I have the typical problem of the pilot light not staying alight after releasing the white button.
I've replaced the thermopile and get 600mV generated and checked for corrosion at the terminal end and all is good and clean.
There is a thermocouple also by the pilot light. Is this also required to work to keep pilot alight? If so, I'll change it as I can't see what else is causing problem,
except perhaps the gas valve itself (hopefully not). Can't find and documentation on the thermopile purpose. Lots of advice about checking/changing the thermopile.
Any advice welcome.
Laars Lite 2 pilot light problem
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Re: Laars Lite 2 pilot light problem
Being a retired heating engineer I can confirm that a thermcouple is used to keep a pilot light burning
The heat playing on the thermocouple generates a small electric current which holds the valve open to the pilot light
William Anders, Repair of furnaces and boilers of all types
Answered Feb 14, 2017
In heating systems a thermocouple is one junction of metals that when heated by a pilot flame generates approximately 25 mv and holds open an electromagnetic valve to allow gas to pass as long as there is a pilot. A second valve in the valve train can allow gas to the burner on a call for heat, but gas is only available when the pilot is lit and the first valve is held open.
In heating systems a thermopile is an assembly of multiple thermocouples that generate approximately 750 mv and actually operates the main gas valve on a call for heat if the pilot is lit.
In both systems on a loss of pilot flame the electromagnetic valve drops out and closes, shutting off gas to pilot and disabling main burner until manually reset and relit.
In some very old thermopile systems, the pilot gas stays on even if the pilot flame goes out. They should be retrofitted with modern gas controls with pilot safety.
The heat playing on the thermocouple generates a small electric current which holds the valve open to the pilot light
William Anders, Repair of furnaces and boilers of all types
Answered Feb 14, 2017
In heating systems a thermocouple is one junction of metals that when heated by a pilot flame generates approximately 25 mv and holds open an electromagnetic valve to allow gas to pass as long as there is a pilot. A second valve in the valve train can allow gas to the burner on a call for heat, but gas is only available when the pilot is lit and the first valve is held open.
In heating systems a thermopile is an assembly of multiple thermocouples that generate approximately 750 mv and actually operates the main gas valve on a call for heat if the pilot is lit.
In both systems on a loss of pilot flame the electromagnetic valve drops out and closes, shutting off gas to pilot and disabling main burner until manually reset and relit.
In some very old thermopile systems, the pilot gas stays on even if the pilot flame goes out. They should be retrofitted with modern gas controls with pilot safety.
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Re: Laars Lite 2 pilot light problem
Thanks Dennis. I'll replace the thermocouple. I notice there are universal thermocouples that are considerably cheaper and more easily available than the Laars. Are they a suitable replacement or are the Laars spec'd differently?
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Re: Laars Lite 2 pilot light problem
Gahamen wrote:Thanks Dennis. I'll replace the thermocouple. I notice there are universal thermocouples that are considerably cheaper and more easily available than the Laars. Are they a suitable replacement or are the Laars spec'd differently?
I'm not familiar with the Laars but check with the universal thermocouple manufacturer as there are different thermcouples or Google "Laars replacement thermocouple"
I just Googled it here in the UK and the Item came up at £27.65 (Jandy Laars R0366000 Pilot Thermocouple nut type )
It looked like a pretty standard thermocouple
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Re: Laars Lite 2 pilot light problem
Yes, it looks pretty standard. It's only £5 on Amazon for a universal thermocouple so makes sense to try it first. BTW: measure the output of the current thermocouple 19mV after about 5 mins of pilot heat.
Thanks for your help.
Thanks for your help.
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Re: Laars Lite 2 pilot light problem
I'm not sure of what the output should be but whenever a pilot failed to stay alight I just replaced the thermocouple
It always worked after
One other thing make sure that the pilot flame envelopes the thermocouple tip
Seeing as you can measure the output, you may want to test before fitting
It always worked after
One other thing make sure that the pilot flame envelopes the thermocouple tip
Seeing as you can measure the output, you may want to test before fitting
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- I'm new here
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LaarsLite2 Boiler
Certikin sand filter
Re: Laars Lite 2 pilot light problem
Problem solved. I purchased a universal thermocouple from Amazon, fitted it, measured voltage = 23mV, perfect, all working again. Thanks again Dennis.
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- Location: United Kingdom
Re: Laars Lite 2 pilot light problem
That's great
A simple cheap job, may be an idea to have a spare as they do fail
A simple cheap job, may be an idea to have a spare as they do fail
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