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Filters/Pump Systems Maintenance & Checkup
March 23, 2009
8:45 am
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Steve Pooler
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Forum Posts: 1127
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November 12, 2008
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If it’s yourself doing the service…There are a few things you can do but since you are probably not equipped or trained as an A/C tech…There are of course some limitations…Hopefully I can point out and describe what you can do…And offer a few hints of signs of trouble without tools like gauges etc…

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~