domestic water pump not cutting out

[Risa]

Hi Folks

domestic water - pumped by a new Jabsco par 4 with integral pressure switch. The pump is new since the old one, as the new, wont cut out when up to pressure. so unless im really unlucky its not the pump/switch.

the system is as follows - st st water tank - reinforced flexible pipe to inlet of pump via one way valve (new) and strainer (new). outlet of pump to taps is speed fit plastic piping, there is a branch off after the pump outlet for the DHW calorifier feed and an ACCUMULATOR!!! ( this I have filled with water and filled with air makes no difference)

there are no leaks from the pipework ( not even a little drip). The pump has been left on inadvertantly for 1/2 hr no drips but no cut off.

its been suggested that teh spring in the pressure switch is the wrong colour/pressure setting????


any thoughts ???

thanks in advance

 

[VicS]

Par max 4

Possibilities are , but not in any particular order.

Dirt in the valves preventing it reaching the cut off pressure. Unlikely as you fitted a new suction side strainer. Hopefully at the same time as the pump.

Defective pressure switch (£22 for a replacement) The parts diagram does not show the spring as a separate part.

Wiring defect keeping the pump running even though the pressure switch has operated.

Poor power supply (it needs 15 amps) resulting in it not reaching full pressure.

A leak somewhere but it will be more than the little weep that causes pumps to periodically cut in. Could there be a leak in the calorifier?
Can you blank off the pump outlet to eliminate the possibility of it being a leak anywhere?

Air ingress into the suction side.

No water in the tank or the tank outlet blocked.

Not possible I suppose to measure the discharge pressure. It should cut out at 40psi.

 

[sarabande]

is the accumulator immediately downstream of the pump ? I'm not quite clear whether it has been set (using the air inlet valve on top) to the correct pressure for the pump.

Otherwise it sounds like the pump is duff.

Jabsco run an excellent online technical support unit.

"mailATjabscoshopDOTcoDOTuk

 

[alan006]

If you can put a temporary stopper in the water pipe directly after the pump, then do so and turn the system on. If the pump runs and then stops you know the pump is ok and you can look for the problem elsewhere. If my memory is correct on some acccumulators there is a small adjustment screw, yours might be set too high for the pressure switch on your pump.
Hope this helps.

 

[nimbusgb]

We went through this just recently on the forum, a lot of suggestions were made.

Are you sure that water is getting to the supply side of the pump in sufficient quantity??

 

[Risa]

thanks Guys

Ill check the power supply when next on board but im pretty sure the connections are good

there are no leaks at all the boat has been completely dry for years ( bar the bottle of beer which leaked whilst being stored in the bilge - that was an interesting thought process when i tasted for salt!!)

air ingress on suction - that one to try


tanks are full so no shortage of suppy - accumulator - how is set for pump pressure - I alwys thought the idea was to compress air so it should be empty ??


trial and error I suppose but thanks for the steer

 

[philip_stevens]

If you have a foot pump in the water circuit, pressure water could be passing through this (with defective valves), back to the water tank. Ideally, there should be a non-return valve between the pressure side and the foot pump outlet.

 

[Risa]

not thought of that one - will give it a go - thanks

 

[VicS]

You did not mention a foot pump in the original description of the system /forums/images/graemlins/mad.gif

If you have one I'd bet Philip is right.

 

[misterg]

Go on then, I'll throw my 0.02p in too:

Have you purged the pump of air thoroughly? I.e. open a tap and let it run until the coughing and spluttering stops?

Andy

 

[SoSageofLorn]

I had the same issue, replacing an existing Jabsco pump with a new one system would not pressurise. The direction of flow on the new pump was opposite to the old pump. Unexpected and well worth checking.

 

[Risa]

thanks folks
there is a foot pump in the galley I could take this out of circuit

i have a check valve between tank and pump - the pump is the correct orientation and the system is bled as we use the pump for filling sink etc and the foot pump for glas water/teeth cleaning etc.

weve been doing this for 7 years Im embarrassed to say so I know there are no leaks

many thanks for the thoughts/advice its appreciated.