Water Pump Issue WP-255-QS

[Artisi]

Back to some of the earlier posts where voltage drops mean pumps cannot spin fast enough to hit cut-off pressure - may I be permitted to offer a possible "fix" to this, a little "Heath Robinson perhaps but probably workable.

I assume that the cut-off pressure switch is of necessity on the outlet or house side of the pump? In which case raising the pressure on that side would trigger the pressure switch and cause the pump to shut off? Looking at this low voltage problem sideways, a 12 volt pump with an in-built pressure switch connected to a car battery and picking up water from a small header tank could pump up the system on the house side via a NR valve (non-return) and thus fool the mains pump into thinking it had done it's job. Such pumps are fitted into boats (I used to build boats) and should be available in LOS. A relay operated via a time-clock on the mains could turn on the 12 volt system at 7.00 for a few hours and a trickle charger could keep the battery charged. These pumps will operate at up to 40psi and have their own pressure switch and are designed for long service life.

That is what is called a "jacking pump" in the fire sprinkler business- it keeps the system up to pressure so the sprinkler pump doesn't start - up thinking it has been called into service.

The problem with your suggestion is -- if someone opens a tap / shower / toilet, the pressure will drop and the house pump will try to come online -- back to the same problem - except if it is only for a very short time and the jacking pump might be able to get the pressure back up before the main pump overheats and shuts down.

[sandmike]

Can the pressure switch be adjusted to operate at a lower pressure ?? This might resolve the continuous running problem ...

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Sent by carrier pigeon

[bankruatsteve]

Can the pressure switch be adjusted to operate at a lower pressure ?? This might resolve the continuous running problem ...

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Sent by carrier pigeon

Most pumps I've seen say "DO NOT ADJUST" - which must mean it can be adjusted but there you go.

[Artisi]

Can the pressure switch be adjusted to operate at a lower pressure ?? This might resolve the continuous running problem ...

.

Sent by carrier pigeon

More than likely yes, but this doesn't overcome the low voltage and overheating of the motor windings - this is the problem.

As usual blame the pump when it has absolutely nothing to do with the pump trying to operate in a way that it has been designed.

[cliveshep]

All dependant on which 12 volt pump is selected but the ones I used could happily supply two draw-offs at once so would probably keep up easly with the aid of the slow main pump.From what I can see Thai draw-offs are smaller than UK ones anyway.

[Crossy]

Of course a suitably sized AVR would solve the issue, and be more cost effective than a battery / charge / 12V pump

[sandmike]

Some UPS's can do the voltage boosting thing too ...

the only AVR'S I've seen are in the several MVA range .... not ideal for the home 555

Sent by carrier pigeon

[The Dark Lord]

On 10/11/2015 at 10:29 AM, wayned said:

Yes they are repairable, I buy my parts from these people in Bangkok and have then sent to me via EMS: https://www.mitsubishi-kyw.co.th/index_en.php?lang=en. If you're anywhere near Buriram there's also an authorized repair center there that repairs or sells parts:

Mr. Bob Manthey

Ruangsangthai Ltd.

114 Moo. 14 Buriram - Phutthaisong Highway 2074

Chum Het, Muang Buriram 31000

Thailand

(66) 044-666-484 mobile 081-069-8324

email: [email protected]

 

Here's a copy of that IPL that Kong Yang sent to me:

WP-255Q3 IPL.pdf

 

If it doesn't cover your pump model contact them and ask them to email you that correct one. If you've never taken one apart before you might want5 to take it to a place that does pump repairs.

Dear wayned

 

could you please repost the PDF file as I am unable to download it. Conversely if you could pm me and attach the file that would be marvellous.

 

thanks

[wayned]

here's the file again WP-255Q3 IPL.pdf

[JAS21]

I have a WP255 M2 pump. It seems to have no pressure reserve at all... the slightest amount of water runnout of a tap and it cuts in and out and in and out.

 

Have drained the tank but that hasn't made any difference to the operation.

 

It needs more than one hose running full bore to keep the pump from cycling on and off. In the past it would operate almost continually on the one hose.

 

The pressure switch looks in good condition and I see it going up and down.

 

So the way forward is ...other than call out Mitsu ...  thanks

[Crossy]

Not sure if this pump has a bladder tank, if so the bladder could be ruptured, new tank I'm afraid.

 

When you drained the tank did you let air in? Is the tank again full of water?

 

[JAS21]

3 hours ago, Crossy said:

Not sure if this pump has a bladder tank, if so the bladder could be ruptured, new tank I'm afraid.

 

When you drained the tank did you let air in? Is the tank again full of water?

 

Yes and Yes ... something is sadly amiss I fear

[wayned]

The WP255's do not have a bladder.  The air in the tank is controlled by item 19 in the IPL that I posted in post #39.  I have used Mitsu pumps for the past 19 years and repair them myself.  I use Kang Yong Wattana for parts. If you contact them they will try to help troubleshoot a problem via email.  Also if you are near Buriram , Ruangsangthai is the authorized repair facility.  I have included all of the contact info in post #27.

 

 

In my experience the problem that you are experiencing is a water logged pump and what you did should have fixed it.  The AC assembly, item 19 above,  could be the problem as it controls the air in the tank.  I've only replaced one in the past 19 years.

 

[Pib]

23 hours ago, JAS21 said:

I have a WP255 M2 pump. It seems to have no pressure reserve at all... the slightest amount of water runnout of a tap and it cuts in and out and in and out.

 

Have drained the tank but that hasn't made any difference to the operation.

 

It needs more than one hose running full bore to keep the pump from cycling on and off. In the past it would operate almost continually on the one hose.

 

The pressure switch looks in good condition and I see it going up and down.

 

So the way forward is ...other than call out Mitsu ...  thanks

 

Couple of comments.  To me Para 1 and 3 seem to conflict with each other....seem to be saying opposite things.   So my comments are based on your para 1.  

 

As already mentioned there is not bladder or diaphragm in the tank.  

 

You sure you "fully" drained the  tank?  Because unless you fully drain the tank the water level does not drop low enough for air to enter the tank at the drain point so the air can be compressed/create an energy spring pressure reserve.    If the tank was fully drained the resulting air charge/compression created when restarting the pump (water coming into tank and then compressing the air on top of the water) would create the energy spring...and even with no functioning air control valve that energy reserve would be maintained for at least several days and the pump would operate properly.   The air control valve is really just to maintain/replenish a very small amount of air as the air in the tank is naturally absorbed into the water over time.    

 

If the pump was fully drained some air leak must be allowing the air to escape very quickly....but this should also result in a water leak at that point which could be easily seen.   I guess there is the possibly of your air control valve being really messed up (rupture diaphragm within the valve along with a dirty ball check valve causing a very strange things to happen).   But as mentioned, draining the tank to let air would make a water logged condition go away at least for several days...maybe  up to around 10 days based on my personal experience with my air control valve problem 3 or 4 years ago.   It's problem was it developed a pin hole size rupture in the rubber diaphragm within the air control valve  and would allow a water logged condition to return after about 10 days.  Drain my tank and it would work fine for about a week, but within another 3 to 7 days it was totally water logged again....even a very small draw of water would cause the pump to turn off and on.   A properly operating WP255 can draw off approx one litter before turning on...and with one tap fully open the pump should run about 5 seconds, turn off about 5 seconds, run about 5 seconds, etc. 

 

Your pressure switch could also be bad.  Although you see that it's turning off and on the switch contacts or spring mechanism could be not working properly....like not tuning on at 2.1bar/30psi and turning off at 2.8bar/40psi which are the pressure on/off settings for the WP255.    Instead maybe the switch is messed up and say turning off and on a 2.7bar and 2.8bar , 2.1 and 2.2, or similar small differential pressure which would appear as a water logged condition but it's not water logged.   Hopefully no one has tried to adjust the switch "without have a pressure guage" to properly adjust the switch to the correct pressures?

 

And finally, you sure you have enough water "coming into the pump?"   If the input source is not providing enough it would cause the pump to run and run, turn off and on quickly as it tries desperately to suck-in enough water.

 

 

 

[JAS21]

It's a puzzle Pib.

 

I drained the tank. I switched the pump back on and draw off less than half a cup full of water .ON OFF ON OFF.

 

I opened more than one hose and it ran all the time.

 

Even though I put two nrv's between mains supply and pump discharge I shut off the mains supply to confirm that the nrv's were not stuck open.

 

Normally I don't need the pump as mains pressure is sufficent. So it could be many months since I last used it ...just stick a bit of bleach in the tank now and again to kill any thingies.

 

Recently the water board seem to have reduced the supply pressure. So when using the upstairs shower, with the heater, it is better with the pump.

 

Suppose I will have to admit defeat and call in Mr Mitsu ..

[Pib]

On my WP255 immediately after I've done a pressure tank drain and then turn the pump back on to let it recharge with water & air (and then let it cycle a few times by turning a tap on for 15 or so seconds), when I "slowly" turn a tap on to let the tap water flow into a measurement container, I get approx 1.1 liter before the pump turns on again.    I usaully do a pressure tank drain about twice a year just to reset the air charge to it's optimum value and then let the pump air control/balance valve do what it's designed to do in trying to keep the air pressure in the tank just right.  It also helps to drain off any settlement that may be in the pressure tank.  Just something I do, need it or not.

 

Now when I say "slowly" I mean just enough water coming from the tap to where it takes 30 seconds or so of the tap running before the pump kicks in.    And I'd measure right around 1.1 liter.  If you try to do the measurement with a tap on full blast you will not get an accurate measurement and I think from memory of trying this before you get significantly less than around 1 liter.

 

And then after doing that drawdown test if I turn-on a tap being fed by a 1/2 inch diameter pipe the pump will cycle on and off approx every 5 seconds.   Usually a person has 1/2 inch pipes feeding their taps, but some folks may have large pipes....like 3/4 or 1 inch.

 

Now if you turn 2 or more taps on full blast you could easily cause the pump to "not" cycle (or cycle very little) as it just needs to keep running to keep up with the water demand.  And I'm talking taps using 1/2 inch pipes...if you have some taps being fed by larger pipes like 3/4 inch or 1 inch then even one tap being open full blast may cause the pump to run full time, especially if the pump "input" line is being fed by less than a 1 inch water pipe.  

 

You could very well have a pressure switch that is just messed up....not cycling at 2.1 and 2.8 bars (a 0.7 bar span/differential) but cycling at some much lower differential pressure....like 2.3 and 2.5, or 2.1 and 2.1, or 2.7 and 2.8, etc...etc..etc.  To ensure the pump is cutting off and on at the correct pressure you need a pressure gauge to check that...you can buy a pressure gauge at most any hardware store which carries a decent supply of gardening stuff....would cost around Bt200.   I've got one so I can maintain/check my own pump when the pump starts acting weird....helps greatly to take the guessing game out of trying to figure out what is wrong with the pump.

 

 

 

 

 

 

[RKASA]

It is a common problem for us that our pump WP305 runs constant and gets warm when we have low power - we live in the sticks a bit and happens often during the rain.  During brown outs we have to turn the pump off.  It won't build enough pressure to kick off.  Check and see if your getting proper voltage at the pump.  Other then that it may sometimes kick in and out to often went the air runs low in the tank - it has no bladder and have to allow air back in about every three months by draining pump down and re starting it.  It is not an uncommon for the tank to saturate if the water source is above the pump such as a tank.   With low voltage it can get rather warm I would say hot and you can smell it in the pump house, but tough as nails it cools off and works fine again when the power is back. 

[Pib]

yea, they have an automatic thermal breaker built into the motor assembly....get to hot and the thermal breaker trips....after about 15 to 30 minutes of cooling off it will automatically reset itself.  Then it can run for X-amount more time before overheating again and repeating this cycle over and over until the motor or thermal relay smoke themselves.   My WP255 acts the same way if the line voltage drops down to around 180V or lower....it just can't built up enough speed with this lower voltage to allow it to reach cutoff pressure.   When my area does experience a low voltage condition, which thankfully is not often, I just turn the pump off until the voltage comes back to normal.