Boiler Overheating, Pressure Release Valve Discharging, Pipes Knocking

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jldamico

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Over the past couple days I've started having issues with my boiler. I have Dunkirk. I do not have a separate hot water heater/tank. There was some knocking, I assumed some air in the system. A couple of nights ago, it got VERY loud and made a sudden...for lack of better word..."crashing" noise". I went down to see a room full of steam and a drip/some steam coming from PRV pipe. I also occasionally get a bang/clicking that SEEMS to be coming from aquastat transformer.

Yesterday, I replaced the expansion tank. No luck.

The odd part is that the major issue..the loud crash and the PRV discharge only seems to occur when someone is showering, not when the systems is calling for heat.

The Honeywell aquastat is set at 160 low and 180 high.

I finally had the chance to actually check the gauges while someone was showering. PSI was climbing at/near 30 and the temperature was at 260. At that point a got some distance from the boiler. lol. Moments later, another PRV discharge/room full of steam.

From what I've read, after excluding expansion tank as the problem, it could be a faulty aquastat? But wouldn't that also cause a problem during the house calling for heat or simply the boiler regulating temp?

Another possibility is pump? Not pushing enough water through the system? Or a coil leak?

Any thoughts would be greatly appreciated.
 

Dana

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If the 260F reading is real you need to get a new aquastat pronto- that's a dangerously high temperature, and would explain the high pressure. With boiler temperatures that high you could even be getting micro-boil collapse banging in the tankless hot water coil causing the

Most hydronic boilers can't be operated over 220F unless something is wrong. Something is CLEARLY wrong it it's hitting 260F with the high limit on the aquastat set to 180F. Most boilers built since 1970 have a separate safety-limit aquastat to keep temps bounded even if the normal operation aquastat fails. How old is this beast? If it was installed during the Clinton's first term or earlier it's probably not worth putting any money into (and I suspect it pre-dates Nixon), and replacing it with something right-sized for the space heating load would be the right thing to do.

Oil or gas?

To get a reasonably accurate handle on the heat load, follow the methods in this bit o' bloggery, or post the relevant fuel use and meter reading/fill-up data here along with a ZIP code (for a more accurate outside design temperature.)
 

essi

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If the 260F reading is real you need to get a new aquastat pronto- that's a dangerously high temperature, and would explain the high pressure. With boiler temperatures that high you could even be getting micro-boil collapse banging in the tankless hot water coil causing the

Most hydronic boilers can't be operated over 220F unless something is wrong. Something is CLEARLY wrong it it's hitting 260F with the high limit on the aquastat set to 180F. Most boilers built since 1970 have a separate safety-limit aquastat to keep temps bounded even if the normal operation aquastat fails. How old is this beast? If it was installed during the Clinton's first term or earlier it's probably not worth putting any money into (and I suspect it pre-dates Nixon), and replacing it with something right-sized for the space heating load would be the right thing to do.

Oil or gas?

To get a reasonably accurate handle on the heat load, follow the methods in this bit o' bloggery, or post the relevant fuel use and meter reading/fill-up data here along with a ZIP code (for a more accurate outside design temperature.)

that was helpfull thanx
 
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