Mitsu WP 155R problem

[proton]

10 years old started to leak from rusty pin holes again. I want to go to home pro get another mrs wants to 'save money' by getting a new tank. Instead of buying the genuine Mitsu one for 3k comes back with a winner product. Seems to work but has no screw lugs to attach the top back on and the problem is it now does not work the same. Instead of the pump staying on it is on off every couple of seconds resulting in the flow pulsing as it switches off and on. Is there a setting for it or is it something to do with the new tank?

[PJ71]

i have a 255 model, think it was about 7K so a new 155 model i'd expect to be less.

 

Don't see the point messing about with a 'fix' tbh.

[proton]

Just now, PJ71 said:

i have a 255 model, think it was about 7K so a new 155 model i'd expect to be less.

 

Don't see the point messing about with a 'fix' tbh.

New is 5.5k at homepro, I agree, all day yesterday driving all over for the tank and the 'mechanic' still not finished it???? Think it could be an air lock.

[MJCM]

Maybe this helps?

 

 

[kwonitoy]

Take the yellow top off.

Open a water tap so you can see where the valve is that is cycling on and off

Look for a set screw on the top of this valve, there is a spring that you can tighten or loosen

Adjust the set screw so the pump will do a longer cycle of on and off.

From memory your spring is probably too tight

If you don't want to do this get a local handyman to help, It's pretty easy once you've seen it done

Edited December 30, 2022 by kwonitoy

[NanLaew]

On 12/30/2022 at 2:01 PM, PJ71 said:

i have a 255 model, think it was about 7K so a new 155 model i'd expect to be less.

 

Don't see the point messing about with a 'fix' tbh.

My original, 15 year-old 255 had pinholes in the tank. Replaced with a 305 to keep the natives clean and watered. Bought a replacement tank on lazada for under 3000 baht and fitted to the old pump. Yai used that pump for a couple of months for her allotment irrigation so it is kept as a tested and working good spare.

 

On 12/30/2022 at 2:04 PM, proton said:

New is 5.5k at homepro, I agree, all day yesterday driving all over for the tank and the 'mechanic' still not finished it???? Think it could be an air lock.

It's possible that the tank is over-pressured. I just had the same happen after a filter change and replacing the pressure switch on my 305. Follow the instructions in the message previously linked.

 

On 12/31/2022 at 12:09 AM, kwonitoy said:

Take the yellow top off.

Open a water tap so you can see where the valve is that is cycling on and off

Look for a set screw on the top of this valve, there is a spring that you can tighten or loosen

Adjust the set screw so the pump will do a longer cycle of on and off.

From memory your spring is probably too tight

If you don't want to do this get a local handyman to help, It's pretty easy once you've seen it done

If you are talking about the pressure switch, no good will come of opening and adjusting it. There's a reason there's a tamper-proof screw on the original pressure switch housing and a label saying don't open and adjust. A new pressure switch is maybe 500 baht while a generic one from Amorn is less than 200 baht and does the job (but make sure you plug the gaps in the base where creepy crawlies can move in and make life-shortening nests!). Also make sure you buy one with the correct cut-on/off pressure range (it's stamped/labeled on the original switch casing).

 

Not having the screw lugs for the cover is inconvenient if the pump is more exposed. The chooks used to knock ours off until I placed a bamboo chook cage over it. Gusts of wind would dislodge it on the allotment. Placing a brick on top kept it in place.

Edited January 1, 2023 by NanLaew

[proton]

47 minutes ago, NanLaew said:

My original, 15 year-old 255 had pinholes in the tank. Replaced with a 305 to keep the natives clean and watered. Bought a replacement tank on lazada for under 3000 baht and fitted to the old pump. Yai used that pump for a couple of months for her allotment irrigation so it is kept as a tested and working good spare.

 

It's possible that the tank is over-pressured. I just had the same happen after a filter change and replacing the pressure switch on my 305. Follow the instructions in the message previously linked.

 

If you are talking about the pressure switch, no good will come of opening and adjusting it. There's a reason there's a tamper-proof screw on the original pressure switch housing and a label saying don't open and adjust. A new pressure switch is maybe 500 baht while a generic one from Amorn is less than 200 baht and does the job (but make sure you plug the gaps in the base where creepy crawlies can move in and make life-shortening nests!). Also make sure you buy one with the correct cut-on/off pressure range (it's stamped/labeled on the original switch casing).

 

Not having the screw lugs for the cover is inconvenient if the pump is more exposed. The chooks used to knock ours off until I placed a bamboo chook cage over it. Gusts of wind would dislodge it on the allotment. Placing a brick on top kept it in place.

As before emptied the system and took out the plug at bottom of tank and drained it, but did not work this time still going off and on. Looking at the pump there is nothing to indicate where it's cycling or a spring and those two valve tops are tight. Maybe unscrewing the top one a bit?

 

 

[kwonitoy]

The valve is under the round cover on the lower left. The top two are part of the pressurized system, best left alone.

[PR3]

Yes the tank was not cheap, but it looks like a stainless steel replacement so will last a long time, a worthwhile investment tbh as they all seem to develop those pinholes after a few years.

I just replaced our Hitachi one for the same reason and had 3 mitsus go at the old house.

Anyways, if you look at the castellated black plug at the top right hand side on the picture, undoing this will let any air out of the pump, however make sure its not pressurised when you do it as it will blow the rubber seal out.

As for the cycling; there can either a leak on the pipework after the pump, an airlock in one of the pipes so make sure you purge all toilets, showers and faucets of air.

Another problem I once had was the check valve from the mains, some systems have it set up so if the pump fails or power outage the mains water automatically comes through. These do eventually fail amd the pump then pressurised the mains water supply if it's lower pressure.

Are you drawing from a tank or directly from the mains water?

PR3

[proton]

1 minute ago, PR3 said:

Yes the tank was not cheap, but it looks like a stainless steel replacement so will last a long time, a worthwhile investment tbh as they all seem to develop those pinholes after a few years.

I just replaced our Hitachi one for the same reason and had 3 mitsus go at the old house.

Anyways, if you look at the castellated black plug at the top right hand side on the picture, undoing this will let any air out of the pump, however make sure its not pressurised when you do it as it will blow the rubber seal out.

As for the cycling; there can either a leak on the pipework after the pump, an airlock in one of the pipes so make sure you purge all toilets, showers and faucets of air.

Another problem I once had was the check valve from the mains, some systems have it set up so if the pump fails or power outage the mains water automatically comes through. These do eventually fail amd the pump then pressurised the mains water supply if it's lower pressure.

Are you drawing from a tank or directly from the mains water?

PR3

Yes direct from mains, mrs wont have a tank for some reason. Drained the system again still the same, always worked before. Tried screwing the spring up and down which does not seem t make any difference at all. Still chugging off and on, will leave it for a while and get a new pump.

[PR3]

A guy I knew up the street pumped straight from the mains and had the same symptoms you have I.e. rapid cycling of the pump,

I have had a tank since I moved here in 2006 didn't really understand the advantage at first but I assure you; having a tanked supply has many advantages and often makes headaches a little easier to diagnose.

Mainly because the pump is dealing with the same conditions all the time.

As a bonus when the water goes off you still have a reserve.

There's a very good chance if you get a new pump it will behave in the same manner as your current one; sorry to say that but seen it a few times where direct into the mains.

If you're reluctant to have a tank it may be better to get used to the pulsing, however as with many electrical things it's not the best choice for longevity of the switch and motor capacitor.

I hope you get it sorted I've had my share of these unwanted surprises and it ain't fun.

PR3

[PR3]

Forgot to mention if the mains supply has air inside after repairs or new connections your pump will have to deal with any potential air lock that has caused.

If it cannot reach the cut off pressure (because its a water pump not a compressor) it might run till something gets rather hot and fails.

Perhaps it's a good time to at least consider getting a tank, if you take the expense aside (which to be fair none of us want) it does make a lot of good sense long term..really.

 

PR3

[sometimewoodworker]

1 hour ago, PR3 said:

having a tanked supply has many advantages and often makes headaches a little easier to diagnose.

Mainly because the pump is dealing with the same conditions all the time.

As a bonus when the water goes off you still have a reserve.

And you haven’t mentioned the fact that all the water authorities ban pumping direct from the mains.

[PR3]

I wasn't aware of that thanks for the information 

 

PR3