New problem for you: household thermocouples, Etc.

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Discussion Overview

The discussion revolves around the use of household thermocouples in gas valves, specifically exploring how to operate a natural gas valve with a small amount of electrical power. Participants examine the functionality of thermocouples in water heaters and propose alternative methods for generating the necessary power, including induction and solenoid valves.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes the operation of household gas water heaters, noting that a thermocouple generates a small current to keep the safety valve open.
  • Another participant suggests using solenoid valves as a potential solution, indicating their compatibility with low voltage and high current from thermocouples.
  • A different participant points out that if power conductors are in the same sheath, it may be difficult to tap power effectively due to magnetic flux cancellation, proposing a method to separate the conductors for better power capture.
  • Some participants express concern about the implications of bypassing safety mechanisms, particularly regarding the pilot flame safety valve, while others suggest that the original poster may have a different, non-dangerous application in mind.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method to operate the gas valve or the safety implications of bypassing existing systems. Multiple competing views and concerns remain present throughout the discussion.

Contextual Notes

There are unresolved questions about the practical implementation of power tapping methods and the safety considerations involved in modifying gas valve operations.

chrishibbard7
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Household water heater thermocouple and power-open gas valve:
Here's the riddle:
(this is not a homework problem, it's a DIY thing)
how can I use a small amount of electrical power to operate a natural gas valve?
Background:
Household gas water heaters have a built-in safety valve that needs a small current of DC to keep the valve open. They have a suspiciously large pilot, which heats a small thermocouple. The thermocouple provides electricity to keep the safety valvle open. If gas supply is interuppted, or the pilot goes out, then no more power from the thermocouple, and the gas valve closes. No gas build-up, and your home doesn't blow up. Nice, eh?
How much power does a household gas waterheater produce? How can I generate the same amount of power by induction? If I have a hefty load (220V, 50A AC) nearby, can I wrap a coil of wire around this (very insulated) power cable to collect enough power to replace the thermocouple? (BTW-not using it to keep a gas line open anymore)

Any other easy ways around this, or another solution? I thought of using yard irigation valves, which use 12V DV to operate, but I *think* they open OR close whenever they get power... I need a simple system, no ICs involved, as it will be outdoors with little protection from the weather. I want to gate to be open when power flows through large power cable nearby.

Any suggestions of help appreciated. Thank you for your time.
 
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It might help if you would say how you intende to use your valve. Solenoid valves is the way to go. There are all kinds of http://www.ascovalve.com/applications/products/SolenoidValves.aspx" .
 
Last edited by a moderator:
That is exactly what a thermocouple valve is. A solenoid valve that is designed to run on the very low voltage and high (relative) current from the thermocouple.
 
If the power conductors are in the same sheath, then you will not be able to tap much powe off of them. You need to separate them so you can capture the magnetic flux from just one conductor, instead of having the multiple fluxes cancel each other out. Is there a practical way to separate the conductors? One way is to make an adapter that takes the cable in, separates the conductors, then recombines them, and has the cable continue out of it. You can put (safe) male/female connectors on the cable, for example, and plug those into your tap box...
 
Averagesupernova,

I really didn't want to get into how to keep your furnance valve open when you loose flame.
 
dlgoff said:
Averagesupernova,

I really didn't want to get into how to keep your furnance valve open when you loose flame.

But I get the impression the OP has some other function in mind, not a dangerous thing like bypassing the pilot flame safety valve:

chrishibbard7 said:
(BTW-not using it to keep a gas line open anymore)
 
But I get the impression the OP has some other function in mind, not a dangerous thing like bypassing the pilot flame safety valve:
Yes, but I want to bring it to the attention of others that might want to try to bypass the saftey.
 

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