Float Switch

[Yellowtail]

I have a water tank on the ground floor, and a water tank on the roof. Pump on the ground floor pumps the water from the ground floor tank to the roof tank. 

 

Right now, there is a float-valve that starts and stops the water from flowing into the tank, which causes the pump to cycle too frequently.

 

I want to install a float switch in the water storage tank on the roof to start and stop the pump that feeds the tank. This should minimize the pump cycling. I will leave the float valve in place in the event the switch fails. 

 

1. Do these typically act as a switch to turn the pump of and on, or do they generally work in conjunction with a contactor to start the pump?

 

2. Are they safe, do I need to worry about getting shocked, and what steps do I need to talk to make sure it is safe?

 

3. Most of these I see look pretty cheap. are there any particular units that work well? I want something decent, and if I could get it from Lazada it would be great.

 

4. How long do they last?  Don't want to get getting on the roof any more often than I have to. 

 

Thanks!

 

 

[Crossy]

I would go for the two-float type, these keep any electrics outside the tank. They also use standard micro-switches which are cheap and readily available.

 

Something like this https://www.lazada.co.th/products/2-adjustable-float-switch-i449722398-s830122226.html

Homepro and the like also have them.

 

If your pump is over 1HP or so, or the cable to the roof is long then I'd add a contactor. A contactor would also increase the life of the switch.

 

We have one that literally failed last week after 3 years of directly switching a 2HP irrigation pump. The switch itself is fine, one of the floats sank!

 

[VocalNeal]

Set it up so that the "top" switch activates just before the existing float would. That way it will all work as clockwork, in the event that one of your floats sinks.

[Yellowtail]

1 hour ago, Crossy said:

I would go for the two-float type, these keep any electrics outside the tank. They also use standard micro-switches which are cheap and readily available.

 

Something like this https://www.lazada.co.th/products/2-adjustable-float-switch-i449722398-s830122226.html

Homepro and the like also have them.

 

If your pump is over 1HP or so, or the cable to the roof is long then I'd add a contactor. A contactor would also increase the life of the switch.

 

We have one that literally failed last week after 3 years of directly switching a 2HP irrigation pump. The switch itself is fine, one of the floats sank!

 

 

The pump is a mitsu 355, so I guess about a half HP, (spec says 350 watts).

 

How does it work, the switches are in series, and the top float breaks at max level and the bottom one makes at the min level and it actuates a little relay that stays on until the top switch breaks?

 

Is that how the power is kept out of the water, the relay is outside the tank?

 

The roof tank is stainless. How does it install, just drill a hole in the top to run the wire out and let the switches hang from that?

 

Thanks

[Yellowtail]

22 minutes ago, VocalNeal said:

Set it up so that the "top" switch activates just before the existing float would. That way it will all work as clockwork, in the event that one of your floats sinks.

 

How do you adjust them?

[Crossy]

It has only one switch.

 

The idea is that when both floats are floating (tank full) the switch is "off" (it's actually a change-over switch). 

When both floats are hanging (tank empty) then the switch is "on".

If one float is floating and one hanging (neither full nor empty) the switch remains in whatever position it was in previously.

 

The switch sits on top of the tank and the string hangs through a drilled hole.

 

You adjust it by sliding the floats up and down the string (I had to add extra string to get the range I needed).

 

Like this but with a longer string.

 

 

[Yellowtail]

27 minutes ago, Crossy said:

It has only one switch.

 

The idea is that when both floats are floating (tank full) the switch is "off" (it's actually a change-over switch). 

When both floats are hanging (tank empty) then the switch is "on".

If one float is floating and one hanging (neither full nor empty) the switch remains in whatever position it was in previously.

 

The switch sits on top of the tank and the string hangs through a drilled hole.

 

You adjust it by sliding the floats up and down the string (I had to add extra string to get the range I needed).

 

Like this but with a longer string.

 

 

 

 

So the switch is weight activated, the weight of two floats engages it, and it stays engaged until the the weight of both are relived?

 

Thanks again

[sometimewoodworker]

1 hour ago, Yellowtail said:

 

 

So the switch is weight activated, the weight of two floats engages it, and it stays engaged until the the weight of both are relived?

 

Thanks again

One further point. There are 2 sets of connections, so you can select the switch to be off with no weight or on with no weight.

 

The on with no weight is a sump pump setting.