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Old 13-11-2015, 12:46   #1
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Little Wonder watermaker runs 10 mins then shuts off

We have a Little Wonder 300 (or maybe 400?) and it runs fine for about 10 mins with good quality (TDS <200), making about 1.5 gallons, then both the high pressure pump and the low pressure pump shut down. We find that the circuit breaker that the high pressure pump is on has flipped. The circuit breaker for the low pressure pump has not flipped but we can't turn the low pressure pump on until we reset the circuit breaker on the high pressure pump. Then the system runs fine for a couple minutes (not as long as the first time) and shuts off.

Any ideas?

I am thinking that pumps take more current when they have to push harder so maybe filters or membranes are getting loaded up. But it does run for a while. And why do both pumps shut off at the same time? (the high pressure pump may shut off a fraction of a sec before the low pressure pump does, not sure).

Thanks for any ideas on what to look at.
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Old 13-11-2015, 17:29   #2
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Re: Little Wonder watermaker runs 10 mins then shuts off

After a bit more trouble shooting, more info:
The system has a high pressure pump with two motors. Using an ampmeeter, we measured 14.7 amps on one, 19.7 on the other (12v). They are on a 35 amp circuit breaker. That flips after about 10 minutes (after making more than a gallon of good water).

The membrane was new 3 weeks ago. It was tested the day we bought it, but at the store, not in our system. As soon as it was installed in our boat, it had this problem. And we have been running in a little bit every other day to make sure it does not sit idle. So I am assuming it is not the membrane. Maybe I am wrong?

The system worked OK for the previous owners, but they had not used the watermaker in quite a while and had not pickled the membrane, so we bought the new one.
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Old 13-11-2015, 18:20   #3
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Re: Little Wonder watermaker runs 10 mins then shuts off

Correction - the circuit breaker is 30 amps.
I am told the motors should draw about 12 amps each. Why is one drawing 19.7? Does that mean it is about to fail?
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Old 13-11-2015, 20:53   #4
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Re: Little Wonder watermaker runs 10 mins then shuts off

Are the power connections all clean and tight at both ends?
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Old 13-11-2015, 22:23   #5
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Re: Little Wonder watermaker runs 10 mins then shuts off

the motor may be drawing more current because it is seeing a lower voltage. Measure the voltage across each motor's terminals when running.
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Old 15-11-2015, 20:35   #6
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Re: Little Wonder watermaker runs 10 mins then shuts off

Hi:
I have a 600 gallon R.O. unit I use in my maple syrup business. When we pop a breaker the first thing we do is look for dirty filters, then volume of fluid coming from the feed pump before the filters. Our factory bench mark coming from the feed pump is 45 gallons a minute. If we don't see the proper bench mark we start looking inside the feed pump. In the past we have found bits of tape, chips of wood etc. plugging the vanes. When we don't get enough sap from our feed pump, we get cavitation in our pressure pump, which automatically shuts us down as the R.O. thinks it is out of sap. I assume you have a feed pump flow meter so find out what your input bench mark is from your manual or manufacturer. In 30 years of operating a R.O. most of our troubles have been like above. Hope that helps, ---- Dan
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Old 16-11-2015, 11:03   #7
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Re: Little Wonder watermaker runs 10 mins then shuts off

Check your output pressure. It has to be adjusted to whatever the manuel indicates and the adjustment will change with water temp. It's probably going to high and overloading the motor. I set mine at 800 and have had same issue. The relief valve is very sensitive so make small adjustments and wait till it all settles in.
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Old 18-11-2015, 11:31   #8
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Re: Little Wonder watermaker runs 10 mins then shuts off

Thanks for all the replies. Farther - the pressure is 800, exactly on spec. Mapledog - we have checked the lines and things seem OK. We talked to the manufacturer and they think either the high pressure pump or one of the two motors are going bad. They want us to send all that to them. We are in Georgetown Exuma. The "rebuild kit" is $1000! And I bet shipping is a couple hundred bucks.

Sent from my D6603 using Cruisers Sailing Forum mobile app
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Old 18-11-2015, 11:41   #9
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Re: Little Wonder watermaker runs 10 mins then shuts off

Is your flow rate exactly what it should be for the 800 psi pressure? If it's over you may have a bad high pressure gauge. Older units had one that only read to 1000 psi and were frequently damaged. Also since Parker Hannifin bought out Village tech the part prices are insane. Top end gasket kit is 6 quarter size o-rings for $160. Available at any hardware store for .25 cents ea.....
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