Mitsubishi WP pumps, "auto-air," and air bladder

[lsemprini]

I am trying to help a friend who has a variety of Mitsubishi WP pumps of varying ages at his large guesthouse (e.g. WP-305Q5, WP-205M2, WP-155Q5, WP-205P, ...).

 

One of the pumps is short-cycling, which would imply that that there is a lack of cushioning/air-bladder in the system that stores up the pressure created by the pump when the pump is running so that pressure can be used when the pump is not running. 

 

The pumps I have experience with all have a separate air bladder, and so the fix to short-cycling is generally to re-charge or repair the air-bladder.

 

However, it would seem that these Mitsubishi WP pumps use an air space in the (single) tank of the pump, without any membrane between the air and water, as their air bladder.  Is that correct?

 

And I noticed that all these WP units have what the local chang like to call an "auto-air," a little plastic spaceship-spaced gizmo that injects a little bit of air into the tank every time the pump stops, both to fill the tank and to re-fill after some air inevitably dissolves into the water.  Is that correct?

 

So when you have a short-cycling WP pump, what is the likely cause and what are the fixes?

 

I can only speculate that some possible causes are the tank is leaking air, or the auto-air is clogged or otherwise not working.  Is that the main cause of short-cycling of WP pumps?  How to search for leaks?  How to diagnose auto-air problems?  What else to look for during diagnosis?

 

We could empty out all the water to start with an air-filled chamber, and that might fix the short-cycling initially, but presumably whatever the problem was before (air leak or bad auto air) would eventually resurface, so that doesn't seem like a useful thing to do.

 

Does anyone have an English-language manual for any WP pump that explains the principle of operation and/or troubleshooting?  I did a number of web searches but could only find Thai and Bahasa Indonesia/Malaysia.

 

As usual, our local small-town chang are no help.  They are convinced that the WP pumps have no air inside them at all...hm.

 

  - Chris Pirazzi

 

 

[lsemprini]

FYI For the benefit of others I found a few relevant details from this very old TV Mitsubishi pump thread here, but I am still looking for more general info on how to diagnose short-cycling:

 

https://forum.thaivisa.com/topic/374519-problem-with-mitsubishi-water-pump/page/5/#comments

Quote

 

Yeap, sure sounds like you have a waterlogged pump...that is, not the proper amount/enough air in the tank the pump/motor assembly is setting on.

Without the right amount of air in the tank to be compressed on top of the water then the pump will cycle on and off very fast like you have decribed...will be running around 90% of the time when a water tap is opened. This compressed air acts like an energy spring/cushion to push water out of the tank when the pump is not running...or said another way it helps the pump push water to your residence without the pump having to run all the time. I have a WP255 and with one tap wide open the pump will run approx. 5 seconds and then turn off for approx. 5 seconds.

After you drain the tank and be sure to let it completely drain because until it completely drains through the drain plug air can not get into the tank; no air in the tank...no energy spring/cushion can be created. If the pump cycle works properly after this draining procedure (i.e., "approx." 5 seconds on and 5 second off) then you need to figure what caused the pump to lose its air cushion. If the air control value (that six sided device screwed into the tank top with a small black/grey PVC hose running to the tank) is not working properly that can cause a loss of the air cushion/cause the tank to become waterlogged after a few weeks. Believe me, I know, as that is what happened to my WP255 once when the rubber diaphragm within the air control valve assembly ruptured with definition of a rupture being a very small tear in the diaphragm...but that's all it took...kinda like a pin hole sized leak in an intertube, a football, etc. I would drain the tank and it would work/cycle properly...then after a few days I noticed it was starting to run longer on each on/off cycle....then after a few weeks it was running most of the time...like only off for 1 second during each on/off cycle. Opened up the air control valve...saw the ruptured diaphragm...bought a new air control valve (couldn't buy just the diaphragm) for approx. Bt700...pump started working fine again....this happened about two years ago...the pump was around 3 years old at the time.

 

 

[wayned]

As said, the pump is most likely w

:water logged" and can be fixed easily by turnig off the input and output valves and draining the tank.  The WP pumps do not use a bladder, they have an Air Control device "the spaceship thingu" that controls the air.>  If the internal diafram is punctured it could cause the problem also.  I've repaired many pumps over the years and only had to replace one A/C device,  They cost about 600 baht and are available mail order from the Mitsubishi Distributor in Bangkok, Kang Yong Wattana.

[lsemprini]

26 minutes ago, wayned said:

As said, the pump is most likely w

:water logged" and can be fixed easily by turnig off the input and output valves and draining the tank.  The WP pumps do not use a bladder, they have an Air Control device "the spaceship thingu" that controls the air.>  If the internal diafram is punctured it could cause the problem also.  I've repaired many pumps over the years and only had to replace one A/C device,  They cost about 600 baht and are available mail order from the Mitsubishi Distributor in Bangkok, Kang Yong Wattana.

 

Thanks!  Any suggestions about how to diagnose whether it is the A/C device vs. other problems that might cause short-cycling?

[emptypockets]

Honestly, look at buying a pump controller and do away with the air reservoir/bladder/whatever. A pump controller will start the pump on low pressure….and keep the pump running as long as there is a demand for water. No more on/off cycling and burnt out pressure switches (unless of course you have a leaky system). You can buy them at places such as Global House etc. A little bit of wiring modification may be needed but its not hard to do.

[VocalNeal]

10 hours ago, lsemprini said:

However, it would seem that these Mitsubishi WP pumps use an air space in the (single) tank of the pump, without any membrane between the air and water, as their air bladder.  Is that correct?

Shut the water off and drain the tank. Using the plastic plug on the side. If the system still cycles there is a hidden water leak. 

[sometimewoodworker]

7 hours ago, lsemprini said:

 

Thanks!  Any suggestions about how to diagnose whether it is the A/C device vs. other problems that might cause short-cycling?

1) unplug the pump

2) turn of the water supply to and from the pump

3) talk the drain plug out.

 

if you get water coming out of the tank inspect the A/C device 

[VocalNeal]

Where does this A/C device fit? I've had two pumps apart and have never encountered one?

 

Is there a picture anywhere?

Edited October 29, 2019 by VocalNeal

[lsemprini]

3 hours ago, VocalNeal said:

Shut the water off and drain the tank. Using the plastic plug on the side. If the system still cycles there is a hidden water leak. 

 

Thanks, that's what I figured, but my question is how to distinguish between different possible causes of the leak, e.g. auto-air/A-C problem vs. a physical leak at some point in the tank vs. other problems.

 

2 hours ago, sometimewoodworker said:

1) unplug the pump

2) turn of the water supply to and from the pump

3) talk the drain plug out.

 

if you get water coming out of the tank inspect the A/C device 

 

? won't there always be water coming out when we take the drain plug, regardless of whether there is any problem?

 

 

[lsemprini]

2 hours ago, VocalNeal said:

Where does this A/C device fit? I've had two pumps apart and have never encountered one?

 

Is there a picture anywhere?

Circled in red here (this happens to be a WP-305Q*). 

 

Looking at my friend's wide variety of Mitsubishi WP pumps, I noticed only some of them have the spaceship; some have no obvious component to put air into the tank.  Does anyone know how the other Mitsubishi WP pumps (only WP, we're not talking about EP here) get air into the tank?

 

Also, I noticed that none of the Mitsubishi WP pumps have a bicycle-type valve to manually put air in.  So the spaceship (or equivalent part) is the only way air gets in there (other than that the pump starts with air and is air after draining, of course, but that's just temporary).

 

It would REALLY be nice if someone could point to an authoritative manual where we could finally get to the bottom of how these WP pumps are really supposed to work.  There is so much mythology and speculation (especially by Thai chang) but there should be an actual answer somewhere!

 

[VocalNeal]

^ Not sure now if mine had one of those? My tank had a leak at the bottom so I replaced the tank.

[lsemprini]

4 hours ago, lsemprini said:

Circled in red here (this happens to be a WP-305Q*). 

 

Looking at my friend's wide variety of Mitsubishi WP pumps, I noticed only some of them have the spaceship; some have no obvious component to put air into the tank.  Does anyone know how the other Mitsubishi WP pumps (only WP, we're not talking about EP here) get air into the tank?

 

CORRECTION -- I just went back over there to look and in fact ALL of the Mitsubishi WP pumps DO have the spaceship auto-air (I was confused by the angle of my other photos).

 

Anyway, still hoping someone can suggest a method of diagnosis to help distinguish leaky tank from busted auto-air from other possible causes.  Thanks.

[wayned]

18 hours ago, VocalNeal said:

Where does this A/C device fit? I've had two pumps apart and have never encountered one?

 

Is there a picture anywhere?

Number 19:

[wayned]

13 hours ago, VocalNeal said:

^ Not sure now if mine had one of those? My tank had a leak at the bottom so I replaced the tank.

If you have a leak in the tank there will be water, it will not cause the pump to cycle.  The leaks mormally occur at weld joints normally where the doubler plate with the nuts are welded inside the tank.  Ive fixed a couple with just a weld on the outside and replaced the whole bottom of the tany on another.  If I remember right a new tank is around 1200 baht.  If you want to see if the A/C valve is the problem just buy a new one and try it.  The ones that I have replaced usually weren't for the cycling problem, they developed a leak where they suck in are on the bottom due to corrosion on the ball valve.  I've only replaced one for a puncture diaphragm.  I actually had a WP-305 that went through the flood and sat surmerged in water for over a month.  I took it apart and cleaned it up and it is still working today at my house in Bangkok.

[lsemprini]

10 minutes ago, wayned said:

Number 19:

Thanks wayned.  Where did those pages come from?  Any chance the rest of the manual is in English?  Even if it's Thai it might be useful to slog through and mine for info.

 

[wayned]

4 hours ago, lsemprini said:

Thanks wayned.  Where did those pages come from?  Any chance the rest of the manual is in English?  Even if it's Thai it might be useful to slog through and mine for info.

 

Like I said, I buy  parts from the distributer in Bangkok.  He sent me and IPL for four pumps many moons ago.

[lsemprini]

9 hours ago, wayned said:

Like I said, I buy  parts from the distributer in Bangkok.  He sent me and IPL for four pumps many moons ago.

 

Do you have any of those manuals in an electronic form (other than the scan you posted above)?

 

[sometimewoodworker]

38 minutes ago, lsemprini said:

 

Do you have any of those manuals in an electronic form (other than the scan you posted above)?

 

Manual

 

Edited October 30, 2019 by sometimewoodworker

[lsemprini]

2 hours ago, sometimewoodworker said:

Manual

 

 

Thanks for the link!

 

I looked at the Thai.  On Page 8 (troubleshooting for the WP series) the only troubleshooting step relevant to short-cycling is the last one, and it just says "there is too little air in the pressure tank" and "empty all the water out of the pressure tank, then 'fill' the pump again (I think they mean prime)."  So not too helpful since that's only a temporary fix.

 

And the auto-air is called in Thai "automatic thing to push air" (p.33) and is part H02301Q00

 

 

 

[Isaanbiker]

On 10/28/2019 at 11:55 PM, wayned said:

As said, the pump is most likely w

:water logged" and can be fixed easily by turnig off the input and output valves and draining the tank.  The WP pumps do not use a bladder, they have an Air Control device "the spaceship thingu" that controls the air.>  If the internal diafram is punctured it could cause the problem also.  I've repaired many pumps over the years and only had to replace one A/C device,  They cost about 600 baht and are available mail order from the Mitsubishi Distributor in Bangkok, Kang Yong Wattana.

I'd think the diaphragm is either punctured, or totally gone.