old water pump id next!

[black sebastian]

Hello again! Having purchased a Jabsco 8 litre accumulator tank to replace the old fettled Godwin.. now faced with the old water pump.. photos attached. Some features I can associate with the annotated diagram on p. 341 of Nigel Calder's manual .. I presume the pressure switch is plumbed off the vert de gris coated part at the bottom of the pump? 

Without disassembling it .. any guesses as to what pressure it could be set to? 

The Jabsco unit is pre pressurised to 35 psi. I believe I should reduce it to 2 psi below the setting of the pressure switch on the water pump. 

Therein lies the question?

p.s.  have tried photoshop enhancing the pump label .. but not much help?

 

Any help again most gratefully received.

Many thanks

Neil Jones

[black sebastian]

p.s. .. cant find a similar pressure switch on image searches .. goodness knows where its from. I have replaced the drive belt on the jabsco pump 4 years ago!

[Tracy D'arth]

It may be old but those Jabsco Par 36950 series pumps are splendid. Very reliable if a trifle noisy, my boat has these. I won't use anything else, all the modern plastic ones are junk compared.

Every spare you could ever need is available from Cleghorn Waring. The low pressure switches are a bit different from the originals but work the same.

 

Easy way to set the pressure in the accumulator is to fit it all, turn on water and electrics, let the pump run till is stops.

Then slowly release the air pressure by pressing the Schrader valve on the accumulator until the pump just comes back on. Job done.

[Tony Brooks]

It looks like a horizontally mounted Square D/D Square pressure switch and it just shows how robust and long lived they are except I can't see the second adjuster. One for cut out pressure and one for cut in pressure. If there is only one it will be for the cut out pressure. Yes, of the green powder.

 

The best thing to do is to depressurise the accumulator to about 10psi with pump off and a tap open. Close tap and run pump until it cuts out and the measure the air pressure inside. if its more than 10psi it will be the same as the pump cut out pressure. Then re-pressurise the accumulator to about half the pressure you just measured (the cut in pressure is typically about half the cut out but on an old switch that may have been adjusted who knows). If the "accumulator" was to be used as an expansion vessel you would pressures it to the cut out pressure.

 

 

 

 

[black sebastian]

Fantastically fast response.. Many thanks. Great advice  now I can progress.

Cheers

 Neil

[Tracy D'arth]

It is a Square D pressure switch without its cover, do you need to alter it? If not I would leave it alone, The standard Par switch would fit into the same hole.

 

On the Square D the long thread nut sets the cut out pressure, ie. maximum and the shorter thread nut sets the cut in, minimum pressure.

 

I've got one and the instructions somewhere if you need help but if the pressures are OK best left.

Edited August 9, 2020 by Tracy D'arth

[WotEver]

8 hours ago, Tony Brooks said:

It looks like a horizontally mounted Square D/D Square pressure switch and it just shows how robust and long lived they are except I can't see the second adjuster.

The shorter one is directly above the longer one in that photo Tony, so that it almost looks like one screw.

[Tony Brooks]

12 minutes ago, WotEver said:

The shorter one is directly above the longer one in that photo Tony, so that it almost looks like one screw.

 

yes I had a closer look after Tracy's reply. It is one screw but two nuts and two springs

[WotEver]

56 minutes ago, Tony Brooks said:

 

yes I had a closer look after Tracy's reply. It is one screw but two nuts and two springs

Nope, it’s two screws. 

[black sebastian]

many thanks

 

neil

 

[Tony Brooks]

10 hours ago, WotEver said:

Nope, it’s two screws. 

I fear my eyesight is deteriorating fast or hopefully its the little laptop screen

[Tracy D'arth]

1 minute ago, Tony Brooks said:

I fear my eyesight is deteriorating fast or hopefully its the little laptop screen

At least you can't have double vision!

 

I've got triple and its a b*gg*r.

[WotEver]

42 minutes ago, Tony Brooks said:

I fear my eyesight is deteriorating fast or hopefully its the little laptop screen

It’ll be the latter. I could only see one screw on my phone but saw both on a 21” screen. 

[black sebastian]

Hello again!

New Jabsco tank fitted  .. but still have same on/off cycling problem with water pump.

 

In folks opinion.. is it likely to require a rebuild of the pressure switch or the jabso par pump .. or both??

 Many thanks, Neil

[Tony Brooks]

Exactly what do you mean by an on off cycling problem?

 

If the pump delivery is greater than the flow from the tap then the pump will cycle. All the accumulator will do is alter the length of the ons and offs so when just filling a cup or kettle it may make only one cycle.

 

Domestic water pumps will cycle unless it has a lower output than the flow from any outlet.

[Tracy D'arth]

11 minutes ago, Tony Brooks said:

Exactly what do you mean by an on off cycling problem?

 

If the pump delivery is greater than the flow from the tap then the pump will cycle. All the accumulator will do is alter the length of the ons and offs so when just filling a cup or kettle it may make only one cycle.

 

Domestic water pumps will cycle unless it has a lower output than the flow from any outlet.

Please explain with reference to Tony's comment above.

 

How do you expect the pump to work? It will only run when you draw water after the pressure drops and will stop after you stop drawing water after a short period whilst it re-pressurises the accumulator.

[springy]

what pressure is in the accumulator, have you set it to the right pressure for your pump/switch

 

springy

[Tony Brooks]

9 minutes ago, springy said:

what pressure is in the accumulator, have you set it to the right pressure for your pump/switch

 

springy

If he followed my instructions in post 4 then he has set the pressure correctly - more or less but if he has not then he won't have.

 

The pressure he gave before that indicated he was mixing up accumulator and expansion tank pressure.

Edited September 3, 2020 by Tony Brooks

[black sebastian]

Hello Tony, I fitted the Jabsco tank ..but tried the first suggestion I had first (switched on pump with taps closed...until pump stopped.. then let air out from schrader valve until the pump cut in again).. 

Performed exactly as it had before... with taps all closed, pump on for about 5 seconds then off for 1 to 2 minutes then on for 5 seconds etc.

I guess the original accumulator  was not the fault but at least I have a much lighter, newer, easily rechargeable tank now!)

 

There are no water leaks so I assume the fault must lie in the old jabsco PAR pump discharge valve (or pressure switch?)

 

Thanks

Neil

[Tracy D'arth]

Either you have a leak on the system that you have not found or the pump needs new valves as the outlet valve is letting water leak back. They are available as spares.

[ditchcrawler]

41 minutes ago, black sebastian said:

Hello Tony, I fitted the Jabsco tank ..but tried the first suggestion I had first (switched on pump with taps closed...until pump stopped.. then let air out from schrader valve until the pump cut in again).. 

Performed exactly as it had before... with taps all closed, pump on for about 5 seconds then off for 1 to 2 minutes then on for 5 seconds etc.

I guess the original accumulator  was not the fault but at least I have a much lighter, newer, easily rechargeable tank now!)

 

There are no water leaks so I assume the fault must lie in the old jabsco PAR pump discharge valve (or pressure switch?)

 

Thanks

Neil

You have let all the pressure out of it. Switch the pump off open all the taps and pump it up with a footpump or bike pump to the water pump cut in pressure. If you don't know the pump pressure then try 1.5 barr

[Tracy D'arth]

10 minutes ago, ditchcrawler said:

You have let all the pressure out of it. Switch the pump off open all the taps and pump it up with a footpump or bike pump to the water pump cut in pressure. If you don't know the pump pressure then try 1.5 barr

I don't think so.

[ditchcrawler]

14 minutes ago, Tracy D'arth said:

I don't think so.

OK

 

[Tony Brooks]

8 hours ago, black sebastian said:

Hello Tony, I fitted the Jabsco tank ..but tried the first suggestion I had first (switched on pump with taps closed...until pump stopped.. then let air out from schrader valve until the pump cut in again).. 

Performed exactly as it had before... with taps all closed, pump on for about 5 seconds then off for 1 to 2 minutes then on for 5 seconds etc.

I guess the original accumulator  was not the fault but at least I have a much lighter, newer, easily rechargeable tank now!)

 

There are no water leaks so I assume the fault must lie in the old jabsco PAR pump discharge valve (or pressure switch?)

 

Thanks

Neil

 What the *!*!XXXX was so hard about:-

 

The best thing to do is to depressurise the accumulator to about 10psi with pump off and a tap open. Close tap and run pump until it cuts out and the measure the air pressure inside. if its more than 10psi it will be the same as the pump cut out pressure. Then re-pressurise the accumulator to about half the pressure you just measured (the cut in pressure is typically about half the cut out but on an old switch that may have been adjusted who knows). If the "accumulator" was to be used as an expansion vessel you would pressures it to the cut out pressure.

 

I don't see anything about letting all the air out in that. If you don't take good advice why bother to ask? As Tracy says you have probably let too much air out of the accumulator but 1.5 bar is not fixed, its about right for a 3 bar (45 PSI) water pump but we have no idea how your pressure switch is set up.

 

We go back to the fact that accumulators do not and can not prevent the pump cycling on and of when in use unless the tap can pass a greater output volume than the pump can supply. If the pressure in the Godwin bladder was about right then the new accumulator will not make much difference to the pump cycling.

[Tony Brooks]

Actually I must apologise for the above because you will have set the accumulator pressure to the cut in pressure but you don't know what that is. However I still think that you don't grasp how the system works and have unrealistic expectations.