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Old 03-22-2016, 08:36 PM   #1
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Installing new AC System 2 Questions

I am installing a AC system in a 37 Hershine tri cabin. I did the math and came up with 24K btu needed. I choose two Webasto 12K FCF units. for two zone control. One split between the stern cabin and salon and the other split between the salon and forward cabin.

Question one: I have one 30 amp service now. I am considering adding a second and putting one AC unit on each, does that sound reasonable?

Question two: The PO had installed a 2" plastic speed log wheel in the hull. My plan is to install a Groco FBV2000 2"seacock to strainer to sea chest. 2" inlet and two 3/4" outlets, one for each AC unit. How does this sound and any ideas on how to make/buy/steal such a seachest. Can it/should it be above the waterline?

Here are some pics of the AC install so far.

Before

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Cleaned up

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In Place for fitting

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Old 03-22-2016, 09:47 PM   #2
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Just found what I need, too bad its PVC. Now how to cast it in bronze, maybe S/V Sunseeker could help. Great videos on You Tube. http://www.svseeker.com/

https://youtu.be/pojdU-dPeM0

Any ideas?
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Old 03-22-2016, 10:37 PM   #3
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You don't need to cast one in bronze. Just use the PVC one you found. Or make a manifold out of schedule 80 PVC if you think you need a stronger one.

And it's a manifold you want not a seachest. Two different things.

Of course you could just use one raw water pump to feed both units with a two outlet manifold coming off the pump.
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Old 03-23-2016, 05:45 AM   #4
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You don't need to cast one in bronze. Just use the PVC one you found. Or make a manifold out of schedule 80 PVC if you think you need a stronger one.

And it's a manifold you want not a seachest. Two different things.

Of course you could just use one raw water pump to feed both units with a two outlet manifold coming off the pump.
+1
In order to accomplish this you will need a pump controller. It takes the signal from each AC unit to turn the pump on when there is a call for cool (or heat). Pump and fittings must be big enough to provide proper water flow if both units should call at the same time. Pump output can be "TEE"'d to provide water flow to both units.
If you are planning on adding another power feed/cord to provide separate input power for the units, would you have a "spot" on your dock to plug it in?

FCF units are reasonably good units. I install many of them.
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Old 03-23-2016, 06:53 AM   #5
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A second 30 amp service will be useful, but you might be able to get by with your existing 30 amp service particularly if you use one raw water pump for both. Each unit will use about 12 amps and the pump will use about 3. So you can run them both as long as there are no other significant AC loads on at the same time.


And although I have never installed a single pump to run two A/C units, I don't think you need a separate controller if they both are on the same shorepower service. Each A/C unit will have a pump relay and you can wire them both to the single pump with no harm done. If you do have separate shorepower services, you will need a controller of some sort.


Another way to avoid the controller is to run both A/Cs from a dedicated separate 30 amp shore power circuit. That will limit you if you dock at a marina with only one shorepower service however.


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Old 03-23-2016, 07:24 AM   #6
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Although I think two 30amp services is the way to go.
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Old 03-23-2016, 08:04 AM   #7
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With the proper style inverter you can run 2 air cond from a 30A shore line.

The inverter will follow the CPS of the power pole and boost the voltage to start the second unit for the 1/2 second it takes.

This does not harm even a small house batt bank.

2 - 30A power hoses work better if there are lots of other AC power loads at the same time .
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Old 03-23-2016, 08:25 AM   #8
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Your not gonna run even one of those units with an inverter for any length of time. However, the Victron line of inverters does have the "start assist" feature that can allow you to start loads that the service line (dock or generator power) normally would have trouble with.
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Old 03-23-2016, 08:38 AM   #9
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In boats with multiple systems running on one seawater pump there is most likely a Pump Relay to receive a signal from each system to tell the pump it needs to run...That is unless it has been bypassed and the pump runs 24/7 from the breaker ( I see this done fairly often)

Lets start with the breaker in the main panel...Most are labeled A/C pump or similar...Some boats may have the pump breaker tied in with one of the A/C system breakers (Ocean Yachts for one used to connect the pump to the Main Salon A/C Breaker) but most should have a stand alone breaker...

The breaker feeds the pump relay and carries the load of the pump only...this power can be either 115 or 230 volts depending on the pump installed...
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Old 03-23-2016, 08:39 AM   #10
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Your not gonna run even one of those units with an inverter for any length of time. However, the Victron line of inverters does have the "start assist" feature that can allow you to start loads that the service line (dock or generator power) normally would have trouble with.
We're a little off the OP topic here, but Magnum has the same thing as well. Agree that an inverter wouldn't run this system long without a boat load of batteries, at around 1800 watts a side.

Personally I like the idea of adding another 30 amp service. Adds a lot of flexibility. Nice looking installation so far!

My old Hatteras ran 5 units off one big Oberdorfer pump, thence to a manifold. Had a pump relay box as described. Worked well. However, if room allows, two separate systems have a lot of advantages, mainly that if one fails, you still have AC somewhere on the boat.
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Old 03-23-2016, 08:46 AM   #11
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Our vessel is set up as stated by Capt Bill. The AC heat pump system utilizes one pump feeding a PVC manifold split to 3 different Cruisairs. The pump suction comes off its own sea cock and strainer.

Thirteen years old, Chinese built and never a hiccup mechanically or electrically!
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Old 03-23-2016, 09:55 AM   #12
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Greatlaker: Nice neat install - like it. Your a/c units look to be below the waterline. If possible your pump and strainer should be too - make priming easier. Don't forget to make anti-syphon arrangements when routing the raw-water supply piping.

I have a single March pump feeding seawater to all three of my a/c units via an off-the-shelf bronze manifold. Pump has its own breaker and runs all the time the breaker is on - one less thing to go wrong. Hopcar, you probably sell these manifolds - standard on many Bertrams.
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Old 03-23-2016, 10:50 AM   #13
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Wow you guys are good and fast! I was planning on two separate pumps mostly due to my lack knowledge of how to wire one pump to serve two units both may be needed simultaneously. The pumps Im considering are $200 ea the Pan World 100 PX at www.Marine Depot.com

So, If I run one larger pump, if wired correctly, it will supply water to both units but one or both my be on at the same time. The unneeded water just flushing thru the unit that is off. Correct?
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Old 03-23-2016, 10:56 AM   #14
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Greatlaker: Nice neat install - like it. Your a/c units look to be below the waterline. If possible your pump and strainer should be too - make priming easier. Don't forget to make anti-syphon arrangements when routing the raw-water supply piping.

I have a single March pump feeding seawater to all three of my a/c units via an off-the-shelf bronze manifold. Pump has its own breaker and runs all the time the breaker is on - one less thing to go wrong. Hopcar, you probably sell these manifolds - standard on many Bertrams.
The units are above the water line under the salon satee. The strainer and pumps will be below the water line near the 2" seacock The pumps and ac units are all 3/4" so I need a manifold going from 2" to 2/4.

I found a Vetus manifold that is one inch supply to three 3/4 outlets, I wonder how 1" can supply 3 3/4 outlets if all are needed at same time?

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Old 03-23-2016, 10:58 AM   #15
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Originally Posted by Greatlaker221 View Post
Wow you guys are good and fast! I was planning on two separate pumps mostly due to my lack knowledge of how to wire one pump to serve two units both may be needed simultaneously. The pumps Im considering are $200 ea the Pan World 100 PX at www.Marine Depot.com

So, If I run one larger pump, if wired correctly, it will supply water to both units but one or both my be on at the same time. The unneeded water just flushing thru the unit that is off. Correct?
You got it!!!!!
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Old 03-23-2016, 11:24 AM   #16
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If you are using only 1 pump, it should have a capacity of 1,000 to 1200 GPH. That would be plenty of flow when both units are running at the same time.

Water will flow through both units, even though only one is operating. 3/4" outlet on the pump (in most cases) "Tee"d to (2) 5/8" OD hoses, 1 to each unit. This is a typical setup.

Check with downwind marine, they have a nice selection of Bronze fittings for this kind of stuff. I am not affiliated with them, Just did a google search.
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Old 03-23-2016, 12:31 PM   #17
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There was no suggestion to attempt to operate an Air Cond on battery power , only to allow the start surge to be taken care of by the inverter.

As second far cheaper solution is possible .

IF the boat does stay cool , the RV folks sell a unit that will only allow one unit to operate at a time.

A simple relay and you could roll your own , load shedding unit.

Single staggered operation might require a bunch of exterior curtains over the windows to handle big sun loads.
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Old 03-23-2016, 12:48 PM   #18
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One more question. Do you all use seacocks for the Ac discharge? What is the aybc rule here? Will I get nicked by a surveyor if I just use a thru hull with hose barb. I plan to put 12" above waterline.
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Old 03-23-2016, 01:06 PM   #19
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I can look up the ABYC standard to check, but I would, that's just my preference.
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Old 03-23-2016, 01:12 PM   #20
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All thru-hull fittings or hull penetrations designed to accept pipes, hoses or valves, terminating below the maximum heeled waterline, shall be equipped with a seacock to stop the admission of water in the event of failure.

Hull penetrations that are not equipped with a seacock shall use reinforced piping or hose that resists kinking and collapse

From ABYC H-27
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