Air conditioners' raw water manifolds

[sndog]

Finally came up with how to exit my AC raw water from the boat. I built two manifolds, at the end will be inputs for water and compressed air for cleaning the lines to each AC unit. 6 units are onboard, 5 of them go to these for exit.

Would love any thoughts or input as always.

Thank you

 

[O C Diver]

What size are the output lines, 1/2"? As most raw water AC pumps are under 10 PSI, lines and valves should be larger to increase flow. Long runs become problematic as the tube walls act as friction. Further, the smaller the line diameter, the faster the water has to travel through it, for the same GPM. Going from 1/2" to 3/4" hose cuts the speed of the water by more than half. Going to 1" hose cuts the speed to 1/4 compared to 1/2" hose.

Optimally, everything should be 1" for the most flow through all the units. Use the valves to balance the flow rates.

Two things effect flow, length of the run, and if units aren't all the same height above sea level.

Ted

 

[sndog]

What size are the output lines, 1/2"? As most raw water AC pumps are under 10 PSI, lines and valves should be larger to increase flow. Long runs become problematic as the tube walls act as friction. Further, the smaller the line diameter, the faster the water has to travel through it, for the same GPM. Going from 1/2" to 3/4" hose cuts the speed of the water by more than half. Going to 1" hose cuts the speed to 1/4 compared to 1/2" hose.

Optimally, everything should be 1" for the most flow through all the units. Use the valves to balance the flow rates.

Two things effect flow, length of the run, and if units aren't all the same height above sea level.

Ted

Thank you for the info. Lines are 3/4". Manifold is 1.5"

 

[O C Diver]

Thank you for the info. Lines are 3/4". Manifold is 1.5"

How big are the units in BTUs? What's the GPM rating on the pump and maximum head in feet or PSI?

Ted

 

[sndog]

3 units are 24k BTU, 3 units are 18k BTU. 24k BTU have a head height of about 5ft, supply run to them of about 20ft, and supply exit of about 8ft. 18k units are head height of -2ft, about 30ft supply run, and about 15 ft of exit run. GPM on pump is 4000 GPH, two of them supplying both through manifolds at the pump, to independent 3/4" ID lines.

 

[O C Diver]

3 units are 24k BTU, 3 units are 18k BTU. 24k BTU have a head height of about 5ft, supply run to them of about 20ft, and supply exit of about 8ft. 18k units are head height of -2ft, about 30ft supply run, and about 15 ft of exit run. GPM on pump is 4000 GPH, two of them supplying both through manifolds at the pump, to independent 3/4" ID lines.

Ok, so the pumps are 65 GPM and the head above sea level is about 5'. At around 15 to 20 GPM per unit, you should have plenty of water. If you have any flow issues, do the tees in 1.5" and step down to 1" for valves and hose to the AC.

IMO, the 45' runs (30' + 15' = 45') will suffer more from parasitic line loss (friction). It might have made more sense to run 1.5" line to the area and put the manifold closer to the units. Maybe you will be ok. If you have flow issues, as above switch to 1.5" tees and 1" lines.

Clearly you have plenty of flow which is a common problem where owners skimp on the pump.

After you install everything, do a flow test by measuring the water stream out of the discharge. This can be accomplished with a 5 gallon bucket and a timer to see how many seconds it takes to fill the bucket. Understand that the pump rating is going to be much higher that actual flow. If you're getting 10 to 15 GPM per unit, you should be fine.

Ted

 

[sndog]

Ok, so the pumps are 65 GPM and the head above sea level is about 5'. At around 15 to 20 GPM per unit, you should have plenty of water. If you have any flow issues, do the tees in 1.5" and step down to 1" for valves and hose to the AC.

IMO, the 45' runs (30' + 15' = 45') will suffer more from parasitic line loss (friction). It might have made more sense to run 1.5" line to the area and put the manifold closer to the units. Maybe you will be ok. If you have flow issues, as above switch to 1.5" tees and 1" lines.

Clearly you have plenty of flow which is a common problem where owners skimp on the pump.

After you install everything, do a flow test by measuring the water stream out of the discharge. This can be accomplished with a 5 gallon bucket and a timer to see how many seconds it takes to fill the bucket. Understand that the pump rating is going to be much higher that actual flow. If you're getting 10 to 15 GPM per unit, you should be fine.

Ted

Great information. Thank you for it and will test it for sure.

 

[Deano]

If your around saltwater don’t forget to bond it.

 

[ranger58sb]

I built two manifolds,

Nifty. What materials? Looks like PVC for the main "tube"? (Tees with 2 or 3 outlets?) PVC valve on each? Bronze (or copper, or stainless?) valves and elbows for the tributaries? Or...?

If your around saltwater don’t forget to bond it.

If it's mostly PVC, how would one bond it?

-Chris

 

[sndog]

Nifty. What materials? Looks like PVC for the main "tube"? (Tees with 2 or 3 outlets?) PVC valve on each? Bronze (or copper, or stainless?) valves and elbows for the tributaries? Or...?




If it's mostly PVC, how would one bond it?

-Chris

The manifolds are pvc, the valves to each out is stainless. The main shutoff is pvc. All ac units run 3/4" hose to each input of the T. It allows an enormous amount of control. And I figured with 1.5" pvc. Probably a good thing to be able to close it completely when not in use.

 

[ranger58sb]

The manifolds are pvc, the valves to each out is stainless. The main shutoff is pvc. All ac units run 3/4" hose to each input of the T. It allows an enormous amount of control. And I figured with 1.5" pvc. Probably a good thing to be able to close it completely when not in use.

Got it, thanks!

-Chris