Mitsubishi WP105Q not switching off

[surat04]

But the cut in/out is not what is listed on spec for that model pump (but very close so should not be an issue).

Listed here as 1.3 and 1.9 rather than item shown at 1.1 and 1.8

http://www.jjpsupply.com/product/detail.php?id_product=7680

The original switch says 1.2-1.8

I'm not going to worry about the 0.1!

[Pib]

Depends on the model year/age as the cut in, cut out pressure specs have changed a little over the years as newer models are released (but same basic model number...just a year newer). Specs for some models have changed by a few tenths of a bar which is minor.

Like below is a spec sheet I had saved on my computer which is probably a 5 year old spec for Mitsubishi pumps...it shows 1.2 to 1.8 bar for the WP105 and is probably closer to the spec for the OP's model which was around 8 years ago. But current year WP105 seem to reflect 1.3 to 1.9 bar (kinda like getting a tad more torque out of an engine that has basically remained unchanged for years).

This operating cut-in, cut-out settings are also not the maximum limits for the pump...you can maladjust the pressure switch to lower or raise the limits....the pump can actually put out a higher (or lower) pressure (probably at least 25% higher based on my tinkering with my WP255 pressure pump (its cut in/cut out pressures are 2.1 and 2.8 bar) while using a pressure gauge to adjust the switch, but then you are operating the pump out of its comfort zone/designed day-to-day operating spec and will surely shorten its lifespan.

If I remember right, I cranked mine up to 3.5 bars while tinkering...it made 3.5 bars no problem but its on-off cycle changed significantly...that is instead of approx a 5 seconds on then 5 seconds off cycle with one water tap full open it changed to like 7 to 8 seconds on and 2 to 3 seconds off....I was now asking too much of the pump for long term operation. Maybe kinda like running a car engine consistently at high RPM...it will sure do that higher RPM but its also shortening its lifespan, using more fuel, etc.. I then set the pressure switch settings back to 2.1 and 2.8 bars....luckily I didn't break anything with my tinkering.

[wayned]

The Mitsubishi definitely use the ribbed type impeller. I had a 155 that did the same thing due to a worn impeller due to the crappy local water supply. The parts are easy to get and the impeller is easy to replace, 4 bolts holding the cover on and 1 holding the impeller on the shaft. The biggest problem is getting the old impeller off the motor shaft. I get my parts from Mitsubishi Electric Kang Yong Watana co.,ltd via EMS. Send them a message and they will send you an IPL for the pump. I only have IPLs for 200 and 300 series pumps. If you replace the pump with any model other than another 105 you will have to redo the external plumbing as they are not fit and form interchangeable.

I tried to post this earlier and it came out blank so I'll try again.

[surat04]

I will hopefully be checking the impeller tomorrow. I will also check the supply voltage as I bought a cheap multimeter today. Thanks for all the helpful ideas.

[wayned]

Actually it difficult to look at the impeller and tell unless it really damaged. The impeller on my 155 didn't look damaged and when I compared it to the new one I really didn't see a significant difference, but I didn't measure them. The new one fixed the problem and the pump is now installed at my house in Bangkok.

As far as your leaky tank problem, Mitsubishi seems to have a problem as they do no not have an internal bladder. Over the past 18 years Ive had 4 tank failures, they all seem to occur at the welds where the doubler plates are welded on at the output connections. The tanks aren't cheap, the last one that I bought for my 255Q3 was 2520 baht delivered.

[Pib]

Strange how some pump pressure tanks fail/rust early. I have a Mitsubishi WP255 which is eight years old...lives out in the open sun and rain here in Bangkok..tank still looks new on the outside...can't speak to what it may look like on the inside...but as of today zero leaks or rust (knock on wood).

Now I installed a Mitsubishi WP85 in my MIL's house in late 2011 (had to live there for a month when I had to evaculate my Bangkok moobaan due to the 2011 Great Flooding). This pump is fully protected from the sun and rain by the house roof and surrounding fence walls. A drop of water probably hasn't hit the exterior of that tank since being installed. But I noticed a few weeks ago it has rust starting at the bottom lip of the tank.

Maybe the MIL's air/water in Nakhon Pathom province is just more corrosive to steel than next door Bangkok air...I don't know....guessing. Maybe the tanks just need to be occasionally rinsed off periodically just like how you need to rinse aircraft off with clean water every month or so to help prevent corrosion especially if the aircraft flew over or is based closed to salt water/the ocean. Maybe my pump getting rained on and/or the wife occasionally spraying pump with the water hose to clean it and its surrounding area has helped keep the corrosion down....it's probably the wife spraying down of the pump occasionally that has helped.

Edited April 12, 2016 by Pib

[surat04]

I finally got round to testing the pump with a new impeller fitted. It still doesn't switch off!

I checked the supply voltage at the pump, it was 218V.

Is it possible that there is actually a problem with the motor and it is not reaching the correct rpm?

I got the impeller from the company mentioned in post #33 by Wanyed. They provide a very good service. I ordered the part on Monday afternoon, it was posted on Tuesday and it was delivered to my house on Wednesday.

Anyway the In-laws are happy they have a new pump and the old one had been resigned to the corner of the shed.

Edited April 23, 2016 by surat04

[Pib]

Strange how some pump pressure tanks fail/rust early. I have a Mitsubishi WP255 which is eight years old...lives out in the open sun and rain here in Bangkok..tank still looks new on the outside...can't speak to what it may look like on the inside...but as of today zero leaks or rust (knock on wood).

Now I installed a Mitsubishi WP85 in my MIL's house in late 2011 (had to live there for a month when I had to evaculate my Bangkok moobaan due to the 2011 Great Flooding). This pump is fully protected from the sun and rain by the house roof and surrounding fence walls. A drop of water probably hasn't hit the exterior of that tank since being installed. But I noticed a few weeks ago it has rust starting at the bottom lip of the tank.

Maybe the MIL's air/water in Nakhon Pathom province is just more corrosive to steel than next door Bangkok air...I don't know....guessing. Maybe the tanks just need to be occasionally rinsed off periodically just like how you need to rinse aircraft off with clean water every month or so to help prevent corrosion especially if the aircraft flew over or is based closed to salt water/the ocean. Maybe my pump getting rained on and/or the wife occasionally spraying pump with the water hose to clean it and its surrounding area has helped keep the corrosion down....it's probably the wife spraying down of the pump occasionally that has helped.

In this thread I mentioned I had installed a WP85 in my MIL's house like surat04 had installed a WP105 in his in-laws house. Well, a few days ago the MIL's WP85 suddenly stopped working. As mentioned in my above post I had installed it new in late 2011. When checking it at the MIL's house today it was just dead. I noticed some ants running around between the pressure tank and the motor...immediately thought to myself maybe ants have got into the pressure switch electrical contacts. I removed the pressure switch protective cover and didn't see any ants...beat on the switch...blew into it....pump still not coming on. I then put a jumper across the contacts to bypass the contacts and the pump starts up. OK, now I know the switch is the problem.

The pump is installed in a tight fitting and dark location and I decided just to unhook it and bring it back to my house to work on it. Since the pump doesn't get used very much I was just surprised that the pressure switch would be bad after only a little over 4 years of light use. I still had hope the contacts were just dirty/had dead ants squashed between the contacts to where they would not make electrical contact. But if the switch was just dead you can buy a new/generic one for aournd Bt250.

Back at home in the light, I looked through the slide slot on the switch to where you can see the electrical contacts...they appeared fully closed/making contact but when plugging the pump in it still does not run....I push on a lever on the pressure switch and the contacts open up and close freely but you really can't see good enough to confirm the contacts are clean. Pump still does not start. So I pull out my burnishing tool (i.e., fine flat file) and slide it back and forth between the contacts a few times. Plug the pump up and it starts. Fixed. I then use the burnishing tool some more on the points to ensure they are good and clean, refitted the protective switch covering doing my best to ensure there are no places for ants to get in (but somehow they frequently seem to get in) cleaned-up/painted a few rusty spots on the bottom feet/edges of the pressure tank. Now good to go...will take it back to the MIL's house in a few days and once again be hailed as the smart and handsome farang (a.k.a., the son-in-law with money).

Yeap, a few ants or other small critters had apparently got into the switch. With the switch contacts normally open when the pump is not running if some ants happen to be between the contacts when the pumps starts up and the contacts close the ants get squashed like pancakes between the contacts...and enough ants getting squashed can keep the points from making electrical contact. Clean the contacts...good for X more years until maybe the next ant squashing occurs if they somehow figure a way into the switch...some ant varieties are so, so small...give them the hole the diameter of a sewing pin and they will go through it when lured in a switch by an electrical field.