Relays with mV coil

Levi G

Member
Join Date
Sep 2015
Location
Alberta
Posts
145
I have a gas appliance I would like to monitor to check to see if it is on or not, this appliance has no power coming to it. It has a Thermopile generator or Powerpile that produces mV, which powers the gas valve. If I could find a relay with a mV coil so I could wire it parallel to the gas valve to monitor if power comes to the gas valve.

Question is: Are there relays out there that have a coil for mV? Does anyone have other suggestions on how to monitor this? Is there something like an aux relay available for these types of valves?
 
the first thing you need to do is determine what the area is classified.
if its rated class 1 or 2, you have to adhere to the hazardous wiring principals
in nec 70.

a voltage amplifier may violate the area classification.

regards,
james
 
This one is only for 100mV, I think these gas valves run up to 700mV. I found a signal conditioner(Phoenix 2810874) that can read that range of mV.
I was hoping there would be a cheaper alternative because with a signal conditioner I now have to add a analog card to my plc.

James, this is not a hazardous location by any means, but thanks for the insight

Keithkyll, can you explain a little more what you mean? This appliance has a pilot (flame) but no pilot light, or are you recommending that I put a temp sensor beside the burner to determine if the burner is on?
 
This one is only for 100mV, I think these gas valves run up to 700mV. I found a signal conditioner(Phoenix 2810874) that can read that range of mV.
I was hoping there would be a cheaper alternative because with a signal conditioner I now have to add a analog card to my plc.

James, this is not a hazardous location by any means, but thanks for the insight

Keithkyll, can you explain a little more what you mean? This appliance has a pilot (flame) but no pilot light, or are you recommending that I put a temp sensor beside the burner to determine if the burner is on?

You could sense the presence of a flame with either a UV detector or a flame rod, which is basically just a ground fault detector that leaks current to ground when exposed to ionized gasses.
 
Where is the Thermopile? Isn't it being heated by a continuous flame, i.e., pilot light? To light the pilot, you rotate the knob to the pilot position, then press down the black button to force valve open to light pilot. After Thermopile warms, you can let go of bypass button, and pilot will stay lit because Thermopile is keeping valve open. You now rotate knob back to operate position.
If anything goes wrong, the pilot will go out.
Are we talking about the same thing?
 
Where is the Thermopile? Isn't it being heated by a continuous flame, i.e., pilot light? To light the pilot, you rotate the knob to the pilot position, then press down the black button to force valve open to light pilot. After Thermopile warms, you can let go of bypass button, and pilot will stay lit because Thermopile is keeping valve open. You now rotate knob back to operate position.
If anything goes wrong, the pilot will go out.
Are we talking about the same thing?

Yes that is exactly what I have, The pilot light is always on, the thermostat then opens and closes the valve.
I would have to put the flame sensor at the burner because I want to monitor if the burner is on or not.

I have never come across a UV detector or flame rod or flame sensor so I will have to look into those.
 

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