Question about Dyna-Glo D-E37 Wall Mounted Panel Heater

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Thermocouple how many millivolts should a thermocouple in a pilot flame be?

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I am assuming you are talking about a type K ( Chromel, Alumel ) type Thermocouple. A junction of these two alloys ( welded together by capacitance discharge) produces 41 micro volts per degree Celsius. As the flame from a perfect air/gas mix produces a flame around 1900 C (propane), and 2000 C (natural gas) . You can simply multiply.

41uV X 1900 = 779mV For propane
41uV X 2000 = 822mV For natural gas

This should give you a pretty good Idea of what you should be looking for. If you are using a standard volt meter to obtain a reading. Touching the leads of the probe to the leads of the meter in affect creates two more thermocouples unintentionally. This will alter your reading only slightly due to the fact that the temperature will be at relatively negligible at the contact points.
Allowing for this distortion you should expect a reading +/- 50mV either way. I hope you find this information helpful. Please take the time to rate this fixya for me. To compensate me for the 4 years of my life I spent cramming weird stuff like this in my head in college and the 5 minutes I spent typing this out for you for free. LOL If you ever need my help select me as one of your experts and I will help you for free.

Posted on Jul 28, 2008

  • George Kohler
    George Kohler Jul 28, 2008

    If you give me the exact type thermocouple you are working with and what gas the heater uses, I will calculate the exact reading you should be reading. I think the above estimates should be accurate enough for your purpose though.
    Thanks Again,


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I replaced the gasvalve and thermalpile in my 35,BTU wall heater I light the pilot and turn the heat on it goes out I ran a new state wire in case of a short but it still does it, did I get a bad...

Did you get the right gas valve for a thermapile and not a 24 volt gas valve? Also I would recheck my wiring.... Here is a article that may be of HELP....... Hope this Helps.....
Thermocouple: A thermocouple is a device made of two different metals which creates a small electrical charge when heated at one end.
Thermopile: A thermopile is a probe that contains multiple thermocouples, therefore it can produce a larger electrical current. Millivolts: 1/1000 of a volt - thermocouples and thermopiles typically produce from 25 to 600 millivolts of power.
Piezio - a spark producing device often used to ignite gas pilots and burners.
Gas Valves Types:
A. Single Thermocouple Only - Used on some gas logs
B. Valves with Thermocouples and Thermopiles - Used on most hearth appliances and gas logs with switches or remote controls or thermostats.
C. ODS Systems - Used on Mostly Vent-Free. Available in manual control or thermostat/remote/switch (combination) valves.
Typical Gas Valve A. Thermocouple-Only
Found in: Most gas log sets with standard safety pilot knob control. Also found in certain gas space heaters and construction-site portable heaters.
Explanation: This type of gas valve used a single thermocouple. A thermocouple is a device made of two different metals which creates a small electrical charge when heated at one end by the gas pilot. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the main burners. Since the thermocouple must be heated before the burner will start, gas appliances often have a startup mode, during which a knob must be depressed and held for 30 seconds or so after lighting the pilot. At the end of the 30 seconds, the pilot should be generating enough electricity for the valve to operate correctly. At this time, the startup knob can be released and the valve turned to an "on" position for appliance operation.
pilotclose.gif Troubleshooting:
Most problems with this type of valve are due to thermocouple problems. Check the following:
1. Connection from the thermocouple to the valve. Clean the threads of the connecting nut with a pencil eraser and re-tighten.
2. Pilot hood and flame direction. The pilot should engulf the top 5/8" of the thermocouple with a decent flame. If the flame hits the thermocouple too low, this can cause the appliance to go out or not generate enough millivolts for valve operation. The pilot hood and orifice should also be clean from soot which could slow or block the pilot flame.
3. Pilot pressure. Many of these valves have an adjustment screw to adjust the pilot flame. A pilot that is too short may allow the pilot to stay lit after ignition, but may not create enough charge to allow the burners to ignite.
4. Overheating: If the unit works for a few hours and then shuts down, it's possible the thermocouple has become overheated. Repositioning of the gas valve and/or pilot may be needed to avoid this problem.
Problems with LP units can also be due to a tank that is nearly empty or a bad regulator at the tank.
B. Thermocouple & Thermopile valve
gas1.gif Found in: Most modern VENTED gas stoves, fireplaces and fireplace inserts as well as vented gas log sets with thermostat or remote control.
This valve is similar to the thermocouple only valve, however has a pilot which heats up BOTH a thermocouple and a thermopile. The thermocouple still acts to prove that the pilot flame is on and allows this flame to continue after startup. The thermopile is used to power a second circuit which is used to open the main valve. This second circuit is powerful enough (300-600 millivolts) to allow the use of a thermostat, wall switch or control switch to operate the main valve. Control of the valve is obtained simply by hooking a pair of wires to two terminals located on the valve.
Startup is similar to the thermocouple-only valve. A piezo spark ignition is used to ignite the pilot after the gas knob is turned to the "pilot" position and depressed. Once the pilot is lit, the knob is held in for 30 seconds to "prove" the heat and then released and turned from the "pilot" to the "on" position. The main burner will then respond to the switch, thermostat or remote control.
Since there is both a thermocouple and thermopile in this valve type, it is important to isolate where the potential problem may be. If the pilot can be lit and stays on after the knob is released, then the problem is probably with the thermopile side of the valve. Here are the most common problems and solutions.
1. Pilot does not light or stay lit after knob is released - Make certain that the Piezo igniter works by checking for a spark between the igniter tip and the pilot hood. If there is no spark, the piezo may be bad or the piezo wire might be shorting to the appliance chassis. It is also possible that the igniter tip needs to be bent slightly toward the pilot hood so the spark jumps to it.
Check carefully that gas to appliance is on and that the valve is in he correct (pilot) position and fully depressed when lighting.
If pilot ignites but does not stay lit after knob is released, then the problem is with the thermocouple not generating enough voltage to the valve. It may be that the pilot adjustment needs to be turned up, or the thermocouple replaced. Another possibility is that the thermocouple may not be being "bathed" fully by the pilot flame. Check your owners manual for a diagram and description of the proper pilot flame and hood adjustment. It is also possible that there is soot or other blockage in the pilot tube, orifice or hood which is reducing the size of the pilot (and also the voltage of the thermocouple).
2. Pilot stays lit, but appliance will not turn on - There are two common causes for this. It is possible that the thermopile is not producing enough millivolts to power the control circuit. The millivolts can be checked with a simple voltmeter (consult the owners manual for proper setting) and adjusted with the pilot adjustment screw. Improper millivolts will also cause the appliance to shut down in the middle of operation.
Another common problem is loose or poor connections or circuits to your appliance switch, thermostat or remote transceiver. This can be isolated by simply using a small piece of wire to jump the "TP" and "TH" terminals located on these valves. If the appliance turns on when these terminals are jumped, then you can be sure that your problem is not in the appliance itself, but further down the switch circuit. Make certain you have used the suggested gauge of wire and that the length for your control runs does not exceed the specs given in your manual.
3. Other possible problems - include wind or back drafts affecting the pilot flame and checking of "spillage" circuits which may be wired into the valve in most B-Vent units.
If all the above checks out, and your valve is still acting weird (i.e., works some of the time), then you may have a defective gas valve in the appliance. Problems with LP units can also be due to a tank that is nearly empty or a bad regulator at the tank.
C. ODS System
Found in: Unvented (Ventless, Vent free) gas logs, fireplaces and stoves. These systems are available in manual or remote control.
ods.gif ODS stands for "Oxygen Depletion Sensor" , a term which accurately describes this valve type. The valve itself is similar in many ways to the two valve types above...with one exception. The pilot tube is a precision mechanism that creates a very stable flame as long as the room air contains the proper amount of oxygen. If the oxygen level in the room air drops even slightly, the pilot becomes unstable and lifts off of the thermocouple (see diagram) causing the gas valve and appliance to cease operation. This type of valve is very reliable, and there have been very few failures of this system - even with tens of millions in use worldwide.

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1 Answer

Will lite but goes out within a min

Make sure the thermocouples not fully engulfed in flame, it needs to be on;y at the tip end as they operate via temperature differential acrosss the thermocouples surface, if the whole thinfs one temp it drops out electrically(makes 30 millivolts) and the electromagnetically operated pilot safety valve closes, thus stopping the main burners operatin as its sensing no pilot exists. try a new thermocouple, about 15 bucks, and set it as described in pilot flame, if that wont do it, the gas valves bad.

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I go thru the process of lighting the pilot light following the directions exactly, but as soon as I let the pilot light switch pop out so that I can turn it to the left to light the heater the flame goes...

The system works off of a thermocouple that is heated by the pilot. The thermocouple creates millivolts that magnetize a head behind the control knob. When you push in the knob the magnetized head behind the knob holds the gas valve open. So obviously the head is not being magnetized. First make sure that the pilot is not plugged and the flame is large enough to heat the thermocouple. Also sometimes you may need to hold the knob for several minutes before the pilot will stay on. Also patio heaters have a safety feature that will cut the millivolt circuit if the heater falls over. It is possible that this safety device is tripped or defective causing the pilot to not stay lit. Also check for any loose wires on the millivolt system.

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Pilot light won't stay lit when you try to turn control knob to thermastat. Is it the thermocoupler, the control valve or the pilot assembly?

Once your pilot is lit the thermocouple sends millivolts to the gas valve to tell it that the pilot is lit and to allow the gas valve to open. Check to see if your thermocouple is in the pilot flame. I f it is then you will need to replace the thermocouple.


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1 Answer

Pilot light won't stay lit.

most common cause of the described symptom overheating the thermocouple! a thermocouple produces millivolts of electricity based upon a differential of temperature between the tip and the base. If it gets too hot it will not work correctly. If the pilot flame is too large or the main burner flame is contacting the thermocouple or the thermocouple is too cheap or old all can cause this issue.

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