Household Water Pump Mitsubishi Q3 Series

[Lev]

Please keep the playground insults and sniping to yourselves.

[Pagey]

Sometime last year the pressure switch on my Hitachi water pump was leaking. An engineer came and replaced it which I watched him do. Now in under a year the replacement is leaking so I took it off, took it to a plumber merchant to get a replacement. I've fitted it but the pump seems to be on all the time for a while even though no taps are running. The electrical contacts seem to show some sign of burning and when I prime it with water the water already inside is very hot as is the housing where I pour the water to prime it.

My question is how important is the spec of the switch ?

I ask this as the original is : On, 140 kpa or 1.4, off 180 or 1.8.

The replacement fitted by the engineer is On 210 or 2.1, off 280 or 2.8

The replacement for the replacement is On 1.4, off 2.8.

Does Nereus or Chas or other people more knowledgeable than me know if it makes a difference?

I've called an engineer anyway I just wondered if I need to buy another replacement at the original spec while I'm waiting for his arrival.

The engineer charged me around 700 or 800 for the replacement switch, I bought my replacement for 300 Baht.

[Nereus]

It sounds like the cut-off pressure is too high for the pump. The water will get hot (warm) if the pump is running without the water going anywhere.

Some pressure switches are adjustable, so it may be possible to tweak the cut off point down a bit.

[HHTel]

Mine is a Mitsubishi WP 305M2
The pressure switch is Off - 2.8 On - 2.1

I've had it for 10 years and gives good pressure upstairs and downstairs as well as the 6 sprinklers in the garden.

I've never had a problem with it apart from adjusting it a couple of times. There is a central screw at the top of the switch. Turn this until the pump is stopped. Then turn on a tap to and adjust the screw just enough for the pump to operate. Then turn off the tap to make sure it switches off.

I'm surprised the switch is leaking. Are you sure it's not just the connection to the pipe that is leaking?

[Pagey]

My pump is actually Hitachi, I just used this thread as I searched for water pump pressure switch.

Tel it's definitely the switch, not the connection. I tried tightening the switch but no water was leaking from the connection and no water is leaking now I have replaced it.

I've tightened the middle screw a bit, this is the one that depresses the large spring, right ? It's a bit difficult as it is close to the wall so I am having to use a screwdriver bit in a pair of pliers as even a stubby won't fit. Doesn't seem to have any effect so far.

BTW, when I disconnect the power from the pump, as I keep doing as I presume it's not doing the pump any good, I still have a decent flow of water to my taps for a while.

Engineer still not arrived.

[HHTel]

Sorry, I was reading the title - Mitsubishi. You will get a flow for a while because of the pressure build up in the system. It is the screw that adjusts the tension on the large spring. You should see the switch next to the spring. 'click' it shut with a screwdriver just in case it's jammed. If it's the spring tension then it will just click open again in which case adjust as I've already said.

[Pagey]

The engineer arrived about 4pm so I left him to it. He did say there could be a leak in the pipes somewhere which is maybe why the pump never shut off so he sent me to plumbers to buy a plastic shut off valve which he fitted just after the pump to isolate the problem. Whilst at plumbers I noticed some very small stubby screwdrivers so bought 1 of each at 15 baht each which he then used to basically do what Tel said and adjust the 'spring' from what I could see until the pump only opened after the taps were turned on.

Thankyou for the replies.

[Monkey Hanger]

Had a problem with my Mitsubishi Pump a few days ago, the pump stopped cutting in when house system water pressure was low.

The pressure switch (the small black cylindrical unit) which is used by the pump to open a set of electrical contacts thus cutting power off to the pump motor when the correct water pressure is reached, was not working correctly.

After disconnecting power I unscrewed the single screw holding the pressure switch cover on, removed cover and found lots of debris inside the switch itself, use WD40 to clear the dirt from between the switch contacts, cover back on pressure switch and power back.

Worked a treat, job done in 2 minutes.