Water pump pressure switch failure

[CygnusV]

Over the last 2 or 3 years we,ve had 2 new water pumps, a Shurflo and a much meatier Johnson. When the Shurflo packed up with pressure switch problems I changed it for a 42PSI - 5.2 gals a minute jobbie. However, after a short while the micro switch on this pump also failed. The marina here is very good and in total they changed the pump at least 3 times. Removing the pump to replace it was a proper pig. I was so fed up I did a lot of checking around and found the cause of the micro switch failures was something known as back emf. This is like a back surge of current that happens when the pump switches off which can burn out the micro switch in no time.

 

I am not suggesting that everyone should themselves do what I did, but if you have a sparky friend, or a tame electrician perhaps they could do it for you.

 

Rather than changing the pump again, I snipped the wires to the integral pressure switch and fitted an external Whale pressure switch. I got this second hand for next to nothing and bought a new micro switch from Ebay for about a pound. I bought a relay for about two pounds and a diode, these were about a pound for 50. So for under 10 quid I had a working pump and have had no further trouble with micro switches burning out, for the last year so far. We are full timers aboard, so our pump is busy everyday.

 

I am not giving a wiring diagram, rather, I am sure there are more qualified people on this forum who can describe how to do this.

 

I have been told that pressure switch problems have become common across most makes of pump. If you are a part time boater, your pump will not get the same use that ours does, so you may not notice a problem.

 

Hope this helps. Stu

[jelunga]

Over the last 2 or 3 years we,ve had 2 new water pumps, a Shurflo and a much meatier Johnson. When the Shurflo packed up with pressure switch problems I changed it for a 42PSI - 5.2 gals a minute jobbie. However, after a short while the micro switch on this pump also failed. The marina here is very good and in total they changed the pump at least 3 times. Removing the pump to replace it was a proper pig. I was so fed up I did a lot of checking around and found the cause of the micro switch failures was something known as back emf. This is like a back surge of current that happens when the pump switches off which can burn out the micro switch in no time.

 

I am not suggesting that everyone should themselves do what I did, but if you have a sparky friend, or a tame electrician perhaps they could do it for you.

 

Rather than changing the pump again, I snipped the wires to the integral pressure switch and fitted an external Whale pressure switch. I got this second hand for next to nothing and bought a new micro switch from Ebay for about a pound. I bought a relay for about two pounds and a diode, these were about a pound for 50. So for under 10 quid I had a working pump and have had no further trouble with micro switches burning out, for the last year so far. We are full timers aboard, so our pump is busy everyday.

 

I am not giving a wiring diagram, rather, I am sure there are more qualified people on this forum who can describe how to do this.

 

I have been told that pressure switch problems have become common across most makes of pump. If you are a part time boater, your pump will not get the same use that ours does, so you may not notice a problem.

 

Hope this helps. Stu

Sureflo had a bad batch of pumps with faulty switches. Made in Mexico now so not such good quality in my view. We have a new one that is very slow to cut in, i.e. cuts in at too low a pressure. To be honest I cannot be bothered to take it out to fix it yet.

[CygnusV]

Sureflo had a bad batch of pumps with faulty switches. Made in Mexico now so not such good quality in my view. We have a new one that is very slow to cut in, i.e. cuts in at too low a pressure. To be honest I cannot be bothered to take it out to fix it yet.

 

I must admit that I did not expect the problems we had with the Johnson. It was actually close to a point where the marina was considering giving us our money back because they were sick of it too. The actual pump is spot on, lots of pressure, now adjustable, and plenty of volume. It just annoys me that for the sake of coppers the designers of these pumps are willing to bank on most people being part time leisure users. Its pathetic really...

[smileypete]

Over the last 2 or 3 years we,ve had 2 new water pumps, a Shurflo and a much meatier Johnson. When the Shurflo packed up with pressure switch problems I changed it for a 42PSI - 5.2 gals a minute jobbie. However, after a short while the micro switch on this pump also failed. The marina here is very good and in total they changed the pump at least 3 times. Removing the pump to replace it was a proper pig. I was so fed up I did a lot of checking around and found the cause of the micro switch failures was something known as back emf. This is like a back surge of current that happens when the pump switches off which can burn out the micro switch in no time.

 

I am not suggesting that everyone should themselves do what I did, but if you have a sparky friend, or a tame electrician perhaps they could do it for you.

 

Rather than changing the pump again, I snipped the wires to the integral pressure switch and fitted an external Whale pressure switch. I got this second hand for next to nothing and bought a new micro switch from Ebay for about a pound. I bought a relay for about two pounds and a diode, these were about a pound for 50. So for under 10 quid I had a working pump and have had no further trouble with micro switches burning out, for the last year so far. We are full timers aboard, so our pump is busy everyday.

Agree, best to use the internal pressure switch to drive the coil of a bog standard 12V auto relay, then use the relay contacts to switch the motor.

 

(If you do a forum search for 'shurflo relay' you'll see I've posted this at least about 6 times since 2008! )

 

cheers, Pete.

~smpt~

[Phil Ambrose]

Over the last 2 or 3 years we,ve had 2 new water pumps, a Shurflo and a much meatier Johnson. When the Shurflo packed up with pressure switch problems I changed it for a 42PSI - 5.2 gals a minute jobbie. However, after a short while the micro switch on this pump also failed. The marina here is very good and in total they changed the pump at least 3 times. Removing the pump to replace it was a proper pig. I was so fed up I did a lot of checking around and found the cause of the micro switch failures was something known as back emf. This is like a back surge of current that happens when the pump switches off which can burn out the micro switch in no time.

 

I am not suggesting that everyone should themselves do what I did, but if you have a sparky friend, or a tame electrician perhaps they could do it for you.

 

Rather than changing the pump again, I snipped the wires to the integral pressure switch and fitted an external Whale pressure switch. I got this second hand for next to nothing and bought a new micro switch from Ebay for about a pound. I bought a relay for about two pounds and a diode, these were about a pound for 50. So for under 10 quid I had a working pump and have had no further trouble with micro switches burning out, for the last year so far. We are full timers aboard, so our pump is busy everyday.

 

I am not giving a wiring diagram, rather, I am sure there are more qualified people on this forum who can describe how to do this.

 

I have been told that pressure switch problems have become common across most makes of pump. If you are a part time boater, your pump will not get the same use that ours does, so you may not notice a problem.

 

Hope this helps. Stu

 

I did similar on my previous boat, just fitted the Whale in-line pressure switch and forgot about it, stay working until the pump gave up the ghost altogether and when I changed the pump was surprised when I found it (until I remembered) might be my age.

 

Phil

[BEngo]

Over the last 2 or 3 years we,ve had 2 new water pumps, a Shurflo and a much meatier Johnson. When the Shurflo packed up with pressure switch problems I changed it for a 42PSI - 5.2 gals a minute jobbie. However, after a short while the micro switch on this pump also failed. The marina here is very good and in total they changed the pump at least 3 times. Removing the pump to replace it was a proper pig. I was so fed up I did a lot of checking around and found the cause of the micro switch failures was something known as back emf. This is like a back surge of current that happens when the pump switches off which can burn out the micro switch in no time.

 

I am not suggesting that everyone should themselves do what I did, but if you have a sparky friend, or a tame electrician perhaps they could do it for you.

 

Rather than changing the pump again, I snipped the wires to the integral pressure switch and fitted an external Whale pressure switch. I got this second hand for next to nothing and bought a new micro switch from Ebay for about a pound. I bought a relay for about two pounds and a diode, these were about a pound for 50. So for under 10 quid I had a working pump and have had no further trouble with micro switches burning out, for the last year so far. We are full timers aboard, so our pump is busy everyday.

 

I am not giving a wiring diagram, rather, I am sure there are more qualified people on this forum who can describe how to do this.

 

I have been told that pressure switch problems have become common across most makes of pump. If you are a part time boater, your pump will not get the same use that ours does, so you may not notice a problem.

 

Hope this helps. Stu

 

 

I thought it was standard practice to fit a Square D pressure switch and forget aboutthe one in the pump and all other switch problems. RS do one too.

 

N

[MikeV]

I thought it was standard practice to fit a Square D pressure switch and forget aboutthe one in the pump and all other switch problems.

Someone gave me that tip when my Jabsco Parmax 4 pressure switch failed. The Square D I've got is fully adjustable for cut-in and cut-out pressure as well, which is useful.

[CygnusV]

 

 

I thought it was standard practice to fit a Square D pressure switch and forget aboutthe one in the pump and all other switch problems. RS do one too.

 

N

This is why this forum is so handy. Id not heard of the square D, but I will check it out and update my site

[Lamby]

Hi,

I have a 24v gale force water pump with a knackered micro switch i have looked at the square D but unsure if i am looking at the right item cost was around £190 does that sound right? if not could someone please put an idiot proof link on here for me?

[RD1]

The biggest problem with micro switches, and most switches in general, is they generally give the current rating of the contacts for ac however in most cases the switches can only handle a fraction of that current for dc, irrespective of the voltage carried.

 

When the ac switch is disconnected, the voltage and current drop to zero a hundred times a second, ( 50 Hz but passes through zero twice per cycle) so as they switch off there is very little current flowing before the contact is opened with a minimum of a spark.

However, with dc, the current tries to continue drawing a spark for longer. This quickly burns the contacts, causing poor connection, so starts to overheat the contacts and then the switch is errr, technical term pending... can't print that lol... I know "broken".

 

A replacement 10 A or even a 15 A microswitch with an ac rating for 230/240 volts will not reliably work at 5 amps dc at 12 volts on a waterpump.

 

The suggestion of using the supply from the micro switch to drive the coil of a heavy duty dc relay, minimum spec 10 amps DC, and the relay contacts to drive the pump will give a greater reliability than the switch alone.

The suggestion of using a "flyback diode", to stop the back emf, or high voltage pulse from any coil or motor or inductive load is proven technology. Cathode of diode to + of relay coil, anode of diode to - side of coil. Note only suitable for DC systems.

Plenty of diodes to choose from, for small relays, boat battery voltage, I find the 1N4001 through to 1N4004 (higher voltage use) or higher voltage, to provide satisfactory service at a very low price. These diodes when forward biassed, in normal apllications can handle upto one amp. The back emf current is very small, but the pulse could be more than 1kV yes a thousand volts, but like static electricity, very little power, so very low current.

 

These flyback diodes are just standard diodes, that when the back emf starts to rise it is immediately clamped to less than 0.7 volts so no high voltage spike can get back to damage the switch contacts, or in many electronic circuits are well proven to protect transistor circuits and microelectronic systems.

 

I hope it helps.

Plenty of circuits of dc relays with flyback diodes on the internet.

Edited January 19, 2017 by RD1

[WotEver]

Hi,

I have a 24v gale force water pump with a knackered micro switch i have looked at the square D but unsure if i am looking at the right item cost was around £190 does that sound right? if not could someone please put an idiot proof link on here for me?

No... nothing like that expensive.

 

Try this one: https://www.pumpsukltd.com/accessories/pressure-switches-gauges/square-d-pressure-switch-9013fsg2.html

Edited January 19, 2017 by WotEver

[Tony Brooks]

Also many car 12V relays with such diodes already fitted - just make sure you strictly observe the polarity. However I have had a car relay (probably around 20 amps DC) running my water pump for about 17 years now.

[ditchcrawler]

Hi,

I have a 24v gale force water pump with a knackered micro switch i have looked at the square D but unsure if i am looking at the right item cost was around £190 does that sound right? if not could someone please put an idiot proof link on here for me?

Whale do one that is much cheaper and designed to switch a DC pump at around £20

https://www.mailspeedmarine.com/in-line-pressure-switch.html?gclid=Cj0KEQiA5IHEBRCLr_PZvq2_6qcBEiQAL4cQ0-lrwQYL9_G433xUZOtznCfPg244nhclzOb0wePPtE0aAgnx8P8HAQ

[Tony Brooks]

Whale do one that is much cheaper and designed to switch a DC pump at around £20

https://www.mailspeedmarine.com/in-line-pressure-switch.html?gclid=Cj0KEQiA5IHEBRCLr_PZvq2_6qcBEiQAL4cQ0-lrwQYL9_G433xUZOtznCfPg244nhclzOb0wePPtE0aAgnx8P8HAQ

 

I think that one has a microswitch inside it so would avoid it unless I was using it to drive a relay as above.

[RD1]

Whale do one that is much cheaper and designed to switch a DC pump at around £20

https://www.mailspeedmarine.com/in-line-pressure-switch.html?gclid=Cj0KEQiA5IHEBRCLr_PZvq2_6qcBEiQAL4cQ0-lrwQYL9_G433xUZOtznCfPg244nhclzOb0wePPtE0aAgnx8P8HAQ

That is a really good price, but again houses a dreaded microswitch again, there is no written specification for the switch's contact rating, also the one originally fitted might be of high quality, and if it requires a replacement, you run into the same problems again, too many clones out there that just can't carry the current.

Personally I would be considering doing the relay mod to this too.

Edited January 19, 2017 by RD1

[ditchcrawler]

That is a really good price, but again houses a dreaded microswitch again, the one originally fitted might be of high quality, and if it requires a replacement, you run into the same problems again, too many clones out there that just can't carry the current.

Personally I would be considering doing the relay mod to this too.

That is fine for you both to say but a lot a boaters wouldn't know how wire a relay in to control it let alone a flyback diode and which way to bias it. In 15 years I have never had a switch fail on a water pump. my shower pump is controlled by a MK light switch and that is still going fine after 15 years as well, I know its not the "correct" equipment to use but its not such a big problem as people make out.

[RD1]

That is fine for you both to say but a lot a boaters wouldn't know how wire a relay in to control it let alone a flyback diode and which way to bias it. In 15 years I have never had a switch fail on a water pump. my shower pump is controlled by a MK light switch and that is still going fine after 15 years as well, I know its not the "correct" equipment to use but its not such a big problem as people make out.

Incidentally, is your boat supply system 12 volts or 24 volts, if 24v the pump current will be half that for an equivalent pump run on a 12 volt system.

 

Re relays, as mentioned earlier, some auto relays have diodes already fitted, and some have 20 amp contacts, for a price under £3

Edited January 19, 2017 by RD1

[Tony Brooks]

That is fine for you both to say but a lot a boaters wouldn't know how wire a relay in to control it let alone a flyback diode and which way to bias it. In 15 years I have never had a switch fail on a water pump. my shower pump is controlled by a MK light switch and that is still going fine after 15 years as well, I know its not the "correct" equipment to use but its not such a big problem as people make out.

 

I have a hunch that many if not most water pumps are wired with undersized cables so the voltdrop prevents the motor reaching its design speed so in turn the current flowing is far higher that the designed value.

 

I am sure your water pump is wired in probably oversized cable so the motor is drawing its designed current, hence the long life.

 

I have documents that indicates a professional marine loom maker used cable for a fridge that HE deemed adequate rather than what the fridge compressor manufacture specified so what straight "fitters out" do re cable size is anyone's guess but I bet it rarely involves more expensive cable.

 

 

 

[WotEver]

Did d everyone miss this post?

 

No... nothing like that expensive.

 

Try this one: https://www.pumpsukltd.com/accessories/pressure-switches-gauges/square-d-pressure-switch-9013fsg2.html

12V 10A rated switch