Wiring new water pressure pumps

[thaisail]

I plan to fit a 2000 liter tank next to the kitchen that will be filled using float switches that will be connected to the 3" submersible pump from the well that is 40 meters deep. So as the water level goes down in the 2000 liter tank the lower float switch will start the submersible pump and fill the tank until the top float switch will stop the pump. The two new pumps described in the link below will be mounted next to each other at the bass of this 2000 liter tank.

 

https://www.lazada.co.th/products/toma-japan-750w-ps-180-gold-premium-edition-i292006020-s487010858.html?mp=1

 

One of the pumps will be connected to draw water from the 2000 liter tank and put cold water pressure to the entire house. The other pump will draw water from the solar water heater mounted about 2 meters higher than the pump suction. There will be thermostatic mixing valve fitted between the two pumps so that the water temperature leaving the mixing valve will not exceed the rating of the PPR pipe which is 10 bar at 60 degree C. My concern is that after a full day in the hot sun during the summer before Songkran, the water temperature in the solar tank can go as high as 95 degrees C or even make steam. I am worried about keep the pressure pump cool enough so that it will not fail. So I look for ideas of how to cool the water coming from the solar tank sufficiently to prevent damage to the pump. One idea is to move the acumulator away from the pump to prevent the rubber diaphragm from being damaged by the heat. I may also have to move the pressure switch to protect it from the heat also. But the thing that concerns me the most is that the motor has thermal protection. I imagine that means that embedded in the windings there is a thermal switch which will open at a specified temperature and stop the pump until the windings cool down. So I am thinking of fitting a fan that that will blow air on the motor and wire the fan into the pressure switch so that when the pump starts so will the fan and of course stop when the pump stops. I also would like to fit a circuit breaker or fuse to protect the pump motor against overload. I guess I have to wait until the pumps are tested and see what the running amps will be. The motor is 750 watts or 1 HP so perhaps someone out there will know the running amps and I can order the right fuses or circuit breakers for the pumps. I throw this plan out there to the community for input. 

[Yellowtail]

Unless I'm missing something, do you not need to push cold water into the heater rather than pulling hot water out? 

[Yellowtail]

And 10 bar seems like a lot of pressure....

 

If it were me I would just use one pump to feed both the cold water and the heater. 

 

 

[thaisail]

10 hours ago, Yellowtail said:

Unless I'm missing something, do you not need to push cold water into the heater rather than pulling hot water out? 

Many solar water heaters cannot be pressurized. They rely on a level control valve similar to the valve used to fill a toilet tank. As you drain hot water from the solar tank, usually mounted on the roof, the cold water will refill through the automatic lever control valve. The way this one works, there are many long tubes of glass each within a larger tube of glass. The space between the two glass tubes is in a vacuum kind of like the old incandescent light bulbs. This way the inner glass tube is perfectly insulated from the outer glass tube so that even in extreamly cold climates the water passing through the inner glass tube can be very hot without transferring the heat to the outer tube. This makes this highly efficient type of solar water heater difficult to pressurize.

[thaisail]

11 hours ago, Yellowtail said:

And 10 bar seems like a lot of pressure....

 

If it were me I would just use one pump to feed both the cold water and the heater. 

 

 

10 bar at 60° C is the maximum rating of the thin wall green PPR pipe that I bought. I will not put more than 2 bars of pressure on this pipe after the hot water pressure pump. I will set the thermostatic mixing valve to keep the hot water at around 50° C. With 150 liters of water in the insulated solar storage tank the water can reach boiling temperature in the summer and steam can be seen at times coming out the atmospheric vent on the top of the hot water storage tank. 

[Yellowtail]

1 hour ago, thaisail said:

10 bar at 60° C is the maximum rating of the thin wall green PPR pipe that I bought. I will not put more than 2 bars of pressure on this pipe after the hot water pressure pump. I will set the thermostatic mixing valve to keep the hot water at around 50° C. With 150 liters of water in the insulated solar storage tank the water can reach boiling temperature in the summer and steam can be seen at times coming out the atmospheric vent on the top of the hot water storage tank. 

So the the heater is an open system. Does the manufacturer not have detailed installation instructions and or pumps they recommend?

 

[thaisail]

 

On 10/15/2020 at 4:44 PM, thaisail said:

https://www.lazada.co.th/products/toma-japan-750w-ps-180-gold-premium-edition-i292006020-s487010858.html?mp=1

Does anyone know where there is a good reference on the internet about sizing circuit breakers for the pump attached? My electrician is recommending 20 amps. But the calculators on the internet show running amps for two 1 HP 750 Watt, single phase 230 Volt 50 Hz automatic water pressure pump as about 5 amps. There is a thermal protection embedded in the windings of motor. I just want to make sure that I protect the motors on these two pumps. I have in my house a separate Chang safety breaker of 20 amps and I want to have the correct size breaker for each pump. Also wire size recommendation would be appreciated also. Right now we have 2.5 mm line and neutral and 1.5 mm earth cable running to the box that both pumps will draw from. But each pump will have it's own safety breaker.  

[sometimewoodworker]

2 hours ago, thaisail said:

Does anyone know where there is a good reference on the internet about sizing circuit breakers for the pump attached? My electrician is recommending 20 amps. But the calculators on the internet show running amps for two 1 HP 750 Watt, single phase 230 Volt 50 Hz automatic water pressure pump as about 5 amps.

You misunderstand the purpose of a circuit breaker. It’s job is to protect the house wiring. Using your 2.5mm cable you can use any breaker of 20A or under. You can put in 5A if you like, it will make no difference to the pumps.