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commissioning water system after long lay up


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1 minute ago, Halsey said:

There is very little difference in cost between 2 accumulators and 2 pumps.

Thoughts................................

 

One of my boats has a Jabsco Par Max 2.9, and it ran like an utter dog until I fixed the non-working expansion vessel. 

1 minute ago, WotEver said:

Would sir like a nice pastel pink?

 

I'd prefer eau de nil please, really...

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1 minute ago, Mike the Boilerman said:

 

One of my boats has a Jabsco Par Max 2.9, and it ran like an utter dog until I fixed the non-working expansion vessel. 

That's the feedback I need ..................I assume despite it saying it didn't need an accumulator it in fact did or was this one of the so called integral ones in the pump unit??

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3 minutes ago, Halsey said:

I assume despite it saying it didn't need an accumulator it in fact did or was this one of the so called integral ones in the pump unit??

 

Eh?

The Jabsco Par Max 2.9 does not have an integrated expansion vessel, it claims not to need one (integrated or otherwise).

I suspect in reality it can be used for long periods without one without getting damaged but mine sounded deeply unhappy and the water came out in rapid spurts if the tap wasn't fully open. 

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16 minutes ago, Halsey said:

has anyone got the Jabsco mentioned above.

 

Replaced our Shurflo with the Jabsco 2.9 a few years back. No noticeable difference, except the price. At the time we bought 2 jabsco's for the price of one Shurflo.

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7 minutes ago, Mike the Boilerman said:

 

Eh?

The Jabsco Par Max 2.9 does not have an integrated expansion vessel, it claims not to need one (integrated or otherwise).

I suspect in reality it can be used for long periods without one without getting damaged but mine sounded deeply unhappy and the water came out in rapid spurts if the tap wasn't fully open. 

I understand that such pumps either vary their speed to maintain a fixed pressure over a range of flow rates or, as I think may be the case with the Parmax, has a bypass valve that is set to open just below the cut out pressure so, in theory, as they reproach cut out pressure the bypass valve opens and vents excess flow back to the inlet.

Some years ago I had a conversation with one of the companies making these and was told they were produced at the behest of volume boat builders to save the expense of an accumulator. They also said that they MUST not be used with an accumulator but their reasoning was very woolly and they appeared unable to answer questions based on basic physics about that statement.  At that time one maker said an accumulator must not be used while another said it was OK. I think, but can not longer be sure that it was Jabsco that were happy for an accumulator to be used.

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4 minutes ago, Tony Brooks said:

I understand that such pumps either vary their speed to maintain a fixed pressure over a range of flow rates or, as I think may be the case with the Parmax, has a bypass valve that is set to open just below the cut out pressure so, in theory, as they reproach cut out pressure the bypass valve opens and vents excess flow back to the inlet.

Some years ago I had a conversation with one of the companies making these and was told they were produced at the behest of volume boat builders to save the expense of an accumulator. They also said that they MUST not be used with an accumulator but their reasoning was very woolly and they appeared unable to answer questions based on basic physics about that statement.  At that time one maker said an accumulator must not be used while another said it was OK. I think, but can not longer be sure that it was Jabsco that were happy for an accumulator to be used.

Thanks Tony - given my issues mentioned above would you leave the pumps as they are and simply replace the accumulators - clearly my concern is that I do all that and then the pumps fail but if the combined unit isn't as good anyway then I've lost nothing - In my Hi Fi purchasing days in the 80's I always bought separates and probably prefer that option - The Jabsco literature is quite tempting as is saving app £120

I don't know enough to make the call here so am happy to be guided by others with more experience.............

Thanks all ....................

18 minutes ago, rusty69 said:

Replaced our Shurflo with the Jabsco 2.9 a few years back. No noticeable difference, except the price. At the time we bought 2 jabsco's for the price of one Shurflo.

with or without an expansion tank??

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30 minutes ago, Halsey said:

thanks but I'll have to stay with the same basic type/design due to very tight space restrictions

Have a look they do various sizes from 2 litres upwards they are all basically the same so you might get away with a smaller one if space is tight, and under £20.

Neil

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5 minutes ago, Halsey said:

Thanks Tony - given my issues mentioned above would you leave the pumps as they are and simply replace the accumulators - clearly my concern is that I do all that and then the pumps fail but if the combined unit isn't as good anyway then I've lost nothing - In my Hi Fi purchasing days in the 80's I always bought separates and probably prefer that option - The Jabsco literature is quite tempting as is saving app £120

I don't know enough to make the call here so am happy to be guided by others with more experience.............

Thanks all ....................

with or without an expansion tank??

I personally very much believe in the KISS principle so I would do away with separate systems for hot & cold water and fit one normal, non-bypass, pump and separate accumulator. The accumulator can go anywhere on the pressure side of the pump providing no one way valve is  between it and the pump. I might be tempted to fit tandem pumps on one system with a switch to select one pump or the other but don't think I would bother. I would probably just carry a spare pump if I were worried about reliability. However having said that I always fit a remote pressure switch and then any reliability issue is usually simple leaks that do not prevent you carrying on using the pump for a while.

Fir years we operated systems on the hire fleet without accumulators AND we used domestic indirect cylinders in some cases without a significant increase in problems so I am not particularly convinced by arguments about cycling and reduced pump life. I just accept domestic water pumps on boats will cycle at times.

As I think I said before I simply can not understand why your system is as it is, it seems overcomplicate for what it needs to do. I suppose if the pumps were low volume/output affairs then the low output would go a long way to preventing cycling be it with some outlet pressure loss but it still seems odd.

I would not buy a bypass valve pump because its another valve to get jammed open.

The expansion tank is a different thing, it will help stop the hot water PRV leaking and will reduce the stress on the calorifier to some degree. I would fit one unless there was no one way valve between the hot water system and the accumulator. In that case the accumulator will also act as an expansion tank to a degree. My boat has been like this for 15 years or more. Some calorifier manufacturers demand an expansion tank, I feel it says more about the strength and design of their product that anything else.

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36 minutes ago, Halsey said:

Thanks Tony - given my issues mentioned above would you leave the pumps as they are and simply replace the accumulators - clearly my concern is that I do all that and then the pumps fail but if the combined unit isn't as good anyway then I've lost nothing - In my Hi Fi purchasing days in the 80's I always bought separates and probably prefer that option - The Jabsco literature is quite tempting as is saving app £120

I don't know enough to make the call here so am happy to be guided by others with more experience.............

Thanks all ....................

with or without an expansion tank??

I left the accumulator in, and de-pressurised it.seems to make little difference either way. 

Edited by rusty69
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Thanks everyone - KISS seems the way to go so I will use what I have for now as it is working, just with no accumulator function, and I'll choose a warmer period in a couple of months time to review the whole set up and sort it all out once and for all - so for now its plan for KISS and do nothing!

As the main water tank has two outlets I will probably set it up as one system with a plumbed in spare - I assume I can simply common up the piping on the services/boat side of the new accumulator so all the changes are made in the current "water services cupboard" with a bit of re-planning I will probably have room for the two pumps and one more "normal" accumulator?

Thanks again, our cruising season starts in earnest next week along with many others I guess - that's about right as more snow is forecast!. 

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