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chh 09-07-2012 08:28 PM

Gas Fireplace Flame Height Control

I have a flame height control knob on my unvented millivolt continuous pilot (with thermocouple and thermopile [for the main burner only I assume]) natural gas fireplace (ECS model VFD26F). I tried using the height adjustment control the other day, and it doesn't seem to be working anymore. Does anyone know how the flame height control works in such fireplaces? Is it just a potentiometer adding/decreasing resistance to the thermopile voltage, and therefore controlling how open the main burner gas valve is? If not, is the knob manually opening/closing a separate valve? What would cause such a valve or potentiometer to become inoperable (even though the control knob is movable) when it is only 5 years old? I should note that this fireplace has only a manual flame hight control on the valve assembly itself: the remote cannot adjust flame height.

From what I've read the gas valve assemblies in this fireplace is not serviceable, and has to be completely replaced for safety reasons if it has a problems. My understanding is that replacing these can cost $600+. The current height is actually pretty good, so I can easily live with it. However, I was curious to know if anyone has seen this before, and if there are any simple solutions out there. Also, should I be concerned with the safety of this fireplace if the flame height control isn't working (i.e. is it likely to start leaking gas)? I've been monitoring the unit for gas leaks, both with my nose, and a wall mounted explosive gas detector, and it seems fine. My guess is that more likely than not, it has been this way for quite a while.

Thanks for any insight you're able to provide!


hvac dude 09-07-2012 10:47 PM

Hi Chris, the valve is much like a dimmer switch for lights it usually works or it dosent sounds like yours chooses not work can leave it and live with the flame height or .. replace vavle , yes usually gas valves are unservicable for saftey reasons. 600.00 is that incl labour i can see how much valve is in my territory if u know a lic , gas fitter that can do the work .

how 09-08-2012 12:41 AM

That control is mechanical. The thermopile generates the voltage to run the gas valve, thermostat or on/off circuit and usually a high limit circuit. The thermocouple is a gas safety control. Both must function properly for the fireplace to operate.
The flame height is strictly a mechanical control within the gas valve.
If the flames look larger than normal, have someone clock the fireplace to see if it's operating beyond it's rating.

chh 09-09-2012 11:22 AM

Thanks for the responses. Some research indicated $600+ including labor, but that didn't take into account the exact valve I have (not sure if I can use a different one in my fireplace). Anyway, I think I can deal without the flame height adjustment for now: the current height doesn't seem to be too high or low.


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