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Utica SFH4150WT oil fired base board..New Honeywell aquastat L7224U..High Limit set 180° with 10° differential...When a zone calls for heat furnace turns on and runs till the 180 limit..At about 175 it starts to make a knocking noise rising in sound and speed and goes on for about 30 seconds after high limit shut off then ceases..This started last year prior to new aquastat.. Noticed the boiler water temp will rise to about 190 in a few minutes and drop as zone uses the water eventually to the 170 start up.. I searched here and gleaned what I could..Went and checked expansion tank for heat and is hot only in top 1/4..Boiler pressure will go from 15 psi to 20 at max temp and then drop down as boiler cools..Oil Service says getting too hot and is boiling [like in an area]? Say to reduce temperature? I did reduce high limit to 175 and seemed to help some, as far as how loud the knocks are..Sorry for long post, tried to give as much info as I could..Thanks, Seb..
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Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
You can choose to do what you want, but you cannot choose the consequences.
You can choose to do what you want, but you cannot choose the consequences.
In old water heaters that noise is sometimes caller percolation, where the flame is heating a mineral layer in the bottom.
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
Some of the other products get injected and left in the system, typically the keep the minerals in suspension, to eliminate to percolation.
I believe the Rectorseal 8 way is a caustic soda, it would be added, circulated and flushed also.
But first narrow down the cause, a pump noise would be a different fix. Scaled boilers usually happen over a period of time, whereas a failed pump may just show up one day.
There is no harm in a boiler cleaning, flush and refill, but it may not be the fix.
If you do the cleaner, check the hardness of the fill water you have, some suggest anything over 8-10 grains should be treated, or buy DI water and fill the system.
How old is the system, when did the noise start?
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
Google water hardness testing and see some simple tests with just soap in a glass of water.
Here is an example for Canadian water hardness.
If you are going through the process of cleaning the system, you want to make sure you put good quality water back in.
htpp://funkyfluff.co/water-hardness-in-canada/
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me