Automatic bilge pump current requirements

[MitchK]

All,
I am getting ready to install a new bilge pump in my N28-2. I will be installing a Rule Lopro900 automatic pump. This is the type of pump with an electronic sensor instead of a float switch. The paperwork for the pump lists how much current the pump needs when running, but not how much current the electronic sensor needs. So I got out my trusty DVM and measured the current. According to my DVM, the electronic sensor needs 1.4 milliamps (0.014 amps). The reason I wanted to know what the current requirements are, is my boat will not be hooked up to shore power at this time, and I currently do not have a solar maintainer/charger installed. The solar is a near future project, and the shore power will have to wait until I rewire the boats AC circuits. Anyway, I will be installing a new set of Optima Blue Top deep cycle batteries in the coming weeks, and the bilge pump will only be connected to the house battery, so I will only have approx. 65 amp/hrs of capacity for the bilge pump. I was concerned that there would be enough current loading from the pump electronic sensor to deplete the battery in a fairly short period of time. That will not be the case. Doing the math, and only discharging the battery to 50%, and the pump motor not running, the battery will be good for 2321 hrs or 96 days, or a hair over 3 months. That means the pumps electronic load is for all intents, a non issue. Of course, this ignores the battery self discharge, or the pump cycling.

Anyway, I figured someone in the group would be interested in the results of the test.

Mitch

 

[SG]

What happens if he pump needs to work occasionally?

I have no idea what the standby on an electronic switch is. I don't know that hit has any load if the contacts aren't closed by current through the water?

 

[jviss]

1.4 milliamps (0.014 amps)

1.4 milliAmps is .0014 Amps, a very little bit of current. (By the way, "Amps" is usually capitalized in honor of André-Marie Ampère).

 

[kloudie1]

Don't know if you are really set on the Optimas, but ya may be much happier with a good regular flooded battery. Check out Maine Sail's DIY site and some comments on AGM batteries..
https://forums.sailboatowners.com/index.php?threads/agm-batteries.147669/#post-980722
and: http://www.pbase.com/mainecruising/boat_projects
Scroll around the excellent articles to find stuff on partial state of charge use..
EDIT: another article to read and consider: https://forums.sailboatowners.com/index.php?threads/agm-batteries-making-the-choice.124973/

 

[MitchK]

Thanks for the replies all. The reason I checked the draw of the electronic switch was to verify just how much current it used in standby mode. It is an electronic switch, so it has to use some power.

An interesting read on the AGM batteries.

I already have a set of the Optima batteries. They were in the boat when I purchased it. I took them out and put in a pair of group 27's (which do not fit properly) I had for a 30+ mile trip under motor power that included two trips through a dam lock. I wanted to make sure there would be plenty of reserve power for that trip. I had planned on putting the Optimas back in for the winter since they are already "old" and I need to put the group 27's back to their normal installation. The date code on one of the Optimas is 2011, and I can not find the date on the other one. The logs that came with the boat said that one of the batteries had been replaced in 2011. Yes, they are probably at the end of their service life. I was going to replace them with the new Optimas in the spring, as that is what was there when I got it, and they seem to have given good service life.

 

[Benny17441]

Pardon my take on this but something seems to be missing. I am quite pragmatic and think that the logical solution to the situation presented is to not connect a bilge pump at all. A small electric bilge pump is basically a convenience item used to discharge incidental water that collects in the bilge so that it does not have to be scooped up manually. The bilge pump is not a safety item as it would not have the capacity to keep up with any significant water intrusion; at best it could only be relied to delay the sinking for a short period of time. If the boat is known to leak then the solution is to locate and fix the leak. Seems to me that given the charging situation that the justification for having a bilge pump is missing.

 

[jviss]

I will be installing a new set of Optima Blue Top deep cycle batteries in the coming weeks, and the bilge pump will only be connected to the house battery, so I will only have approx. 65 amp/hrs of capacity for the bilge pump.

Just wondering, since the Optima Blue Top deep cycle I've seen is 66Ah, if you are installing "a set," why don't you have 132AH of capacity?

 

[Ron20324]

Post #1 says he only has ONE house battery. "pump will only be connected to the house battery".

 

[jviss]

Post #1 says he only has ONE house battery. "pump will only be connected to the house battery".

Post #1 also says "new set of Optima Blue Top deep cycle batteries." Note "set," denoting a collection, and "batteries," plural.

 

[Maine Sail]

Mitch,

#1 When doing consumption/discharge battery math it is always best to calculate based on a max discharge floor of 50% DOD... So if your house battery is 65 Ah you have only 32.5 Ah of usable Ah capacity, not 65Ah... If you are on a mooring, with no solar, you can't expect to get back to more than about 85% SOC using an alternator. This yields about 35% usable capacity of a 65Ah battery or 22.75Ah before you hit 50% depth of discharge..

#2 If your meter read 0.014A then it looks like; 0.014 X 24 = .336 Ah for every 24 hour period
.336 X 7= 2.35 Ah per week. If you start at 85% SOC you have about 9.7 weeks before your bank is touching on 50% SOC. Still, not a big deal if you use the boat regularly.

#3 You could not pay me to install any of the auto sensing bilge pumps. The reliability of these pumps is questionable at best and they rate very high for me in terms of marine product failures.. A premium grade bilge switch, like the Ultra Junior, yields the best long term reliability. Couple that with a diaphragm pump for nuisance water and you have a long lived reliable system.

 

[Ron20324]

Post #1 also says "new set of Optima Blue Top deep cycle batteries." Note "set," denoting a collection, and "batteries," plural.

"and the bilge pump will only be connected to the house battery, so I will only have approx. 65 amp". Note, THE is singular for his switch installation. This does not refer to the SET he bought- only THE one as installed.

 

[jviss]

"and the bilge pump will only be connected to the house battery, so I will only have approx. 65 amp". Note, THE is singular for his switch installation. This does not refer to the SET he bought- only THE one as installed.

Why don't we let the original poster resolve the ambiguity. When I asked the question, I was asking him.

 

[SG]

To me JViss’ observations about effective capacity of the batteries material.

If one were really concerned with the background load of a (much maligned) electronic switch in standby, then the real concern is what happens when the auto bildge pump cycles just a bit.

By the way, while I like the simplicity of a “normal” float switch. , in our forward sail locker we have had to use an electronic switch because a float switch gets “fooled” if we are beating for extended periods intonthing it needs to pump. The electronic switches’ problems have only been that every 4 to 5 years they die. But they have lasted longer up there then then the float switches—which, aside from using amp hours needlessly by cycling he pump, they would prematurely “age” the pump.

 

[jviss]

I have spent a ridiculous amount of time lately researching bilge pump switches. The reason is, that my zincs are eroding very quickly, and I think it's because of a DC leak.

My bilge pump switch is like the Rule 35A, such that there are almost always wires in the bilge water. Over time the watertight integrity of the insulation and splices degrades, and you have energized wires conducting to the bilge water. The keel bolts are in the bilge water, and the seawater completes the circuit through the prop. This particular zinc, on my Max-Prop, was gone in 2 1/2 months.

There are a couple of switches with no electrical wires or switches in the water that are of interest to me. The first, and the one recommended by my surveyor, is the USS Ultra Pumpswitch family. These are expensive. They consist of a plexi tube, perforated at the bottom, with a float inside and the switch on top. The other is the Groco AS100. This one senses the pressure increase in a tube against a diaphragm with the open end in the bilge. The diaphragm and switch assembly is mounted high and dry. This one is street priced about 1/3 of the Ultra.

I'm inclined to go with the Groco.

Both my bilge pump and sump pump are ITT pumps, can't recall the model number, and i think they are impeller-type pumps, not diaphragm.

I will leave the shower sump switch as-s, since it is isolated from the bilge water.

 

[MitchK]

Thanks for the many replies. I Was not intending for a difference of opinions to occur here. So let me clarify. First, there are two batteries. One is for the engine, the other for house loads. They both can be parallel up while the engine is running for charging, but when I turn the master switch to off when I leave the boat, the pump is only connected to the one battery. So my math was in error. Should have used 65A for the calculations. Second, I was specifically wanting to determine what the load from the electronic switch was. I intentionally left out the periodic running of the pump. I have no intentions of going more than a couple of weeks max between visits to the boat, at which time, when I return, I will continue to vacuum out the bilge until I get all of the leaks repaired. After the first of the year, I will have access to 24/7 shore power, just for the next month or so, I do not have 24/7 access.

The reason for the electronic switch vs a normal float switch, is the configuration of the bilge in my boat. Access to the deepest part of the bilge is very difficult, there does not appear to be enough room to position the float switch in the bottom of the bilge. The pump and float switch that is currently installed, sets a couple of inches above the bottom of the bilge on some sort of spacer blocks. This allows the bilge to hold approximately 3 gallons of water, that the current pump cannot remove. I really need to get the old pump out and determine exactly how much room I have.

The root cause of this entire discussion is that there are minor leaks from a number of sources. I am eliminating these leaks as fast as I can so that the bilge pump will become a non issue. In a different post, I spelled out that I had located and repaired the worst leak, which was the stuffing box, which I finally got resolved, at least for this winter. The other leaks are due to rain at the Beckson Portlights, the four main cabin port lights, and another somewhere up in the bow, I am thinking the source of that one is around the hoses that enter the chain locker. I got one of the Beckson ports, replaced and re-bedded. I am hoping to get to the other one this weekend, weather permitting. So the long and short of it is, I am identifying and eliminating the various leaks as quickly as possible, and the bilge pump is a stop gap measure trying to keep the bilge dry. The boat is not in danger of sinking due to these leaks, even if I left it for a few months with no operating bilge pump.

And just a clarification on the automatic bilge pump. The pump has four operating modes. The first is manual, where I have to flip a switch to turn it on. The second is a low water level automatic mode (1.3"), the third is a high water level mode ( 2"), and the fourth, is that the pump turns on and runs every few minutes to check for water. I plan on using the low water level and the manual mode. Either mode will pump the water level down to approx. 1/2".

I think I have clarified all the questions.

Thanks again,

Mitch

 

[Ron20324]

No worries, Mitch- I read it correctly in #1, but thanks for additional info.

 

[MitchK]

Well, went to the boat today. The bilge was almost completely dry. just a bit of residual from the leaking stuffing box. Did discover the stuffing box was still leaking, maybe 5 or six drops in the last 48hrs! I put a small catch below the stuffing box when I was done adjusting it, and there were a few drops of water when I checked today. I can live with that.

Now the bad news, the new Rule Lopro900 bilge pump will not fit. The electronic sensor forces the pump too far back in the bilge, and the suction end is wedged between the sides of the bilge, raising it up about an inch. Not sure what I am going to do now. So the search is on for a narrow pump with either automatic or float switch. Anyone have any ideas?

 

[SG]

Buy a VERY Small Rule for the lowest point of the bilge.

Put the bigger one up higher and wire it as a back-up. Have the second bilge pump's sensor/switch up higher too so it really is a back-up.

Put the bigger back-up with a light or buzzer so if it's called into action, you get an alarm.