Relay for bildge pump

[stormalong]

Originally Posted by Bawlmer

I don't know how adding complexity to a system can make it more reliable.

By protecting low current capacity float switches with higher capacity relays.

By protecting switches that cannot handle arcing with relays that have better contacts.

By protecting expensive custom pressure switches (talking FW domestic and deck wash pumps) with a common to all pumps, less expensive, more reliable, easier to change relay and having spares on board.

[rslifkin]

As a general rule of thumb, assuming a discharge head (combined lift and hose resistance) somewhere in the 4 - 5 foot range, I usually figure 60% of rated output for a large pump, 50% for a small pump. That should adequately account for voltage drop and other factors CharlieJ mentioned to get a more realistic picture of what to expect from the pump.

That's where the 2200 gal/hr for a Rule 3700 came from in my example. On a good day with power being supplied to the batteries it'll do better. In my installation, there's about 3 feet of lift from the pump to the high point in the hose, plus about 10 feet of 1.5 inch hose with a few large, sweeping bends to the thru hull, that's about 4 feet of total discharge head (ignoring that the hose drops back down to the thru hull, so the real-world head should be somewhat less once the hose is filled). So once we take the numbers from Rule for what it should do, then account for some voltage drop, less than fully charged batteries, etc. it should still be unlikely to end up pumping less than 2200 gal/hr.

[Bawlmer]

Originally Posted by stormalong

By protecting low current capacity float switches with higher capacity relays.

By protecting switches that cannot handle arcing with relays that have better contacts.

By protecting expensive custom pressure switches (talking FW domestic and deck wash pumps) with a common to all pumps, less expensive, more reliable, easier to change relay and having spares on board.

I can't speak to other uses but I have had 3 boats with bilge pump float switches and all have worked well and never needed attention. The switches are rated for the draw of their associated pump. I yield that if you are dealing with a specific current draw issue a relay should be considered. Simply dropping one into a circuit to address what may or may not be an issue is trying to fix something that is not broken.

[stormalong]

Originally Posted by Bawlmer

I can't speak to other uses but I have had 3 boats with bilge pump float switches and all have worked well and never needed attention. The switches are rated for the draw of their associated pump. I yield that if you are dealing with a specific current draw issue a relay should be considered. Simply dropping one into a circuit to address what may or may not be an issue is trying to fix something that is not broken.

I don't know how you use your boat. I lived aboard and cruised the world for 19 years. With shower draining into sump and frequent use of domestic water and deck wash pumps I can say that float and pressure switches are not up to the task. They are not designed for the loads put on them. The manufacturers are happy to sell replacements at high prices that will have to be replaced again and again.

There is a reason for the ubiquitous headlight relays that all car makers use. The relays are cheaper and more reliable than the the switches.

[Jimmyhenry]

I had a relay in the starting circuit of my starter, and I have one in the circuit of my fresh water pump, the reason is that the fresh water pump uses a small micro switch, the high current causes the switch to fail pretty quickly, replacing the switch is a lot of work.
The relay is designed to handle far more current than the pump pulls, and relay replacement is simply a plug in affair[/QUOTE]

Assuming the micro switch is pressure sensitive, then having a relay before the pump does not reduce the load on the micro switch. Once the relay is triggered the full load gets exerted on the micro switch anyway.
Pete

[stormalong]

Originally Posted by Jimmyhenry

I had a relay in the starting circuit of my starter, and I have one in the circuit of my fresh water pump, the reason is that the fresh water pump uses a small micro switch, the high current causes the switch to fail pretty quickly, replacing the switch is a lot of work.
The relay is designed to handle far more current than the pump pulls, and relay replacement is simply a plug in affair

Assuming the micro switch is pressure sensitive, then having a relay before the pump does not reduce the load on the micro switch. Once the relay is triggered the full load gets exerted on the micro switch anyway.
Pete[/QUOTE]
No,the relay is operated by the microswitch. The only power through the microswitch is the power to operate the relay. This is electricity 101.

[Jimmyhenry]

Originally Posted by stormalong

Assuming the micro switch is pressure sensitive, then having a relay before the pump does not reduce the load on the micro switch. Once the relay is triggered the full load gets exerted on the micro switch anyway.
Pete

No,the relay is operated by the microswitch. The only power through the microswitch is the power to operate the relay. This is electricity 101.[/QUOTE]

Got it. That is clever wiring. And simple also. Thank you.

Pete

[skenn_ie]

For my domestic water, I bypassed the small pressure switch on the pump with a big clunker that has a diaphragm about 2" in diameter. It has a pressure and hysteresis adjustment, contacts (3/8" in diameter)for positive and negative, and has been going flawlessly for about 5 years. The boat is my home, and was my daughters (she used a lot more water than I do). I get through about 150 Imperial gallons/month.

[Seamentress]

Hi All.
Interesting thread, with lots of relevant and technical information!
From my own experience, I have been living full time aboard for 12 years now.
My boat was purchased in the USA, California to be exact, and for the first 3/4 years I didn't have a problem with bilge pumps or float switches.
I sailed the boat down the Pacific west coast to the sea of Cortez where I have been for the past 9 years.
Bilge pumps and float switches have been the biggest pain the a"" for me since I arrived here, I cannot recollect how many I have gone through, certainly more than 10 of each.
I have tried switching brands, Rule Johnson, Sea Flow, none have lasted more than a few months.
I have re wired the complete circuits. ( there are 3 pumps in various compartments). Still, pumps and switches have failed.
The problems have been many and varied, I've had pumps which the shaft broke on, obviously a manufacturing issue, at least 2 of them!
I've had pumps which just refuse to operate!
I've had pumps which run erratically, I've had pumps which seem to run just fine but won't lift the water over the elbow. Just about every problem you could think of.
Float switches, just about as unreliable.
I had one float switch, which was fitted in CA before I set off down here, which was in a high water alarm circuit. No pump, it's only function was to complete a circuit and sound the alarm, so the amperage going through it was milliamperes.
It operated under duress, 1 time, during Hurricane Odile in 2014 Granted it did its job, but it would not switch off after that one operation!
I've had other float switches that do likewise, won't switch on, others that won't go off, others that feed the pump at a reduced amperage so the pump appears to be the problem, you name it, I've experienced it.
And the replacement costs for pumps and float switches down here is not inconsiderable,
Oh, as a side, I see now that the Rule float switches are now the rolling ball type, that used to be available years ago, instead of the none Mercury rubbish that's been available here

Now, as I'm a retired diesel mechanic, and well used to seeing electrical problems on trucks and cars, I decided to add an extra layer of complexity, ( as some previous persons call it ).
I used a conventional Bosch type relay, as in the post number 2 in this thread, I fixed it into a small Tupperware container and sealed the lid and all holes that I drilled for wiring with a silicon sealer.
So it is totally waterproof, It is protected by a simple in line 20 amp fuse, and wired directly from the house battery bank.
I did this about 18 months ago!,,, and Violla!!! No more problems with that bilge pump or float switch.
So for me it fixed a problem that new equipment would not fix.
Incidentally, I need to put relays in both other pumps, as I have had to replace one in my shower sump just last week. ( the shaft broke on that one)
A relay probably wouldn't have avoided that happening, but it was less than a year old, so I'm sure these things are Cr?? Anyway.
Just my experience!,

[Rotten Ricky]

As a former farm boy and former electrician, I suggest that sailors look at float switches from industry or farming as these items are often far more reliable by being for serious heavy duty. Yet they are often cheaper - probably cos they do not have that magical word "marine" attached.

Sump pump switches might be cumbersome but they are cheap and tough! They could get a kick from Bessie the cow! The float switch mechanism is often totally sealed but make sure external connections are above the water level and well protected from the saline marine environment.

Also, as has been mentioned, using a double-pole switch or relay, using terminals that are wired in parallel, can work well. One pole will usually make contact even a microsecond before the other and will take the impact of the arc created. The second contact is usually clean and reliable cos it does not take such a beating from the arc. I always use double-pole switches and relays where possible, and the difference in cost is minor compared to the reliability and longevity.

There is also virtue in the redundancy concept of having two separate float switches wired in parallel for the same pump.

Cheers and stay safe from The Bug!

RR.

[Steve DAntonio]

Originally Posted by Discovery 15797

If you are going to state 'it's the law' or 'it's against the law,' please reference (link) the specific law and to which country it is applicable.

An outdated method was typically to include a 3 position switch inline with the bilge pump. (auto - off - manual), and some manufacturers such as SeaDog, Johnson, & Rule still make such switches.

However, according to the most recent ABYC standard ABYC H-22 the automatic bilge pump must be operable when ALL panel switches and battery selectors are to the OFF position. Here is an example.

I verified this with 2 different surveyors after 1 told me I had to remove my switch and wire directly to the battery. The insurance co. also confirmed as a condition for insurability.

(The reason for the change was that too many chuckleheads either rewired their boats with the bilge circuit connected to the main battery switch, and/or the 3 position switch was inadvertently switched to the off position when the owners left the boats and the boats flooded/sank.)

Truth be told...my primary bilge pump is now directly wired w/o a switch. My secondary bilge which was automatic is now switched and safety wired to the auto position.

You aren't required to wire a bilge pump directly to the battery, but you should wire to a source that cannot be switched off with the battery switch. My preference is to wire what's called a "24 Hour Circuit" to the line side of the battery switch, which may be more convenient than wiring to the battery, and less likely to be upset with battery replacement.

"However, according to the most recent ABYC standard ABYC H-22 'the automatic bilge pump must be operable when ALL panel switches and battery selectors are to the OFF position'." I'm curious, where did you get this, from a surveyor? That language is not present in ABYC H22 Bilge Pump Systems.

From ABYC H-22 (I sit on the committee that amends and updates this standard)...

22.8.12 Bilge pumps with automatic controls shall be provided with a readily accessible manual switch to activate the pump.
22.8.13 Manual switches for bilge pumps shall be readily accessible.
22.8.14 Pumps with automatic controls shall be provided with a visual indication that power is being supplied to the pump.

ABYC E-11 does say the following...

11.6.1.2.1 A battery switch shall be installed in the positive conductor(s) from each battery or battery bank with a CCA rating greater than 800 amperes or 100 Ah if CCA is unavailable.

NOTES: Conductors supplying the following may be connected to the battery side of the switch:
1. Electronic equipment with continuously powered memory;
2. Safety equipment such as bilge pumps, alarms, CO detectors and bilge blowers;
3. Battery charging equipment;
4. Impressed current systems.


Note the word "may", while it's a good idea it's not required.

I would not install a relay in a bilge pump circuit unless I had a very long wire run, and then only if I could not use a wire size large enough to keep voltage drop below 3%.

This article covers bilge pump installations in detail, switch arrangement is explained on page 58 http://stevedmarineconsulting.com/wp...umps147_05.pdf

[Rotten Ricky]

Steve,
Thanks for your dedication and wizeness to promote best practices and safety.
Having just suggested the use of a un-conventional, non-marine trade float switch, is there any requirement that items for use in boat must be blessed with the costly "marine" tag?
I would think that so long as it can handle the job in the marine environment and is installed competently, it would be hard to draw the line between the two categories. It sounds like it might be the bean counters and attornies at insurance companies that might be trying to enforce their own "law". If that is the case one might just have to follow their rules to maintain a valid legal insurance contract.
RR.

[Steve DAntonio]

There isn't a yes or no answer I'm afraid, in some cases "marine" really does mean it's different and necessary, alternators and starters on gasoline inboards for instance must be ignition protected, even though automotive versions will work. Having said that, many of the yacht construction projects with which I'm involved use industrial mechanical and electrical equipment that works very well in that environment, better in many cases than marine gear, or there is no marine specific gear for those applications.

It's not unreasonable for an insurer to insist on adherence to standardized marine equipment or practices, like that which meets ABYC, CE or other recognized bodies. But beyond that if they are insisting on something that is outside ABYC's scope, I'd request that in writing and not rely on the surveyor's verbal comm's, because in this case it seems he or she is mistaken. Again, while wiring a auto bilge pump to a 24 hr. bus makes sense, it's not required.

[stormalong]

Originally Posted by Steve DAntonio

I would not install a relay in a bilge pump circuit unless I had a very long wire run, and then only if I could not use a wire size large enough to keep voltage drop below 3%.

I would agree with you if the float switches and pressure switches on "pleasure boat" grade marine pumps was actually designed and built to handle the loads and electrical transients of the real world. As they are not I will use relays to make up for their shortcomings.

MOVs and other arc suppression solutions also work but be aware that MOVs break down after repeated cycles. They are intended for occasional voltage spikes, not regularly occurring events. https://zerosurge.com/truth-about-movs/

[David Mathis]

If reliability is a concern, just get an extra pump and install it near the pump with the reliability concern. Avoid any other related reliability issue by running a separate ground wire to the negative terminal then run a separate wire directly from the positive battery terminal to the switch then to the pump. Now you have no need for a separate relay as the two pumps are on independent systems. This is simpler than adding a relay plus the boat has a second pump. Pumps and wire are cheap.