Boiler CLUNKING

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Old 08-07-16, 05:32 AM
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Boiler CLUNKING

Hi all- forum noob here. First I'm a handy guy even built my own house, contractor for 30+yrs but know nada about the tech end of boilers altho I roughed in the entire house plumbing & 4 zone base board to the manifold and let the pro hook the rest up. To my point....My 19 yr old Crown Aruba ABF70-EID kettles bad during heating. 4 zones+. I'm pretty sure the gauges are ok as I've set the temp from 140-200 at different times and it still bangs away.I should also point out we have a indirect water heater and that gets used a lot mostly from my adult kids taking looong showers despite my efforts to minimize that. I guess from all I have read its mineral deposits inside the cast exchanger. Looking at options i see
1) de-scaleing/flush.
2) replacing just the cast exchanger.
2) new boiler
So, just how effective would the flush actually be (and can it be done)? Do you see the broken up deposits while draining or are they still disolved? As a side curiousity, since the hot water heat is a closed sysytem is there a finite amount of deposits collected on the exchanger and thus the water is "purifeid" or will it cause issues forever?
Replacing, cost effective? I contacted Crown and actually can get a new block assembly for about $1K. And most likely will be replacing related piping/guage hook ups.
New. Lots of money.....
This boiler has never had an issue since installation except for the banging that has grown over the yrs. Would really like to give the cheap fix-of course!_ with a flush but not sure how effective it would be or even how to do it. Suppose i can hire a pro too.
Ok- I rambled a lot here and just needed to vent somewhere, thanks to those (any lol?) that took the time to read... would appreciate any tips and advise!
 
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Old 08-08-16, 09:06 AM
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It is not clear if "clunking" is classic water hammer/knock which is caused by steam or air passing through water.

Hydronic systems are usually not run above 180F because of scaling. Running a 200F may be a contributing factor. With gauge tolerances factored in you may be closer to 212F. I would use a second digital temperate gauge which usually are more accurate. Test it in boiling water to be sure.

Out-door-resets go for $150 and would be a positive thing here. It will keep water at 180F. Just monitor the overshoot when "call for heat" ends. Some set at 180F will overshoot to 190F or more. If it overshoots, lower the high setting by the amount it does. Beware of using the "automatic" setting on some. While trying to avoid "short cycling" some cause major temperature overshoot.

I am running a 60 year old cast iron Weil-McLain at 85%+ efficiency. It is a lot easier to clean than newer boilers. Would only replace a old cast iron when it developed repairable leaks or had other major issues.

The simplest thing to try is boiler cleaner. First time I used it you could smell the higher temperature coil surfaces on convectors in the rooms. It may not cure the clunking but is a worth the effort for $20 or less.
 
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Old 08-08-16, 05:34 PM
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What is the system pressure? If less than 15-18 psi (cold), jack it up.
 
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Old 08-08-16, 06:45 PM
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I am running a 60 year old cast iron Weil-McLain at 85%+ efficiency.
Im sure combustion... actuals probably 40-50%..
 
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Old 08-09-16, 09:39 AM
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Label on my Weil-McLain boiler reads 1.80 GPH. Now is firing at .79 GPH (measured) a 50% reduction. In sizing heat exhangers for systems reducing through-put raises efficiency.

Stack temp ranges from 320F to 350F, varying according to water temp controlled by out-door-reset. Subtract room temp of 70F and look at charts for efficiency. To avoid condensation issues, circulators are disabled when return water drops to 135F.

I had read old Brookhaven National Labs report on passive losses as a guide. W-M boiler has added external insulation and internal baffles plus automatic stack vent. Even vent pipe is insulated before automatic vent to lower static heat loss. Before adding insulation it was a 180F "heat pipe" sucking BTU's out of boiler when not running. Especially in spring and fall when it does not run much that loss 24 hours/day adds up.
 
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