Low Voltage to 12v water pump

[Rockhopper]

Hello all!

 

Hoping one of you lovely peeps might be able to help me and my husband resolve an issue with our water pump.

 

Our water pump switch on the main 12v switch panel has been turning itself off during showers and when the washing machine is running more and more over the last 6 months. This last week it wouldn’t even allow a tap to run for 2 seconds before switching off. Now the pump is not working at all and when we switch it back on via the panel nothing happens. 

 

We want to try and identify if there is a problem with the power supply or the pump itself.

 

We have tested the voltage to the pump with multi meter and the reading is coming back as 1.4v. We don’t believe this is normal and it should be reading 12v right?

 

Please what steps can we take next to further identify what the issue may be? 

 

Apologies if all this sounds very simple to the experts out there, we are completely new at fiddling with electrics and water pumps

 

Thanks in advance all!

 

Kind regards

 

Sarah

 

 

[Alan de Enfield]

11 minutes ago, Rockhopper said:

Our water pump switch on the main 12v switch panel has been turning itself off during showers and when the washing machine is running more and more over the last 6 months. This last week it wouldn’t even allow a tap to run for 2 seconds before switching off. Now the pump is not working at all and when we switch it back on via the panel nothing happens. 

When you say "switching itself off" do you mean the 'switch in the fuse box' is 'tripping' ?

 

Is it a 12v washing machine ?, or, is it just the pump is not pumping water to the washing machine ?

 

Is anything else affected ?

[Rockhopper]

I’ve added a picture of the switch that keeps turning itself off, its the switch on the main 12v panel.

 

Its just the pump is not pumping water to anywhere, taps or washing machine. 

[Detling]

The reset label suggests they may be overcurrent trips as well as switches. On my boat there is a reset button beside each switch. If they are trips then it would suggest the pump is taking more current than it should, it maybe 'stiff' so the motor is having to work harder to turn the pump, due to a failed bearing. Others will be along with better suggestions soon.

 

[Alan de Enfield]

25 minutes ago, Rockhopper said:

I’ve added a picture of the switch that keeps turning itself off, its the switch on the main 12v panel.

 

Its just the pump is not pumping water to anywhere, taps or washing machine. 

Faulty rocker switch ?

Or over current tripping the switch ?

 

Can you get to the back of the panel ?

If so try swapping over the water pump wire to the shower pump switch and see if it still happens.

Edited July 18, 2019 by Alan de Enfield

[WotEver]

56 minutes ago, Rockhopper said:

We have tested the voltage to the pump with multi meter and the reading is coming back as 1.4v. We don’t believe this is normal and it should be reading 12v right?

Yes it should. As others have said, it’s either the pump or the switch. My money is on the switch (which is a circuit breaker/MCB). Alan’s test will prove it quite quickly. 

Edited July 18, 2019 by WotEver

[WotEver]

 

When you look at the back of the panel look for any writing on the ‘switches’, specifically something like ‘6A’. When you do Alan’s test firstly check that the Shower Pump switch has the same writing as the faulty Water Pump one. 

Edited July 18, 2019 by WotEver

[Tony Brooks]

If you have undersized wiring or even lowish batteries the motor will not be bale to run up to speed and at lower speeds its effective "resistance" to current flow is lower. This allows an otherwise good motor to draw excess current and maybe trip the breaker.

 

I am not saying this is the problem but if it is undersized cables changing the pump and/or breaker/switch will have little effect. However I suspect the switch.

 

If you know how to do it measure the voltage between pos and neg close to the pump with the pump running and report back.

[Rockhopper]

Ok, we have the panel off and the shower pump says 8A and the water pump says 10A. Most others are 15A. what should we try swapping it with?

[Rockhopper]

My other half has removed the 10A from the water pump switch (see picture) and has put a 15A in its place. The 15A is from the radio and 12v and we don’t use that.

 

To our joy the water pump is working again!

 

Question is, are we ok to continue using the 15A for the water pump or could that cause problems over time? Sorry, our electrical knowledge is somewhat lacking!

[Tony Brooks]

As so often please not the breaker is NOT rated for DC so if or when it trips or when you turn it off with its load working it may well burn its contacts or weld them together. MY guess is burned contacts.

 

I doubt the water pump is wired in anything less that 2 sq mm CCSA cable and if so the cable is good for 20 amps or more so it should be safe. Even if its old PVC wiring I think 2 sq mm was rated at 17 amps so still OK.

[Rockhopper]

Hi Tony

 

I’m not clear with what you are saying in your first paragraph, please could you clarify? - thank you!

 

In terms of using 15A for the water pump, I just read ‘Fuse:15amp’ on the pump itself (see picture) so we should be ok?

[Alan de Enfield]

10 minutes ago, Rockhopper said:

Hi Tony

 

I’m not clear with what you are saying in your first paragraph, please could you clarify? - thank you!

 

In terms of using 15A for the water pump, I just read ‘Fuse:15amp’ on the pump itself (see picture) so we should be ok?

 

 

Basically - those 'switches' are not supposed to be used on 12v DC, they are designed for 220v AC.

 

You may think that 12v is much less than 220v - BUT DC has a very different effect on the contacts. (DC will burn them out)

 

The AC ones are much cheaper than the Dc equivalents so it is quite common to find them used on 'budget' boats.

Edited July 18, 2019 by Alan de Enfield

[Tony Brooks]

5 minutes ago, Rockhopper said:

Hi Tony

 

I’m not clear with what you are saying in your first paragraph, please could you clarify? - thank you!

 

In terms of using 15A for the water pump, I just read ‘Fuse:15amp’ on the pump itself (see picture) so we should be ok?

 

 

Basically its the wrong circuit breaker as are all the others in all likely hood. Mains stuff at home is AC that is the current turns itself off and goes the other way 100 times a second so as soon as the contacts part the current has switched itself off so the breaking contacts can't spark. With DC the current keeps flowing so thee breaking contacts create a spark and a s12V DC tends to  require higher currents that 240V AC to do the same job the sparks are likely to be larger.

 

I am only going by the characters moulded into your breaker. The manufacturer may say they are OK on DC but it does not say that. When new they will break at the correct   value but may not continue to do so if the contacts burn.

[Rockhopper]

My other half has removed the 10A from the water pump switch (see picture) and has put a 15A in its place. The 15A is from the radio and 12v and we don’t use that.

 

To our joy the water pump is working again!

 

Question is, are we ok to continue using the 15A for the water pump or could that cause problems over time? Sorry, our electrical knowledge is somewhat lacking!

[Rockhopper]

To clarify, the boat was built in 2002 and the pump that was fitted originally by Liverpool Boat Company connected to a 10amp fuse. That is no longer in use and we have found it in storage on the boat.

 

Since then, the previous owners replaced said pump with a newer pump that was connected to a 15amp fuse. It has become apparent today with taking off the mains panel that he didn’t change the breaker switch over, so the newer pump requiring a 15amp fuse was connected to a 10amp fuse. We have just realised that today.

 

We’re going to check the swap over of switches with a couple of neighbours to be sure as we want to make sure we’re safe above all else!

 

Thank you all for your super helpful feedback, sincerely appreciated  xx

 

P.S. All noted on the AC and DC front, we’ll look into making the changeovers so we can remain safe!

Edited July 18, 2019 by Rockhopper

[WotEver]

26 minutes ago, Rockhopper said:

are we ok to continue using the 15A for the water pump

Yes

[WotEver]

21 minutes ago, Rockhopper said:

All noted on the AC and DC front, we’ll look into making the changeovers so we can remain safe!

A couple of points to note. The arcing that Tony B described is most damaging to the switch contacts when you switch the pump off when it’s running, as opposed to switching it on. Switching it on and causing it to run will also arc somewhat but usually in a less damaging manner. So to lengthen the life of the switch, never switch the pump off while it’s running. 

 

Secondly, fitting an ordinary switch into the feed to the pump will avoid you having to switch that breaker off and on at all. Assuming that you have a convenient location to fit one. Any boat electrician could do this for you. 

[Rockhopper]

? Thanks, appreciate that ??

[Kudzucraft]

1 hour ago, Rockhopper said:

Question is, are we ok to continue using the 15A for the water pump or could that cause problems over time? Sorry, our electrical knowledge is somewhat lacking!

NO! 

 

Well, I have to make an assumption saying this but you should NEVER replace a fuse or circuit breaker with a larger rated one except for maybe testing.

 

The purpose of a fuse is to protect the wiring, not the device hooked to it, the pump.  Different size wire can only safely handle a certain amount of amperage (a measure of how much electricity is flowing  through the wire).  As electricity flows through the wire it heats up.  To much electricity and it can overheat and cause a fire.

 

This is where I have to make the assumption that the wire was rated for at least 10 amps. Since you have now replaced it with a 15 amp switch/fuse it will allow 50% more electricity to flow through the wire before it trips. If the pump or the wire develops a short the wrie could overheat and lead to a fire.  So no, you need to place it with a 10 amp unless you know that the wire size going to the pump can is rated for 15 amps.

[Rockhopper]

Thanks Kudzucraft, do you know where we might buy these type of switches for boats at all? I’m struggling to find something online. Alternatively, is there a way of checking if the cable is rated for 15amps?

[WotEver]

39 minutes ago, Kudzucraft said:

NO! 

 

Well, I have to make an assumption...

And your assumption is that the pump wiring is smaller than 2mm²?

 

My assumption would be that the cable would be at least 2.5mm², possibly larger. Cable used in 12V circuits on boats is invariably selected to minimise voltage drop, not the smallest that can carry the current. I’ve never seen a major manufacturer use anything smaller than 2.5mm² for wiring to the water pump. 

 

 

Edited July 18, 2019 by WotEver
It’s a pump, not a puma.

[Kudzucraft]

3 minutes ago, WotEver said:

And your assumption is that the pump wiring is smaller than 2mm²?

 

I stated my assumption.

[WotEver]

21 minutes ago, Rockhopper said:

is there a way of checking if the cable is rated for 15amps?

Do you have any 2.5mm three core mains flex kicking around?  If so, take one core and look at the thickness of the copper wires - ignore the insulation. Compare that to the thickness of the wires feeding the water pump. Are they similar?

2 minutes ago, Kudzucraft said:

 

I stated my assumption.

Which is unlikely in the extreme. 

[Kudzucraft]

25 minutes ago, Rockhopper said:

Thanks Kudzucraft, do you know where we might buy these type of switches for boats at all? I’m struggling to find something online. Alternatively, is there a way of checking if the cable is rated for 15amps?

No, sorry I don't.

 

 

2 minutes ago, WotEver said:

Which is unlikely in the extreme. 

What are talking about?  All I said was  

Quote

This is where I have to make the assumption that the wire was rated for at least 10 amps.

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Edited July 18, 2019 by Kudzucraft