Ac Pumps Wired In Tandum?????? Help!!

[ron6785]

I have a single thru hull that feeds two seawater pumps / two AC units. Here's the problem, I think this is an improper installation, these mermaid remote units were installed by PO.

If both units are running no problem, If only one unit is running the water stream is significantly reduced and there are air in the exit stream, which means I think that what ever unit is running is pulling air thru the unit that isn't. This causes an air vac problem in the unit not running so when it tries to start there is no water and air in the line so pop goes the high pressure switch.

Short of buying a bigger pump that will handle both AC"S can I rewire the pumps so they both operate when either or both AC"S are running in effect having both pumps act as one ??????

 

[Pascal]

i tried that a few years back, I was told by both the pump manufacturer and also by AC tech, that i could have 1 thru hull/strainer, then a Y going to 2 pumps and 2 AC each...

it didn't work very well, and soon one pump failed.

seems to me that if one pump is running, it might not suck air but it will pull enough water out of the other pump intake hose to prevent it from priming...

either use one larger pump or 2 sea cocks.

 

[REBEL]

Ever consider check valves? seems Hatteras was fond of them on the potable / city water setup. The other alternative is to build some type of seachest for the pumps to draw supply for both pumps from with two strainers as well. The seachest can be all prebuilt from fiberglass, glued into place and assembled with the main cock closed and then merely open it as required rebel

 

[ron6785]

Ever consider check valves? seems Hatteras was fond of them on the potable / city water setup. The other alternative is to build some type of seachest for the pumps to draw supply for both pumps from with two strainers as well. The seachest can be all prebuilt from fiberglass, glued into place and assembled with the main cock closed and then merely open it as required rebel

the problem with check valves in this application is that these sea pumps are not self priming so they are not capable of creating enough vaccum pressure to open the check valve.
The obvious answer is to replace the two pumps with a larger pump. However that pump would be getting electrical curren from both unit compressors of 110 each or 220 from both so there must be some sort of splitter/transformer that reduces the 220 to 110 for the pump and if thats the case then you should be able to do the same thing for two pumps.

 

[Boatsb]

I have 2 units running one pump and I do not have a problem. How would 2 110 units give the pump 220?

I think this is an electrical issue that would be easily solved with a contactor and some wiring.

 

[Pascal]

there is no voltage issue, multiple systems on one pump have relays (triggers) so that any unit can start the pump.

if your ACs are 220v, then the pump will usually be 220 as well.

 

[bigbill]

ron, is one pump enough for both ac's? if so, why not put manual valves in line, and use one pump for both units, and have a backup pump already plumbed in case of a pump failure, just switch a couple of valves and your ac is back running. bigbill

 

[ron6785]

there is no voltage issue, multiple systems on one pump have relays (triggers) so that any unit can start the pump.

if your ACs are 220v, then the pump will usually be 220 as well.

The pumps are 110, but the pumps are activated by the compressor relay and and I have one line from each 16500 AC unit, connected to an individual pump. When I have both units running the exiting water streams from both units is clear water and strong. If the lower State Room unit shuts down and then cycles while the upper unit is running it will not prime and of course the high limit breaker pops.

If only the lower unit is running it will operate fine except for air bubbles in the exiting water stream.

 

[solanderi]

FWIW,

I have been cleaning and servicing my AC system which consists of a thru-hull to a March AC-5C-MD which is T'd at the pump outlet to two Cruise Air units. The two Cruise Air water outlets are Y'd to a thru-hull just above the water line.

If it is helpful to the thread, according to March and Cruise Air (among others), this is a common and adequete setup as long as the pump has enough capacity for the job. In this case March says that the model I have will handle up to 48,00 BTU's.

http://www.marchpump.com/

Conspicuously missing is a strainer between the intake and the pump. Is there any preferred strainer. Thank you,

Greg
1985 45C
Hat Time
N. Bay Village, FL

 

[Jaxfishgyd]

My two 16,000 units use one pump. That's what CruiseAir told me when I called them before having the compressors replaced in 2000... Zero problems. They also warned to use the proper size pump, not to go bigger as it would not cool the coils properly....
I'm at work but "think" it's a 1500 gph rated pump

 

[Tim Powell]

ron, is one pump enough for both ac's? if so, why not put manual valves in line, and use one pump for both units, and have a backup pump already plumbed in case of a pump failure, just switch a couple of valves and your ac is back running. bigbill

BILL THAT IS THE WAY MY 45C IS RIGGED IT WORKS WELL /// ESPECIALLY IF SOMTHING BRAKES LIKE THE PUMP JUST SWITCH VALVES... TIM

 

[REBrueckner]

If you have an infrared thermometer, check the raw water discharge temp from each unit when temps have stabilized....then check with both units running from one pump....did it raw water discharge heat up??

Sounds like a larger diameter thruhull could also solve your problem. ....

 

[ron6785]

ron, is one pump enough for both ac's? if so, why not put manual valves in line, and use one pump for both units, and have a backup pump already plumbed in case of a pump failure, just switch a couple of valves and your ac is back running. bigbill

llBill, each pump is 450gph, and so one pump would not be enough to handle both 16,500 units. It is fairly common to have One pump feeding multiple units as others in the thread have mentioned, and of course I could install a bigger pump which would solve the problem, however these are perfectly good 2.0amp March pumps, unfortunately installed improperly.

What I want to do is get both of the pumps I have to act as one. That is whenever either AC unit is on both pumps are activated this will eliminate the back feed of air from the unit that is not running. The problem each 16,500 unit is on a different leg of the electrical panel so I have a line coming from each compressor relay fo a total of 220 and I need to step that down so I have 110 running to the pumps.

 

[ron6785]

If you have an infrared thermometer, check the raw water discharge temp from each unit when temps have stabilized....then check with both units running from one pump....did it raw water discharge heat up??

Sounds like a larger diameter thruhull could also solve your problem. ....

The problem , as I see it is that I have an incorrect installation from the get go. I have on thru Hull, which goes thru the strainer and then T's with a line going to each pump. When both AC's are running no problem, however If one shuts off and the other keeps running it pulls air all the water back thru the unit that is not running and so with air being pulled from the exit discharge of the unit you get air in the line of the unit running and reduced flow. I only lose prime on one unit.

I'm going to try to rearrange the pumps to a point lower in the hull to see if that might help the priming situation. Of course that won't help the air and reduced flow. will let you know what happens.

 

[ron6785]

there is no voltage issue, multiple systems on one pump have relays (triggers) so that any unit can start the pump.

if your ACs are 220v, then the pump will usually be 220 as well.

Pascal, your right however if one pump is handling multiple units and they are on different legs of your electrical panel board then you have the potential for 220 going to the pump so there must be some sort ,for lack of a better term , step down /rectifyerthat will only let 110 go to the pump, if you have a 110 system which I do.

You can put what I know about electrical on half of a head of a pin. What I essentially want to do is avoid the cost of buying a bigger pump to handle both units and electrically connect the two pumps I do have so that regardless of which unit is running both pumps will run which will eliminate the air backfeed from the unit not operating. Like I have said when both units are running there is no problem. There must be a way to activate both pumps from either AC.

 

[ron6785]

I have 2 units running one pump and I do not have a problem. How would 2 110 units give the pump 220?

I think this is an electrical issue that would be easily solved with a contactor and some wiring.

If both of the units your running off of one pump are on the same leg of your electrical panel then you don't have a problem but if each unit is on a different leg then you have a lead from each compressor carrying 110 for a total of 220 the way I understand it. They make some sort of device so that if multiple units are activated the pump only gets 110v signal. My problem is I don't know if it can be used on more than one pump.

I'm looking for one of you electrical guru's to tell this electrically challenged Texan how to do it.

 

[Pascal]

Pascal, your right however if one pump is handling multiple units and they are on different legs of your electrical panel board then you have the potential for 220 going to the pump so there must be some sort ,for lack of a better term , step down /rectifyerthat will only let 110 go to the pump, if you have a 110 system which I do.

You can put what I know about electrical on half of a head of a pin. What I essentially want to do is avoid the cost of buying a bigger pump to handle both units and electrically connect the two pumps I do have so that regardless of which unit is running both pumps will run which will eliminate the air backfeed from the unit not operating. Like I have said when both units are running there is no problem. There must be a way to activate both pumps from either AC.

on my boat, i have 3 ACs and the pump on one leg, and one AC on the other one. The pump is hooked up to a relay box. whenever any of the 4 compressor need to come on, it will trigger a relay that will turn the pump on. but no matter what, the pump is still powered by its own 120v breaker.

in your case, switching to one larger pump means you need to add that relay box.

the alternative is to keep using two pumps but with another thruhull...

not sure what is cheaper and easier...

 

[ron6785]

on my boat, i have 3 ACs and the pump on one leg, and one AC on the other one. The pump is hooked up to a relay box. whenever any of the 4 compressor need to come on, it will trigger a relay that will turn the pump on. but no matter what, the pump is still powered by its own 120v breaker.

in your case, switching to one larger pump means you need to add that relay box.

the alternative is to keep using two pumps but with another thruhull...

not sure what is cheaper and easier...

Pascal, right thats what I need, I have two on each leg so the relay box is the answer and there is no reason that the breaker has to be at the panel, so I may be able to locate it closer to the pumps which would be the most cost effective way to proceed .

Thanks for you imput. Ron

PS> It worked I located the pumps lower in the bildge and the priming issue was solved. I however, still have the air backfeed probllem. However both AC are working , seems to me that a relay box could serve the same function for two pumps, unless the relay box is part of the pump.

 

[Fanfare]

My 1966 boat came with two March pumps on a T, but designed to have only one running at a time, the other being a spare. One switch decides which is running. The strainer has only a small vacuum, pumps are not the best at self-priming, but fine once started, nor can they suck much debris through the slotted strainer into the screen inside the thru-hull. Not the best as the thru-hull location is half way between the keel and the chine in the back of the ER. It seems to be shallow enough to need frequent cleaning. I think deeper would be better. I suspect Hatteras put them near the water line so their air-cooled motors don't get flooded by any leaks.

If your setup is similar I don't think you should be drawing air into this system. I would check the March pump seals for wear. But I have also had pinhole and larger holes in my bronze piping on these pumps. This is either from electrolysis (unlikely, they are bonded), cheap Chinese bronze pipe replacements from West Marine, or just erosion from the constant flow of sea water. If any AC is on the pump runs continuously which ususlly means all the time. Eventually the pipe begins to leak and it gets my attention. The pinholes are really pretty neat as they are often quite smooth inside and there will be several which are not yet big enough to break through the pipe.

I don't have the model number of the pumps here, but one pump can service 4 AC units totaling 50,000 BTU. When I changed the original split system servicing the fwd salon or the galley/fwd cabin to a dedicated system by adding a 4th compressor I put in a valved manifold system isolating the unused pump, but in retrospect this was overkill and unnecessary.