Laars Lite 2 pilot light problem

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Gahamen
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Laars Lite 2 pilot light problem

Postby Gahamen » Wed 23 May, 2018 11:59

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.


Denniswiseman
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Re: Laars Lite 2 pilot light problem

Postby Denniswiseman » Wed 23 May, 2018 15:19

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.
Gahamen
I'm new here
I'm new here
Posts: 4
Joined: Wed 23 May, 2018 11:44
My Pool: 40x20ft roman end
LaarsLite2 Boiler
Certikin sand filter

Re: Laars Lite 2 pilot light problem

Postby Gahamen » Thu 24 May, 2018 03:27

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?
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 1338
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Laars Lite 2 pilot light problem

Postby Denniswiseman » Thu 24 May, 2018 04:06

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
Gahamen
I'm new here
I'm new here
Posts: 4
Joined: Wed 23 May, 2018 11:44
My Pool: 40x20ft roman end
LaarsLite2 Boiler
Certikin sand filter

Re: Laars Lite 2 pilot light problem

Postby Gahamen » Thu 24 May, 2018 05:23

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.
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 1338
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Laars Lite 2 pilot light problem

Postby Denniswiseman » Thu 24 May, 2018 05:35

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
Gahamen
I'm new here
I'm new here
Posts: 4
Joined: Wed 23 May, 2018 11:44
My Pool: 40x20ft roman end
LaarsLite2 Boiler
Certikin sand filter

Re: Laars Lite 2 pilot light problem

Postby Gahamen » Sat 26 May, 2018 03:32

Problem solved. I purchased a universal thermocouple from Amazon, fitted it, measured voltage = 23mV, perfect, all working again. Thanks again Dennis.
Denniswiseman
Pool Industry Leader
Pool Industry Leader
Posts: 1338
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Laars Lite 2 pilot light problem

Postby Denniswiseman » Sat 26 May, 2018 07:55

That's great
A simple cheap job, may be an idea to have a spare as they do fail

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