WP305QS Pump Continuous Running

[carlyai]

I have a Mitsubishi WP305QS pump that won't reach the cutout pressure of 2.8 bar. It reaches about 2.6 bar but continues to run. I emptied it and refilled but still the same problem. I replaced the cutout switch with a 1.4 to 1.9 switch and it cutout at 1.9 and stopped running, so I changed the pressure switch. Same problem, won't get to 2.8 bar and keeps running. 

I didn't know what else to do so I took it to the pump shop (100 km away) for him to fix. One week later and they informed me that they tested the pump and it won't stop running, but the specialist pump guy, who is also the aircon guy is out installing aircons and don't know when he will get to my pump.

So I thought the only other things that can be changed are the air charger and the impeller. Now I have previously changed an impeller on another pump with a big difference in output flow rate but I don't know if it would effect the cutout pressure. I'm not too sure what the aircharger does, but it might pressurise the tank so the pressure switch cuts out.

We need the 300 W pump to work Wifey's irrigation system so I was thinking of getting the pump back and installing a new aircharger and impeller.

Will this solve my problem?

[Swiss1960]

I dont know whether your problem will get solved with all you describe to change.. but given the distance to the pool shop and from a personal experience with my pump, it might just be cheaper in the long run to replace the pump.. pumps, even your size, don't cost the world

 

[HashBrownHarry]

55 minutes ago, Swiss1960 said:

I dont know whether your problem will get solved with all you describe to change.. but given the distance to the pool shop and from a personal experience with my pump, it might just be cheaper in the long run to replace the pump.. pumps, even your size, don't cost the world

 

Correct, about 7K

 

This faulty one you could easily use for another purpose and just remove the plug when not in use.

[HashBrownHarry]

For the OP.

 

Where are you buying the spare parts for this pump?

 

Thanks.

[carlyai]

7 minutes ago, HashBrownHarry said:

Correct, about 7K

 

This faulty one you could easily use for another purpose and just remove the plug when not in use.

Thanks, but I really want to know if changing these parts could solve the problem. 

[sezze]

Sounds like impeller failure . The airtank does not create this kind of failure . Only thing the airtank does is preventing the pump constantly switching on/off , which is not the problem you describe . Not reaching its final pressure is obstruction in watersupply ( you must have checked that ) , leakage ( you would see it ) , impeller worn out .

If it is possible , try to feed the pump with a higher suction pressure , to see if it switches off . I guess you got a barometer somewhere , since you mention you do have 2.6 bar and it shuts down at 2.8 . Impeller failure does deliver less pressure and by that it means lower flow , basic pump technique .

Finding the replacement is the trick , but it surely is available somewhere . You can try here and send them the question

https://www.lazada.co.th/products/300gx-12-12-part3ppm10450b-i334916743-s649338850.html?spm=a2o4m.pdp.0.0.4ed2676e8eKbPs&promotionId=203470500077879

 

 

[carlyai]

8 hours ago, sezze said:

Sounds like impeller failure . The airtank does not create this kind of failure . Only thing the airtank does is preventing the pump constantly switching on/off , which is not the problem you describe . Not reaching its final pressure is obstruction in watersupply ( you must have checked that ) , leakage ( you would see it ) , impeller worn out .

If it is possible , try to feed the pump with a higher suction pressure , to see if it switches off . I guess you got a barometer somewhere , since you mention you do have 2.6 bar and it shuts down at 2.8 . Impeller failure does deliver less pressure and by that it means lower flow , basic pump technique .

Finding the replacement is the trick , but it surely is available somewhere . You can try here and send them the question

https://www.lazada.co.th/products/300gx-12-12-part3ppm10450b-i334916743-s649338850.html?spm=a2o4m.pdp.0.0.4ed2676e8eKbPs&promotionId=203470500077879

 

 

Thanks. The pump is at the shop with all replacement parts.

The pump had been operating in adverse conditions with no water now and again.

What's the pump symptoms for a failed air charger?

[carlyai]

Thanks. The pump is at the shop with all replacement parts.

The pump had been operating in adverse conditions with no water now and again.

What's the pump symptoms for a failed air charger?

[sezze]

14 hours ago, carlyai said:

Thanks. The pump is at the shop with all replacement parts.

The pump had been operating in adverse conditions with no water now and again.

What's the pump symptoms for a failed air charger?

By air charger you do mean bladder tank ?

It makes pressure of the pump more equal . When pump is off , since water doesn't compress a lot , even the smallest drop will cause the pump to start again . This creates a pressure spike , putting the pump in Off position again , resetting the situation again . So it is noticed by multiple on/off switches of the pump , and you certainly will know it , since the effect is very clear ( did have that failure a few y back ) . The bladder tank creates a pressure bubble so a small droplet doesnt create a pressure drop .

[carlyai]

No I meant that black thing like a flying saucer on the top of the tank connecting the pump inlet....I thought it was called and air charger but no matter. Thanks for the other explanation.

Went to get the pump today as no one had the time to fix it and tried many places but no impellers. Got home and took the impeller and body out, bit pitted, took it in to the Tractor shop and they're trying to order me replacements. Thanks for your help.

[carlyai]

It seems funny that a shop needs to look at and send pics of the part to order from a distributor. It seems you can't just order for the WS205QS pump. This wasn't just one shop that wanted to see the part. Maybe the impeller part is not cross referenced to a pump type. 

Pic of impeller and housing. It's difficult to look at and see the difference between an old and new impeller, but there is a large difference in flow.

[mran66]

if no leakages visible, you need to double-check that no leakage in water supply line that would let air to leak into the pipe when pump is on and sucking water from the line. that could lead to behaviour you described. also, if the housing rubber gasket has leak on suction side could cause it

 

if in the garden/field, maybe a frog or some other stuff in the input line?

(is the water coming from well or city water line?)

 

also, if the air charger diaphgram has torn or has hole, could be that. just disconnect the pipe from housing and block the line with your finger to test. if no change in behavior, then unlikely the air charger. if pressure gets to 2.8 with finger on the hole, it is leaking air in thru and needs to be replaced

 

 

if you just need a pump for irrigation, could well try a cheap solution rather than branded, less than 1000 baht for a pump with pressure switch and small accumulator. If only pump less than 700...i guess as good as Mitsubishi for your application. many choises for pumps for this type of use for under 1000

 

https://www.lazada.co.th//products/i605030862-s1139046897.html?spm=a2o4m.cart.0.0.12436108QZ2Uvk&urlFlag=true

 

 

Edited June 21, 2020 by mran66