Knight oddity...

Hvacman

I rose up out of bed this morning resigned to that cold shower, for giggles I went down into the dungeon and reset the boiler, to my surprise it started up normally and has been doing so all day...

Word from my distributor is that low gas pressure will cause the fan to try and compensate by ramping up during the start of the trial for ignition...

I saw this happening at the time but failed to realize what I saw! The display would flash "fan high" for an instant as it transitioned from pre-purge to ignition.

I will confirm the diagnosis with my manometer as soon as the boiler tells me I've got low gas pressure again. :-)

Kudos to Delta T/ API of NH and their techie Tim Cutler for the excellent support and speedy response to my questions!

Hvacman

Knightmare... :-)

No not really a Knightmare but I got the dreaded "no hot water" call from my wife this afternoon. My Knight has locked out with a "high fan" failure. I have many Knights I've put in commercially with no failures but my own will force me to take a cold shower in the morning! Per the literature this failure is due to the combustion blower running 30% faster than it is supposed to, I assume to prove flow. I have checked the combustion and exhaust pipes for blockages, checked the pressure tubing from the intake elbow to the gas valve for blockage or damage, removed and cleaned the burner with compressed air, checked for condensate backup and flushed the trap, inspected the blower wheel, cleaned the HX, and checked all the fuses. (I mentioned the fuses because this boiler will throw you a red herring called "manual reset high limit tripped" if the fuse on the t-stat circut is blown).
I will speak to my distributor in the AM, anyone have any ideas? The boiler did fire one time after I reassembled it, in my haste I cycled the t-stat on my indirect to test and it never fired again... I should have waited till I had a full tank of DHW before I got excited and cycled it!

Brian

Greg Gibbs

One of two things...

Brian, the Tan wire on one of the harness

hot_rod

I have had a similar

lockout under DHW loads only.

A few times the boiler would surge, the fan would rev up and down quickly for a few minutes on DHW call and finally lock out on high fan speed. I cleaned and rechecked and re pluged all the connectors and it has been fine for 6 months or so now.

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