Water pump won’t shut off

[starman]

 

Ive just got rid of  a troublesome Seaflo water pump and fitted a new Sureflo as it has like for like connectors. 

Worked fine for a few days. Then we left the boat for a week, came back today, turned water back on, opened taps and the pump runs but won’t turn off! 

The water runs fine from all taps and I can’t find any trace of leaking anywhere.  It’s been cold here but not cold enough to blow pipes. 
Baffles me. 

It’s a surecal calorifier with accumulator, expansion vessel, prv and non return valve. 
Any suggestions very gratefully received. This water system is jinxed!

 

[ditchcrawler]

Check voltage at the pump terminals with the pump running

[starman]

7 minutes ago, ditchcrawler said:

Check voltage at the pump terminals with the pump running

Only 10v which I’m very surprised at. 

[Tracy D'arth]

You are either losing water from somewhere that you can't see or the pump has a valve inside that is not sealing. Could you have got something foreign in the pump? I don't see what the voltage at the pump has anything relevance.  But 10v means you have a poor connection, too thin wiring or flat batteries.

Edited December 4, 2021 by Tracy D'arth

[Tony Brooks]

31 minutes ago, starman said:

Only 10v which I’m very surprised at. 

 

Sort that ASAP, it will cause the pump to draw more than the designed running current and that way leads to overheating and burning.

 

Best check the voltage at the battery terminals with the pump running to see if it is a battery or wirirng problem.

Edited December 4, 2021 by Tony Brooks

[starman]

7 minutes ago, Tony Brooks said:

 

Sort that ASAP, it will cause the pump to draw more than the designed running current and that way leads to overheating and burning.

I must admit it does baffle me: the cables are 4sq mm along 30ft which should give about .5v drop and the connectors are crimp at the fuse box and Wago at the pump. 
I’ll check it all tomorrow. 

[Tony Brooks]

6 minutes ago, starman said:

I must admit it does baffle me: the cables are 4sq mm along 30ft which should give about .5v drop and the connectors are crimp at the fuse box and Wago at the pump. 
I’ll check it all tomorrow. 

 

Assuming 8 amps draw then I make it just under 1V drop over 30 ft and if that 30 ft is just the positive run you have another 30 f ton the negative so that would give close to 2V less at the pump than at the battery.

[Tracy D'arth]

4mm is a bit thin over 60 feet run.  Rule of thumb, 1mm per meter one way. so 30 feet away  I'd go for 10mm,   6mm as a bare minimum. But that is unlikely to be the reason for it running on.

[starman]

8 minutes ago, Tony Brooks said:

 

Assuming 8 amps draw then I make it just under 1V drop over 30 ft and if that 30 ft is just the positive run you have another 30 f ton the negative so that would give close to 2V less at the pump than at the battery.

It says max 4.5a on the pump. Based on that the 12v Planet calculator said 0.5a. 
 

Now you’ve got me alarmed!

[Tony Brooks]

13 minutes ago, starman said:

It says max 4.5a on the pump. Based on that the 12v Planet calculator said 0.5a. 
 

Now you’ve got me alarmed!

I used 8 amps because I seem to recall my Jabsco instructions said fuse at 10 amps. At 4.5 amps the VD over 30 ft seems to be just over 0.5 volt as you say as long as that is 30ft in total. that is 15ft out and 15ft back. However the slower most electric motors run the higher the current they draw so if you are down on voltage the speed will be sower and the current would be more than  4.5 amps.

[starman]

7 minutes ago, Tony Brooks said:

I used 8 amps because I seem to recall my Jabsco instructions said fuse at 10 amps. At 4.5 amps the VD over 30 ft seems to be just over 0.5 volt as you say as long as that is 30ft in total. that is 15ft out and 15ft back. However the slower most electric motors run the higher the current they draw so if you are down on voltage the speed will be sower and the current would be more than  4.5 amps.

But is this connected to the pump not turning off?

[MtB]

Well obviously the pressure switch is not operating. This could be because the low voltage at the pump terminals is not allowing the pump to develop enough pressure to operate the switch, or the switch could be goosed. Sureflo is not a well regarded brand, I gather.

 

A quick and dirty way to find out which it is, is to start the engine. The 14.4v alternator voltage should boost the voltage at the pump to the design voltage of 12v or so and if the pump now shuts off, your new pump is just fussy about the voltage. If it still fails to shut off, the switch is goosed. 

 

 

Edited December 4, 2021 by MtB

[Tracy D'arth]

If it was a defective pressure switch, the pump would be going over pressure and the PRV would be dumping. I reckon its valves/s not closing.

[Tony Brooks]

18 minutes ago, starman said:

But is this connected to the pump not turning off?

 

As MtB says it may well be the pump can not develop sufficient pressure so you need to get 12V to the pump. Do as he says and try it with the engine revving.

 

Tracy may also well be correct. The valves in the pump may be allowing pressure back into the tank. I fitted a flap type NRV on the pump inlet pipe to help guard against faulty pump valves. The easiest way to check is to get 12V at the pump and see what happens.

[starman]

Thanks all Will do the engine running test tomorrow and hopefully that will provide some answers. 

[Jen-in-Wellies]

Assuming your boat has a cabin bilge separate from the engine bilge, it is worth checking the cabin bilge for unexpected water at the stern end. Hopefully there is an access hole somewhere that you can take a look.

[MtB]

1 hour ago, Tracy D'arth said:

If it was a defective pressure switch, the pump would be going over pressure and the PRV would be dumping. I reckon its valves/s not closing.

 

Yes that could be happening, and if it were, the pump would run all the time! 

 

Could the OP perhaps check the PRV outlet is not dumping through to outside please? It may not be immediately obvious from inside the boat.

[starman]

12 hours ago, starman said:

Thanks all Will do the engine running test tomorrow and hopefully that will provide some answers. 

Engine running and pumped stopped. Hooray and thanks. Volts reading 14.4 at  engine and 14.1 at pump. 
PS to MtB and JiW I did check bilge and PRV last night too. 

Edited December 5, 2021 by starman

[MtB]

3 minutes ago, starman said:

Engine running and pumped stopped. Hooray and thanks. Volts reading 14.4 at  engine and 14.1 at pump. 

 

Excellent news, in which case this is puzzling:

 

14 hours ago, starman said:

Only 10v which I’m very surprised at. 

 

Your 0.3v volt drop between engine and pump, is that with the pump running?

[Tony Brooks]

23 minutes ago, MtB said:

 

Excellent news, in which case this is puzzling:

 

 

Your 0.3v volt drop between engine and pump, is that with the pump running?

 

1. Agree news wise but the boat was left for a week so was something left on? Could a battery be developing an internal short.

 

2. That is the vital missing info. If it was not then its an invalid test.

 

Unless something was left on It would be a good idea to think about a cell short. I think these are sealed batteries in a proper engine room. Being sealed the amount go gassing and level can't be checked but after some hours of charging feel the batteries for a local hot spot and check for the rotten egg smell but that would probably not be present until much later in the battery degradation.

 

 

[Tracy D'arth]

Glad you seem to have solved the problem. Its not puzzling, its bizarre, don't see the connection at all.  Another school day.

8 minutes ago, Tony Brooks said:

 

1. Agree news wise but the boat was left for a week so was something left on? Could a battery be developing an internal short.

 

2. That is the vital missing info. If it was not then its an invalid test.

 

Unless something was left on It would be a good idea to think about a cell short. I think these are sealed batteries in a proper engine room. Being sealed the amount go gassing and level can't be checked but after some hours of charging feel the batteries for a local hot spot and check for the rotten egg smell but that would probably not be present until much later in the battery degradation.

 

 

Don't go sniffing too long, hydrogen sulfide is an accumulative poison gas.   Still puzzled by this behaviour.

[MtB]

20 minutes ago, Tony Brooks said:

 

1. Agree news wise but the boat was left for a week so was something left on? Could a battery be developing an internal short.

 

2. That is the vital missing info. If it was not then its an invalid test.

 

Unless something was left on It would be a good idea to think about a cell short. I think these are sealed batteries in a proper engine room. Being sealed the amount go gassing and level can't be checked but after some hours of charging feel the batteries for a local hot spot and check for the rotten egg smell but that would probably not be present until much later in the battery degradation.

 

 

 

Another bit of crucial but missing info is the domestic battery voltage when the OP measured the pump terminal voltage at 10v in Post No 2. The domestic batts might have been heavily discharged. Again on reflection, we don't know if that 10v was with the pump running or with the pump off. 

 

 

[Tony Brooks]

1 hour ago, MtB said:

 

Another bit of crucial but missing info is the domestic battery voltage when the OP measured the pump terminal voltage at 10v in Post No 2. The domestic batts might have been heavily discharged. Again on reflection, we don't know if that 10v was with the pump running or with the pump off. 

 

 

 

That is what I suggested in about post five but it did not seem to get picked up

[TheBiscuits]

1 hour ago, MtB said:

we don't know if that 10v was with the pump running or with the pump off. 

 

I assumed it was with the pump running as the OP says it won't shut off.

 

 

[MtB]

9 minutes ago, TheBiscuits said:

 

I assumed it was with the pump running as the OP says it won't shut off.

 

 

 

The thing is, with the engine running to OP reports a 0.3v drop in the pump wiring. This does not seem consistent with the 10v reported at the pump terminals with the engine off, unless the batteries were down at 10.3v when the 10v was measured, or unless the 14.1v result with the engine running is with the pump OFF. 

 

If it is with the pump OFF, this 0.3v drop indicates a horribly poor connection in the wiring as there would otherwise be no volt drop with no current flowing. A poor connection could however also explain the unusually low 10v pump terminal voltage with the engine OFF. 

 

 

So, my prediction is this fault and failure of the pump to shut off with the engine OFF, is down to a poor electrical connection somewhere in the supply wiring.