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1 minute ago, MtB said:


There is one on thunderboat? Which one??!

 

 

 

Still bitter you got a whole thread dedicated to you on there?

 

🤣🤣🤣🤣

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  • 4 months later...
On 31/05/2022 at 22:50, nicknorman said:

The accumulator is to smooth out the water pump cycles when the demand (tap opening) is less than the pump delivery rate. So it should fill up when the pump runs, and nearly empty when the pump isn’t running, the pump should cut in just before it’s empty. Which means the accumulator air pressure (with pump switched off and taps open) should be a bit below pump cut-in pressure. Typically this means around 15psi.

 

The expansion vessel doesn’t have a direct impact on the pump. It’s purpose is to prevent excessive pressure build up in the calorifier (hot water tank) because the calorifier is often fed through a non-return valve, meaning the volume of water is “trapped” so that when it is heated up, it expands and pressure becomes high. So the expansion vessel should be empty when the pump has just run, but fill up if the water is subsequently heated. In other words, its pressure (with pump off and taps open) should be around the pump cut-out pressure, perhaps around 30psi.

 

Once you have set the accumulator to roughly the right pressure, and because the air pressure can never be less than the water pressure and is normally equal to it, you can measure the air pressure in the accumulator just after the pump has cut out, and this will tell you what to set the expansion vessel pressure to.

… because the aim is to avoid the accumulator becoming totally empty before the pump cuts in.

OK.

So I need a new direct water supply pump 

To replace PAR-MAX 25 psi serial number 08080181

Auto, ### which is illegible 

Model #####illegible

Will the Jabsco PAR MAX HD4 

12V 15 LPM  25psi be the replacement?

There are bizarre instructions how to cut off water supply, the standard lever tap  does not move, I will have a cork on hand!

I take it that the accumulator has water in one side and air in the other ? Not that I need to know or understand! Imho!

 

 

 

 

 

 

 

 

Edited by LadyG
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On 31/05/2022 at 22:35, Sneill said:

Hi guys 

need a bit of guidance on my my mates plumbing issues . As I understand it the system has 2 vessels plumbed into the pipe work . One being an accumulator and one being an expansion .what pressures do these need to be set at for the pump to work properly? 
ta in advance 

No need for an expansion tank,

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26 minutes ago, Laurie Booth said:

No need for an expansion tank,

 

Disagree unless you know where the NRV is in the water supply system - that is unless you want to risk splitting the calorifier.

 

Edited to add: unless you are sure the system does not use any form of calorifier or indirect cylinder.

 

Edited by Tony Brooks
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3 hours ago, Tony Brooks said:

 

Disagree unless you know where the NRV is in the water supply system - that is unless you want to risk splitting the calorifier.

 

Edited to add: unless you are sure the system does not use any form of calorifier or indirect cylinder.

 

Yep

 

3 hours ago, Tony Brooks said:

 

Disagree unless you know where the NRV is in the water supply system - that is unless you want to risk splitting the calorifier.

 

Edited to add: unless you are sure the system does not use any form of calorifier or indirect cylinder.

 

Yep

3 hours ago, frangar said:

What’s your justification for that statement? 

Waste of money

 

3 hours ago, Tony Brooks said:

 

Disagree unless you know where the NRV is in the water supply system - that is unless you want to risk splitting the calorifier.

 

Edited to add: unless you are sure the system does not use any form of calorifier or indirect cylinder.

 

Yep

3 hours ago, frangar said:

What’s your justification for that statement? 

Waste of money

 

3 hours ago, ditchcrawler said:

Popcorn time

:)

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6 hours ago, LadyG said:

OK.

So I need a new direct water supply pump 

To replace PAR-MAX 25 psi serial number 08080181

Auto, ### which is illegible 

Model #####illegible

Will the Jabsco PAR MAX HD4 

12V 15 LPM  25psi be the replacement?

There are bizarre instructions how to cut off water supply, the standard lever tap  does not move, I will have a cork on hand!

I take it that the accumulator has water in one side and air in the other ? Not that I need to know or understand! Imho!

 

 

 

 

 

 

 

 

 

Bump

 

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10 hours ago, Laurie Booth said:

No need for an expansion tank,

 

Calorifiers tend to last much longer if the hot water side of the system is fitted with an expansion vessel, especially if there is a NRV on the cold water supply pipe to the calorifier. Otherwise the calorifier itself becomes the expansion vessel.

 

6 hours ago, Laurie Booth said:

Waste of money

 

 

Only if you can find a new calorifier cheaper. 

Edited by blackrose
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11 hours ago, LadyG said:

OK.

So I need a new direct water supply pump 

 

I don't understand the question. What's a direct water supply pump? I think you mean a domestic water pump.

 

You can replace your old pump with any make/model you like it's up to you. If you want something similar then just make sure it's the same voltage, compare the cut-in & cut-out pressures and the flow rate (LPM). To make life easier you might want to buy a pump with the same connections.

 

Before changing the pump you need to isolate your water tank turn off the pump and open some taps to relieve the pressure in the system. Have some towels ready to mop up the residual water.

Edited by blackrose
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56 minutes ago, blackrose said:

 

I don't understand the question. What's a direct water supply pump? I think you mean a domestic water pump.

 

You can replace your old pump with any make/model you like it's up to you. If you want something similar then just make sure it's the same voltage, compare the cut-in & cut-out pressures and the flow rate (LPM). To make life easier you might want to buy a pump with the same connections.

 

Before changing the pump you need to isolate your water tank turn off the pump and open some taps to relieve the pressure in the system. Have some towels ready to mop up the residual water.

Thanks, yes looking at midland chandler's they call it a direct water supply pump it's to supply the domestic taps. It's difficult to be sure everything is the same, ie fittings, I'll have another look when on my tablet. It's the same make,but I don't know the exact spec except it's psi and voltage.

Edited by LadyG
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1 hour ago, LadyG said:

Thanks, yes looking at midland chandler's they call it a direct water supply pump it's to supply the domestic taps. It's difficult to be sure everything is the same, ie fittings, I'll have another look when on my tablet. It's the same make,but I don't know the exact spec except it's psi and voltage.

 

Aren't the cut -in and cut-out pressures on a label on the body of the pump? They normally are on Jabsco pumps. Anyway it doesn't really matter if you buy a new pump with different pressures as you'll probably have to reset the pressure of your accumulator tank anyway - and your hot water expansion vessel, if you have one.

Edited by blackrose
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3 minutes ago, blackrose said:

 

Aren't the cut -in and cut-out pressures on a label on the body of the pump? They normally are on Jabsco pumps. Anyway it doesn't really matter if you buy a new pump with different pressures as you'll probably have to reset the pressure of your accumulator tank anyway - and your hot water expansion vessel, if you have one.

 

Disagree with the different pressures do not matter part. It is important you ensure the new pump's cut out pressure is (say) at least 5psi lower than the PRV opening pressure. If it is close then the PRV may jump as an outlet is shut or even judder under water hammer. If it is above then the PRV will open. Both cause excess pump running.

 

If you have an instant gas water heater or like a strong shower then the delivery volume may be important as well. You can get a rough idea of the delivery by timing how long it takes to fill a milk carton of known capacity from a fully open cold tap. As long as the accumulator has air in it the cut-out pressure will be the air pressure as the pump cuts out. A car tyre pressure gauge will be near enough.

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6 minutes ago, Tony Brooks said:

If you have an instant gas water heater or like a strong shower then the delivery volume may be important as well. You can get a rough idea of the delivery by timing how long it takes to fill a milk carton of known capacity from a fully open cold tap.

In practice, the flow rate is usually limited by the pipework bore, length, valves and angles. For example, my pump is 11lpm, but in practice it can deliver about 6lpm. If you want, for example, to increase the shower flow rate, measure the actual flow rate first. If it is significantly below what your current pump can deliver, see about increasing the bore size of the pipe work between the water tank and pump and between the pump and shower. Going from 15mm to 22mm OD pipe is going to have an effect. Just fitting a higher flow rate pump is probably not. Flow rates that pump makers quote are with the outlet open and no pipework, so unrealistic in most cases on a typical boat.

13 hours ago, LadyG said:

OK.

So I need a new direct water supply pump 

To replace PAR-MAX 25 psi serial number 08080181

Auto, ### which is illegible 

Model #####illegible

Will the Jabsco PAR MAX HD4 

12V 15 LPM  25psi be the replacement?

This should be fine. The cut out pressure is the same, which is important, if you have a cauliflower. The flow rate of 15lpm is high, so you should see similar flow rates at the taps and shower as before.

 

13 hours ago, Laurie Booth said:

No need for an expansion tank,

On my boat. New calorifier with no expansion tank split after four years. Replacement calorifier with expansion tank is still going after eleven years. Others on here with similar experiences. Calorifiers are in the hundreds of pounds. Potable water expansion tanks are in the tens of pounds. 

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7 hours ago, blackrose said:

 

Calorifiers tend to last much longer if the hot water side of the system is fitted with an expansion vessel, especially if there is a NRV on the cold water supply pipe to the calorifier. Otherwise the calorifier itself becomes the expansion vessel.

 

 

Only if you can find a new calorifier cheaper. 

If the HWT is in the off position and the WP is turned off all will be OK :)

Edited by Laurie Booth
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14 minutes ago, Laurie Booth said:

If the HWT is in the off position and the WP is in the off position all will be OK :)

 

Warning - if you are new to bat water systems this post might be confusing. Water pumps have two switches, I don't know which one is being referred to here, Even if we are talking about the electrical supply switch (rather than the pressure switch) the calorifier will still be necessarily pressurized unless the system had been depressurised before heating the calorifier.

 

In fact the only time the above would b true is if it said hot water tap OPEN and water pump turned off/isolated.

 

I note the smiley but still think it is a misleading statement.

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2 hours ago, Tony Brooks said:

 

Disagree with the different pressures do not matter part. It is important you ensure the new pump's cut out pressure is (say) at least 5psi lower than the PRV opening pressure. If it is close then the PRV may jump as an outlet is shut or even judder under water hammer. If it is above then the PRV will open. Both cause excess pump running.

 

Yes that's true. To clarify, I just meant it doesn't matter if LadyG changed her old pump for a new one with slightly different cut-in/out pressures, as long as the accumulator & expansion vessel pressures are reset to suit the new pump. I wasn't suggesting she buy a pump with a high cut-out pressure above the PRV opening pressure.

Edited by blackrose
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1 hour ago, Laurie Booth said:

If the HWT is in the off position and the WP is in the off position all will be OK :)

 

Perfect, that could be a solution to lots of boat equipment related issues... engines, gearboxes, electrics, etc. Just leave everything switched off and don't use anything and all will be OK! 🤣

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19 minutes ago, blackrose said:

 

Yes that's true. To clarify, I just meant it doesn't matter if LadyG changed her old pump for a new one with slightly different cut-in/out pressures, as long as the accumulator & expansion vessel pressures are reset to suit the new pump. I wasn't suggesting she buy a pump with a high cut-out pressure above the PRV opening pressure.

 

Bear in mind who was asking the question :D

 

I agree that unless the old pump cut out pressure was very close to the PRV setting a few PSI or litres per minute difference will make little difference.

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4 hours ago, Jen-in-Wellies said:

On my boat. New calorifier with no expansion tank split after four years. Replacement calorifier with expansion tank is still going after eleven years. Others on here with similar experiences. Calorifiers are in the hundreds of pounds. Potable water expansion tanks are in the tens of pounds. 

Did you keep the hot water tap turned on and the water pump turned off?

 

Edited by Laurie Booth
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