Honeywell l8148b with vs820c gas valve uncovered issues firing and replacement


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Old 11-23-16, 10:07 PM
J
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Honeywell l8148b with vs820c gas valve uncovered issues firing and replacement

Hi everyone, im a silent admirer of the site, also a licensed plumber in Mass. I have read 4 threads about this control and have not seen a few issues I have been having.

I have this outdated control on a us boiler burnham 406b.natural gas, standing pilot millivolt forced hydronic with 2 seperate pumps for 2 seperate floors, wired together as one zone. ( I'm assuming because the radiators were never scrapped and it's to push the higher volume of water as there is only 1 thermostat wire. The L8 was d.o.e. and The replacement model j has an immersion well and this dead one does not. Question1 what's the correct replacement
Question 2 how do I test the power pile and gas valve meaning how do I jump it to fire? I'm asking because I'm getting like .2-.4 v reading but can not get the valve to open. Pilot is lit and is a standing pilot if I jump red and white from the pile it shuts the pilot down. So gas valve is functioning in one way. I need to replace this customers control Friday morning and would love to show up with the correct control and would like to know if I need the gas valve or power pile. My thinking says the low voltage reading can only be from the pile and it's good. Just confused why no boiler fire. Other things I know
The old control L8 was jumped out
No voltage from L8
2 aquastat s on other side of boiler 2 different model numbers one must be low, the other high.
Thank you anyone in advance who has time this holiday to take a minute for me I greatly appreciate it. Happy thanks giving.
 
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Old 11-23-16, 10:33 PM
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Welcome to the forums.

The powerpile needs to generate approx 3/4 of a volt.... that's .75 volts which is much higher than you measured. You may have a lazy/dirty pilot light not capable of powering the gas valve.

On page 4 of the gas valve manual is the wiring diagrams. Do you have a three or four terminal gas valve ?
honeywell/resources/TechLitDocuments/95-0000s/95-6994EF.pdf
 
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Old 11-24-16, 05:46 PM
J
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Thanks for the reply, I have a 3 terminal triangle shape. I also have pictured and the boilers pdf manual just not sure how to post them
 
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Old 11-24-16, 05:57 PM
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I believe your right, I was also able to jump the valve when I first arrived and couldn't repeat it. So the .75 completes the loop between the hi lo aquastat s and the end switch on the L8 controller making it fire? And I believe you were about to tell me its the 2 th terminals on the gas valve that should make it fire?
The only thing I don't know now is why the replacement L8 j controller has a well on it. Thanks again.
 
 

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