AC Install Help

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Golfman25

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Need help quick. I am starting the install of an AC unit. I currently have a 1/2 inch intake already in the hull. The intall kit came with a 3/4 intake. All openings to the pump are 3/4 except for one -- the hose nipple into the strainer, which is only 1/2 inch. Anyone see any problem with just leaving the 1/2 intake in, instead of using the 3/4 intake? My understanding is once the nipple reduces to 1/2 inch, that is the best flow you'll get to the pump -- so what does it matter if the reduction to 1/2 inch is made at the intake instead. Thanks in adavance.
 
How big is the unit? The 10K on my regal was all 1/2 inch and it did well.

If it were me, I would go with the current intake. My limited fluids experience taught me exactly what you stated. You are going to get no more flow than the smallest hose.
 
Keeping the largest hose size for as long as possible will provide the best flow. Both the orifice sizes and the diameter of any long hose runs will effect flow rates. A system with 1/2 inch orifices at both ends of a 3/4 inch hose will have slightly better flow rates than the same system with a 1/2 inch hose. This is due to the flow resistance from the hose itself.

But I think you should not have any problems with an intake the same size as the strainer inlet.

Mike
 
Go with the 3/4 inch. Intake lines should be as large as possible to keep pressure drop in the system as low as possible. Restricting inlet conditions in any way is NEVER a good idea. Inlets will ALWAYS get smaller due to buildup. Starting out with a 3/4 will make this effect harmless.
 
quote:
Originally posted by OLD HOUSEBOATER

Go with the 3/4 inch. Intake lines should be as large as possible to keep pressure drop in the system as low as possible. Restricting inlet conditions in any way is NEVER a good idea. Inlets will ALWAYS get smaller due to buildup. Starting out with a 3/4 will make this effect harmless.

Click to expand...


I agree OHB, however, he already has a 1/2" in place. He needs to take into account the gained advantage of not disturbing the current thru hull.

Something just crossed my mind. What if the A/C company put the wrong strainer in the kit.

What do the directions say and what does the MFG say about your situation?
 
Usually straight AC units or Reverse Air units are rated for a minimum GPM or GPH flow rate. If 1/2" will do it and the unit isn't that large I guess you could use it. Your logic is correct the smallest fitting will be the restriction point and choke the capacity and efficiency. I have all 3/4" AC hoses with no 1/2" adapters. It is real important to hit the flow rate minimum or you will be replacing expensive components on your once new AC unit. Hoses do and can build up internal crud depending the water you boat in and if the vessel is trailered or stays in a slip. Not hitting the flow rate will cause freezing and the unit may cycle more than needed to allow the system to properly cool down.
 
You could always use the 1/2 thru hull then adapt to 3/4 hose on the output to minimize flow loss.
 
I've been around a long time and worked on a lot of units. I don't remember seeing 1/2" used on marine air conditioners. The inside of a 1/2 hose fitting would be pretty small for anything over 5000 BTU.
 
Ok, thanks guys. I thought I might be able to save some time since the passage eventually reduces to the same 1/2 inch. It's getting late in the month and I'd like to launch.

I went ahead and spent a cold, rainy, afternoon removing the old thru hull. You know the one you can't reach with normal sized arms, you can't see with the cavas up, can't get a wrench around, and sticks to the silicone sealant like its 5200+. Got it out and went home to dry off.

So now I am left with a small hole which I need to make larger. Hole saw wants to walk all over. Looking at making a plug or a step drill bit to help locate. Maybe a dremmel tool as a last resort.
 
Drat! My vote was for leaving the 1/2 inch. My Meridian has 3/4 BUT it is supplying FOUR air conditioners.
 
Can you use the 1/2 inch holesaw inside of the 3/4 holesaw then it wont walk. I know it works on larger size holesaws but dont know if there is enough threads to hold them both on the same arbor. Rich
 
Remember to seal the edges of your hull fiberglass after you enlarge the hole. I usually use marine tex.
 
without posting the model# there's no point in asking us here as we are all guessing. you need to read the installation instructions to see what they call for. if you dont find the answer from the installation manual, call the mfg and ask them. there are two issues, flow in GPH as others have noted and the other is water speed. the second is relavant to salt water in particular. barnicals and other forms of sealife do not like water that moves above a certian feet per minute. sorry i cant recall the number, but that speed is driven by the GPH and diameter. if you can achieve your GPH with too large a diameter hose your FPS drops off.
 
When I did this exact same task.......I temporarily silicone'd a piece of scrap wood over the existing hole from the inside of the hull...........then carefully re-drilled the new hole from the outside. The scrap wood worked well to help center the pilot drill bit on the holesaw. Then just removed the scrap wood and silicone ...........done.

Good Luck...........

ps.......good advice.....don't forget to seal the edge of the fresh cut thru the hull.
 
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