44 db heating air question / info

Labbur

Labbur

New Member
Aug 2, 2009
71
Georgia fresh water
Boat Info
2008 44DB
Engines
Cummins qsc 500
Can anyone add to this information I have obtained about water flow to my 3 Cruisair heating / air units. I have questioned that the 1,500 psi pump does not supply enough water flow to the 3 units for 100% performance. My 2008 DB has three units one 1,800 and two 1,600. The 1,800 needs 375 gals per hour and the 1,600's need 300 gals per hour each. I checked the output for each. The 1,800 on the bridge has about 190 gals and the other two cabin about 210 gals. I checked with Sea Ray and they use the 1,500 psi pump in the bridge boats and 1,000 psi on the dancers. I called Cruisair about this and in facts met them to discuss at the FT L boat show. If you want max cool need max flow. Have to admit I have not checked air tempt output but when it it above 90%, the cabin air struggles. I read several of you discussing the issues of air not cool enough. Anybody looked at this pump and water flow issues? Thanks in advance.
 
My dealer put a separate 1000 gph (psi?) pump in when we added the bridge air. We have nice cooling throughout. Just an option.
 
Didn't you answer your own question. You stated that the 1800 BTU unit needs 375 gallons per hour but you only measured 190 galllons per hour? You have a large enough pump if you have a 1500 gallon per hour pump. there are just too much restrictions in the line to and from the unit to get the required gpm to the unit. My opinion is that you did the right thing by figuring out what the manufacturer needs to make the unit work properly, then you measured the amount of water running thru the unit. I love Sea Rays. I will always own a Sea Ray, but that doesn't mean that they always get everything 100% the perfect. I have found that there is only so much they will spend in the way of figuring the best way to install anscillary items such as AC systems. You wanted an AC system. They gave you an AC system. You want cold air, you got cold air. It is up to us as owners to tweak them to make them run 100% efficient. Assuming you have the standard 5/8" water lines running to your system, sounds like you need to replace the 5/8" with 3/4" or even 7/8". A 1500 gph pump also has an inlet to outlet pressure rating. Otherwords, if you take the outlet hose off the pump and measure the total water running thru the pump right at the pump outlet, you will most likely get 1500 gph flowing thru it, but once you start adding piping to the discharge side of the pump, you are not going to get 1500 gph anymore. Based on your numbers, you are flowing 610 gph. Bigger diameter and/or shorter hoses mean less restrictions. Less restrictions means less friction(pressure) loss and therefore more GPM delievered to the units. Hope this helps.
 
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Not sure, so check me on this. I think the AC units will shut off with an overtemp or overpressure warning if there is not enough water flow....
 
Thanks for posting very informative details. I'm in the process of gathering all necessary info for bridge A/C installation and was debating regarding the pump. I think I'm conviced that adding new and dedicated pump is the answer instead of T-ing off existing one that might already be undersized for salon and fwd A/C units.

Can you guys recommend a good source for the pump and/or A/C units? I was trying to find the new version of 1600 Turbo.
 
Hampton said:
My dealer put a separate 1000 gph (psi?) pump in when we added the bridge air. We have nice cooling throughout. Just an option.
Click to expand...

Was it worth it to add the bridge air? Seems like a LOT of work and cost for possibly marginal value (lots of greenhouse to heat/cool).
 
I can only comment in regards to heating. Since we start our season early and end late we get to experience colder days/nights. On the sunny day the bridge stay very warm and on around 60deg (+/-) it's very comfortable in a t-shirt. However, at night when we gathered on the bridge the temp drops drastically. We use a small heater from HD and it effortlessly keeps the bridge temps very comfy allowing us to be only in t-shirts while it's 50deg (+/-) outside.

Obviously, cooling is another story and I'd love to hear more comments regarding the bridge A/C units.
 
First_Mate said:
Not sure, so check me on this. I think the AC units will shut off with an overtemp or overpressure warning if there is not enough water flow....
Click to expand...

This is correct, but overheating is a far cry from maximum efficiency cooling. There are several other steps in between: Good cooling, weak cooling, barely cooling, not cooling, then overheating.
 
Alex F said:
I can only comment in regards to heating. Since we start our season early and end late we get to experience colder days/nights. On the sunny day the bridge stay very warm and on around 60deg (+/-) it's very comfortable in a t-shirt. However, at night when we gathered on the bridge the temp drops drastically. We use a small heater from HD and it effortlessly keeps the bridge temps very comfy allowing us to be only in t-shirts while it's 50deg (+/-) outside.

Obviously, cooling is another story and I'd love to hear more comments regarding the bridge A/C units.
Click to expand...

Beautiful boat. It was definitely worth it for us. We have a turbo 16,000 BTU upstairs. It is quiet, provides a lot of cooling, and has great airflow. We can make it comfortable on any sunny day and down right cold on any cloudy day. The only time it is in inadequate is when cruising with the windows closed with sun shining on the Admiral's seat. There is no vent on that side. I plan to add one. With sun on any other seat, you just move. With sun on me, I have a huge vent pointing at me. That is the one that needs to be tapped in to to add another vent.
 
I really think Sea Ray has under powered this system. Pumping water all the way to the bridge, takes a lot. Thanks for your comment. I am working with Sea Ray for a fix. I plan to re-check my output flow again this weekend.
 
Thanks for the time you spent on your reply. I am going to double check the flows one more time. Your thoughts will help as I look things over. I have also thought that the T bar where all the units plug in is too small. This bar or branch tube seems very small and would restrict flow. I think your spot on. Starting with 1,500 and using all the branch pipes and so on would not produce what is needed. I had a friend who owns a Dancer 44. His intake hose was too small. He replaced it with a larger hose and dropped the output temp I think 3 degrees. Thanks again.
 
I have found that most units no matter how they are installed, regardless of tubing sizes or duct work sizes and so forth, will work at 70 to 80% efficiency. For instance, lets say that the issue is that the ductwork is too small. In this case, you don't have the proper air flow into the compartment to counter act the heat gain by outside sources. However, because the air is moving slower than it should, it stays in the cooling coil a little longer than it should and actually comes out a little cooler than it would have been if it had been moving faster. The point is that even bad installations will work decently most of the time. it is the last 30 to 20% of efficiency that is really what makes the difference on the hotest of hot and coldest of cold days. and to gain that last 30 to 20% it is usually never one specific thing. It is usually a little tweak here and a little tweak there that gets it working closer to 100% efficient. I have worked and reworked my 24,000 BTU cockpit AC/heat system to the point where it just is what it is. I now have the unit located inside closed compartment with supply and return ductwork from the Cockpit to the compartment and have another 7000 BTU unit whose only purpose is the keep the AC unit compartment cool. The only way I got it to work even better was to tint the glass windows down a notch and completely black out the overhead sunroof hatches. And even then, the best I can do is keep the cockpit 20 degrees cooler than the ambient outside air temp. Another tip I learned from an installer was to have as little ductwork and possible and make what ductwork you have as big as possible. He said that one big outlet was better than a ton of little ones scattered around the cooled space. I did what he said and he was right. I have one 7" piece of hard ductwork that leads directly from the 24,000 BTU unit and dumps into the cockpit with one large diffuser directed up to the bottom of the hardtop. Works like a champ. Hope this helps.
 
Thanks for the time spent on our reply. I am going to double check the flows one more time. Your thoughts will help as I look things over. I have also thought that the T bar where all the units plug in to is too small. This bar seems very small and would restrict.
 
what size system did you put in the bridge and what was the size of the pump that is being used with the two bottom units?
 
I have 4 separate zones and Searay set it up with 3 lower zones on one pump and a separate pump for the bridge. The bridge has different requirements because it needs greater head pressure to raise the water.

Alex, try Depcopump.com and look at the March Pumps.
 
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That is an interesting point also. I replaced the pump on a friends 40 Dancer this summer and in the box with the pump it showed how to plumb the hoses for multiple outlets. it showed that how the hoses were plumbed right off the pump made a big difference as to how much water got to each unit. From the factory, the 48 dancer has three units as standard. 1, 12000B BTU unit and 2 7000 BTU units. They run all three off one 1500 gph pump. The 12000 BTU unit is in the Salon, one of the 7000 BTU units is in the back bedroom, and the other 7000 BTU units is in the front Bedroom. Well you can imagine how much water was actually getting to the front unit? very little. the manifold off the pump was a tee with three outlets. Just by switching the hose that ran to the front unit to the center outlet drastically increased the flow to the front unit. I noticed an increased cooling efficiency of that unit immediately without noticing any diminished performance of the other two units. It made sense that Sea Ray would put the 12000 BTU unit hose on the center of the tee because it was the largest and needed the most flow. What they failed to realize was that since the front bedroom was the furthest away, the pressure loss caused by having that unit fed by one the side outlets of the pump manifold caused very little water to reach that unit. I actually ended up building all new less restricting manifolds for both of my pumps and run two of the units off one pump and two units of the other 15000 gph pump that used to be specifically for the optional 24000 BTU cockpit unit. Again, it is the little things here and there that make up the last 30 to 20% of efficiency.
 
Another thing to thing about is that there are no solenoid valves that restrict flow to the units that are not being used. If one unit is on, there is water flowing to all three units if your unit has a three zone system on one pump. I found that the one pump that Sea Ray uses for the Cockpit/Helm areas are usually oversized from a GPH standpoint. What they really need is a pump that pumps more PSI. You would have to look at the specific pump curves to see actually what is going on but I don't think these types of pump will pump twice the pressue when you cut the flow in half. Otherwords, a 1500 gph pump that will pump a head of 20 feet will not pump a head of water 40 feet if the flow is only 750 gph. So I can see a real problem existing with your bridge boats if cooling lines are not installed in the least restricted way as possible and no matter how you pipe it you have to raise the water from the engine room to the bridge. I am guessing maybe 12ft or so. the rule of thumb is you need a 1/2 a pound of pressure to raise water one foot. So you have at least a 6 pound loss of pressure just due to elevation before water even starts flowing.
 
We have 3 systems on our boat, we have a 3000 gph pump. Still struggles when very hot or very cold. Make sure your lines are clear, no scaling etc
 
cod said:
I have 4 separate zones and Searay set it up with 3 lower zones on one pump and a separate pump for the bridge. The bridge has different requirements because it needs greater head pressure to raise the water.

Alex, try Depcopump.com and look at the March Pumps.
Click to expand...

I stand corrected. Thanx for pointing me to the Decopump website. Good stuff. It looks like if you drop the flow in half on one of these centrifigal pumps, you actually get 10 times the pressure across the inlet and outlet of the pump . However, if your raw water cooling lines are too small or clogged in any way at all it doesnt' really matter what pressure you have, you just won't get the flow. The friction factor in tubing is directly proportional to area of the tubing cross section and the area is directly proportional to the sqaure of the Radius. Other words by doubling the diameter of the tubing, you reduce the friction loss by 400%. If you go from a 5/8 tube to a 3/4 tube, you have only increased the diameter by 20% but you have reduced your friction caused by the same amount of flow by 44%. Big difference.
 
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