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Can't cool boat down
January 9, 2010
1:10 pm
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Steve Pooler
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Forum Posts: 1127
Member Since:
November 12, 2008
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Sand Dollar said:

Thanks for the prompt reply! I'm really liking this site.

I located the unit at the low point in the cabin of the boat. On an F32 the salon is up and you go down 3 steps into the galley, dinette, head, and V birth. The unit is installed under the lower station across from the galley, and there is plenty of room for air to circulate in the compartment.

Originally the ducts were set up with one going to the V birth, another in the dinette, and one in the salon, exiting about half way from the floor & ceiling on the stb. side. Quickly saw that this was not working, so I re routed the duct form the dinette to the floor in the salon under the lower station blowing out into the salon. Both air flows seem to get to the ceiling, but still can't keep up.

In any number of conversations with Flagship, they say that the unit is working fine because the difference in the room temp, and the cold air discharge is 15 to 20 degrees.

The Matsushita compressor gets very hot, almost too hot to touch,it's the canister attached to the compressor that ices up. I have questioned them as to whether this unit is undersized also, and if it was charged fully at the factory. Thy are cute, saying that if someone other than Flagship touches the unit it voids the guaranty, and I need to spend $125 to send it to them. They say that I undersized the unit, I say nearly 3,000 F 32's were built over 20 years using 16k split system units with no complaints.

I have never had AC on a boat before, so I'm not knowledgeable as to what to look for

Finally I have re routed all three ducts to blowing in the salon, still no luck.

Comments by others have been from the unit needs a charge (brand new unit?)

The old window tint is causing heat absorbtion (considering 3M reflective tint replacement)

The black sunbrella windshield bra in absorbing heat.

All of these seem to be somewhat true, but not sure that they are the cause.

Other AC units on F 32's (not Flagship) have a much colder air output more like 40 degrees, where this unit seems to start hot 60 degrees, and slowly cool down.

What next?

Thanks


First…I would not necessarily be concerned with the compressor being hot…It's the nature of the Rotary type in that the shell is the discharge canister (hot gas)

Older piston type compressors ran at room temp to slightly warm.

Second…All units do not start out cool…It's not how A/C works…Flagship is correct on the 15 to 20 degree exchange although I would debate that it should be 15 to 18 degrees…If it's more than 18 degrees then you have a air flow restriction/problem…They may say 20 degrees to cover themselves with the lack of flow three 4″ ducts provide…

To explain further using the 15 degree figure…If it's 90 degrees in the cabin you should only expect 75 degree discharge…As the cabin cools that differential is maintained and now when the cabin is 80 degrees you should expect 65 degree discharge…and so on…

A 40 degree discharge would indicate that the evaporator coil is around 25 degrees and of course will freeze the humidity in the air that is passing over it thus blocking more air flow & compounding the problem…A 25 degree coil would be more for refrigeration applications than A/C.

Also…Colder air discharge does not necessarily mean the unit is performing better because if it can't exchange that air up to design parameters…Say 550 CFM of air exchange for 16K…Then you are not removing the the rated amount of heat…Your just blowing colder air out…and removing less heat… 

Most all R-22 A/C systems are designed around this differential…even at home…

If in fact your unit is operating within the 15 to 18 degree parameter…Then it is doing all that it can do…

One thing I might look for is if in it's present location…Is it sucking hot air from somewhere else like the bilge, thus adding heat load…This would make the differential lower (below 15 degrees)…So when taking your TD measurement…Be sure your thermometer is right in front of the evaporator coil and not out in the room.

Without knowing operating pressures at a given cabin & water temp…It's going to be hard to speculate much further, but I still say your comment about icing after awhile points to lack of air flow…But that should show in your TD measurements as a High TD (above 18 degrees)

Loss of refrigerant is another story…But a simple test is to feel the tubing as it exits the evaporator on it's way back to the compressor after about 5 mins of operation…It should be Beer Can Cold & sweating…but not frosty…Frosty means loss of refrigerant or as we already said…Lack of air flow…Beer Can Cold at that point is usually a pretty good indication that the system is fully charged.

Steve~

January 9, 2010
11:44 am
Sand Dollar
Guest
Guests

Thanks for the prompt reply! I'm really liking this site.

I located the unit at the low point in the cabin of the boat. On an F32 the salon is up and you go down 3 steps into the galley, dinette, head, and V birth. The unit is installed under the lower station across from the galley, and there is plenty of room for air to circulate in the compartment.

Originally the ducts were set up with one going to the V birth, another in the dinette, and one in the salon, exiting about half way from the floor & ceiling on the stb. side. Quickly saw that this was not working, so I re routed the duct form the dinette to the floor in the salon under the lower station blowing out into the salon. Both air flows seem to get to the ceiling, but still can't keep up.

In any number of conversations with Flagship, they say that the unit is working fine because the difference in the room temp, and the cold air discharge is 15 to 20 degrees.

The Matsushita compressor gets very hot, almost too hot to touch,it's the canister attached to the compressor that ices up. I have questioned them as to whether this unit is undersized also, and if it was charged fully at the factory. Thy are cute, saying that if someone other than Flagship touches the unit it voids the guaranty, and I need to spend $125 to send it to them. They say that I undersized the unit, I say nearly 3,000 F 32's were built over 20 years using 16k split system units with no complaints.

I have never had AC on a boat before, so I'm not knowledgeable as to what to look for

Finally I have re routed all three ducts to blowing in the salon, still no luck.

Comments by others have been from the unit needs a charge (brand new unit?)

The old window tint is causing heat absorbtion (considering 3M reflective tint replacement)

The black sunbrella windshield bra in absorbing heat.

All of these seem to be somewhat true, but not sure that they are the cause.

Other AC units on F 32's (not Flagship) have a much colder air output more like 40 degrees, where this unit seems to start hot 60 degrees, and slowly cool down.

What next?

Thanks

January 9, 2010
10:13 am
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Steve Pooler
Admin
Forum Posts: 1127
Member Since:
November 12, 2008
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Greetings & Welcome Sand Dollar~

I was just over at the Flagship site looking at the 16.5K package to know what we're dealing with...

What I would ask is...Where are the three 4" discharges run to ?...Are they all in the main cabin or is it just one or two ?

Where do they blow out ?...Up high, or down on the deck ? (cold air falls)

From your description of icing I would first look at air flow...Specifically lack of...

I can say that Cruisair or Marine Air would never recommend three 4" discharges on a 16.5K unit (maybe for a 12K)...It's just not enough area to allow the needed amount of flow for the BTU...But that's what Flagship offers for that unit in their kit...So unless they get this complaint all the time (icing) it must be enough for that unit (maybe it's not really 16.5K ?)

Typically a 16K unit would use 7" duct from the blower to a splitter...Then that splitter should have a 6" outlet for the large cabin and then maybe a 5" outlet that could then again be split two ways for smaller cabins.

You might first check the ducting for restrictions (as in kinks) or leaks that might cause cold air to recirculate back into the return air...

You could also remove the duct (and splitter box) to see if it ices that way...Make sure it's not blowing back on itself for the test...

Also...You might want to read this post about air flow & icing to get a better idea of what I'm getting at here... /forum/troubleshooting/ac-system-ices-up/ 

At the very least I would guess you need to do some ducting improvement...

Steve~

January 8, 2010
11:24 pm
Sand Dollar
Guest
Guests

Hi all

I'm a newbie that just discovered this site, and I'm looking forward to learning and hearing what you all have to say. Boat in RI, and in the summer it gets real hot sometimes with temps in the mid to high 80's to 90 for periods.

Have a Trojan 32' with a Flagship 16.5k ac electronic control (robertshaw?)& three 4" outlets, Salon windows have tint, and curtains, windshield has a black bra. Problem is that when the temperature is in the Mid 80's the unit cannot cool the boat, can't keep up, and never shuts off. Eventually the canister on the compressor has ice form on it and I have to shut off the unit to thaw it out. As the temp goes up outside, the temp in the boat also rises until I have to give up and open the windows to get a breeze. everything seems to be working fine, just can't keep up.

Basically all 32' Trojans have the same size A/C unit,(not Flagship though) and they don't seem to have a problem. The unit is new, only two years old. Flagship is useless,

Any thoughts on what the problem and fix might be?

Thanks!