Can I put two water pumps on the same circuit?

[seanfoster]

Hi All,

I'm turning my attention to the wiring of my refit project (so no doubt more questions to come!).

I have two small pumps for the heads and galley sinks, each draw 3 amps max and will rarely be used together, the distance between each is about 2.5m (it's a small boat!).
As I only have one breaker left on my switch panel, I would like to put both on the same circuit, would it be ok to wire them in series, or should I have a separate feed for each one?

I'm thinking of running the positive through to the first one, then on to the second one, and returning the negative back to the common negative busbar.

I've yet to size the cable, but in general would this be safe?

Any advice would be appreciated!

 

[pvb]

Yes, you can put them both on the same breaker circuit, but they must have their own positive and negative feeds, you can't wire them in series.

 

[seanfoster]

Yes, you can put them both on the same breaker circuit, but they must have their own positive and negative feeds, you can't wire them in series.

Thanks for that!

 

[alahol2]

I'm thinking of running the positive through to the first one, then on to the second one, and returning the negative back to the common negative busbar.

I've yet to size the cable, but in general would this be safe?

What you describe is not wiring them in series, it is wiring them in parallel and is perfectly OK and safe. Make sure the wire and fuse are sized to allow both pumps to be run at the same time.

 

[John the kiwi]

What you describe is not wiring them in series, it is wiring them in parallel and is perfectly OK and safe. Make sure the wire and fuse are sized to allow both pumps to be run at the same time.

I concur with both points.
While both pumps together may seem unlikely, if something can happen, sooner or later it will happen...
Cheers
John

 

[LadyInBed]

If each pump draws about 3A on startup, then towire them both into a 5A breaker should be ok, you will probably get away with having the 2nd pump start up with t'other running.

 

[VicS]

If each pump draws about 3A on startup, then towire them both into a 5A breaker should be ok, you will probably get away with having the 2nd pump start up with t'other running.

The snag may be that when the circuit breaker is first closed after the boat has been unused for a period both pumps will start and run at the same time because the pressure in both systems has been lost, assuming pressurised systems of course, I dont think he said the circuit breaker was only 5A

The Op has not explained why he is installing two pumps rather than a common system for both galley and heads.

 

[Alpha22]

I suspect it is a none pressurised system...... but still, I'd rather have a bit of extra pipe than fuss with two pumps.

I have seen systems with two pumps PLUMBED in parallel so as the flow rate drops the second pump kicks in..... multiple showers..... If you could imagine that on a boat....??

 

[cryan]

If you wire them in series you couldn't use the pumps independently of each other. for this reason: http://www.instructables.com/id/Operation-Game/step16/About-Parallel-and-Series-Circuits/

Make sure your wiring, insulation and fusing/breakers are able to cope comfortably with the highest current that could be drawn not the highest current you expect in normal use. ie, make sure they have capacity for both pumps running full pressure at the same time.

 

[seanfoster]

Thanks for all of the replies everyone, much appreciated, the system is a very simple non pressurised system, basically I just wanted to replace the manual foot pumps with an electric one, I bought a couple of cheap £15 ones from ebay and they work remarkably well, almost identical to a jabsco one that I had been looking at.

I've now sized my cable taking into account the distance, I will feed each one separately but run them to the same 5A breaker.