Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

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Allan Olesen
Posts: 62
Joined: Sat Dec 31, 2016 9:45 am

Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by Allan Olesen » Sat Dec 31, 2016 9:59 am

Hi. New member from Denmark here.

I am in the process of fitting a Rule 25S-6WC pump into a Tiderace Xplore. This is a pump of the type which starts every 20 seconds to feel if it is dry or flooded. I got the inspiration for buying this model from a post by Douglas Wilcox in this forum, so I thought that this is probably the best place to ask.

While testing the pump, I have noticed something strange: When running dry, it either runs for less than 0.5 seconds or a little more than 2 seconds. Never anything inbetween. I have not found any pattern in this behaviour.

Has anyone here had the same experience and perhaps an explanation?

I was thinking that it may be caused by changes in battery voltage, but I haven't yet tested that.

According to my measurements, it uses approx. 1A when running dry. If it does that for 2 seconds every 20 seconds, I will use 0.1 Ah every hour. That is a bit excessive. And noisy...

sleepyfolk
Posts: 61
Joined: Sat May 14, 2016 9:31 pm

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by sleepyfolk » Sun Jan 01, 2017 4:10 pm

I see the spec says it should only use 0.5a over 24 hours whilst self testing, and has a 2.5 minute test cycle, not every 20 seconds. Maybe it's not quite right, can you change it?

On this thread here viewtopic.php?f=45&t=124256&start=30 there a lot of good ideas about different pumps and switches etc, one of the guys fitted a Rule pump with a WaterWitch auto switch, the links are on the thread but that won't use any power up or be noisy every few minutes either, similar to my whale smartsub but a bit more compact, depending on your battery size I can't see the point of having a pump that continually uses the battery up

Allan Olesen
Posts: 62
Joined: Sat Dec 31, 2016 9:45 am

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by Allan Olesen » Sun Jan 01, 2017 4:33 pm

sleepyfolk wrote:I see the spec says it should only use 0.5a over 24 hours whilst self testing, and has a 2.5 minute test cycle, not every 20 seconds. Maybe it's not quite right, can you change it?
No, 20 seconds is correct for the 25S-6WC model. You have probably found a spec sheet for the more common 25S model.

0.5 A over 24 hours does not make sense. Are you sure it didn't say 0.5 Ah?

sleepyfolk
Posts: 61
Joined: Sat May 14, 2016 9:31 pm

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by sleepyfolk » Sun Jan 01, 2017 5:31 pm

The site I looked at says "Draw During Automatic Check: 0.5 Amps in a 24 hour period" but you're right - I guess they mean ah or as you say it doesn't make a lot of sense, must have been the 25S I saw - that 6WC seems a bit harder to find.
When I was doing mine I came across those ever cycling pumps in the jet-ski world and a few people moaning about flat batteries which is why I went the other way and opted for solid state sensing.

Not much help so far I'm afraid, I'm always intrigued by things like this though! Have you tried supplying it from a different battery and seeing if it behaves in the same erratic manner?

Chris Bolton
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Joined: Sun Aug 22, 2004 11:33 pm
Location: NW England

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by Chris Bolton » Sun Jan 01, 2017 7:29 pm

The current will probably be higher on starting than running, so 2s won't use four times the Ah that 0.5s does. My guess is that there's some logic that checks after 0.5s and concludes "Wet / Dry / insufficient evidence" with the subsequent action "run / stop / test again at 2s" - and in some cases, there's insufficient evidence. Which leads me to wonder what the pump uses to detect Wet or Dry - maybe load on the motor? If it was just detecting moisture using conductivity probes or similar, it wouldn't need to run. If it's motor current, battery voltage could make a difference, although which direction that would be in is stretching my knowledge of electrical systems!

Allan Olesen
Posts: 62
Joined: Sat Dec 31, 2016 9:45 am

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by Allan Olesen » Sun Jan 01, 2017 10:11 pm

sleepyfolk wrote:Have you tried supplying it from a different battery and seeing if it behaves in the same erratic manner?
I have tried switching the battery. The first battery had 70% charge, and the second battery was charged to 100%. With the second battery, the spin is now 6 seconds!
Chris Bolton wrote:The current will probably be higher on starting than running, so 2s won't use four times the Ah that 0.5s does. My guess is that there's some logic that checks after 0.5s and concludes "Wet / Dry / insufficient evidence" with the subsequent action "run / stop / test again at 2s" - and in some cases, there's insufficient evidence. Which leads me to wonder what the pump uses to detect Wet or Dry - maybe load on the motor?
Yes, it detects load on the motor. That is well documented.

I don't know if the exact method of detecting load is known, but I assume it is a simple measurement of current drawn by the motor. It could also be a detection of motor RPM, but that would probably be more expensive.

The initial current is approx 1.1 A, and it falls to around 0.8 A during the 6 second spin. At least that is what my somewhat slow multimeter tells me. So the battery discharge will be more or less proportional to the spin time.

Your theory about the pump performing a second test if the first one was inconclusive seems sound. However, the pump is completely dry - it hasn't seen water for a week. So the test should at least not be inconclusive due to water trapped in the pump (which some users have been reporting for this pump).

Anyway, perhaps the pump wants a little water for lubrication, so it is partly loaded when running completely dry. (Even though the manufacturer says that it can run dry). I guess I should go and wet the pump and see what happens...

Allan Olesen
Posts: 62
Joined: Sat Dec 31, 2016 9:45 am

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by Allan Olesen » Sun Jan 01, 2017 11:05 pm

Allan Olesen wrote:Anyway, perhaps the pump wants a little water for lubrication, so it is partly loaded when running completely dry. (Even though the manufacturer says that it can run dry). I guess I should go and wet the pump and see what happens...
Replying to myself:
I submerged the pump in water and let it run for a minute or so, and then I pulled it up. That brought down the spin time to a little less than 3 seconds.

Then I did it once again, this time letting it run submerged for 23 minutes. That brought down the spin time to less than 0.5 seconds.

After letting it run on the living room floor for 15 minutes, spinning up for 0.5 seconds every 20 seconds, I was very happy. And then it again started spinning for 2 seconds...

Conclusion: Apparently this pump likes water. So I will have to do a capsize whenever I hear it spinning for several seconds. Which is probably a good thing.

The good news:
After all that testing, the battery is still 80% charged. So it seems that I will be able to empty more than 2 tonnes of water out of my cockpit and still have some juice left for charging my VHF from the pump battery.

sleepyfolk
Posts: 61
Joined: Sat May 14, 2016 9:31 pm

Re: Rule 25S-6WC pump intermittently running 0,5 or 2 seconds

Post by sleepyfolk » Sun Jan 01, 2017 11:21 pm

You've done some interesting tests, seems we'll never know the exact answer! if it empties the boat plenty of times it's all good. Hope the occasional cycling doesn't get to annoying !

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