You must be logged in to post Login Register


Register? | Lost Your Password?

Search Forums:


 






Minimum search word length is 3 characters – Maximum search word length is 84 characters
Wildcard Usage:
*  matches any number of characters    %  matches exactly one character


Forum
Marine-AC Topics
Troubleshooting
A/C not as cold

A/C not as cold
Print this Topic
Page: 1  2     
Post
Admin

Steve Pooler

posts 1127

11:01 am July 15, 2011
Print this Post
11
0

One thing to note when removing the duct…Do it with the fan running on High…

See if you notice a major drop in fan speed when removed vs connected  Wink

Still want you to check TD with it removed though…

 

Steve~
Member

biohazard

posts 17

11:28 am July 16, 2011
Print this Post
12
0

Post edited 12:03 am – July 18, 2011 by

Alright I did some testing.  

 

The intake to the exhaust was around 17-19 degrees with an IR gun.  I forgot to grab the thermometer so today I will go back and retest. The air pressure felt good and  was blowing decently. It was only about 73 degrees outside so it wasnt a very good test.  Today will be much hotter and I can really put it threw some testing.  I could not tell if the blower slowed down when I hooked it back to the ducting, 

 

I will grab measurements today also, here are some pictures of the ducting.

The 1st picture is the duct off the fan.  On the left there is a small tube that runs a/c to the head, inside the main box theres a piece of aluminum that directs a portion of the air that way.  That vent is fairly useless so I removed the tube and put tape over the hole for now to test with.

http://i405.photobucket.com/albums/pp133/bionetworks/IMG_20110715_200400.jpg

 

This is where the tube goes from the first juntion box.  It splits here to a vent above it for the cabin and forward berth, and another tube goes along the side of the boat to the aft cabin.

http://i405.photobucket.com/albums/pp133/bionetworks/IMG_20110715_200408.jpg

 

Insulation pulled back you can see the actual size of the tube, I am not sure what it is though I will try to measure today.

http://i405.photobucket.com/albums/pp133/bionetworks/IMG_20110715_200417.jpg
Admin

Steve Pooler

posts 1127

12:11 pm July 16, 2011
Print this Post
13
0

If the ductwork is restricted the blower will SLOW DOWN when duct is removed & SPEED UP when connected back…

I do need those duct measurements and DO NOT block anything off while testing or otherwise…

Doing so defeats the purpose of the test…We want to test the ductwork as it is to see if it was the problem…

Later we may remove branches to isolate/identify the problem run…

 

Steve~
Member

biohazard

posts 17

2:15 pm July 16, 2011
Print this Post
14
0

Steve,

 

I know it will slow down or speed up, I am not noticing anything.  The blower is very loud and hard to tell if it was so I would just say its not slowing down. Not significantly enough to make a difference I can tell at least.

 

I blocked the ducts after taking temp readings, just to see if that improved airflow.   I have unblocked the tube since then.  

 

Measurements are as follows.  6'' fan exhaust to 6'' inlet on 1st junction box.  Splits to 2'' tube and 6'' tube going to 2nd juntion box.  6'' tube on 2nd junction box spluts to 5'' tube going up to cabin vents and 3 1/2'' – 4'' tube going to aft cabin.  

 

The 5'' tube going to the cabin vents MAY go to anther juntion box because there are 2 cabin vents back to back on the bulkhead the vents are on.  One vent is for the forward cabin, the 2nd vent is for the main cabin area  Both have 3 1/2'' – 4''  tubes inside the vents.

 

There is minor leaking in the junction boxes as well.  I cant find my thermometer anywhere, so I am stuck with my IR gun for now.  The unit is running pretty well today, its been running decent ever since I cleaned it but I still have a 20-22 degree difference in the air intake grill and closest vent.
Admin

Steve Pooler

posts 1127

8:13 am July 18, 2011
Print this Post
15
0

Post edited 9:59 am – July 19, 2011 by Steve Pooler

OK Ryan…If it's not slowing or speeding up then it may not be too bad, but without gauges to watch suction pressure when you remove & re-connect duct I can only guess…Pressure will lower with restriction, and as I said will cause icing at lower cabin temps…When the cabin is hot it won't matter as much…More on this in a minute…

From the pictures my guess is it's not flowing as it should/could and here is what I notice…

First off the connection from the unit blower to the first splitter should be 7"…Not 6"…But your connection is so short it may not restrict much….However it really should have 7" feeding the second box…

The second box concerns me too…The 5" should be 6" even if it's later split…The 4" would then be ok…

The restriction starts at the first box with the 6" that should be 7"…

I have also never been a fan (no pun intended) of the box style splitters as you have…They don't promote free flow of air with the square corners, and also don't have adjustable diverters inside that can help you direct flow…

We use/sell Plastic Tee's & Y's that do have adjustable diverters but they also promote the flow of air without the back pressure of dead ends like you have in your first box…There is a certain amount of restriction right out of the blower because it immediately hits a dead end…

You never have told us where you are & the climate you are in, but you have mentioned temps of 73 outside so I can guess you are not down here  Wink  Right now it never gets below 80 at night and we maintain a 85 to 95% humidity…plus we have 90 degree seawater in the marinas…

With that type of heat load down here, your system as it is may never ice, or only do it late at night…We don't usually set our t-stats below maybe 74…

Let me add this…Air Conditioning is what is called a "High Temp" system, and it's designed to remove large amounts of heat, but only down to say 68 degrees cabin temp with good air flow (picking up more heat) without running system suction pressure below 32 degrees…

Much below that 68 degrees cabin temp, we are getting into Refrigeration system parameters that do run their coils below freezing temps (but also have coil defrost heaters)….

Restricting the air flow in a A/C system will tend to cause that coil to get to freezing temps sooner, and thus cause us to raise the thermostat setting to keep the system from icing…

This is why colder air discharge is not better as most folks think….

  • The A/C system that only has 15 degree TD will actually get the cabin colder than the system with 22 degree TD…Before icing occurs….
  • The 15 degree TD is also an indication that the system is actually grabbing more heat than the 22 degree system…
  • The 15 degree system will cool the same cabin quicker than the 22 degree system…
  • And as the cabin temp drops, the same TD is maintained, so the air does come out cooler (in both systems) but the 22 degree system will ice up first because it's coil is colder at any given cabin temp…

Hope that makes sense…Smile

 

Your control (if digital) should have a de-icing feature (look in your manual for how to activate it) but proper ductwork for the job is always better if you want to run down to 68 degrees.

 

Steve~
Member

biohazard

posts 17

12:27 pm July 18, 2011
Print this Post
16
0

Steve,

 

I am in Minnesota near the twin cities. Right now we generally have 80's – 90's at 80-90% humidity.   I nromally set the a/c unit for 74-75 degrees.  The problem I had been having is it would struggle to keep the cabin at 79 – 80 degrees.  Then I noticed the a/c lines would be frozen with ice and performance would get worse.

 

Since cleaning the unit  the lines still condense but they are not freezing now.  I also noticed (this boat is new to me) that the sump for the condensation was not working.  I have fixed that issues over the weekend now so there is not as much moisture in the a/c tray.  I re-blocked the small 2'' line off from the inside of the 1st junction box.  This seems to have helped alot, the cabin is able to cool below 79 degrees. 

 

I think for an end game I am going to remove both junction boxes, install a new insulated 7'' line from the a/c unit, to a Y junction where the 2nd junction box was.  This should greatly improve airflow and while I am at it I will make sure there are no leaks as the unit is seeping cold air at the junctions.  I also did not think square junction boxes were a good idea, just sounds like they will cause issues to me.
Admin

Steve Pooler

posts 1127

3:27 pm July 18, 2011
Print this Post
17
0

I would Guess that since your cleaning you are probably Ok…But that all that I have said still applies…

You don't have anywhere near the heat load that we have down here…

Also your water temps are much cooler so not much load there…

If you want new splitters let me know…They can help !

Steve~
Page: 1  2  
Topic RSS

About the marine-ac.com Forum

Forum Timezone: America/New_York

Most Users Ever Online: 29

Currently Online:
8 Guests

Currently Browsing this Topic:
2 Guests

Forum Stats:

Groups: 5
Forums: 11
Topics: 398
Posts: 2369

Membership:

There are 334 Members
There have been 143 Guests

There are 2 Admins
There is 1 Moderator

Top Posters:

GeorgeH – 47
Angela – 45
z28jimi – 25
MexicoMike – 21
reefgeorge – 21
ThirdHatt – 18
davidwigler – 17
Mr. Dee – 17
biohazard – 17
mixman – 16
Ultimate Indulgence – 15
sabrejocky – 14

Recent New Members: becsvet, adjustrite, blackwatch30, DWB, Raymond, pbrads1021, sizematters, cgeist, TMorse, Iproff, Ernie Jones, Holsum69

Administrators: Steve Pooler (1127 Posts), Scott Pooler (13 Posts)

Moderators: Steve Pooler (1127 Posts)



 
Bookmark and Share