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Froggy

Water pump kaput!

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Hi

Our potable water pump is inoperative. It's the one on the left in the photos. There's no life in it at all. What are the chances that it's definitely the pump, or could it be one of the other components in the circuit, and if so what would be the best way to identify the faulty component? I'm pretty sure it's not the on-off switch on the control panel because it worked briefly when turned back on and then failed without this switch being operated again. The pump wasn't used for a few days in hot weather, so is it possible that it could be something as simple as an airlock?

The pump in situ is a Jabsco Par Max 2.9. I replaced the other pump in the photograph (for our pumpout toilet) a couple of years ago with the same model following advice from this forum. If i need to replace the potable water pump would there be any advantage in upgrading to a Par Max 4? We have a drinking water filter in the circuit in the galley, when this has been used the existing pump has worked in fits and starts, i.e. cut out and restarted at intervals of approx 2 seconds due, i'm assuming, to the pressure switch either in the pump or the separate switch in the circuit; this also happens when taps are only turned on to a low dribble and might possible have shortened the life of the component that has failed. Given that the pressure cut-in and cut-out specifications of both the Par Max 2.9 and 4 are identical, would upgrading to a 4 make any difference to this issue?

 

Thanks in advance.

IMG_20200602_191748 - Copy.jpg

IMG_20200602_193535 - Copy.jpg

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1) Disconnect the wires from the faulty pump and use them on the 'good' pump. If it works then the wiring is fine and the pump is faulty. or

 

2) Use a test meter and see if the connections are live, and the voltage sufficient for the pump (low batteries ?)

  • Greenie 1

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....

Edited by Bod
same question asked.

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Have you got 12V+ at the pump terminals? Check both sides of the pressure switch contacts - it may be the pressure switch which has failed - especially as you have had frequent pump cycling.

Is your accumulator pressure correctly adjusted?

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1 hour ago, magnetman said:

It looks a bit like a square D pressure switch. I think @Tony Brooks might know a thing or two about those. 

Yes and for some reason both poles have been utilised as a double pole switch but I don't see that as a likely cause. If it was me I would measure the voltage across the two input terminal (one red and one black wire) and then on the two output terminals that run to the pump motor. If both places have 12V + voltage the pump should be running, if its not then the motor is probably had it. The Op could then try giving the pump body a whack with a slipper or trainer heel - never a hammer or metal because the motor probably has permanent magnets and they shatter too easily. If the motor starts I would suspect worn brushes or a bearing seizure. The pump's own switch seems to have been bypassed as I would expect.

 

If the input terminals gives voltage and the output ones no voltage then the switch is suspect.

 

If there is no voltage on the input terminals then it could be the pump's on-off  switch, a fuse, faulty circuit breaker or bad cable connection. If the voltage on the switch inputs are less than 12V then put a piece of card between on set of contacts and if the voltage rises to 12V + its a high resistance between battery and pressure switch so again check the  switch, fuse etc. the look for  poorly connected terminals and undersized wiring.

 

If pushed to guess I would suspect the motor.

 

The cycling when the filter is in use I think is to be expected because the filter will restrict the flow so the pressure rises, pump cuts out, pressure falls so pump cuts in. All more or less normal.

 

Edited to add: as the switch might be an AC switch I would use both contact sets for the positive. there is no need to switch the negative. This will reduce the load on  each contact pair when it opens and thus reduce the propensity to arc and burn the contacts.

Edited by Tony Brooks
  • Greenie 1

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You can see the contacts on the Square D.   Y- shape Shown in the picky just behind the vertical rod with spring washer and nut that adjusts the cut-in pressure.     Check there is voltage at the inputs: the right hand pair in the phot  appear to be the positive terminals and the left hand pair  the negative ones  then push the Y shaped piece away from the spring to bring the contacts together.  The pump should run if it is OK

N

 

  • Greenie 1

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I wonder if the pump’s internal switch has indeed been bypassed...?

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41 minutes ago, WotEver said:

I wonder if the pump’s internal switch has indeed been bypassed...?

Now you say that and I had a close study of the first photo I think you may be correct. I think I can see a shadow of a red wire below the blue switch housing. If that is true then its probably best to bypass the inbuilt switch by cutting the red wire that runs  from switch housing to motor body close to the switch and connect that to the square D switch.

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I had a water pump blow a fuse once due to being left unused for an extended time.  I think the brushes must have got a bit stuck to the commutator and it took more current than usual to get it going. Equally possible it was a slightly seized bearing. 

 

Also if the battery voltage is low then the motor will attempt to draw more current leading to a higher probability of the fuse blowing. 

Edited by magnetman

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9 hours ago, Tony Brooks said:

Yes and for some reason both poles have been utilised as a double pole switch but I don't see that as a likely cause. If it was me I would measure the voltage across the two input terminal (one red and one black wire) and then on the two output terminals that run to the pump motor. If both places have 12V + voltage the pump should be running, if its not then the motor is probably had it. The Op could then try giving the pump body a whack with a slipper or trainer heel - never a hammer or metal because the motor probably has permanent magnets and they shatter too easily. If the motor starts I would suspect worn brushes or a bearing seizure. The pump's own switch seems to have been bypassed as I would expect.

 

If the input terminals gives voltage and the output ones no voltage then the switch is suspect.

 

If there is no voltage on the input terminals then it could be the pump's on-off  switch, a fuse, faulty circuit breaker or bad cable connection. If the voltage on the switch inputs are less than 12V then put a piece of card between on set of contacts and if the voltage rises to 12V + its a high resistance between battery and pressure switch so again check the  switch, fuse etc. the look for  poorly connected terminals and undersized wiring.

 

If pushed to guess I would suspect the motor.

 

The cycling when the filter is in use I think is to be expected because the filter will restrict the flow so the pressure rises, pump cuts out, pressure falls so pump cuts in. All more or less normal.

 

Edited to add: as the switch might be an AC switch I would use both contact sets for the positive. there is no need to switch the negative. This will reduce the load on  each contact pair when it opens and thus reduce the propensity to arc and burn the contacts.

 

Tony, many thanks for your detailed response - and also to everybody else who has contributed. I'm going to have a detailed inspection of the pump and switch over the weekend taking your comments into account, and will report back because it's the least i owe people who have taken the time to respond. I have a simple multimeter, and also still have the old toilet pump, which was removed due to leaking seals but still operated when i removed it.

 

Unless there is a fuse within the motor then i don't think there is a fuse involved in the circuit, the 12v wiring in the boat uses circuit breakers and this definitely wasn't the issue (unless the breaker is faulty but i think this unlikely). Additionally, it's unlikely to be low battery voltage (which is what i first suspected) because i ran the engine to charge the batteries up and it didn't resolve the problem. I'm also pretty sure that the pump switch hasn't been bypassed, the original wiring appears to be intact including the red lead running down the body of the pump.

I can see what your saying regarding the pump cycling, Tony, when the water filter tap is used, but do you think replacing with a Par Max 4 would be of any use, given the cut-in and cut-out pressure specification is i think the same as the Par Max 2.9? I'm guessing that it would chuck out larger volumes of water per cycle (and so require less cycling for a given quantity of water) but would still actually cycle. What do you think? If this is the case, i'm not sure that the extra £100 for the Par Max 4 can be justified. However, according to the boat manual it was originally fitted with a Par Max 4.

 

David Mack, i have to admit that i don't have any knowledge with regard to the accumulator. How would i test for correct pressure? I haven't taken it apart but there doesn't seem to be any obvious way on the externals of the unit for adjusting pressure. I don't fully understand why this component is even required when the toilet pump circuit doesn't incorporate one, would i be correct to assume that if's solely for the purpose of activating the switch when taps are opened? If this is the case could an airlock possibly be the problem and is this an increased possibility due to a period of inactivity during hot weather? We've had the boat for over three years now and have never experienced such a problem before.

 

Finally, would i be correct to assume that the vertical blue component in the top picture is a filter? If so i guess that this may require cleaning since it's never been done whilst we've had the boat. Having said that the water tank is stainless steel and so i wouldn't expect much debris to get into the pipes. The red button on that unit appears to be a bleed button; i've operated this a few times but it hasn't resolved the problem.

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1. Remember we had a horn fault a few days ago that turned out to involve a faulty circuit breaker.

 

2. A higher output volume pump will make it be more likely to cycle at any given outlet flow. If you don't want cycling you need a pump that produces less volume output than that which the tap/shower can. A higher output pump is likely to make cycling worse.

 

3. The blue thing looks like a filter and it looks as if what might be a red telltale button has popped out and that may indicate excess pressure drop across it.

 

4. Most but not all accumulators have a plastic cover thing on the domed end. this unscrews to reveal a car tyre type valve. With pump off and taps open a tyre gauge on it will show the pressure within.

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With the pump switched off and a couple of taps open to release the pressure in the system, you should set the accumulator pressure to a few psi below the pump's cut-in pressure which should be shown on that label on the pump body. You can adjust the pressure of the accumulator with a bicycle pump if it needs more pressure.

  • Greenie 1

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2 hours ago, blackrose said:

the pump's cut-in pressure which should be shown on that label on the pump body.

Except that he's using a Square D external pressure switch (although there is some doubt as to whether it's wired correctly)

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7 minutes ago, WotEver said:

Except that he's using a Square D external pressure switch (although there is some doubt as to whether it's wired correctly)

I think its wired exactly as its designed to be but as you pointed out the pumps own switch is still in circuit. If it were my boat having established there was 12V+ at the pump cables on the Square D I would simply cut the red motor cable and attach it to the Square D. Knowing how "reliable" the pump  switches are I think there is a very good chance it will work.

 

The reason I would not use double pole switching at the Square D is simply to try to prolong the contact life. On the hire fleet we only used one contact set so if needed we could simply swap the contact used but it was never necessary. As I said earlier not being sure its a DC switch I would probably parallel the contacts so they both share the load.

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21 minutes ago, Tony Brooks said:

As I said earlier not being sure its a DC switch I would probably parallel the contacts so they both share the load.

Agreed.

 

As the pump's own switch appears to have been left in circuit (which is what I meant about 'not wired correctly' as opposed to the contacts used) it's quite possible that it's failed - just like they usually do.

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4 hours ago, Tony Brooks said:

1. Remember we had a horn fault a few days ago that turned out to involve a faulty circuit breaker.

 

2. A higher output volume pump will make it be more likely to cycle at any given outlet flow. If you don't want cycling you need a pump that produces less volume output than that which the tap/shower can. A higher output pump is likely to make cycling worse.

 

3. The blue thing looks like a filter and it looks as if what might be a red telltale button has popped out and that may indicate excess pressure drop across it.

 

4. Most but not all accumulators have a plastic cover thing on the domed end. this unscrews to reveal a car tyre type valve. With pump off and taps open a tyre gauge on it will show the pressure within.

 

3 hours ago, blackrose said:

With the pump switched off and a couple of taps open to release the pressure in the system, you should set the accumulator pressure to a few psi below the pump's cut-in pressure which should be shown on that label on the pump body. You can adjust the pressure of the accumulator with a bicycle pump if it needs more pressure.

 

Thanks again for your help everyone. Tony, I had a quick look at the accumulator and didn't notice a car type valve (the body is metal and i simply removed the nut on the top) but then i wasn't looking for one so will have another look over the weekend.

 

So, given what blackrose says above, perhaps once i have got a working circuit i could adjust the cut-out pressure at the D switch or reduce the pressure at the accumulator to prevent cycling, or am i missing something here? The original fit-out of the boat did include a Par Max 4 (or at least, that's what the manual says, but i have previously noticed one or two discrepancies in it). However, apart from the cycling at the water filter the flow from the existing Par Max 2.9 was adequate, including when the shower was in use, and i guess that overall having a more powerful flow might just make it more likely to waste water. The boat started life in a hire fleet so perhaps the Par Max 4 was originally fitted on the assumption that there might be more demand on the circuit, for example somebody having a shower whilst somebody else was in the galley using the taps there.

 

One thing that really confuses me though is that, if you cut the red lead at the pump switch and connect to the D switch, how does this setup provide a circuit to the pump? There is then no positive current going to the pump, only a negative out? What am i missing here? I'm at work atm so don't have the pump in front of me but isn't the red lead from the pump to the D switch the same lead that then runs to the back of the pump, otherwise what would be the point of the pump switch if the red lead bypassed it and feeds the motor directly? I'd need to be convinced that cutting the lead is a good idea because it would then probably invalidate the warranty.

 

Edited by Froggy

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Are you now saying this is a brand new pump? If so then its probably faulty. if not its likely to be out of warrantee so cutting the wire is not an issue. You may find that if you take the blue box of the pump you can disconnect the red wire but then you will have some form of terminal on the end that may make joining it to another wire to the square D difficult.

 

Somewhere on the CYLINDRICAL pump body (in your case I think its in the end opposite the pipe connections) there will be a black and red cable coming out of the pump. These feed the motor. The red (positivist cable) then looks as if it runs through the pump feet and connects to the pump's own pressure switch below the blue box at the pipe end. I fully expect there is another red cable coming out of the box running to the Square D switch.

 

Now ignore the cable running from the blue box to the Square D switch, well you can remove it from switch if you want. Its the other one that we are interested in, the one that takes the 12v positive from the pumps own switch to the pump motor. If you cut this at the pump switch end or disconnect it from the pumps own pressure switch and connect it to the D square switched 12V + terminal the electricity will flow direct from the D Square to the motor without passing through the unreliable pump switch.

 

 

Adjusting the pump cut out and cut in pressure on any pressure switch may or may not have an effect on the cycling. If the pump tries to deliver a greater volume of water from the open outlet than can flow from the outlet the pressure will rise to the pump cut out pressure and the cycling will start. Increasing the pressure may force more water from the tap so the cycling period is longer but it is still likely to cycle at some point. if you want to stop cycling totally you need  a pump that is of a lower output than the tap/shower can handle, a pump that alters its speed according to pressure so as the pressure rises the pump slows down, or arguably something known as a bypass pump that starts dumping water back to its inlet as the pressure approaches the cut out pressure.

 

Be aware the the maximum water pressure shoudl be (say) at least 5psi below the system's PRV opening pressure and probably rather more.

 

As cycling is all to do with pump flow V tap flow messing with the accumulator pressure is unlikely to prevent cycling but will alter the cycling period so if you are filling a cup or maybe a kettle it seems the cycling has gone but try filling the sink and it will probably come back.

 

 

  • Greenie 1

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39 minutes ago, Tony Brooks said:

Are you now saying this is a brand new pump? If so then its probably faulty. if not its likely to be out of warrantee so cutting the wire is not an issue. You may find that if you take the blue box of the pump you can disconnect the red wire but then you will have some form of terminal on the end that may make joining it to another wire to the square D difficult.

 

No, this was just a hypothetical situation where i had determined for certain that the existing pump was at fault and i had to replace it. I guess there is nothing to lose, as you say, in trying to bypass the cutout switch on the existing pump (which is well out of warranty since it was on the boat three years ago when we bought it) to see if the pump comes back to life.

 

Thanks also for the additional information you provided re. the wiring setup and the effects of cycling, it has clarified things and it would seem that there is probably little to gain from replacing the pump, if this proves necessary, with a Par Max 4, which is best part of £100 dearer than a Par Max 2.9. It still begs the question though as to why a Par Max 4 was presumably used in the original fit-out, assuming the boat manual data is correct.

 

I think i now have the information i need to ascertain what has failed in the circuit and i'll report back when i've had another look during the weekend.

Edited by Froggy

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29 minutes ago, Froggy said:

 

It still begs the question though as to why a Par Max 4 was presumably used in the original fit-out, assuming the boat manual data is correct.

 

 

I think it was, as someone said, was it you, its an ex hire boat and it was probably to allow more open taps at  any one time.

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I have the same pump and a different problem. Ii regularly kicks in for say 10 seconds, even when there are no taps open. Presuming that I don't have a leak, is it more likely that it's faulty or that the pressure vessel is knackered?

Many thanks

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2 minutes ago, Tracy D'arth said:

No, you have a leak,

 

or faulty valves in the pump.

Agreed.

 

Check that the PRV isn't dribbling.

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