Knight Boiler Clunking Noise after Power Outage - Now Temp O/Shoot


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Old 10-24-14, 05:54 PM
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Knight Boiler Clunking Noise after Power Outage - Now Temp O/Shoot

Hi All:

I just posted this, but I must have done it wrong or put it in the wrong place.

Anyway, I posted here once before and it was well worth it. I think I have a serious issue, but no harm in asking. I have a Knight 105 btu gas boiler, 3 zones, 2 floors

Was running great, until big storm in MA Wednesday night. We lost power for 14 hours. As the power was going out, it flicked 3 times over a minute span, then gone.

Power came on while I was at work. It was cold in the house. I checked boiler display and it said 'setpoint met'. Heat was set to 69, but it was 61 in the house. I shut the boiler off, waited a minute and turned it on. It started normally, purge then ignition, and display started at SH = 20%. Then it NORMALLY has an accelerating fan-like noise as SH ramps to 60 to 80%. Instead, it started clunking, SH immediately went to 100%. Water temp went to 160 degrees (normally goes to 140 I think), and error message was 'Temp O/Shoot'. System stops. Tried it a couple times when boiler was cold, same result.

I kind of undertand the Temp Overshoot, only because I think maybe a board got surged or something, but the clunking has me confused, and I am hoping that the clunking indicates that it is a simpler issue. By simpler, I mean less expensive.

Any thoughts very much appeciated.
 
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Old 10-24-14, 05:58 PM
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What exact model Knight boiler do you have?

Can you describe the 'clunking' a bit more? Did it sound as if it was coming from inside the boiler?

Can you tell if the SYSTEM PUMP is running? (I believe it may not be)

Can you take some pics so we can see and tell you what to look at?
 
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Old 10-24-14, 06:14 PM
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Knight KBN105

it is a knight KBN105.

The clunking is internal, it happens during the period where the SH normally ramps up. 4 or 5 bangs, then a kind of sliding noise, like something is supposed to open but can't due to obstruction. You can normally watch the display go from 20% sequentially up to 60 or 80%. Instead it goes from 20 to 100 in the blink of an eye.

Then it goes silent as the output temp keep climbing with the Tem O/Shhot message.

Uploading pics now, 2 minutes.
 
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Old 10-24-14, 07:12 PM
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I'm still strongly suspecting that a pump is not running...

You have manual? Note where the pumps are connected on the terminal strip and check for 120VAC when boiler is firing.
 
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Old 10-24-14, 07:35 PM
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OK, Thanks, I do have manual - I will find it and check it out. Thanks for responding.
 
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Old 10-25-14, 08:11 AM
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And even if there is 120VAC at the terminal strips, the pump itself may be 'seized'. The wet rotor pumps have a tendency to do this from time to time.

You can usually tell if the pump is running by feeling the pipes to and from the pump.

Remember, there will be cooler water coming back and hotter water going out.

If all the pipes are cool, it's a good bet that the pump is not running.

I'd like to see some clearer, closer, pics so I can see hot the boiler is piped.
 
 

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