Gas Boiler not firing up- circ pump and draft inducer running ok

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Old 09-14-14, 10:30 AM
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Gas Boiler not firing up- circ pump and draft inducer running ok

My system:
-Dunkirk gas boiler circa 1990 fitted with a Honeywell Aquastat Relay (L8184E).
-4 zone valves (White Rodgers brand)
-intermittent pilot that is piezio/electronic(?) lighted.
-pressure switch (connected with a tube to the blower) between the Aquastat Relay and the electronic board near the gas valve (24v).

The symptoms:
I turn a thermostat on (to call for heat) and the draft inducer blower and the circulator pump start up and continue to run but the burners do not fire up. When the system was working last spring there would be rapid clicking of the piezio/electronic igniter and the burners would fire up. Now, as I said, the igniter is silent and therefore the burners don't fire up. I do not smell any gas.

I've searched the internet for the last two days but haven't found another post that describes the problem I'm having, close but not close enough.

Any help or advice would be greatly appreciated. Thanks!
 
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Old 09-14-14, 02:54 PM
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Well, my son and I figured it out. First of all we had been testing for 24VDC when we should have been testing for 24VAC. By switching over the meter we traced the problem to the pressure switch interrupting the current from the aquastat relay to the spark igniter. We though we had a defective pressure switch after we jumped the wire around it and the boiler fired up. Then I tried blowing, then sucking on the hose to the pressure switch and realized the pressure switch was working as the boiler fired up when sucking (drawing a vacuum) on the pressure switch. I stuck a wire into the blower hose connection to clean out any obstruction.

When that didn't work I we decided to confirm that the exhaust duct wasn't plugged up. We started by removing the duct at the boiler and discovered the flap on top of the blower wasn't opening when the blower was on. We cleaned up the frame around the flap so it would open and close freely then tried it out. And it worked!

So a lot of hours this weekend researching and trouble shooting but in the end we fixed it and didn't have to buy any parts nor call in a pro. And I learned a lot about boilers that will come in handy in the future. I also cleaned out the burners on the way so, baring any other failures, its ready for the winter heating season.
 
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