Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 11-08-2019, 13:06   #1
Registered User

Join Date: Aug 2019
Posts: 2
Advice on using 1 pump to service two devices

On my boat, a thru-hull and seacock control raw salt-water that is pumped to an A/C unit. It's a 120V circuit. When Iím not using the A/C I want to use that same pump for my desalinization watermaker. That way I wonít need to put another hole in the bottom of my boat - the fewer of those, the better, right? I tried putting in a second pump but it didnít deliver enough water to the watermaker because the water was going through the lower A/C unit and being discharged overboard because the A/C unit is lower. Would it work if I put a "Y" connector and two valves after the pump to divert the output to either the A/C or the watermaker? Also, I need advice on how to wire the pump when Iím using the watermaker. The A/C unit automatically turns the pump on or off to control the temperature of the unit. The pump itself has the standard three wires, black is power, white is neutral and green is neutral. Can I put in a separate 120V electrical switch to turn on the pump when I use it for the watermaker or could this create a problem with the A/C unit? As I said, these two devices will never be used at the same time. Any help or suggestions is appreciated. Gary
__________________

GaryLosAngeles is offline   Reply With Quote
Old 11-08-2019, 13:11   #2
Registered User

Join Date: Jun 2019
Posts: 28
Re: Advice on using 1 pump to service two devices

You could buy a pump relay box from dometic and wire the pump outputs on the watermaker and AC to a relay of the correct voltage.
This allows one pump to drive cooling to anything that calls for it via the relay.

What are the specs of the AC?

What pump is in there? Im guessing its a March 500gph if you only have one ac on it.
__________________

Coolerking is offline   Reply With Quote
Old 11-08-2019, 13:19   #3
Registered User

Join Date: Dec 2018
Posts: 24
Re: Advice on using 1 pump to service two devices

I wouldn't advise trying to use the same pump, but if you wanted to drive the same pump from two devices, you would use a relay like this: https://citimarinestore.com/en/micro..._stations_9800

If either device calls for the pump to turn on, the board will give power to the pump. This is commonly done for boats with multiple A/C units that use a single seawater pump to feed them all.

Is the watermaker a 120V system? What is the required flow rate and pressure for this boost pump? What is the air conditioning pump you are using? A/C pumps like the small March ones are cooled by the water flowing through them. If you restrict the flow too much by trying to run it to your watermaker, you could cause a problem. Adding a y and valves would certainly allow you to control the flow, but do you really want more fittings and valves in a raw water circuit with the potential to flood/sink your boat?

Depending on the watermaker requirements, I would instead advise splitting off the intake to the a/c pump strainer. This avoids having the put in another thru-hull and seacock. Add an appropriate boost pump (and strainer) for your watermaker and wire it so it comes on with the watermaker.
Gary S is offline   Reply With Quote
Old 11-08-2019, 13:30   #4
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 21,490
Re: Advice on using 1 pump to service two devices

You could install a 3 way valve, 1- both - 2
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 11-08-2019, 14:30   #5
Senior Cruiser
 
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 35,655
Images: 241
Re: Advice on using 1 pump to service two devices

Greetings and welcome aboard the CF, Gary.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Old 11-08-2019, 14:51   #6
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 25,981
Advice on using 1 pump to service two devices

An air conditioner pump doesnít supply enough pressure for a water maker.
Be nice if it did though, cause those pumps run forever and donít fail.

You need higher pressure because the feed water has to be filtered usually to 5 microns and still have plenty of pressure left after going thru the filter to ensure the HP pump doesnít cavitate.
Usually thatís at least 10 PSI to the HP pump after all losses.
a64pilot is offline   Reply With Quote
Old 11-08-2019, 16:32   #7
Registered User

Join Date: Aug 2019
Posts: 2
Re: Advice on using 1 pump to service two devices

In the system I have, the pump I'm concerned about only supplies raw water to the high-pressure device.
Gary
GaryLosAngeles is offline   Reply With Quote
Old 11-08-2019, 17:01   #8
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 25,981
Advice on using 1 pump to service two devices

Quote:
Originally Posted by GaryLosAngeles View Post
In the system I have, the pump I'm concerned about only supplies raw water to the high-pressure device.

Gary


Iím confused, you said you want to use one pump to supply two devices?
If you use a watermaker type LP pump to run the AC, your going to go through a lot of pumps.
If you try to use a March type pump, itís not enough pressure to supply the high pressure pump, March pumps give good flow but little pressure.
You need more pressure than one of those can make to push enough quantity of water through a filter, plus you need pressure to the suck side of the HP pump to prevent it from cavitating.
Itís a piston type pump so it pumps in surges, during those surges if you donít have good pressure, there will be a negative pressure and the pump may cavitate, if it cavitates, itís going to wear quickly.

You need about 10 PSI of pressure at the inlet side of the HP pump to prevent problems, you can go higher with no issues and Iím sure a little lower, but Iíd try to maintain about 10 PSI min.
a64pilot is offline   Reply With Quote
Old 12-08-2019, 13:39   #9
Registered User

Join Date: Jan 2013
Location: Ormond Beach, Florida
Boat: 1988 Wilbur 34
Posts: 198
Re: Advice on using 1 pump to service two devices

My boat is set up just as you describe: One pump provides water to both the A/C unit and the water maker. The pump has its own switch on the breaker panel as does the air conditioner and the water maker. All that is necessary is to turn on the pump and verify the water flow prior to switching on the A/C or water maker.
Seighlor is offline   Reply With Quote
Old 13-08-2019, 18:10   #10
Registered User

Join Date: Jun 2019
Posts: 28
Re: Advice on using 1 pump to service two devices

Quote:
Originally Posted by Seighlor View Post
My boat is set up just as you describe: One pump provides water to both the A/C unit and the water maker. The pump has its own switch on the breaker panel as does the air conditioner and the water maker. All that is necessary is to turn on the pump and verify the water flow prior to switching on the A/C or water maker.

Is the pump breaker you describe powering the relay box I pointed out?

Or does the water flow regardless of whether cooling is being called for/ RO in operation?

I have seen this done lots of times.

As a general rule, most seawater cooled ac systems need about 3.0 gpm per ton (12,00btu/hr) capacity. Most seawater pumps are spec'ed to deliver about 4.0 gpm under ideal conditions, before plumbing and all of that.

Look at the Btu rating, do the math for the amount of water flow you need per hour/or minute and your set.

The Cu-Ni condensers like clean water flow, no cavitation, just enough water to do the job in all conditions, then they last a loooong time.
I've also seen them washed out and leaking in a few years due to way too much water flow.
Coolerking is offline   Reply With Quote
Old 14-08-2019, 13:47   #11
Registered User

Join Date: Jan 2013
Location: Ormond Beach, Florida
Boat: 1988 Wilbur 34
Posts: 198
Re: Advice on using 1 pump to service two devices

Quote:
Originally Posted by Coolerking View Post
Is the pump breaker you describe powering the relay box I pointed out?

Or does the water flow regardless of whether cooling is being called for/ RO in operation?

I have seen this done lots of times.

As a general rule, most seawater cooled ac systems need about 3.0 gpm per ton (12,00btu/hr) capacity. Most seawater pumps are spec'ed to deliver about 4.0 gpm under ideal conditions, before plumbing and all of that.

Look at the Btu rating, do the math for the amount of water flow you need per hour/or minute and your set.

The Cu-Ni condensers like clean water flow, no cavitation, just enough water to do the job in all conditions, then they last a loooong time.
I've also seen them washed out and leaking in a few years due to way too much water flow.
There is no relay. As noted, the pump is on its own breaker panel switch. When on, the water flow is constant without regard to operation of the RO or A/C.
Seighlor is offline   Reply With Quote
Old 14-08-2019, 17:22   #12
Registered User

Join Date: Jun 2019
Posts: 28
Re: Advice on using 1 pump to service two devices

Totally wrong setup, The seawater pump should NEVER run unless the AC unit is calling for cooling.
What make of vessel are we talking about?
What make AC?
If you are only using it for the one AC unit, then it should be wired to the units pump outputs in the main control box, if you have more than one AC unit, and only one pump, then you have a relay box somewhere (which would explain the pump breaker being required) and the triac in it is shorted closed, which would make the pump run on power up.
__________________

Coolerking is offline   Reply With Quote
Reply

Tags
pump, service

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Using oSENC charts on multiple devices svspirited OpenCPN 2 04-05-2019 06:40
Anyone Using Spot Devices??? MoonlightSailor Product or Service Reviews & Evaluations 51 06-01-2019 23:50
Pump, Pump, No Pump ...Repeat and ...Die Capn Bri Plumbing Systems and Fixtures 17 23-12-2015 21:46
Two Engines, Two Alternators, Two Banks scurvy dog Electrical: Batteries, Generators & Solar 2 16-02-2014 05:48
Two solo cruisers , Two boats OR Two Captains One Boat colo.sail General Sailing Forum 8 17-12-2011 16:36



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 11:37.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.