Not another Mitsu' water pump saga!

[RickBlaine]

Sorry, this may have been done to death, but my experience with a house water pump might help someone searching here.

I bought a new house 4 years ago. We're on mains water but also have a parallel system with a 1000litre tank and Mitsubishi WP 105QS water pump.

From day one the pump would cut in and out rapidly whenever water was drawn, and I didn't think that sounded right. (My background is electronics, not mechanics, so bear with me). After looking on the internet, I adjusted the pressure switch until the pump cycled nice and slow - about every five seconds with two showers running. Later I read the warning on TV about not adjusting the switch without a pressure gauge. Oops.

Everything was fine until, months later, the pump stopped suddenly. I discovered the water feed valve was letting in air. We have those awful red and blue inline cut-off valves each side of the pump - I think they're the cheapest the builder could find. I replaced it with a metal gate valve and all worked again.

A while ago, the pump stopped again, overnight. Next morning when we discovered the problem, the pump body was hot to touch, as though it'd been trying to run against its own pressure.

I let everything cool (I assume there's a thermal cut-out?), and it restarted okay.

It did it again a few weeks ago, again at night. The water pressure must be higher at night, which may or may not be significant.

Then yesterday it stopped again. This time it was ants, all over the contacts, a problem others have had on TV.

I reluctantly began to dismantle the switch - only for it to slip out of my fingers and spring apart. I know, I should have photographed it first. After half an hour of frustration I found this YouTube video of a Thai guy assembling the exact same pressure switch!

https://www.youtube.com/watch?v=_z9oNZdmW94

I don't know who he is or why he's doing it, there's no commentary and the comments are in Thai but it was a relief.

 

I appear to have slowly worked through nearly all the pump's problems.

Time will tell if the 'late night phantom run' will return, or if, inadvertently, I've fixed that one as well by dismantling and cleaning the switch.

[bankruatsteve]

Thanks for the saga.  There's probably some Mitsu fans that will want to check it out sooner or later.  Hitachi and Grundfos don't seem to have so many problems.  Not trying to start anything... just saying.

[RocketDog]

You are simply missing a pressure tank. Add one and your problems are gone.

http://m.homedepot.com/b/Plumbing-Pumps-Well-Pumps-Systems-Pressure-Tanks/N-5yc1vZbqld





Sent from my SM-G930V using Thaivisa Connect mobile app

[RocketDog]

https://www.google.co.th/url?q=https://m.youtube.com/watch%3Fv%3DlTdTk5Z4La0&sa=U&ved=0ahUKEwiI0-CP88PRAhXMOY8KHaZoBhoQtwIIHTAB&sig2=9OYBV3iUyDLIi7Ynx-vxgg&usg=AFQjCNFFwQRkfRSk6zBbfGgmjj8T5ltYjQ


Sent from my SM-G930V using Thaivisa Connect mobile app

[Crossy]

Quote

I reluctantly began to dismantle the switch - only for it to slip out of my fingers and spring apart.

 

There is an engineering term for this which I teach all my underlings (along with SNAFU and FUBAR) which is "ping f--kit", it goes "ping" you say "f--kit", it is invariably, as you found, a switch of some sort.

 

Quote

I've fixed that one as well by dismantling and cleaning the switch.

 

If I'm reading correctly, the switch dismantled itself with no assistance from you :)

 

Glad you sorted it :)

 

[Pib]

When you say the pump body was hot/overheat/had stopped, that must have been after it had been running for a long time...cycling on and off.  Correct?  

 

These type of pumps will need overheat, the thermal switch will trip, and after 15 to 30 minutes the thermal switch will reset and the pump will start running again.  Now if there is a problem such as the pressure tank being waterlogged (loss the air they needs to be in the tank), it will cycle on and off quickly with the on time probably being around 90% of the time and off time the remaining 10%,   Normally the on-off time will be approx 50% say for a WP205 and higer model.  But model WP85, WP105, and WP155 will have an higher on time and may run continuously with one tap wide open....but say with a tap half way open they should have approx a 50-50 on-off cycle.

 

Definitely do not mess with the pressure switch settings unless you have a pressure gauge to see if the the switch is way out of adjustment; otherwise, you will probably just make things worst.   Really should be a need to adjust a switch if it's the specific switch for  your model; if a generic switch that can fit several different models of various pressure settings and you need to set the pressure for you particular model then yes do some adjustment.   For a WP-105 the on/off pressure settings are 1.3/1.9 bar.

 

Should be no reason to disassemble a pressure switch as a corroded/ant infested electrical contact can be accessed from a side window on the lower portion of the switch.  I've done it a couple of times.  You can stick a burnishing tool, small file, fine sandpaper to clean the contacts.   Or just spray contact cleaner or pressurized air into that contact access window to clean out any critters that may have made a home there.   But to properly clean the contacts you need to take a burnishing tool/small file/fine sandpaper to the contacts to get the corrosion and carbon built up off....you can do that through the contact access window on the switch....should be no need to disassemble unless it some non-Mitsubishi off-branch with no window to access the contacts.

 

Did it on my MIL's WP85 just yesterday as I removed the pump from her house due to a small tank leak, got the small hole on the bottom of the tank fixed via brazing for Bt100 at a small shop (took them about 5 minutes),  brought it to my home to repaint the brazed area and just do an overall check of the pump such as cleaning the switch contact and disassembling the air control/balance valve (maintains the proper air pressure in the tank) in order to ensure the value rubber diaphragm was not ruptured (it can develop pin hole size ruptures) and the value and its check valves were just clean.    

 

Regarding the tank leak due to corrosion, it was on the underside of the tank where the bottom plate and side plate meet and it was caused by corrosion starting on the inside of the tank due to funky water in my MIL's village.  The pump is in a covered area and stays dry as bone during rain.....still looks new after over 5 years but I expect the inside of the tank may have more corrosion in it....time will tell.  I have already priced out a replacement tank from Mitsubishi Support Services in Bangkok...cost would be Bt1,567.55....but if more leaks occur I'll just have them fixed via brazing at Bt100 per repair.     I have a 9 year old WP255 pump at my Bankgok home and with the Bangkok being much cleaner/less corrosive than in my MIL's provincial village....my pump has never developed a tank leak due to corrosion (knock on wood).   Of course a person could always buy one of those pumps with a "stainless" steel pressure tank but those pumps are significantly more pricey than a pump with a steel tank.

 

On these pumps if your line voltage drops to around 180V or below, they will probably run and run as they can't build up enough speed to build up the pressure to the cut-off point....that is, 1.9bar for the WP-105.  When they run and run, they overheat and then shutdown due to the thermal switch kicking in.   When my Bangkok moobaan had some brownout/low voltage problems a couple a years ago when the voltage got to 180V my WP-255 would just run and run when it needed to turn on to rebuild pressure....run until it overheated and shutdown.  Similar thing happened when the pressure tank got water logged due to a bad air control/balance valve...it would cause a pulsating shower, pump run and run, overheat, and shutdown.  Fixed the waterlogged problem...it was back to running normally....could literally run all day and night without overheating since it had a proper on-off cycle.

 

Water pressure being higher at night would not cause a problem; water pressure being low at night would not cause a problem as long as there is enough water in the storage tank or soi lines "to suck."   Now of course a empty storage tank or dry soi lines would cause the pump to run and run trying to suck in water...run and run means overheat and shut down.

[RichCor]

...are you sure the pump isn't depleting your well's draft reserve charge (running it dry), then sucking air at the pipe foot and losing it's water vacuum?

 

Someone in our household decided it would be a good idea to by a 15kg washing machine and run back-to-back loads, which then overdrafts our well in the dry season, but the water pump keeps on running and trying to recreate that vacuum necessary to bring water up ...until it overheats and shuts down.   

[RickBlaine]

15 hours ago, RichCor said:

...are you sure the pump isn't depleting your well's draft reserve charge (running it dry), then sucking air at the pipe foot and losing it's water vacuum?

 

Someone in our household decided it would be a good idea to by a 15kg washing machine and run back-to-back loads, which then overdrafts our well in the dry season, but the water pump keeps on running and trying to recreate that vacuum necessary to bring water up ...until it overheats and shuts down.   

I don't know if it's just terminology, but I think we're talking about 2 different systems. I don't have a well, I have a dual water system. We're connected to mains water, which supplies the house and fills a 1000 litre water tank. The tank then supplies the water pump, which feeds in to the supply going to the house. When the mains pressure is good, the pump doesn't activate. If the mains pressure is low (or off), the pump works and draws water from the tank. The tank gives us about 5 days of water without mains.   

Thanks.

[RickBlaine]

17 hours ago, Pib said:

 

Pib.

Thanks for your comprehensive reply.

 I'm not sure about the overheating pump problem - it was stopped when we got up. Your point about low voltage may be significant, as it's conceivable that one of us used the toilet, the pump started, but, if the mains voltage was down overnight, the pump kept running until it overheated. The first thing I checked each time was the water level in the 1000 litre tank - no problem. Even without mains water we've got about 5 days of water in the tank and it's never run dry, as far as I know.

I know I shouldn't have messed with the pressure setting, but we live on a new-build estate, and I can still hear some of my neighbour's pumps, left on the original setting, clicking on and off at a high rate. I can't believe that's healthy for an electro-mechanical device.

Yeah, I saw the little access window for the contact points, and could have cleaned them, but wasn't sure what other damage the ants may have done - none, as it turned out.

So far I've not had the 'pulsing' problem that you mentioned.

If the overheating continues, I think the next thing is to'reset the pressure tank, in case it's become waterlogged, if that's the correct terminology. To do that I just open the bottom nut and drain it?

 

[wayned]

18 hours ago, Crossy said:

 

There is an engineering term for this which I teach all my underlings (along with SNAFU and FUBAR) which is "ping f--kit", it goes "ping" you say "f--kit", it is invariably, as you found, a switch of some sort.

 

 

If I'm reading correctly, the switch dismantled itself with no assistance from you :)

 

Glad you sorted it :)

 

 

I once tried to dismantle a pressure switch for my Mitsu WP-155.  It went ping and the bits are still in a jar in the workshop!  I keep them to remind me not to try it again!!!

[RickBlaine]

I don't know if anyone looking at Mitsu problems will see (or be interested) in this, but just to finish the saga;

The pump eventually stopped for good (RIP). I dismantled it, and found it would turn easily on its bearings, but would stick when reassembled - something warped, presumably through overheating once too often.

We changed to a Hitachi (WM-P150XS). The box says it's 'quiet operation', but it's no quieter than the Mitsu was. Had to alter the pipes, Hitachi is 1", Mitsu 3/4", but so far, no problems.

I'm not ragging on Mitsu, most of my neighbours on the estate have not had problems, so maybe we were just unlucky.