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~

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Due to new 2010 EPA regulations regarding the phase out of our long used R-22 A/C refrigerant systems…

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.

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.

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…

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…Hopefully we will get more info at the Miami show next month…

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.

Who knows…We may end up not having split systems under 16K available in the future…

Steve~

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It’s the time of year that we all need heat…Even here in Florida this year…Global Warming My…?

Anyway…

Below is a post I answered in the Hatteras Owners Forum, and it seems to be a subject that many of you all are searching for answers to this time of year…It also applies to cooling in the summer, but is mostly about system Icing & the causes…I’m also going to  link this article to a Forum post here on this site so that anyone that may have questions or need further clarifications may ask away there… 

Quote:

Originally Posted by SeaWhisper Don’t mean to jump on this thread ! Steve if your following, I have been experiencing an a/c problem also but on the heat mode side. I have 4 A/C system with one giving me a icing problem on the compressor unit. Starting on the suction side and loop tubing of the remote unit is freezing up with heavy ice. The compressor is hot to touch. Check air handling unit… High fan, clean filter giving out warm air. Water flow thru compressor unit and 3 other unit’s has a high flow rate. Water temp is around low 50’s. I can switch the unit to cool mode and it will melt the ice of the compressor unit… Your thoughts on what may be causes the heavy icing…. Low freon? Unit is a 16,000 btu maybe 2 years old, with smxir controls. Thanks…

Mike~

First I need to clarify what you mean by…”Starting on the suction side and loop tubing of the remote unit is freezing up with heavy ice. ”

Do you mean the water coil ?

If so…Then it would be hard to know that the unit in question is actually getting proper water flow by looking over the side…Since all the 53 MY’s I can remember, had a single overboard discharge fitting with a 4 unit manifold attached.
You would need to remove the hose for the unit in question from that overboard manifold, and either let it run into the bilge or a bucket…It’s not uncommon to have a blockage or some kind of growth restricting one unit’s seawater flow….This can cause what you describe.

Yes the compressor will run a bit hotter in the heat mode…

Icing is always an indication of Low Pressure…What is causing that low pressure is key to solving it…Duh ?

First…Pressure & Temp correspond with refrigerants…The lower the pressure of the refrigerant…The lower the temp of that refrigerant…

If you place a jug of refrigerant in a room and connect a pressure gauge to it…then let it get to room temp by just sitting there…
With a pressure temp chart for that particular refrigerant (in this case R-22) you can tell the temp of the room by the pressure shown on the pressure gauge…If that room is 32*…The gauge will read somewhere around 56-58 psi. (the chart I have with me right now jumps from 30 to 35 degrees so I’m guessing a bit but that’s close)

When running in heat mode the water coil is the evaporator and is on the low side of the system (cold part) the air handler is the high side (hot part)

In cooling they switch duties because the Reversing Valve will send the refrigerant around the system in the opposite direction.

Thus a “Reverse Cycle” system also known as a Heat Pump…

Back to what I started saying about Icing being an indication of low pressure…

Air Conditioning is what we call a High Temp System…Designed evaporator temps above freezing (32*)…Therefore “Low Pressure” in a R-22 A/C system is defined as below that 58-56 psi I mentioned earlier…Which will cause icing by freezing any moisture that is in contact with that surface thus blocking flow…Either Air or Water (depending on which mode you are running in)

A/C (and refrigeration) is all about moving or removing heat, since there is no such thing as Cold…Just the absence of Heat…Making it feel Cold…

In the heat mode you are picking up heat from the water with the water coil and dumping it into the cabin, using the refrigerant as the truck to carry it, and the fan in the cabin to dump it out of the truck…Cooling is just the opposite, and uses the Cabin coil to load the truck with heat, and the water to dump it out.

Any restriction…Ice, Air Flow, Water flow etc…Will affect how much of that heat can be picked up by a designed size coil in both the heat & or cool modes.
This is why icing is not good with A/C…Refrigeration is another story since it usually has defrost timers & heaters…A/C does not, or should not need due to the temp range it was designed to operate in…with Above 32* evaporators.

The biggest problem with icing the water coil in heat mode is the danger of freezing the seawater in that coil & blocking flow completely…Thus causing expansion, and a rupture of that water coil…
This will allow the freon to leak out into the water, and the water to leak into the freon circuit, effectively ruining the complete system by pumping that seawater throughout the system with the compressor.

Low amount of freon causing icing ?…Yes this can also act the same as flow restriction…

Either way…Low freon, or Flow restriction…If the truck/s can’t get full for every circuit (restriction) or don’t start full (low freon) you are not moving the designed amount of heat that the system was made to transfer…Both of which will cause Low Pressure on the on the suspension of the trucks…

Back to:
Low pressure = Low temp = Icing…
Icing = Restriction = Less Flow = Lower Pressure…etc…etc…
One compounds another.

I know that was long guys…But I hope it helps in a lot of these questions…I know it can be confusing, or boring to read but it’s all part of understanding what is happening…
I tried to put it into the easiest layman’s terms I could think of…If you have any questions on what I said just ask & I will try to clear them up.

Steve~

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Below is another copy of a  post I made in the Meridian Owners Forum…If you want the full jest…http://www.meridianyachtowners.com/forum/forums/thread-view.asp?tid=1957&posts=15#M18424 

Hi Mark…Don’t know if you are still watching this thread, or if you have seen my thread over in the “Introduce Yourself” forum but here’s my take…

It seems that when the system was flushed, that it was flushed just well enough to break loose some stuff…Now it is floating around in the hoses and randomly blocking flow where it now lodges from time to time…
Once the pump shuts off the water drains back, and with it the loose stuff moves…Only to lodge again maybe somewhere else when the pump starts again…

If the water flow does not look right to you (and you obviously have been watching it since new) then it is not right, and will continue to get worse…Changing the pump will not fix a thing unless the pump had a problem…It can only pump water thru unrestricted passages, and that water it can pump will re-direct to the un-restricted passages…Like said…Path of least resistance.

From descriptions here & in the thread I started…It seems the 459 has what I would call a odd or improper A/C plumbing/pump setup…

This happens sometimes with boat builders…Generally speaking…In my experience the only way to get them to make a change in a poor setup is for enough customers to have a problem and complain…No amount of prodding from us A/C guys ever seems to help in effecting that change…It’s a shame too because we are the ones dealing with this stuff everyday…They deal with building boats everyday…

So what is the fix ?…Well marine growth will always be a problem but there are a few things that can be done to help…

Over the years the A/C systems that boat builders install have gravitated to the Self Contained all in one units as opposed to the Split/Remote systems that most utilised for years…They don’t need guys with refrigerant certification to install or buy these All in One units…They are easier to install, and freon leaks in connections of copper tubing line runs are no longer something they need to worry about warrantying….All they have to do now is run power, water hoses from the pump, and duct…

The problem with this is the water runs are now much further than when the “Central” type systems were installed all in one location close to the pump…Back then we had very little growth problems (just scale buildup in condensers that was easy to remove) and flow was much easier to plan & maintain…

What I have found since this change is that the further, and or higher you pump seawater…The more problems you will have with growth, and it has also created the problems I describe below with using larger pumps…

Directing a pumps flow to units of varying distance & height for even flow to each…Is a challenge to say the least !
Generally their answer is to install an oversized pump in an attempt to brute force flow…

No I have not seen a 459 but it has been described as having two units on the bridge and 2 down below…I don’t care how they manifold this setup…It still going to be very hard to get the proper flow to each unit, and the least little restriction can and will upset any kind of balance they have designed into that system…The Pump has to overcome the height (Head) it needs to pump to the units on the bridge so it likely has been over sized just to do that with enough volume for those units…The remaining water can then supply the lower units…

Over sized pumps are never really the best answer over time (though it may be cheaper for them) because a over sized pump attempting to pump thru say four 5/8″ condensers (in this case) is (even when the system is clean) likely not pumping it’s rated flow which will cause it’s impeller to cavitate…This causes cavitation burns to the bronze impeller & pump housing…Thus causing premature pump head failure.

Again having not seen the install…My answer would be to install two pumps…One for the upper units, and one for the lower units…
They both could then be sized for the job presented, the systems & pumps would be much happier with less overall maintenance.

Steve~

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Copy of recent e-mail to Marine AC.com…

Hi Steve, love your web site – lots of great info. ! Our company does a lot of yacht maintenance / mechanical preventive maintenance type stuff here in Wilmington, N.C. – my question is, do you have an opinion concerning back flushing the sea water lines on marine air conditioning systems ? That is, do you think there is any benefit to occasionally (2 or 3 times per season), removing the water discharge hose and connecting a dockside water hose to the unit and pumping water backwards through the system. I have talked with some individuals who believe that doing so helps to remove/reduce the amount of marine growth in the coils and hoses, eliminating the need for or reducing the frequency of acid cleaning. Any advice or opinions you can offer would be greatly appreciated

Bill

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Recently I was on a boating message board and came across a discussion about pumps and some troubles folks had experienced.

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…

Steve~

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We have touched on seawater cooling and lack of…Now what about if you have a intermittent problem, or the pump won’t start at all ?

In boats with multiple systems running on one seawater pump there is most likely a Pump Relay to receive a signal from each system to tell the pump it needs to run…That is unless it has been bypassed and the pump runs 24/7 from the breaker ( I see this done fairly often)

Lets start with the breaker in the main panel…Most are labeled A/C pump or similar…Some boats may have the pump breaker tied in with one of the A/C system breakers (Ocean Yachts for one used to connect the pump to the Main Salon A/C Breaker) but most should have a stand alone breaker…

The breaker feeds the pump relay and carries the load of the pump only…this power can be either 115 or 230 volts depending on the pump installed…

The individual systems aboard will then have their own breaker that powers/protects each A/C system & it’s wiring…These can also be 115 or 230v supplied…The reason I describe this is that some boats have a mixture of system voltages…Hatteras for example, always supplied one of the smaller systems as 115v and the rest as 230v…They would then install a 115v pump so that if all that is available on the dock is 115v, you can still have at least one cabin of A/C for crew/kids while the owners/parents go to the resort for the night without starting the generator (Well this has always been my assumption and nowadays most docks will have 230v anyway)

There have been many types of pump relays over the years…Some with mechanical relays (in previous times) but most for many years have been “ignition protected” solid state designs…Here are the most current & popular versions that I see, and a few of the most common failures…

Some were for built for only 2 systems and could not be expanded for more…Marine Air still makes a 2 unit relay (2PRP) but they also offer one that can handle up to 6 systems (6PRP) on one pump…you don’t have to utilise all if you have say 3 or 4 systems, and it actually gives you spare circuits to re-connect a system to if the one it’s connected to were to fail (that is if you have the 6PRP)…These relays are just a metal box with a single circuit board and all needed components on that board…Other than complete board replacement, there are no repair parts available/needed.

Cruisair went about it a bit differently…Years ago they offered one pump relay that could handle up to 8 systems on one pump (PR8X) and it came with individualised components, all of which could be replaced…The “Circuit Board” & separate” Triac” (solid state relay that switches & carries the pump current) came with the box…You could then add “Triggers” for as many units as needed, and you could also select trigger voltage (115 or 230) to match the system voltage feeding it….These triggers of course were/are replaceable with two screws & two plug on wires in the event of failure…

The only problem with this Pump Relay was the box was a bit large for smaller areas in boats that may only need 2 or three triggers…So they built a smaller box that can house all the same basic components (circuit board & triac) but only has room for up to 3 triggers…It can also be purchased with the triggers pre-installed for either 2 or 3 systems (PR3X-?) The question mark would be the number of triggers pre-installed (either 2 or 3)…They still offer the PR8X, and it can also now be purchased with triggers pre-installed but either box is not hard to add/install trigger/s in…

The main purpose of these relays is to run the pump when a system is calling for it…That means any system that is running a compressor (Some with just fan, IE: older Three knob cabin control-ed systems)…But if a trigger circuit in either type box fails (Marine Air, Cruisair, or any manufacturer) the pump may run for one or more systems…But not for the one that has the failed trigger circuit…

This sometimes causes confusion because if any one of the good triggers starts the pump…All systems that are connected to that pump will get seawater, and thus run normally….

However if the system/s with the good trigger/s cycle off, and the one with the bad trigger either continues to run, or starts up with the others off…It may/should shut down randomly with a fault code on the cabin display.

The easiest thing to do to verify if you have a problem is to test run each system” individually” to verify if you are pumping water with just that system running…If you find a system that won’t start the pump, the trigger circuit (in the pump relay) for that system has likely failed.

Also if the pump won’t run at all…These Pump Relays all have fuses installed either inside the box (Newer automotive type pull out fuse) or in a typical twist type fuse holder mounted thru the box ( It’s how Ocean Yachts gets away with running the pump on the salon breaker)…This should be one of the first things to check….If the fuse is blown, and then blows again after replacement, it’s time to look at the pump & associated wiring for shorts or bad/wet connections.

These Pumps & Relays are pretty easy to troubleshoot with a volt meter and a bit of common sense, but going into that here would be a bit long for all models…If you want help with your individual installation, I’ll be more that happy to answer in the forum troubleshooting section http://marine-ac.com/forum/troubleshooting/

Just let me know what you have and we can solve it there together…If you have another brand of equipment or model of pump relay, it’s likely that I have seen a few…We can figure those out together too…

Steve~

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I notice from the Google searches…That A/C System Icing is a search done often..

Though there can be many reasons for system icing…There are a few that the DIY boater can rule out before calling the service guy ( I can discuss other reasons in the forum but here are a few of the basic answers)

• Direct Expansion A/C (as opposed to Chilled Water) systems rely heavily on Air Flow across the evaporator coil in order to pick up the designed amount of heat the system was engineered to remove (BTU) and any loss of that designed air flow can cause the system to Ice.

Regardless of freon charge (explained later) the system must first and foremost have the correct amount of air flow…So air flow should be the first thing to check…Below are some reasons for reduced air flow…

• Dirty or clogged Return Air Filters…Some systems may have two filters installed…One at the Return grill, and a second that shipped with the unit on the evaporator fins ( folks tend to forget this one, or never knew it was there in the first place)
• Dirty or clogged evaporator coil/s due to not cleaning, or No/Poor return air filters installed.
• Fan Speed Adjusted Too Low (Sometimes done to attain a quiet blower)
• Undersized Return or Supply Ducting for the BTU System installed…This was the installers responsibility to size correctly, but all too often there is not sufficient space for where they want to run to size it properly…Thus a problem for the systems life, which is most always shortened dramatically from this practice…They should find another way, or reduce the size of the system to match the installation…Blowers can only move rated flow thru the proper sized duct.

 Another reason which sometimes is overlooked…

• Very Cold Cabin…The colder the cabin…The less heat there is to pick up…Thus more Air Flow is needed to increase the amount of heat (that’s now not there) being picked up…A/C systems are called “High Temp” systems…they are designed to do exactly as the name implies…Air Condition…Not Refrigerate…That’s what Refrigerators & Freezers are designed to do…Your A/C system is not designed to cool much below 68 degrees F…Though it will try to do so if you ask it…
• Most of the newer Digital Cabin Controls have algorithms to “help” with this by shutting off the compressor for short periods until the desired room setpoint is attained, but they are not defrost cycles with coil heaters like you might find in a system designed to run at lower temps. 

Last but Not least is…

• Low Refrigerant Charge causes Icing…You Ask Huh ???…Why would low freon cause it to ice ?…I thought the more freon the colder…Not So with refrigerants…I’ll try to explain briefly…

Pressure & Temperature Automatically Correspond with Refrigerants…The Lower the Pressure…The Lower the Temperature of the refrigerant ( and Vise Verse) Regardless of how much is in there…I’ll leave it at that for now but can explain further in another article, or in the forum if requested.

• The question here is…Why is the system low on freon ???

These systems are sealed, and should not require seasonal charging, like automotive systems that tend to leak because they have rubber hoses, o-rings & compressor shaft seals…These systems are all copper tubing, with soldered & mechanical flare joints.

• Did someone let out freon because the unit was running high pressure ? (usually an indication of  loss of seawater flow, or a dirty condenser)
• Has the system started leaking due to a poor connection (Flare or otherwise) or maybe electrolysis eating away at solder joints ?

If So…Then the leak needs to be located & repaired to save burning up the compressor…The compressor is the heart of the system, it’s expensive, and relies on the proper amount of refrigerant return to stay cool…It will run Very Hot without enough Freon return regardless of seawater flow…and even if the system (air handler or tubing) is icing…The compressor will run hot from that lack of freon.

Hope this helps answer a few questions, but if not…Or if it creates more…Drop me a line (preferably in the forum so that others can benefit as well)  Always glad to answer.

Steve~

Everyone can access it, but registration is required to post…I don’t share that info…You can find the link at the top of any of Marine -AC.com’s pages…Just click on “Forum”…Or you can click on this http://marine-ac.com/forum/

We are slowly growing, and I seem to notice from the searches what folks do to find Marine-A/C.com. I also see that many are either not finding the forum and/or asking their questions…

So again I would like to offer the suggestion that you “Check It Out”

Please don’t be afraid to ask anything you would search for answers for in any search engine…In my experience there are Not a lot of sites (if any) offering personal answers out there for the Marine A/C & Refrigeration field, and it’s one of the main reasons I have offered this forum section.

Join in with questions and comments…Hopefully together we can make this a one stop source for your marine a/c info,  experiences & troubleshooting.

I personally look forward to interacting with everyone…

Note: If you do decide to register & participate…Please input your location in the space provided as it helps to know your climate without having to ask.

Steve~

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Since they are not like home A/C controls…Sometimes marine A/C controls are misunderstood…Hope this can clear up some misconceptions…

They do provide the same function as in home systems as they are designed to keep the temperature in the cabin/room at a selected temp within a few degrees…

But different than Home…They can (and most do nowadays) offer more/different features than we use at home depending on the type of marine control that is installed…We can cover some of those features here but first we need to define which type of control is installed…Although there have been and are many types and models of controls with several variations…

Lets first describe the most popular two main types…

Manual Controls…

The old standby that has been around for many years is the three knob manual control (non digital) it has/had 3 control knobs each with a different function & was/is available in either a vertical or horizontal, rectangular form factor…

The typical function of each knob was as follows…

• The first knob was a function knob with Off, Start (sometimes labeled Fan) and Run positions…

The functions of each position were pretty much self explanatory except that the Start/Fan position ran the fan but also started the seawater pump so that you could look over the side of the boat to verify it was pumping water before selecting Run.

The Run position sent power thru the thermostat which then would decide whether to start the compressor in the cool, or heat mode depending on cabin temp, and the position of the thermostat knob…(more on that in a minute)

• The second knob was a Variable Fan Speed control (not usually available at home)

It was useful at night for lowering blower noise to watch TV etc…(how low was low was adjustable but the control needed to be removed to adjust this parameter with a small screwdriver)

• The third knob was the thermostat…

This was the most misunderstood function of this control because it had no temp numbers (It was also the hardest to explain to folks)  Most would just crank it to it’s coldest setting thinking that the further they turned it…The colder the air would come out…That’s true in a way, but it’s not a function of the control, and A/C does not work that way…I will try to explain…

Regardless of control setting or type…All R-22 A/C systems work on a 15 to 18 degree temp exchange design…Meaning that the air coming out of the discharge grill should be 15 to 18 degrees colder than what is going into the return air grill (if it’s more, or less than that, there is likely a problem with the system or installation)

So if it’s 90 degrees in the space being cooled…don’t expect much colder than 75-72 degree air coming out the discharge with any R-22 A/C system…But as the room/cabin cools, that exchange is maintained, and the air continues to come out colder by 15 to 18 degrees of what goes in….Lower room temp=lower discharge air temp.

The thermostat tells the compressor when to run or not run, and energizes the reversing valve when reverse cycle heat is needed to maintain cabin temp of the setting on the dial (position of the arrow)…Generally speaking…A properly calibrated t-stat set with the arrow pointed vertical should maintain around 70-74 degrees cabin temp…Anything to the right is a colder cabin, and to the left of vertical is warmer…The T-Stat will allow the compressor to run until the cabin gets to the selected temp (on the knob) at which point it cuts power to the compressor until the cabin either warms or cools a few degrees, at which point it then again sends power back to the compressor/reversing valve as needed to bring the cabin back to selected temp.

These controls offered very little in system protection and thus it was not advisable to run the A/C system unattended for very long.

Digital Controls…

Started hitting the market in the mid 80’s…They at first like any new product, had a few weaknesses and thus some early problems, but as they matured they have now become the standard, and are very reliable…

 They also allow the marine A/C manufacturers to offer extended warranty periods when installed with new equipment because of the system fault protection/shutdown features they provide, along with the many other benefits/features…I can’t count the compressors & pumps they have saved for my customers…Many of them don’t realize it either, but they do help immensely…

The features & protections offered by these newer microprocessor based cabin/system controls are likely too many to mention here but I will list some of the more important below…

Protection:

• High Pressure Shutdown…Loss of Seawater flow…This can save a compressor and or seawater pump failure, from running without water. (Did you check that strainer & thru hull ?)
• Low Pressure Shutdown…Loss of Freon or a dirty air filter…Can also save a compressor….
• Low AC power Shutdown…One of the worst things for a compressor is low voltage.
• Seawater Pump shuts off with compressor (on single system boats) so that pump can be saved from no water burnout of pump head (this will also protect pump if only one system is run while away on multi system boats)
• Programmable Time Delays…So that multiple systems don’t all start at once when shifting from Shore to Gen or vise verse causing tripped breakers and/or heavy surges.

Features:

• Digital Display of Setpoint (Temp you want the cabin to be) & Actual Temp of that cabin.
• Much more accurate temp control. (when compared to the 3 knob control or others)
• Automatic Fan Speed control…Fan speed can be controlled by how far away you are from setpoint…Manual speed is also an option so that if you don’t want it to change it won’t.
• Ability to program Continuous or Intermittent Fan (Like the Auto fan feature at home)
• Humidity Control program…System can be activated to remove humidity only while away..This greatly reduces run time while keeping mold out (you probably won’t find this feature in most home controls)
• Some have IR remote control availability/operation.
• Some have networking ability…So that they can all be linked and controlled from a central (keypad) location, or from any individual control location aboard.

These are some of the most important features, but the controls are fully programmable for many more user adjustable functions (depending on model)

If you have one or more of these digital controls…The not so funny thing I find here in West Central Fl…Is that about 95% of the boats I go on have never had the digital controls setup for the boat/installation…

The A/C manufacturer has a set of Default settings they ship the controls programmed with…These are just that…Defaults that the manufacturer feels that all systems should operate safely with once installed…It’s generally thought that it’s the installers responsibility to perform the calibration…Unfortunately it’s likely that the boat builder or original installer did not do this for many reasons…One of which might be they don’t know about them ?…

Anyway as I said…Most of the boats I go on still have the factory defaults set in the controls, and a lot of these boats are many years old…They are by no means the best settings for each installation or system, and again if you have these controls, you may find that you will enjoy your system/s much more if you get your trusty A/C guy out to to go thru them…Or get the manual out yourself to take a look….

Many also ask if the newer digital controls can be retrofit to take the place of others…Yes they can…I have installed them on just about every application of marine A/C made in the last 40 years…Yeah…That’s longer than I have been working on marine A/C but I do/have seen some old stuff still in operation…and Usually after we install one on a boat and calibrate it…The owner almost always wants another…

Thanks for reading, and Comments are always welcome…

Steve~