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Post purge setting

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Roy_10
Roy_10 Member Posts: 8
How long should the burner post purge be set for?

We recently installed an MPO147 boiler vented into a chimney. The installation, operation and service instructions have boiler sequence of operations printed on page 32 but may need updating. The sequence states that there will be a pre purge for 10 sec. And a post purge for the last 10-sec. The primary control shipped with the burner has a fixed pre set 15-sec. Pre purge. The post purge is adjustable 30 sec., 2 min., 4 min., or 8 min. and came set at 2 min. Should the post purge be set to 30 sec?
FYI - The stack temp is running 350 – 400deg. Also couldn’t install the 2nd pass flue baffles because the over fire pressure became positive. Draft at breaching is .04 and almost .01 over fire without the baffles.
Would a CO2 reading taken after the post purge is complete be sufficient to tell if a 30-sec. post purge is long enough, if reading is at or near 0?
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