Pressurization of the freshwater system?

[JDCAVE]

I have had 2 Shurflo Extreme Pro Blasters (5901-2212) fail due to the failure of the pressure sense switch. In both cases the pumps work fine. I have sourced new pressure switches and am in the process of reinstalling them. Actually it's a pretty simple fix but the switches are $50 each at Defender. I'd like to reinstall one one of the pumps back in the system as the Jabsco replacement is a lower pressure pump and puts out low pressure with the inline filtration system.

So the question is: Are these failures due to being under pressure for an extended period of time? Should I depressurize the FW system when away? I turn the pump off but perhaps a pressurized system is the reason for the failure of the switch.

Jim

 

[Ski in NC]

When leaving my boat, I (usually) turn off pump and open a faucet. Also crack open a faucet with pump off when turning water heater on from cold. I don't have an expansion tank anywhere so thermal expansion raises pressure a good bit. Shurflo pump, no failures in 9yr.

Do you have a pressure tank in system? That should keep from getting thermal expansion pressure spikes.

 

[Sealife]

As full time liveaboard cruisers, our system has been under pressure for over 2 years now. I would hope that is not causing your problems.

 

[JDCAVE]

As full time liveaboard cruisers, our system has been under pressure for over 2 years now. I would hope that is not causing your problems.

Ski: yes, I have an expansion tank. One other possibility is these switches are shorting out somehow. While the boat is pretty dry, those quick disconnects sometimes weeps a bit.

Jim

 

[ulysses]

Pressure or lack thereof should not have any adverse effects on the switch/sensor. I would assume that you are using the proper size wiring and of the proper voltage for the pump.
The pump is primarily designed as a "washdown" pump. Therefore there may be some duty cycle differences using it as a domestic fresh water pump.

You mention that you have an accumulator tank on the system. Have you recently tested it for air volume ? It is not uncommon for those small tanks to experience a loss of air and become "waterlogged" creating a quick cycling issue with the pump. That will indeed wear out a pressure/sensor switch fairly quickly. There should be an air valve on your tank that you can pump some more air into when the system is not pressurized. at least 1/3 of the tank should be air.

 

[JDCAVE]

You mention that you have an accumulator tank on the system. Have you recently tested it for air volume ? It is not uncommon for those small tanks to experience a loss of air and become "waterlogged" creating a quick cycling issue with the pump. That will indeed wear out a pressure/sensor switch fairly quickly. There should be an air valve on your tank that you can pump some more air into when the system is not pressurized. at least 1/3 of the tank should be air.

The system remains pressurized when the pump has been off for weeks.

Jim

 

[ulysses]

The system remains pressurized when the pump has been off for weeks.
Jim

i understand and that should have absolutely no bearing on the switch. If the pump is off at your main breaker neither the switch nor the pump will be energized. If the system still has pressure then it simply means there are no leaks on the pressure side of the system. That is a good thing. Your switch would not come into play at all.

The question remains..does your pump cycle quickly on and off when you are using a medium amount of water?

 

[JDCAVE]

No it doesn't cycle on and off.

 

[C lectric]

I do not have your pumps but I used to go through those darn switches.

They are often tiny switches and are not really suitable for long term switching of motors or other inductive loads. They are intended for signal type loads or non inductive applications.

They may be good quality units such as Cherry or Microswitch but just not the right units.

Motors when shut off can often produce a LARGE voltage from a collapsing magnetic field which is energy. That voltage can be much, much higher than then supply voltage although of very short duration. Nonetheless it will burn the contacts causing failure.

I used an industrial pump control switch such as the one below:
Square D Well Low Water Cut Off Pump Pressure Switch 20/40 PSI FSG2J20M4BP | eBay

The first one lasted about 20 years dieing two yrs ago so I'm on the second now. The contacts are much larger. I also wire both motor leads[ + & -] through the contact sets. Also use a diode which helps kill that back flash from the motor.

It may not work with all pumps especially the new electronic controlled units that are variable speed. But for other ON/OFF control pumps it should work fine. Just a matter of locating it as they are about 2.5" X 3.5" X 4" {guess]

The turn on and off point are adjustable from the one I have shown. This particular unit will also shut off the pump if the system leaks enough to dump pressure. It means you do have to go down to manually use the over ride if all pressure has been released untill enough pressure has been built to keep the switch closed.

The following does NOT have the safety loss of water protection:
https://www.amazon.ca/Square-Schnei...coding=UTF8&psc=1&refRID=4YJNPN2RXNKA1S1ZJXVH


Just a suggestion.

 

[ulysses]

C lectric: The switches that you are recommending are the standard in the well water industry. They are somewhat adjustable through their range of pressures and come in several pressure ranges. They can also adjust the difference between the cut on and shut off psi.
What might be of concern on a boat though is whether they are ignition protected, which I do not think they are. I would probably not use one on a gas boat. Furthermore with these newer pumps the switches are pretty much integral to the pump and not readily mounted away from the pump head.

 

[Wxx3]

As said above, if you turn off your pump when away, it doesn't know the pressure.

I think it's a crappy pressure sensor switch. I had a pump that was only a year old, pressure switch went out while in Maine. bought new pump, but also sent Shurflo back to them, they sent me anew one and it's been fine for the last three years.

If you are suspecting your connections, I would change them before you do anything else.

 

[HiDHo]

My Shurflow Revolution 4008 pressure switch lasted 2 1/2 years with the last year full time live aboard use before becoming erratic. I think the contacts get fouled from 12vdc arcing, best deal on replacement for me was ebay for $16. The replacement is simple, two contact wires and three screws, 5 minute job.

 

[dhays]

When leaving my boat, I (usually) turn off pump and open a faucet. Also crack open a faucet with pump off when turning water heater on from cold. I don't have an expansion tank anywhere so thermal expansion raises pressure a good bit. Shurflo pump, no failures in 9yr.

I always try to remember to turn off my fresh water pump when I leave the boat. However, I have never thought about depressurizing the system as well. Probably not a bad practice.

 

[C lectric]

C lectric: The switches that you are recommending are the standard in the well water industry. They are somewhat adjustable through their range of pressures and come in several pressure ranges. They can also adjust the difference between the cut on and shut off psi.
What might be of concern on a boat though is whether they are ignition protected, which I do not think they are. I would probably not use one on a gas boat. Furthermore with these newer pumps the switches are pretty much integral to the pump and not readily mounted away from the pump head.

Yes, they are not ignition protected so would not be suitable/safe for gas boats.
I forgot about that.

I was aware that many newer pumps may not be possible to use one of these but if the actual motor wires are accessible then it should be possible to use one.

If you have a variable speed pump then I would not recommend the use of the switch I suggested unless you want to go back to the ON/OFF only operation and use an accumulator.

However, if you are really having trouble with those installed switches it may be worth while to at least examine your pump and system to see if the pump switch can be used.

 

[ulysses]

Yes, they are not ignition protected so would not be suitable/safe for gas boats.
I forgot about that.

I was aware that many newer pumps may not be possible to use one of these but if the actual motor wires are accessible then it should be possible to use one.

If you have a variable speed pump then I would not recommend the use of the switch I suggested unless you want to go back to the ON/OFF only operation and use an accumulator.

However, if you are really having trouble with those installed switches it may be worth while to at least examine your pump and system to see if the pump switch can be used.

Absolutely agree with all. I am not sure if what the pump mfg. calls a "pressure switch" on the newer variable speed pumps are really what we call a pressure switch. It is my belief they operate more as a flow sensor or differential between upstream and downstream pressures and not really as a true mechanical switch. Given that assumption, the pressure rating for the pump is based more on max speed type of situation.

 

[JDCAVE]

"C": Thanks for that info. So you would plump that into the water system somewhere and control the pump with that switch, bypassing the old one? That would work, for sure. The boat is diesel, so that's ok. For now, I will use the replacement switches for the Shurflo, but will consider this option in the future.

 

[C lectric]

If you wish to pursue the switch let me know. I have some photos and a hand drawn sketch of what I did. SOme one else a year or so ago asked about this mod. as they were going nuts in the charter boat with frequent switch failures.
I assume it worked for them but I never did hear back and with a forced computer change and a huge cleanup, for me, I lost the name.

Yes, mine is plumbed between the accumulator and the pump. Strictly speaking it would be best just after the accumulator but I have never detected any erratic operation from pulsations. It turns on, runs, turns off.

 

[C lectric]

Absolutely agree with all. I am not sure if what the pump mfg. calls a "pressure switch" on the newer variable speed pumps are really what we call a pressure switch. It is my belief they operate more as a flow sensor or differential between upstream and downstream pressures and not really as a true mechanical switch. Given that assumption, the pressure rating for the pump is based more on max speed type of situation.

I don't know either about the actual operation. I suspect the opening of a tap produces a slight pressure drop which will turn the pump on. If the drop increases the variable controller would run the pump faster in an attempt to maintain pressure.

Or as you suggest it actually senses flow and again runs the pump motor faster or slower to match flow demand.

I set mine up so long ago these new pumps were not around, at least not for boats of my size and price range. By the time they arrived in a form I would consider mine had been working well and reliably for many years so saw no need to change and no inclination to find out the exact operation. Lazy.

Some folk get good operation and some get lousy, just like the older pumps.

 

[JDCAVE]

The question remains..does your pump cycle quickly on and off when you are using a medium amount of water?

Ulysses: This "cycling" has recently started with the washdown pump, which is of the same make and model number. Does this mean that the pressure switch on this pump is also beginning to fail?

Jim

 

[JDCAVE]

If you wish to pursue the switch let me know. I have some photos and a hand drawn sketch of what I did.

Yes. I am interested. I'll send you an email to let you know particulars. I have 3/4" ID braided waterline.

Jim

 

[ulysses]

Ulysses: This "cycling" has recently started with the washdown pump, which is of the same make and model number. Does this mean that the pressure switch on this pump is also beginning to fail?

Jim

No, not necessarily. The cycling will most likely shorten the switches life though. Does your wash down pump system also employ an accumulator tank?

 

[JDCAVE]

No accumulator tank. Also, we turn the pump off and disconnect the hose once the anchor is aboard.

 

[ulysses]

No accumulator tank. Also, we turn the pump off and disconnect the hose once the anchor is aboard.

In that case you might try the following in order to reduce the cycling:

Plumb in an accumulator tank.
Adjust water flow so that is as great as the pump is capable of producing. That will allow the pump to come on and then not shut off again until such time as you have lifted your anchor.

Good luck.

 

[Lepke]

Almost all of these small pumps use a micro switch if you open the switch housing. The switch is common and can be had for under $5 on ebay, etc.
But as C lectric says a separate switch will last longer, is adjustable and so on. The pumps themselves don't last very long under maximum pressure and heavy use. The diaphragms wear out quickly and the pump no longer reaches full pressure or volume. I use a shallow well pump now.