Water Pump Protection

[vcu33]

I have read all the post about home water pumps and i think the Mitsubishi WT-255 or one like it will work fine for my one bath and kitchen house. My question is about pump protection if the water supply runs out. Now i have a 1000 L water tank about 3 meters high at the base. The city water only runs in the morning and afternoon so we have a pump to fill the tank and gravity provides enough pressure for the toilet and sink but not the shower. That is why I want a pump for the house. A few times in the past the toilet flapper has gotten stuck open at night and by morning the tank was empty. I'm sure if i were able to hear the pump cycle on and off more than normal i would have a reason to check for a problem but if i am sleeping i'm sure i would not hear it. Can anyone tell me if the pump comes with some kind of shut off device to prevent the pump from running with no water supply or what i need to do to protect it. I have no knowledge of pumps so any info would be great. Thanks

[harrry]

First job on the to do list.

Fix toilet flapper.

[lopburi3]

They normally have a thermal overload which will shut off the pump when it overheats but perhaps a larger tank would be better if support can hold it.

[Artisi]

you could install a float level control unit wired in series with the pump, set it at a low level to isolate the pump if and when the level drops to your pre-determined low level and to re-connect the pump once the tank starts to re-fill.

[Pib]

The Mitsubishi WT series has a thermal overload switch built into the pump motor, which protects it from overheating like when there is no water to pump to build up pressure and, in turn, the pump will run continuously until overheaing. But the overload switch acts like an auto reset thermal circuit breaker in that it has to get hot to disengage the motor and then it resets itself in about 10-15 minutes of cooling down....then the pump starts up again and the overheat cycle can start again....since the pump motor is still kinda warm it won't take as long to reach the "too hot" condition again and cause the overhoad switch to disengage again for 10 to 15 minutes....then the cycle repeats X-amount of times until something just burns up completely.

I have a Mitsubishi WT-255 and one time when the little booster tank the motor/pump sets on became water logged the pump was switching on and off so much (quick cycling) the pump motor would overheat and stop working for 10-15 minutes. After it cooled off, it would start running/trying to pump again.

Fixed the water logged condition of the booster tank by removing the drain plug, "completely" draining the booster tank which allowed air into the tank, screwed back in the drain plug, turned back on the power and water inlet/outlet, and have been good to go since. Over time the air in the tank had been absorbed by the water allowing the tank to become water logged. Be sure to turn off power to the pump and turn off the water inlet/outlet if possible before draining the booster tank. The key is to ensure the booster tank "completely drains in order to allow air to rush in from the drain plug at the bottom of the tank....partially draining the tank does not allow any air in.

[Artisi]

You shouldn't rely on the motor over temperature switch to safe guard your pump motor in poor installations, this is last resort measure should other safety shut-down systems fail.

[vcu33]

Thanks for all the info. I think i will install the pump close to the window so i can here it during the day if something goes wrong and maybe me or the wife will here it if something happens at night.

[Pib]

Fixed the water logged condition of the booster tank by removing the drain plug, "completely" draining the booster tank which allowed air into the tank, screwed back in the drain plug, turned back on the power and water inlet/outlet, and have been good to go since. Over time the air in the tank had been absorbed by the water allowing the tank to become water logged. Be sure to turn off power to the pump and turn off the water inlet/outlet if possible before draining the booster tank. The key is to ensure the booster tank "completely drains in order to allow air to rush in from the drain plug at the bottom of the tank....partially draining the tank does not allow any air in.

I need to correct myself on my above statement. While completely draining the tank allowed a new air charge, this new air charge only "fixed the waterlogged problem for about a month" before pulsating water from the taps would become very noticeable and pump overheating would begin.

I finally fixed the root cause of the tank becoming water logged by replacing the "air charger valve" (a.k.a., air volume control, air-water balance valve) on my Mitsubishi WP-255. A small hole had developed in the air charger valve rubber diaphragm which prevented the valve from sucking in a very small amount of air into the tank on every pump on/off cycle to compensate for the amount of tank air that naturally gets absorbed into the water. When the air is gone in the tank you no longer have an air spring/cushion to continue to push water out of the tank/into your home's water pipes when the pump turns off. Air can be compressed to store energy; water can be compressed very, very little. So, with no air spring in the tank, the pump motor needs to switch on much more often, which means it gets hotter. And this quick/frequent pump on/off cycling can make it run too hot and cause the motor's built-in thermal circuit breaker/relay/thermistor to temporarily open shutting down the pump motor...then the motor cools off enough in about 10-15 minutes to allow its thermal circuit breaker to re-engage, the pump motor starts running again, after X-amount of minutes it gets too hot again and shuts off....and this cycle continues to repeat. A vicious cycle. How often and when it repeats will depend on your water usage.

And of course, no water input to the pump (the pump running dry) will cause the same pump motor overheating problem since the pump can never reach the its water pressure switch "cut-off" pressure. All the pump's pressure switch senses is the output water pressure is too low so I need to turn on the pump and build up water pressure...but it can't since there is no water....the pump then runs until it overheats and its thermal circuit breaker turns the pump off for a while until the motor cools a little. A vicious cycle.