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Seawater pump requirements for two 5000btu units?
September 27, 2009
10:00 am
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Steve Pooler
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November 12, 2008
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Glen~

Just to be clear...There are 3 ways you could go with water flow...

  • Single 1000 pump to all three units and the PR3X-3 relay...Single 1" thru-hull...
  • Individual pumps (one for each unit) 500 for the 16K and two 250's (one for each 6K) Three 3/4" thru hulls & related strainers
  • Individual pump, thru hull (3/4") & strainer for the 16K (500 GPH) Then a 500 GPH pump for the Two 6K units, a PR3X-2 and One centrally located 3/4" thru hull & strainer.

If you go with the single 1000 GPH...The manifold feed line needs to be no bigger than 3/4"...If you want to call me I can explain how I would build the manifold....It would be easier on the phone...

If you go with a single 500 GPH for the 2 aft units...That manifold feed line is 5/8"

With the Gen/inverter into the mix you will need to consider that you will also need to power the pump relay breaker (if installed) in your main panel...How that is done is up to you & your guys down in the BVI...But I thought I would mention it.

The 16 should start just fine on a Honda 3K, and might even start fine on the 2.5K inverter.

As far as reliability of the Cruisair pump relay...It's very reliable...And it's parts have been standard production for as long as I can remember...

As opposed to Marine Air's relay box (several models) that requires a complete board replacement...Each & every part of the Cruisair box is individually replaceable and can be carried as spares for not much money....Triggers, which are the most common failure in both boxes are $29 each from Cruisair for instance...With Marine Air that would require a complete board replacement.

Failure of a trigger would just mean that one unit would not start the pump...Until the trigger is replaced...The Cruisair box can also be "jumped" in a matter of seconds to get the pump to run 24/7 (shut off pump with breaker) until service can be applied...

When I service one...I usually leave the jumper I make up for the customer inside the box so it is always there if needed, It's just a matter of plugging it in, and a screwdriver is only needed to remove the cover of the box.

Steve~

September 27, 2009
9:07 am
Glenn4533
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Steve,

    I am thinking that if I go with the 1000GPH pump, I would would pump a 1″ water line up to setee in the salon. Before it feeds the 16K unit there I would install a manifold in the water feed line. How would I configure the manifold? It would need to be three outlet. (1″ intake to 3/4″ – 3/4″ – 3/4″ outlets ???)

 Two of the manifold outlets would have to travel back down the port and starboard hulls to the aft cabins to supply the 6k units?

Glenn

September 27, 2009
8:48 am
Glenn4533
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Steve,

     Thank you for this information. It is exacly what I am looking for. Also thanks for the e-mail quotes on the A/C units and accessories. Your prices are great and we are definitely going to do business.

    One of the reasons I was hesitant about a 1000 GPH pump was that I want to try and keep my amps as low as possible.  I was surprised to find in the Cruisair spec sheet (** you don't have permission to see this link **) show that the 1000 GPM shows slightly less amp draw than the 500 GPM Pump (2.5 vs 2.2).

    As you know, I am planning this install A/C for shore power use mostly, with occasional use with a small portable generator. Honda has a new 3000 watt “Handi” that look pretty neat…. but I am not sure if it would have the guts to power the 16K.

   I also considered the fact that if only one (aft) cabin was being slept in, I may be able to run a single 6K unit off my 2500 watt Freedom Inverter to get through the night. I have 5 large gel cell batteries in the house bank. I'm unsure of the amp hours at the moment, but I like the idea for not listening to the generator if just one cabin is being slept in. This would not be something I would not do often as I would not want to deep cycle the battries very often… but it would be cool (no pun intended) to run one 6K unit off the inverter  once in a while.

  The drawback on my “single cabin on house bank/inverter” idea seems to be that if I supply the aft units of the 1000GPM pump running, I would be drawing 2.2 amps for the pump.  If I install with their own 250 GPM pumps those pumps draws just 1 amp. Thats not a lot less but I would like to keep the battery bank on as strict a “diet” as possible when the inverter is the A/C supply.

  Can you speak to the reliabilty of the Cruisair Pump Relay boxes? Do the benefits gained by less pumps offset the increase of complexity? Would I be ignoring the “K.I.S.S.” approach to the installation if I went with a relay box?

 As I write I am leaning toward the 1000 pump and relay box. I need to nail this decision down since the boat is being hauled next week and I have to decide if I need a single 1″ thru hull intake… or 3 @ 3/4″.

Thanks in advance.

Glenn

September 26, 2009
9:28 pm
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Steve Pooler
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I guess I should add...

If your plan is for the 16K to have it's own pump...That pump would connect directly to the pump connection at the 16K's electrical box.

No relay is needed and that pump will run from the 16K's power & breaker...The pump should be a PMP500L

For the aft units to run on one pump I would recommend:

  • One more PMP500L because of the distance & head we discussed earlier.
  • One PR3X-2 to receive signal from each 6K unit when either or both call/ask, and thus starts that pump.

Steve~

September 26, 2009
9:15 pm
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Steve Pooler
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Glen…You said the 16K will have it's own pump…But yes a PR3X-3 would have three triggers for three units supplied water by a single pump.

In your case that single pump would need to be 16K + 6K + 6K = 28K = 2.33 tons of A/C x 250 GPH per ton = 582.5 GPH.

You generally step up one size in pump if it's over…So you would need a 1000 GPH pump to run all three units on one pump.

  • No there is no such pump relay that operates two pumps…No need for one, and a single unit with it's own pump does not need a relay at all.
  • There are only pump relays that can accept multipule units that are fed seawater by one pump.
  • Each & every pump connected can start that larger seawater pump.
  • If any unit calls for the pump…The pump starts, and then pumps through all units connected.
  • All units must be off for the pump to stop.

Pump capacity must still match BTU capacity of 250 GPH (or more) per ton of A/C.

  • 250 GPH per 12,000 BTU (one ton) PMP 250L
  • 500 GPH…24,000 BTU ( two tons) PMP 500L
  • 1000 GPH 48,000 BTU (four tons) PMA 1000

And so on…..

Guess I was typing my last post while you were typing yours…Sorry…Was watching the Gators and mine took awhile…

Steve~

September 26, 2009
7:45 pm
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Steve Pooler
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Glen~

I started to explain in the second post of this thread....

  • Each A/C unit will have a (clearly labeled) pump connection that sends out 115v (normally to a pump) when the compressor starts.
  • Instead of sending that 115v to a pump...You send it to a trigger in the pump relay (yes hard wired) usually #16 two conductor wire.
  • The pump is wired to the "pump" terminals in the pump relay (yes hard wired too) with #16 three conductor wire.
  • There is a trigger for each of the 2 units in the pump relay box which tells the relay to send power to the pump.
  • The relay has 115v from it's own breaker & turns on & off the pump power...#16 Three conductor also. (from the panel breaker)
  • The pump actually runs on that pump relay breaker...Not from either unit's power.
  • There is NO CXP cable connection to the pump relay or HT control for the pump.

The reason for the pump relay is so that one unit won't try to start the other's compressor by a back feed of power.

The connections inside the PR3X are clearly labeled Pump & Power and a diagram resides on the inside of the cover.

I can probably come up with a diagram if you need it now but it really is very simple once you open the box.

A PR3X-2 will come with two 115v triggers already installed....each is connected to a terminal strip that you connect the two conductor wire from each unit's pump connection to each trigger.

Steve~

September 26, 2009
7:28 pm
Glenn4533
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Steve...

 I did just find a (2003) wiring diagram for the PR3X

I think I see where I am wrong. It looks like a pump relay box is for a single pump only. I guess if I want to eliminate the chances of startup of the 16k unit and an aft unit at the same time I can't do it. I would have to go with a single pump for all 3 units... Is that true?

Glenn

September 26, 2009
5:36 pm
Glenn4533
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Steve,

      I am considering a single pump for the aft cabins so I can eliminate a pump, a through hull and a strainer. I want to keep the 16k unit on it's own pump. This way I have some A/C working if one pump fails. I like the idea of a pump relay box so both units (and pumps) will not kick on at the same time and draw startup amps at the same time.

  I looked at spec sheet for the PR3X-2 pump relay box and have a few questions.

1)  I understand how the pumps are wired... to the triggers and you wire 115 volts from A/C panel (it's own breaker) to the Relay Box...but how do you wire the controls and display keypads? Do you run a CXP cable from each unit to the Relay Box and then another CXP cable from the Relay Box to the display/keypad?

 Does the Relay box accept the "phone plug" type plug on the end of the CXP cables or do they have terminal blocks and the canles need to be cut and terminal wired?

 I can find a general spec sheet for the PR3X-2 relay box online... but no wiring diagrams on pictures of the box with the cover off. Any chance you have a wiring diagram you can send me?

2)  Am I right to consider using the PR3X-2 Relay box for my configuration? Can I feed that box infomation from my 3 units (1-16k on its own pump, and two 5--6 k sharing a pump) and take advantage of all the benefits that the Relay Box offers...i.e. staggered starting of the units and still use three separate (SMXht) keypad/displays?

I feel like I am missing something. Am I on track?

Glenn

September 21, 2009
10:08 am
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Steve Pooler
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I might also add that if you do decide on the one 250 pump & relay....The Tee should be centrally located where it's equal height & distance to each unit...

You have the best chance of getting equal flow to each unit this way because water will take the path of least resistance.

Steve~

September 21, 2009
8:26 am
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Steve Pooler
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Hi Glenn~

You have mail…

Pumps…Yes you may be pushing it with a 250 pumping that distance…

You might get away with it in a cooler climate than the BVI…You can still try it though…

I would make sure to use a 3/4″ thru hull, valve & strainer…First off the 250 will pump better with that size, but if you find the condensers on the 5k units running hot…The worst you would have to do is step up to a 500 pump....The correct size plumbing for the 500 will already be installed.

You will need a two unit pump relay which will be Fed 115v from it's own breaker in the main panel…Then you just connect the "Pump" connections in each unit to the pump relay with #16 two conductor wire...

You could also use just one pump/strainer for all three systems…A PMA1000 would do it, and use the same pump relay with another trigger added.

The 250 pump is a good pump to have around for acid flushes, emptying bilges, water beds, whatever…  Cool

Thing is…If you buy another Zephyr KIT…You are going to have another 250 pump…

Steve~ 

September 21, 2009
7:48 am
Glenn4533
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Hi Steve,

      I am planning a 3 unit install in my 40' sailing catamaran. I plan to put a single 16000 btu Stowaway Turbo for the salon and forward cabins, and two separate 5,000 btu units in the aft cabins.

      I am considering my water pump/strainer configuration.

      I currently own a new 250 GPM Cruisair water pump.

      I am thinking that I want to keep the 16k unit independent, with a separate 500 gpm water pump and strainer, and use my existing 250 GPM pump for the aft cabin(s)

      As far as the install of two separate 5000 btu Cruisair units in the aft cabins, I am debating whether I should install two separate pumps/strainers. It seems like it would be cost effective to have a single pump and single strainer to feed both units.

      My question is: Would the 250GPM pump I own be sufficient to cool both 5k units.

      Let's say the thru-hull pick up will be in the port hull. I would install the 250 GPM pump, then wye the hose to feed the A/C unit in the port hull and also go up (about a 4' lift), across the bridge deck (about 15 ') and back down to the A/C unit in the starboard hull.

 So I have two questions:

1) Would I be asking too much from my 250 GPM pump to cool two 5k units in this configuration? (Cruisair "guidelines" say 250 GPMs per 12000 BTUs.... but I am concerned that I am pushing the envelope ).

2) It seems like I would save the cost of: one thru-hull, seacock, 250 GPM pump, strainer and labor on these. I would have to buy a pump relay and labor to install that.  A single pump would also save some amps when/if on generator.

 Am I on track with my thinking? Any thoughts on my configuration?

Thanks in advance!

Glenn