I Recently received an email from a gentleman named Tyler…

Tyler was inquiring about a DIY job installing Marine A/C on a 30 foot sailboat, and then running the Marine Air Conditioner on an inverter when he was away from shore power.

His question asked about wattage draw of a 8,000 BTU Cruisair self contained Turbo AC unit & if I thought the 8,000 BTU marine ac unit would be large enough for his 30′ Irwin.

Since this “Air Conditioning on Inverter” question is being asked more & more often now days, I thought I would post my answer here for everyone’s review…

Hi Tyler…Thanks for asking~

It’s not really as simple an answer as you might expect…But I’ll try to keep it somewhat simple…So here goes…

• The 8K Turbo unit is rated to draw 5.5 amps which using the conversion formula of 5.5 amps X 115 volts = 632.5 watts in cool mode (slightly more in heat)
• The 10K Turbo unit draws 6.7 amps X 115 volts = 770.5 watts in cool (slightly more in heat)
• Depending on your location (seawater & air temps) 10K is likely better suited for a 30′ sailboat…At least down here in central Florida…
  

Cruisair Stowaway Turbo Unit (SMXII) W/R410A 10,000 BTU Marine AC

OR

Marine Airrr Vector Turbo Self Contained A/C 10,000 Btu W/410A

Yes they can be run on an inverter, but starting amps can be many times the run load, and that can depend on several factors such as the inverter’s quality & the voltage it maintains during that surge…

The inverter’s Surge rating is as important as it’s continuous wattage rating…And as with anything electronic… Over sizing is usually best for the life & performance of the product…Don’t plan on just the minimum needed.

Also…A Dometic “SmartStart” can be added to any A/C unit to reduce it’s starting amperage draw/surge by as much as 65%…In my experience they really do live up to the claims…

Once started…How long your battery bank can run the A/C depends on a few things too…

• Size of the bank in amp-hours…Meaning size of each battery & how many batteries connected in parallel (Two 100 amp hour 12 volt batteries connected together in parallel provide for a 200 amp hour bank…4 would be 400 amp hours etc..)
• Length Of, and Wire Size, run…DC Voltage to the inverter tends to drop pretty quickly (length of run is measured as a total of both to & from batteries)
• The Longer the DC Voltage Run…The Larger the wire needs to be to limit voltage drop & overheating…(It’s why Tesla won out with his AC voltage we now use over Einstein’s DC voltage back in the day)
• Duty Cycle of the A/C (actual compressor run time to pull down to & maintain a given set point temp)
• Duty Cycle is usually figured as a compressor run percentage of overall time on…
• Then also figure the small draw of the fan & pump…Which may, or may not cycle with the compressor (Now days with the digital t-stats most pumps cycle with the compressor but the fan may not, or is selectable)

Most battery manufactures recommend not running batteries below 50% charge state before re-charging (so figure battery amp hour rating 50% less than actual rating)

As a general rule of thumb…It’s a 10 x conversion for DC to AC amperage…10 amps of AC amp draw (uninterrupted) per hour is around 100 amp hours of DC removed from the batteries…

So taking the 6.7 amp figure from the 10K unit above…Figure 67-70 DC amps being removed from the batteries (actually inverters are never 100% efficient and differ in ratings so YMMV but 10x is easy to figure)

Basically, It takes a pretty large battery bank to get a full nights sleep…Then you must figure recharge time to replace that amperage used & the charging system…Alternator or Charger output rating determines that factor…But other questions are…

• How long do you have to run the engine to replace that energy ?
• Or how long do you typically run the engine a day, and is it enough ?

To run that 10 K Dometic Turbo unit 9 hours (one hour pull down, 8 hrs sleeping) and I don’t think you can find a similar sized unit that draws less…figure say…

• 7.7 amps running (6.7 unit amps plus 1 amp for the pump) 7.7 x 10 (basic DC to AC conversion factor) 77 amps x 9 hours = 693 amp hours used…
• 693 x .80 (80% duty cycle) equals 554 amp hours without loss thru wire, inverter efficiency, etc…
• Then double that for the 50% discharge factor the battery manufacturers recommend & you would need a battery bank capacity of 1,108.8 amp hours…
• That’s 11 or more 100 amp hour 12v batteries…
• Or you could use six pairs (12 batteries @ 225 Ah per pair) of 6 volt golf cart batteries for a capacity of 1350 amp hours…This should keep you above the 50% discharge for a full night of sleep in slightly less space than twelve 100 Ah 12 volt batteries that would only total 1200 Ah…

If you want to keep the cabin cool 24/7…

• Does the alternator have enough output to keep up with the draw without the battery bank loosing percentage of charge & are you taxing that alternator doing so ? (at maximum output all the time)
• Or can the alternator “Catch Up” After some engine off time while still running A/C underway ?
• Meaning do I need to consider a larger alternator to do what I want without it overheating causing shorter life ?
• Typically the standard alternators on small diesels or sailboat auxiliary engines range from 35 to 65 amp output…

There are trade offs…Yes it can be done, and is…

You can play with the figures for differing usage, but knowing all this info going in provides for fairly realistic operational & pocketbook expense expectations…

Hope that helps…Any questions please ask…

For folks reading this in Marketplace…We are linking this post to the “Installation” section of the Forum here on Marine-AC.com so that it can be discussed further if needed…

Steve~

Dometic – 5 Things You Need to Know Before Buying a Marine Air Conditioning System

Any questions…Please Ask.

Steve~

I have installed several and found the claims to be true…

The instructions are pretty straight forward, but I can also provide an installation video…

Steve~

NEW FOR 2010, Includes SMXII power/logic box and a TSEP5… SMXir & SMXht keypads, and CXP cable are sold separately.

Call or E-Mail for discounted pricing.

Note: Picture may show “Optional” compressor sound shield which is sold separately.

This is just a note to confirm that I offer FREE Troubleshooting help for your Marine A/C & Refrigeration issues…But I ONLY do this in the FORUM section…If you can’t take the time to register & ask in the FORUM…I usually won’t respond…(this section is not setup for dialog/discussion…it’s only setup for comments)

My only request in return is that you Consider me when buying replacement parts, or units…And that if local, you also consider my services….But how’s they saying go ?

No Purchase Necessary…That price can’t be beat at half the cost !!!

All you need to do is join & ask in the FORUM section most relative to your issue  http://marine-ac.com/forum/

Post your own title (thread) in the section that applies, and I’ll be happy to respond with my best honest advise…

Thanks Again,

Steve~

Here’s what I can share at this point from the Cruisair/Marine Air perspective & what I have been told.

Self Contained R-22 units are no longer in production…sort of…

Since 417a is a drop in replacement for R-22 you can get the R-22 units (but they are shipping charged with R-417a)

We are told that the R-417a drop in replacement refrigerant for R-22 is 17% less efficient than the R-22 in the same unit (like running 60Hz equipment on 50Hz power)

So if you bought a new R-417a unit…You can evacuate the R-417a and re-charge that unit with R-22 to realize the same performance as a R-22 unit that was purchased before the production change…

You can also evacuate a older R-22 system & recharge with 417a…But the 17% performance drop still applies…

R-22 refrigerant should still be available for quite some time yet…But…The price will climb pretty quickly.

Edit:  5/1/2011…2020 is slated to be the end of production of R-22 in the US…None will be imported either…But at that point, if you still have an operational R-22 system, it can be evacuated and re-charged with R-417a.

The new R-410a cannot be used in a R-22/R417a system even with evacuation…It’s not compatible with the oil in the 22 system & the pressures will run too high in that system (metering devise is not set for it either)

My distributor has about 3 months worth of sales of units with R-22 available, but after they are gone he will only stock the new R-410a units….And is now only ordering Self Contained unit with the new R410a.

5/11/2011…R-22/R417 self contained units are no longer in stock.

Split or Remote systems are a whole different story…

One thing they are the same in is that none of the existing systems can run the new R-410a, but they can run the R-417a with the 17% drop in performance….but the problem is bigger with small split systems.

Typically the 16K & smaller split systems have always used piston type compressors as opposed to the rotary type that have been used in self contained units for many years now…

The reason for this is that the rotary type compressor does not lend itself well to long copper line runs…
Rotary crankcases don’t hold enough oil for the migration of oil with the refrigerant throughout the longer line runs in split systems…
It’s my understanding that the rotary can run out of oil before it has a chance to return with the refrigerant, and thus can ruin itself in a split system from lack of lubrication.

The compressor manufacturers are being forced to phase out production of the lower efficiency piston compressors by the EPA or whomever…

5/1/2011…We still have no info on when this might happen but as of this date…Replacement R-22 split system units with the older piston compressors are still in production…But only ship with R-417a which can be evacuated after installation & replaced with R-22 to maintain efficiency.

Scroll compressors would be a great alternative, but as of yet…The compressor manufacturers have not developed Scroll compressors in the smaller sizes that are required for our smaller Marine split systems (the larger than 16k marine units are using scrolls now)
I guess they figure the Marine market is too small to develop new small scrolls for, and that the rotary’s are fine for the home window unit market (which is what the the rotary’s were developed for)

I know that Dometic Cruisair/Marine Air has been testing small splits using rotary’s for quite some time now…So far they aren’t saying much…

Until then…They are only offering the same piston type smaller split systems and shipping with R-417a (the drop in replacement for R-22) to meet the new regulations….The Larger splits (over 16K) will be available as either R-417a (mainly for replacements of the older R-22 units) or the new R-410a units, but to utilize R-410a condensing unit you must also change the air handler…No need for new copper tubing runs.

Dometic is now offering their new “Emerald Series” split/remote systems with rotary compressors (16K & below) Also with  TXV’s (thermostatic expansion valve) metering devises at both the condensing unit & air handler (2 TXV’s)…Larger than 16K “Emerald Series” systems are Scroll compressors.

Steve~

First & Foremost are Filters…and not just the Sea Strainer I talked about in my last article….But the ones in the Return Air path too…

Direct Expansion A/C (as opposed to Chilled Water) systems rely heavily on good air flow to keep from icing up in the cool mode (Low pressure) or shutting off due to High pressure in the heating mode…

Generally speaking…Most boats may have two Return Air Filters per system or control…Some have more if there are more than one air handler on that system (compressor)

If you have a small cabin adjacent to another that the fan operates off the control in the other cabin (or just has a speed control installed in that small cabin) this may be one instance….

The trick to finding air handlers is to first look for the return air grill…

Once you have located the Return air Grill (also a likely spot for the first filter) it should be removed…Check if a filter is installed on the back side of the grill…If so remove it and set it aside…

Now with a flashlight…Look into that hole to see the path the air would take…At the end of that path should be the air handlers location…You may have to open another cabinet, or locker to gain access to that location, and boat builders can be very inventive in placing them in out of the way places…Ones that sometimes seem impossible to get to, but in most cases a panel can be removed for access…Here is where the second filter is located…On the aluminum fins of the evaporator coil…

All major manufacturers of marine A/C have shipped their units with a filter installed at the factory for some time now…If there is not one there…It has likely been removed after the system was installed…

I have serviced boats that the owners never knew of this factory installed filter…Or the air handler’s location for that matter…Thus when I removed the filter it looked like a piece of carpet…We all know Air does not flow thru carpet too well…

The manufactures install them there not knowing if a filter is going to be utilized in the grill at system installation…and If it is a clean path to the air handler (one that is not likely to get dust from another path) this filter can sometimes be discarded if it is tough to access, but it is better to have both in most cases…

In boats with multiple controls (more than one system) follow the above procedure till you have all the filters in hand…Take them out to the dock and have fun with the water hose…That is unless someone has installed the throw away fiberglass/paper filters, in which case I would recommend you replace them with some foam filter material that you might find at your marine A/C dealer…Or what Home Depot/Lowes etc…offers for home window A/C units.

Now either wait for them to dry…Or shake them out and re-install…A little water on them will not hurt a thing…

If you can get a good look at the aluminum fins…Check to see that they are not also clogged…If they are…That’s another story, and it’s probably time to call you’re A/C guy to clean them because he has access to cleaning solutions that work real well for this…and also likely has the equipment to do the job right…With less mess…

If you want to clean them yourself with a squirt bottle & garden hose…He may even sell you some cleaner, or you can try Home Depot…However what they offer never seems to work as well as what he gets from the wholesale A/C supply house…

Before you close the cabinet back up you should also check the condition/operation of the condensate drain…Especially after washing the coil…All that stuff that got washed off is now in the condensate pan and could have clogged the drain fitting/s or hose…

Best way to test this is with a quart or two of tap water…You can add some bleach/Lysol/whatever to kill bacteria…But first I would run some plain water into the drain pan to find out if the drain is clogged…This way you won’t have to suck out the bleach water to avoid it dripping onto surfaces when you remove the hose to blow it out…

Please Note: If you have to blow out the hose or fittings, and the only way you have to do so is by mouth…Try to find a clean piece of garden hose or the like to attach to the existing fitting or hose…These hoses are where bacteria like the Legionaires Virus live…You don’t want the old hose, or the condensate water to touch or enter your mouth!!!

Once you are done…We are ready to start up the system/s…

This is a good time for you to check the seawater pump & its pump relay operation (for boats with more than one A/C system supplied seawater by a single pump)

A seawater pump relay is a box connected to the pump that receives a signal from each separate unit…and then tells the pump to start pumping seawater when each, or any unit calls for it (starts to run)

They are easy to verify if they are working properly just by starting one system…Waiting for the compressor to come on…and then either looking over the side of the boat for water discharge, or if the pump actually runs by hearing it start…

Once you verify that that system started the pump…Switch the control off for that system…Wait for the pump to stop…Then follow the same procedure for each system by itself…You don’t want to run more than one system at a time for this test as it may be one of the other systems that brings the pump on…

If one of the systems does not bring the pump on…There is a problem with the pump relay box…Over the years there have been many kinds/models of pump relays, and to say how to troubleshoot each here would be kinda lengthy…However if you feel you have a problem, I will be happy to discuss your model/issue in the blog if you like…Otherwise you probably need to call Ole Faithful A/C Guy…

Now that we have verified Good seawater flow overboard and pump relay operation…We can run all systems…Do so for about half an hour….

Now we need to locate each compressor…

There are basically two kinds of direct expansion marine A/C systems.

• Self Contained units…sometimes called Stowaways or Cabin Mates…These are all in one units where the compressor, condenser, evaporator & blower are all on the same base…They are usually located behind the return air grille, and under a settee or in a closet…They are more like a window unit than central A/C…As the compressor is almost in the living space and thus you can get a bit more noise…Though now days the newer rotary compressors are pretty quiet.
• Split Systems…Sometimes called Remote…These are more like the central systems you may have at home…In that the compressor & condenser are “Remotely” located and connected to the Air handler/evaporator section by copper tubing to carry the refrigerant…These systems are quieter, and have more flexibility in that they can have more than one air handler/evaporator running off one compressor…and thus allow for installation in smaller cabinets, with smaller units, to reduce air noise even more…The total of air handler BTU just must pretty closely match the condensing units capacity….

Now that we have located the Compressor/s and they have run for a half hour…Be certain they are still running in cool mode…If not…Lower the temp setting of your control (t-stat)

Now locate the seawater condenser…It’s the tubes that horizontally (most are horizontal but some are vertical) wrap around the top of the compressor (condensing) unit…there should be at least two water hoses connected to it (some have 4) and with the palm of your hand…Grab the top coil….It should be Warm…but not Hot…

If it is Hot in more than one place…The unit is not performing as it should and is probably drawing more amperage than designed…

A couple of likely reasons…

• Seawater flow is not up to spec…Look for restrictions
• Seawater condenser is dirty…Needs to be flushed with an acid solution…Similar to the radiator in your car…At any rate…Not enough heat is being removed from the refrigerant…
• Not likely…But an overcharge of refrigerant…Maybe that last A/C guy didn’t do so good?…Or was it a buddy that said he knew what to do?
• Even less likely…Someone replaced the seawater pump with one that doesn’t have enough GPH pumping capacity for the system…Maybe somebody’s buddy was trying to save him a buck or two…You may laugh, but I’ve seen that happen too…Hey…He meant well!
• Most of the above reasons are probably best to call the A/C guy…Not the buddy…However you can & I will walk you thru flushing a coil to remove the scale that acts like a insulating blanket preventing proper heat transfer…Just at another time…

This next test is mostly for owners of Split/Remote systems…

Most of the newer Self Contained systems use what is called a Rotary compressor…Some of the older ones are still around that use the older reciprocating (piston) type…and to determine which you have is hard to explain if you have never seen either…But the Rotary type is usually slightly taller, and a lot skinnier than the Piston type…Have you got a Fat compressor matey?

Anyway…A piston type compressor that is too hot to touch on top…Is likely low on Freon…Rotary’s run Hot but Piston’s do not…

If either type is Cold or sweating…That’s another set of possibilities…

• Lack of air flow due to…Dirty filters or coils…Hey I thought we did that?
• Overcharge of refrigerant…That buddy again?
• Ductwork that is too small (or even crushed due to the space it was run thru) to properly handle the flow of air that the system BTU requires…We could blame…But let’s not…It won’t do any good anyway, and it’s gonna get too in depth here…Again we can discuss it in the blog for each individual circumstance…
• Last but not least…In a split system…Multiple Air handlers that don’t add up to compressor/condensing unit BTU…We won’t go into that here either….

This is getting a bit long…So in closing…I hope I have helped some…I look forward to answering any questions that I might…

Think of you’re A/C guy this New Years…I’m sure he thinks of you too…I know I do…

Steve~

The original poster had a March magnetic drive pump that would not pump water, and after the usual back flush & priming sugguestions he could still not get it to pump water…Just before I read the thread he had found that either something had gotten past the strainer (or he didn't have one) and had lodged between the impeller magnet and the pump housing stopping the impeller from turning, but not the motor from running…

Then the questions & discussion centered around how their systems reacted to loss of water flow and how & when their pump ran…Some of it was info that was a bit misleading for others depending on what type of system & control they have…So I posted these two posts below to try to help out…It's good info so why not share it here on my own site too ?

• My first post…

I'm glad the Chief Alen sorted out his pump problem but I thought I could add a bit of info to the thread…

If it is a single A/C system installed (not more than one compressor or control) there will be no need for a pump relay.

If it is a older Cruisair 3 knob type cabin control…Yes the pump will run with the fan and not cycle with the compressor unless it has been changed or is a newer digital control.

The thought back in those days was that when wired to the fan circuit…The owner could verify flow over the side before switching the system to run…They have since re-thought, and have changed that practice/wiring…

Yes it can also be wired to the compressor circuit so that it will cycle with the compressor…
It can be a simple change, but first you need to find where the pump wire runs to…Some run to the unit, and others are run to the terminal strip that should be within 3 feet of the cabin control….You then just remove the black pump wire from under the red terminal (Cruisair) and reconnect it along with the purple compressor wire…The pump should then cycle with the t-stat/compressor.

The other thing to watch for with the March Mag drive pumps is if they are run dry for very long…They will heat up enough to melt the plastic on the back side of the impeller around the ceramic shaft, and also the impeller mating surface of the plastic head itself…
The impeller may appear to rotate fine when the cover is removed but it won't when the pressure of the cover is against the impeller with the cover installed…If this is the case…The housing & impeller can be replaced, or you can also get the complete head without having to replace the whole pump.

Steve~

• Then another gentleman posted…

“I guess I must have the ideal system. If the water flow is disrupted on mine…the breaker trips.”

• My reply…

That is a good thing…But not actually a function of design of the A/C system or control.

I'll try to explain…

Most Marine A/C units with manual cabin controls have what is called a “Line Voltage” automatic reset high pressure switch (meaning it is actually carrying the compressor current) that trips around 425 psi, but then resets itself at around 325 psi…

Mermaid was one exception…They had/have a Manual reset Hi PS Switch with a push to reset button…Anyway…

Normal system operating high side pressure is somewhere between 200-250 psi depending on water flow & the temp of that seawater…

Also…In a Normal startup (system has been idle for a few minutes) the low & high side pressures will be equal (or very close)
This pressure will depend on ambient air temp but it will not ever be much over 196 psi (that's assuming a 100 degree cabin)and usually much lower.

The compressor has a fairly easy time getting rolling against that kind of pressure….But at where the pressure switch resets (325 psi) it has a much tougher time and thus draws much more amperage (than normal) in trying to re-start against that High pressure…Therefore tripping the breaker…

Units that didn't come with a start relay & capacitor have a harder time starting than ones that did come so equipped…

The ones that came equipped usually will start on lower dock power, and also may re-start at that 325 psi if the breaker is not closely matched to the size system it is powering…

Breakers are most often spec'd for wire size & distance to any given piece of equipment (under normal load conditions) for that equipment…The wire is also sized to be able to carry that projected load.

So you might see…There are trade offs…

Tripping that breaker weakens it a bit every time…Yeah I know…It shouldn't happen that often…And it does protect my A/C & Pump…

But having a unit that did not come with start components can mean the difference of being cool, or not being cool with marginal dock power (Like at a lot of backwoods marinas, and behind many homes) It can also mean a given unit may or may not start on a smaller gen set or inverter with other essentials running…

Tanqueray…I'm not saying your unit does or does not have start components…I'd have to know what you have to know that, but I can also say to everyone that a start kit can be added very easily to most all systems that don't have a relay & capacitor already installed if your situation warrants it…

The reason most manufacturers didn't use them was cost…I can also add that up until a few years ago Cruisair had them on all their units.

Note: The digital controls of Cruisair/Marine Air handle Hi/Ps much differently than manual controls….But that's another post…

Edit Note: Since the time of this original post, Dometic Cruisair/Marine Air has come out with a patented SmartStart that far out performs a standard hard start kit, or even a real start capacitor/relay…I should also add that I have personally installed them and they really do live up to the claims.  

We offer them in our store…Just click on the link below to see it, and it’s info…There is even a video…

http://marine-ac.com/2010/11/0…..-assist-2/

Steve~

These two-stage systems use circulated water as a heat transfer medium. The warmed or cooled fluid is piped through a closed loop from the tempering unit in the engine room to any number of air handling units throughout the boat.

Dometic’s unique reverse-cycle design provides very efficient heating, even in relatively cold seawater temperatures, in many cases eliminating the need for separate heating systems.

Dometic offers a complete line of single-compressor and staged multi-compressor systems from 1.5 tons up, utilizing state-of-the-art compact modular tempering units.

We offer local Service & Sales here in the Tampa Bay / West Coast Florida area…

We also offer help on the forum http://marine-ac.com/forum/ with any troubles you might be having or not understand…Just drop us a line or two. Or just Contact Steve here…

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CoolBreeze’s two-stage operation is totally automatic based on two user-defined set points, and can easily be installed on boats of all types and sizes. It is available as factory-installed OEM equipment and it can be retrofitted onto existing boats as an aftermarket product. CoolBreeze uses
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