Line voltage low water cutoff

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GerryB

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Location
woodbridge, ct. USA
A plumber I do work for wants me to wire a line voltage low water cutoff for a boiler. I said I never did one but ok it couldn't be to hard. I looked online and the wiring is basically what I thought, just goes through the cutoff and to the boiler. What caught my attention is in the principles of operation for this cutoff (WATTS was the brand I was looking at), it said "water is used as a conductor" for the cutoff. I was thinking this was some kind of a float switch. I guess this probe is somehow isolated? all the water couldn't be electrified.
 
iwire

iwire

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Location
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GerryB said:
A plumber I do work for wants me to wire a line voltage low water cutoff for a boiler. I said I never did one but ok it couldn't be to hard. I looked online and the wiring is basically what I thought, just goes through the cutoff and to the boiler. What caught my attention is in the principles of operation for this cutoff (WATTS was the brand I was looking at), it said "water is used as a conductor" for the cutoff. I was thinking this was some kind of a float switch. I guess this probe is somehow isolated? all the water couldn't be electrified.
Click to expand...

Do not worry, I have Taco brand line voltage low water cut off on my own home boiler and it also uses a probe that uses the conductivity of water to work.

There is a PC board and a small power supply on board that handles the probe. They don't send line voltage into the water.
 
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GerryB

Senior Member
Location
woodbridge, ct. USA
gar said:
151025-0917 EDT

GerryB:

Most water is relatively conductive because of disolved salts.

Thus, there are many descrete point liquid level controls made that use an insulated probe inserted into the tamk at the desired sensing level point.

See http://forums.mikeholt.com/showthread.php?t=107643 for more information and a prior comment of mine.

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Thanks gar, very interesting. So the water or distilled water is not a conductor but tap water, salt water are because of the ions or whatever (electrons?) that can move around in it. (I had to look at your profile to see how you knew so much about it:)
 
Fulthrotl

Fulthrotl

~Autocorrect is My Worst Enema.~
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GerryB said:
Thanks gar, very interesting. So the water or distilled water is not a conductor but tap water, salt water are because of the ions or whatever (electrons?) that can move around in it. (I had to look at your profile to see how you knew so much about it:)
Click to expand...

the public utilities use a water cannon to wash insulators on poles on live lines...
demineralized water is what they use so it doesn't track back to the spray rig...


http://www.electrotechnik.net/2010/12/hot-washing-of-insulators.html
 
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GoldDigger

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Retired PV System Designer
gar said:
151025-2355 EDT

GerryB:

See http://forums.mikeholt.com/showthread.php?t=149517&highlight=water+conductivity+measurements

I believe there was a thread somewhere where I supplied some conductivity measurements on several different water sources, but the search function on this site is too poor for me to find it.

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Click to expand...

The thread you want is this one: http://forums.mikeholt.com/showthread.php?t=107643

Two others that came up in the search are
http://forums.mikeholt.com/showthread.php?t=126521

and
http://forums.mikeholt.com/showthread.php?t=149517 (the one you found)

The search function on this site is next to useless, but the following Google search did just fine:
site:mikeholt.com water conductivity gar
 
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