water pump, pressure accumulator

[Pib]

I'm guessing there should be 2 adjustments-one for the lower pressure limit and one for the upper but I can only see one screw on the top that could have anything to do with an adjustment.

I can only speak to how the pressure switch on my Mitsubishi pump works. The adjustment on the very top adjusts affects both the upper and lower pressure points (i.e., pump cut off and pump cut on). So, just for example say the upper and lower pressure points were 2.8 and 2.1 bars, respectively, making an adjustment which raised the upper pressure to 3.0 bar would also raise the lower pressure point to 2.3 bars.

Also on my pressure switch, more on the lower portion of the switch, is a smaller screw that affects the "range/span" of the upper and lower points. Tweak it and it could change the range from say 2.8 to 1.9, 3.0 to 2.1, etc.

So, consider one adjustment the overall adjustment and the other one the range/span adjustment. Most important: Don't try making any adjustments without a pressure gauge because you could really mess up things...both the upper and lower pressure points are important to correct and reliable operation of the pump. Some might think, I'll just adjust the upper and lower point to be the same...well, that will probably result in overheating and quick failure of the pump unless it's designed to be a "continuous" operation pump. Plus, if your pump design type comes with a pressure tank, which the majority seem to do in Thailand, you will just be defeating the purpose of the pressure tank whose purpose is to offload the need for the pump to always run.

If buying a generic pressure switch be sure to buy one that is rated for the upper & lower pressure point of your particular pump even if they have adjustments inside because the generic switch come in various pressure ranges (e.g., 2.8-2.1 bar, 2.0-1.3 bar, etc) and possibly can only be adjusted slightly around their upper/lower pressure points.

[Chilon]

Thanks for the comments everyone. Tried various settings on the one available adjustment that does adjust a spring above the points. I can get it to work perfectly for a few hours with taps occasionally being turned on and off, After after 4 hours or so a tap is opened and the pump comes on as before but stays on. Happened at 730PM when it should have been cooler than 4 hours prior so I can't believe it is heat related and in any case the pressure switch shouldn't be generating much heat. I switch off the electricity and wait a few hours and it is then OK for the next few hours.

I've now bought a replacement switch( brand name Sebora) but whilst it looks like it is the correct size it doesn't actually fit so I'll keep looking.

[Pib]

Thanks for the comments everyone. Tried various settings on the one available adjustment that does adjust a spring above the points. I can get it to work perfectly for a few hours with taps occasionally being turned on and off, After after 4 hours or so a tap is opened and the pump comes on as before but stays on. Happened at 730PM when it should have been cooler than 4 hours prior so I can't believe it is heat related and in any case the pressure switch shouldn't be generating much heat. I switch off the electricity and wait a few hours and it is then OK for the next few hours.

I've now bought a replacement switch( brand name Sebora) but whilst it looks like it is the correct size it doesn't actually fit so I'll keep looking.

Sounds like your pump "motor," like my Mitsubishi pump, may have a built-in thermal protection device which acts like a circuit breaker when the "pump motor" overheats like when running too long/too much. The thermal protection automatically resets itself after approx 15-30 minutes as the device cools down because the pump motor cools down. I had this overheating problem with my pump before because the "air control balance valve" was defective/ruptured which prevented the pump pressure tank from maintaining an air cushion/spring (i.e., caused a waterlogged pressure tank) which caused the pump motor to run the great majority of the time (like 90% of the time) versus an approx 50-50 on-off cycle say with one tap fully open. Without the pressure tank working properly the pump had to do almost all the work when it was designed to be assisted by the pressure tank.

If your pump is on-off cycling "a lot" with little or no water draw this can cause a pump to overheat/shutdown if your pump design is the type with a small pressure tank...or your pressure switch contacts could be sticking together as it gets hotter due to the electrical sparking that naturally occurs each time the switch engages...but if it's engaging too often and the switch is too old with lot of burnt carbon deposits on the contacts the switch contacts can fuse together when hot but be forced open with the pressure switch spring pressure when the switch cools off due to pump shutdown caused by the thermal protection device kicking it. Or if really bad, the switch contacts can permanently fuse together. But if the "core" problem is being caused by a waterlogged pressure tank possibly being caused by a defective/ruptured air control valve then replacing the pressure switch won't fix your problem because the pump motor would continue to overheat and be shut down by its built-in thermal protection device.

[T_Dog]

Chilon.... Can you tell us more about your system? Does it draw from a well, tank, or a public system? How many watt Hitachi pump is it? Does it ever lose prime where you have to add water again?

As PIB points out, these pumps do have temperature protection. If you lose prime or if it can not pull from the source, the pump will overheat and shut down. We just lost prime last week after a year of solid running due to a brown out. Our line voltage was running below 200 volts, and our 250 watt pump can not build enough pressure to shut down at that low voltage. The pump continued to run, boiling off the suction side water, losing prime, and then shutting down due to excessive temperature. You might want to check the line voltage to see if you might have the same problem.

Pump problems can be rather frustrating and I feel your pain!

[Pib]

Chilon.... Can you tell us more about your system? Does it draw from a well, tank, or a public system? How many watt Hitachi pump is it? Does it ever lose prime where you have to add water again?

As PIB points out, these pumps do have temperature protection. If you lose prime or if it can not pull from the source, the pump will overheat and shut down. We just lost prime last week after a year of solid running due to a brown out. Our line voltage was running below 200 volts, and our 250 watt pump can not build enough pressure to shut down at that low voltage. The pump continued to run, boiling off the suction side water, losing prime, and then shutting down due to excessive temperature. You might want to check the line voltage to see if you might have the same problem.

Pump problems can be rather frustrating and I feel your pain!

My pump will do the same thing during a brown out... and the brown out voltage only needs to be down around 180V. So during times of low voltage I turn my pump off if I plan to draw any water.

Sent from my Onda V971 tablet

[Chilon]

Thanks. The pump is a 250W Hitachi drawing from a 1000L tank which sits on the same base as the pump. The pump feeds two rooms, one on ground level and one on the first floor. The supply tank is full and the pump never needs priming. It is rated to 2KPA which is around 29Psi and has a small 1L pressure tank.

The problem I have is that the pump doesn't shut down which I assume means the contacts are not opening. If it shut down prematurely or didn't supply the required pressure I would suspect as Pib and T_Dog say that the motor overheating switch was operating or line voltage was insufficient or perhaps some other reason.

If it happened each time I would suspect the adjustment of the pressure ( which I have meddled with) but this only happens after a few hours of correct operation ( and at different times of the day). The duty cycle of the pump is light with maybe 5-6 tap openings of 30 seconds or less each hour before it malfunctions.

There will be a reason but right now my best guess is that the contacts are sticking shut but why this should happen has me beat...the pressure switch doesn't seem hot and the contacts have no reason to heat up as there is no sign of rapid on/off cycling.

[Pib]

Thanks. The pump is a 250W Hitachi drawing from a 1000L tank which sits on the same base as the pump. The pump feeds two rooms, one on ground level and one on the first floor. The supply tank is full and the pump never needs priming. It is rated to 2KPA which is around 29Psi and has a small 1L pressure tank.

The problem I have is that the pump doesn't shut down which I assume means the contacts are not opening. If it shut down prematurely or didn't supply the required pressure I would suspect as Pib and T_Dog say that the motor overheating switch was operating or line voltage was insufficient or perhaps some other reason.

If it happened each time I would suspect the adjustment of the pressure ( which I have meddled with) but this only happens after a few hours of correct operation ( and at different times of the day). The duty cycle of the pump is light with maybe 5-6 tap openings of 30 seconds or less each hour before it malfunctions.

There will be a reason but right now my best guess is that the contacts are sticking shut but why this should happen has me beat...the pressure switch doesn't seem hot and the contacts have no reason to heat up as there is no sign of rapid on/off cycling.

OK, since you say the pump only has a 1L pressure tank (more like a pressure bottle) it must be a constant pressure pump design like pictured below.

I was assuming you had the type design pictured below which is not a constant pressure type as the pressure varies a little and the pump/manifold assembly sets on top of a 15-20L pressure tank.

With the type you have you also have the contant flow valve which plays in its operation. But your pressure switch could still very well be the problem with intermittent sticking together. My pump had that problem once (mine pump design is like the second picture above with the large pressure tank)....it would just keep running after I knew it had built up pressure and there was no water taps on or any leaks...but when I tapped the pressure switch with a screwdriver handle the pump turned off....that sharp jar unstuck the the switch. I first tried cleaning the contacts with some very small files I had and that helped somewhat but the contacts were worn/pitted pretty bad. New switch fixed my problem...not to imply it will fix your problem.

[Chilon]

Pib,

Yep-that's a picture of the same pump I have. Your previous problem sounds similar, if not identical. I'll try and get the correct pressure switch and also have a go at smoothing the points.

Sounds similar to what I used to do for my car back in the 60's when it wouldn't start -invariably I'd sandpaper the points and that would fix the problem.

[Pib]

Sounds similar to what I used to do for my car back in the 60's when it wouldn't start -invariably I'd sandpaper the points and that would fix the problem.

Yeap, been there, done that, got the tee-shirt. And a matchbook cover could be used to set the points spacing until you found your spacer set buried somewhere in the toolbox. I miss my 66 Chevelle.

[Chilon]

Mine was a 64 Isuzu Bellett, probably not sold in the US. Tough as nails but had it's limits. I turned it over 6 times attempting a high speed manoeuvre one night, after leaving quite a bit of rubber down the road which totalled it. Then upgraded to a $500 1968 Bellett which survived my ownership intact.

On the pump situation I managed to trigger the overheating cut out when I adjusted the switch all the way down and it seemed OK for an hour or two but somewhere along the line it came on, stayed on and I missed hearing it. It then overheated and stopped. Seems fine now and at least I know the overheating cut out works.

Called into Global at Phitsanulok and sighted the same model but this one had more information on the side of the pressure switch. Apparently the 2kpa specification is the minimum pressure, the maximum is 2.6kpa. I has mistakenly thought the 2kpa on the nameplate was the maximum.

With this new information I went to Kamphaeng Phet and returned the switch that didn't work( they refunded my money since they sold out of the correct size) and managed to find another shop that had a Hitachi switch with the correct settings.

Now all I have to do is install it without screwing it up......

[Laucha]

fix Accumulator water pump VDO Clip

fix Accumulator water pump Hitachi, Mitsubichi etc

 

 

 

Edited June 11, 2019 by Laucha