I have question concerning a float in a cistern that controls a deep well submersible pump. The float is the type that hangs from its cord like a basement sump pump. 1. Can this float be used to switch only one leg of the 240 volts going to the pump controller? 2. Is there an electrical hazard with a 120 volt potential in the water in the cistern?
Cistern Float
- Thread starter Crem
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charlie tuna
Senior Member
- Location
- Florida
Re: Cistern Float
if the cable is rated for the voltage and also the enviromental conditions -- which most are ---the float is molded directly onto the cable... and the internal contacts are rated for the starting current of the pump----what the problem?? on larger pump motors they have relays and are started by a contactor and i have found even then, the control voltge is 120 volts.
if the cable is rated for the voltage and also the enviromental conditions -- which most are ---the float is molded directly onto the cable... and the internal contacts are rated for the starting current of the pump----what the problem?? on larger pump motors they have relays and are started by a contactor and i have found even then, the control voltge is 120 volts.
Re: Cistern Float
The reason that I am asking this question is to find out if this method is up to code or not. I can't seem to find any data on this. A few cistern applications in my area are wired this way. My main concerns are the voltage in the cistern even if the float and cord is rated at 240 volts and the fact that only one pole of the 240 volts is opened. I can add a 24 volt transformer and a relay, but this makes it more likely to fail than the simple direct wired float. I also wonder about the float contacts always making contact under the low current application of only powering a small coil.
The reason that I am asking this question is to find out if this method is up to code or not. I can't seem to find any data on this. A few cistern applications in my area are wired this way. My main concerns are the voltage in the cistern even if the float and cord is rated at 240 volts and the fact that only one pole of the 240 volts is opened. I can add a 24 volt transformer and a relay, but this makes it more likely to fail than the simple direct wired float. I also wonder about the float contacts always making contact under the low current application of only powering a small coil.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Cistern Float
Yes there is an electrical hazard if the wire or float fails.
This application would fall under Art 430. The overcurrent protection for the float switch cord would be based on the size of the cord.
What is the overcurrent protection and the cord size?
If the float is tapped, then the size of the cord and its wiring must be based on the control circuit tap rules in table 430.72(B).
The wiring must all be a chapter 3 method. The float flexible cord is not a chapter 3 method.
I have installed a lot of float switch control systems and they are all 12 v or 24 v, or a listed system.
Yes there is an electrical hazard if the wire or float fails.
This application would fall under Art 430. The overcurrent protection for the float switch cord would be based on the size of the cord.
What is the overcurrent protection and the cord size?
If the float is tapped, then the size of the cord and its wiring must be based on the control circuit tap rules in table 430.72(B).
The wiring must all be a chapter 3 method. The float flexible cord is not a chapter 3 method.
I have installed a lot of float switch control systems and they are all 12 v or 24 v, or a listed system.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: Cistern Float
The direct answer is that a control need not open both circuit conductors, but a disconnect must.
As an example, most new central-AC units have only a single-pole relay, but the disconnect is a two-pole.
The direct answer is that a control need not open both circuit conductors, but a disconnect must.
As an example, most new central-AC units have only a single-pole relay, but the disconnect is a two-pole.
Re: Cistern Float
Thanks everyone for your replies. It looks to me like this float type of control that I have described is ok to use if all of the other wiring meets the code. This goes along with the way a well supply place and several well people around here said they do it in WI and MN.
In this application, the submersible pump is a 1/2 HP at around 5-6 amps and I believe that it is fed from a 20 amp double pole breaker. The float cord wire size is #16. According to table 430-72(b) column C, it looks like the float cord should be a #14 wire. What about the ground fault protection that they mention there? Is that considered the circuit breaker? The reason that I became involved and decided to ask about this, is because the float switch cord was exposed and damaged. It was not protected according to code. Actually the whole thing needs to be rewired as the power to the outside controller is supplied with a hanging cord.
Thanks everyone for your replies. It looks to me like this float type of control that I have described is ok to use if all of the other wiring meets the code. This goes along with the way a well supply place and several well people around here said they do it in WI and MN.
In this application, the submersible pump is a 1/2 HP at around 5-6 amps and I believe that it is fed from a 20 amp double pole breaker. The float cord wire size is #16. According to table 430-72(b) column C, it looks like the float cord should be a #14 wire. What about the ground fault protection that they mention there? Is that considered the circuit breaker? The reason that I became involved and decided to ask about this, is because the float switch cord was exposed and damaged. It was not protected according to code. Actually the whole thing needs to be rewired as the power to the outside controller is supplied with a hanging cord.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Cistern Float
I forgot to add that this is not a location where humans will be in the water, its different from a swimming pool. There are thousands of installations with electrical equipment in water, such as wells. Installed safely they present no risk.
A simple solution to the float problem is to install a fuse on the circuit to it. Some starters can have a fuse kit installed.
Thanks for taking the time to look up the code reference. I often only cite the section, if you don't have an NEC then you are in the wrong place.
I forgot to add that this is not a location where humans will be in the water, its different from a swimming pool. There are thousands of installations with electrical equipment in water, such as wells. Installed safely they present no risk.
A simple solution to the float problem is to install a fuse on the circuit to it. Some starters can have a fuse kit installed.
Thanks for taking the time to look up the code reference. I often only cite the section, if you don't have an NEC then you are in the wrong place.
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