll snap a photo of that box next weekend and post it here.

 

[scottinsydney]

Another day with my head in a hole..... this time removing a burnt out air con blower in the stateroom. I don't understand why Hatteras installed two air handlers when one larger one would have been just fine.



++++

So the project investigation continues.

- The 240v aircons will all work from the inverter at 50/60HZ. The 120v aircons will only work at 60HZ
- The pumps are 120v 60HZ.
- Our boat is 120v/240v 60HZ for the genset and the Victron inverter with autotransformer is programmed the same.
- We proved that the 5000 watt inverter can start and run aircons <16K BTU.
- The aircons all seems to use about 1000 watts each and the pumps about 100 watts.
- We ran the aircons on the inverter and the pumps off the genset. This was fine for our test, but possibly the 240v inverter and 120v genset phases would be out of sync. Best to now run both from the genset or both from the inverter/autotransformer.
-If I had a choice between the old 3 knob aircon controls and SMX versions, I would choose the 3 knob version as they are so simple.

Ok, now we know it all works in principle. But how to sort out the power switching and the circuit breakers to make it as easy as possible?

The conundrum is: pumps are 120v, two of the seven aircons are 120v, all aircons need to operate independently at the same time set either on inverter or genset WITHOUT having to reset any engine room switches MOST of the time. eg. The 25K BTU Salon will always operate off the genset. The stateroom may operate off the inverter or genset . But the pumps are 120 volts and there are two 120 volt aircons.

It would be very messy switching for two voltages and all the aircons. Plus the circuit breakers. Plus the pumps. And I'm not sure it be hands off. It would be a birds nest of wiring.

So my DRAFT solution is to power the two small 120 volt aircons from a 240 volt supply and use a step down 240-120 volt transformer. The pumps could be run off the 120v genset or single phase from the /autotransformer. (If I changed the pump voltage then I would need to change the existing triggers etc). As the inverter will ALWAYS be on, then the pumps can quite happily be powered MOST of the time by the inverter. Remember we are running a "silent ship" with no genset to remind us an aircon MIGHT be on so best to leave the pumps with a continuous power supply. The pumps do make a hum but realistically I am the only person who would take any notice.

This all means we have greatly reduced the number of switches and CBs. We only need a single 240v 1-OFF-2 changeover switch and a single mini circuit breaker / enclosure for each aircon mounted next to the old AC panels. We would also need a changeover switch / CB for each 110v pump.

 

[oscarvan]

- We ran the aircons on the inverter and the pumps off the genset. This was fine for our test, but possibly the 240v inverter and 120v genset phases would be out of sync.

I've read this three times now, and while I can't give you specific thoughts (yet) my flags are up.... I would proceed with great caution, and running off ONE source may be a good policy.

 

[scottinsydney]

So Oscar's flags had us back down to the boat this morning staring at the AC panel wiring and CBs, wondering what is the path of action?

The voltage step down boxes described in my previous post were a thought bubble, but would have worked.

So how do we do all this without modifying the AC panels, pump triggers and aircon voltages? How do we play the cards we have been dealt with the entrenched wiring in a 40 year old boat? If you are into brain teasers, then this project is for you.

After much navel gazing we have developed a plan to keep the AC panel intact, functional and with no modifications. We can use a 1-OFF-2 change over switch for each aircon. And a 1-OFF-2 switch for each pump. Plus a CB for each. Voltages for all components remains the same. We have now drawn out the wiring diagram and it should, in theory, work.

In the Starboard engine room we will only connect the inverter/autotransformer to the 120v twin guest room and 240v lower level aircon. The 120/240v Victron autotransformer is ideal for this project with its split phase L1-Neutral-L2 output. So that means a maximum of three changeover switches and three circuit breakers on the Starboard side. This is manageable with no bird's nest of wires.

Grounding will be through the original AC panel buss bar or via the inverter's grounding relay. (I do not have technical answer yet for grounding an aircon circuit when the 3 Pole 1-OFF-2 change over switch is in the OFF position. Perhaps there are multiple grounding points in an aircon system? Any opinions.)

We have ordered a couple of change over switches and CBs and will test this new design next week. If it all works, great. If not, then we'll try again.



Starboard AC Panel- Salon 25K BTU aircon will not be connected to inverter. 11 &12 is the Analytic Systems 32v battery charger.


Starboard AC Panel as it is today.

 

[rourkeh]

The unicorn of boating.
It has been tried by many and the best they could do to date is to run a single 6,000 btu unit overnight.
You will kill whatever batteries you use with the heavy cycling and depletion and that is going to be a large cost.
Soft start units will help but not as much as you think.
If you are using standard marine A/C units there will be a very high amperage draw every time the compressors come on line. The only A/C units that have inverter based technology with variable speed compressor ( which is what you need ) are Frigomar. I have them on my other boat so I am familiar with the benefits.
If you wanted to build a battery/inverter based system to run A/C units you would need too start with Frigomar and work from there.
Good luck, let us know if you become the first success story.

 

[oscarvan]

You will kill whatever batteries you use with the heavy cycling and depletion

You mean like in an electric vehicle capable of 1500-2000 cycles? This is exactly what LiFePO4 was designed to do. Yes, you need a lot of it, but in that respect the OP's math is sound.

 

[scottinsydney]

Thought I would give you an update of the project.

To date we have:

- Installed the AC power cables from the genset room inverter to the port engine room and then on to the starboard engine room.
- Installed a 3 Pole Master Circuit Breaker (MCB) in the port engine room, along with a distribution box going to starboard engine room.
- All cables have been sheathed in conduit and secured to the bulkheads.
- Installed 3 x 1-OFF-2 crossover switches in a single housing in starboard engine room.
- Modified the load cables going to the air conditioners (Starboard side only so far)
- Tidied up 36 years of wiring additions and modifications to starboard AC panel.
- Installed circuit breaker distribution box for starboard air cons and pump. 240v circuits are double pole CB and 120v is single pole CB.

For lower level (located above genset room which we call the "Office" with its 12K BTU air con and #2 pump:

- Tested changeover switches and aircon with running generator which is Position #1. All OK.

- Tested changeover switches and aircon with operational inverter which is Position 2. All OK.

Then sat on sofa being cooled for one hour listening to no noise at all. Wow, it really works! No more genset. My silent ship.

Basic tests..... when warmed up the total watts consumed by 12K BTU air con plus pump is 1000 watts. 5000 watt inverter had no simultaneous start up issues for pump and condenser. On a sticky warm night it should still be possible to halve the watt hours consumed using the thermostat.

As a test I used a domestic fan in the office blowing down the lower corridor and all areas became more pleasant. So at a pinch this single Office aircon may well take the humidity sting out of Bow, Office, Twin and OSR.

+++++++

Over the next few days we will tidy up the wiring to make it all look neat and as OEM as possible. I'll then post a few photos and some of the lessons learned. I bet that we will need to adjust our battery charging voltage upwards a little. I'll also wager we will need another big battery and a larger inverter.

The boat is heading north of Sydney next month and to an air conditioning man's marina for three days to overhaul the seven units and find a few leaks.

 

[cww]

I mean - I’m interested / following along with this. It’s a fascinating project. That said I can’t imagine what this is costing vs. a couple of larger water lift mufflers and soundown insulation for the generators. Marine ac compressors and air handlers are far from unobtrusive. In my boat the a/c’s are louder than the generator. At first I was going to chalk it up to soundshielding and upgraded muffler, but thinking about it, that has been true for every boat I’ve had with a/c. In my boat you can’t really hear the generator inside, but you can definitely hear the a/c. I question whether the desire to run your a/c’s is ever going to leave you with that perfect silent night on the hook. There will always be some irritating mechanical noise, and IMHO the genset is a minor offender compared to a/c units.

Just curious, what is the actual end goal? Noise? Decreased fuel burn? Ability to cruise remote destinations? Leaving the boat anchored for extended periods? What I keep wondering is what makes this $100k setup preferable to a $1200 generator auto-start box and going a knot or two slower on the way there and back to hit your fuel usage goal? Generators don't burn that much fuel. Usually in the range of .5-1gph. If you're not using a/c all the time, then running the generator to charge the batteries for an hour or two a day while you cook whatever you were going to cook anyway, and use hot water for the shower that you were going to take anyway, works out fine. If you want to extend those intervals then you could always add *some* capacity to the house bank, but it wouldn't need anything like this.

In the end what I keep wondering is if you're using the air conditioning anyway, then short of turning the entire boat into one big solar panel, and probably not even then, how does this avoid the need to use the generator regularly to recharge the batteries? And if that's something that's happening regardless, I come back to what is this doing that a battery monitoring generator auto-start unit wouldn't do? If the boat is unattended with all the normal stuff turned off, then what are you going to get, a few hours of total runtime per week to keep the batteries up? Even at our newly inflated gas prices, that's still nothing. At a couple gallons a week to keep the batteries charged with an auto-start, you could ("theoretically" - since in reality you can't actually leave it that long due to storms and other maintenance needs) leave your boat anchored out for almost 10 years before you'd make it through 1,000 gallons of fuel. What is the advantage?

 

[scottinsydney]

A very good analysis, but perhaps you have missed that we have reused all of the older existing Cruisair units. Nothing has been replaced.

The total cost of the AC and DC air con conversion has been US$300 or less in parts. This allows us to use the already installed lithium battery and inverter. OR we can still use the genset. We can have a mix of aircons running on genset or inverter. (This will be clear when I post the photos.)

We all hate the noise of the generator on the lower level. Its noise reverberates through the lower level. The kids cannot watch the TV in the area above the genset room. No additional shield is going to mask it's mechanical noise. Its the way the boat is.

The gensets historical fuel consumption with 500 hours use each year for the past six years was reducing the range of the boat and unbalancing the two tank levels. The cost of diesel was never a factor.

So we will now able to visit the boat on the swing mooring for a couple of hours and have air con without the genset. The solar panels will charge the battery up over the coming days. At anchor we can have aircon / dehumidify at night without the generator running. We are at anchor for weeks during our holidays. The boat never visits a marina. The condenser is silent but there is a slight hum from the pump which is OK.

++++++

This DC air con project is separate to the installation of the lithium battery system, The DC air con conversion makes use of the advantages of the lithium battery and Victron inverter system. The total cost so far of the lithium battery components is US$4000 for the 48v / 200 ah battery, US$300 for one single solar panel and US$3500 for the inverter and other Victron parts. The battery project continues as we get ready to install more solar panels on the flybridge hard top.

 

[cww]

A very good analysis, but perhaps you have missed that we have reused all of the older existing Cruisair units. Nothing has been replaced.

The total cost of the AC and DC air con conversion has been US$300 or less in parts. This allows us to use the already installed lithium battery and inverter. OR we can still use the genset. We can have a mix of aircons running on genset or inverter. (This will be clear when I post the photos.)

We all hate the noise of the generator on the lower level. Its noise reverberates through the lower level. No additional shield is going to mask its noise. Its the way the boat is.

The gensets historical fuel consumption with 500 hours use each year for the past six years was reducing the range of the boat. The cost of diesel was never a factor.

We are now able to visit the boat on the swing mooring for a couple of hours and have air con without the genset. The solar panels will charge the battery up over the coming days. At anchor we can have aircon / dehumidify at night without the generator running. We are at anchor for weeks during our holidays. The boat never visits a marina.

++++++

This DC air con project is separate to the installation of the lithium battery system, The DC air con conversion makes use of the advantages of the lithium battery and Victron inverter system. The total cost so far of the lithium battery components is US$4000 for the 48v / 200 ah battery, US$300 for one single solar panel and US$3500 for the inverter and other Victron parts. The battery project continues as we get ready to install more solar panels on the flybridge hard top.

My apologies, looking at the picture of that battery, it would never have dawned on me that it was only $4k. That would be $15k+ stateside. This may not be as far off as I thought it was. I'm with you on not replacing the a/c's, if you have older blue cruisair's, definitely keep those and just replace the compressors if/when they fail. They're excellent units. The newer ones are crap by comparison. From looking at everything in your pics I honestly thought it would have cost more than that.

 

[scottinsydney]

So here is where we have got to.......



Power from the inverter and auto transformer enters the Port engine room's blue door circuit breaker enclosure from conduit below. This enclosure has a 3 pole 20 amp MCB (Master Circuit Breaker) for the L1-N-L2 output.

Inverter power to the Starboard engine room exits the enclosure and goes to the square terminal box to the right. The cable then travels downwards under the floor to the other engine room.






The inverter power cable enters the Starboard terminal box from below.

Then there are three 1-OFF-2 crossover switches for the twin room, pump #2 and Office.

The next terminal box directs generator/shore power to the crossover switches. This same terminal box directs either genset/shore or inverter power to the blue door circuit breaker enclosure box. We chose 10amp CBs. Above the blue enclosure is another terminal box that connects to the load (air cons).

++++++

It all works. About 1000 watts for a 12000 BTU aircon.

The most challenging aspect was physical layout and placement of the boxes. No wiring was changed or modified inside the AC panel.

More difficult will be creating the layout for the Port side aircons because of all the existing wiring runs on the bulkhead.

CB amperage are deliberately low.

The terminal boxes allowed us to keep everything modular and are all part of the same product range.

There is of course much more to tell and above is only an outline.