Am I killing my boiler slowly?

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dbsuz05
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Post by dbsuz05 » Sun. Oct. 29, 2017 11:27 am

I have a burnham 23” round coal boiler, burning bit coal. My question is water temps.. circulator runs constant feeding 13 large cast iron radiators. I believe I am avoiding thermal shock by keeping the circ on full time. But the big question is. Am I killing the boiler itself by running it at say 100 degrees? In stead of having boiler isolated and running it at say 160-180 range. Should it be a plate exchanger then to rads? Large storage water tank? If I ran my boiler at 160 degrees it would roast me out of the house! So I have been running it lower temps for that reason. I have installed a web stone air separator. The system runs quiet. No air bubbles to be heard. Any ideas greatly appreciated. I just don’t want to kill this old piece of iron!

 
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Post by coaledsweat » Sun. Oct. 29, 2017 12:29 pm

A primary secondary plumb is probably a solution for your conundrum. Yes, you are killing the boiler. Oxygen disassociates from water at 154°, so running at 100° means your water is full of it. I would never run lower than 140° for that reason.

 
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Post by Pacowy » Sun. Oct. 29, 2017 12:36 pm

I believe 140 is also the magic number for avoiding condensation issues.

Mike

 
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Post by Rob R. » Sun. Oct. 29, 2017 1:13 pm

You need to make some piping and control changes to keep the boiler around 160 degrees. You can do this with bypass piping, or a primary/secondary arrangement.

Primary/secondary would be my choice, that way you can have full flow through the radiators and control the boiler temp. Separately.

 
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Post by franco b » Sun. Oct. 29, 2017 3:23 pm

Though I agree that it is good to have the temperature at 140, I doubt you are hurting the boiler. Those I serviced were just about all steam which meant that air was present all the time. Even dry returns held up very well.

My concern is how the temperature is controlled. I would like to see at a minimum a reverse aquastat that would start the circulator when water temperature rises too high. Running it all the time obviates that, but what happens with an electric failure? In my experience old hot water systems were gravity and open at the top with an expansion tank.


 
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Post by dbsuz05 » Sun. Oct. 29, 2017 3:44 pm

I will do some checking on primary secondary piping. Right now it’s just piped into the oil boiler then goes on to the rads. There is a strap on aqua stat on the boiler that turns circ on at a selected heat point. But I leave it at 80 so it runs constant. For fear of 60 degree water going into the boiler when it is at say 150 degrees. I also have a gravity setup. It’s connected to my ceiling. It also uses a strap on stat. It is connected to a normally closed valve. So if power goes out valve opens and I get gravity flow. It does work I know because I’ve had power failures and when pump stops the boiler will not overheat. Tried and true for 5 years now. 2 more questions please.... is a mixing valve used for the primary secondary piping? Special controller box? This is a very tough thing for me to wrap my head around!! And how about oil boilers that are turned on say once a day. Then they cool down. Are oil boilers themselves being killed slowly because they are not always sitting on 150 plus? Trying to understand how “any” home boiler could possibly sit at correct temps 150 plus, year round. Unless of course it heats your water. These questions are keeping me from sleeping! Haha. Just want the best for this old relic boiler. I’m 33. Need it to last a lifetime!

 
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Post by franco b » Sun. Oct. 29, 2017 4:21 pm

Most oil boilers are used for hot water as well, so are kept at 150 plus. Cold boilers and smoke pipes are subject to corrosion, mostly on inside surfaces subject to summer humidity.

In my experience cast iron holds up very well in contrast to steel boilers used for steam.

Rob will have to answer the other questions.

 
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Post by coaledsweat » Sun. Oct. 29, 2017 4:49 pm

It doesn't need to sit at 150+, it needs to obtain 150+ to rid the water of oxygen.

 
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Post by hotblast1357 » Sun. Oct. 29, 2017 4:51 pm

Once the water is rid of oxygen, where does the new oxygen come from?

 
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Post by McGiever » Sun. Oct. 29, 2017 5:15 pm

We're talking molecular oxygen, it can get in past pipe threads at each and every joint for starters. Then there is the bladder/ diaphram and any PEX pipe, yes, even oxygen barrier is just thin coating. Can deteriorate in sunlight and of course abrasion.
It is a constant fight that cannot be overlooked.


 
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Post by hotblast1357 » Sun. Oct. 29, 2017 5:27 pm

Ok so we don’t really have closed loop systems, just somewhat closed.

 
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Post by Lightning » Sun. Oct. 29, 2017 7:05 pm

McGiever wrote:
Sun. Oct. 29, 2017 5:15 pm
We're talking molecular oxygen, it can get in past pipe threads at each and every joint for starters. Then there is the bladder/ diaphram and any PEX pipe, yes, even oxygen barrier is just thin coating. Can deteriorate in sunlight and of course abrasion.
It is a constant fight that cannot be overlooked.
So oxygen will permeate thru pex and pipe joints into the system even though it's fighting pressure to enter?

 
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Post by snuffy » Sun. Oct. 29, 2017 7:24 pm

So that (the PEX) explains the very dirty water I drain (from the 1st cold water line from the main) periodically at my mom's house. When I had some remodeling done to her home PEX replaced some of the copper lines.

Based on what I see coming from the PEX I'll spend the money for copper in the future. Anybody else see this happen?

 
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Post by McGiever » Sun. Oct. 29, 2017 11:53 pm

Lightning wrote:
Sun. Oct. 29, 2017 7:05 pm
McGiever wrote:
Sun. Oct. 29, 2017 5:15 pm
We're talking molecular oxygen, it can get in past pipe threads at each and every joint for starters. Then there is the bladder/ diaphram and any PEX pipe, yes, even oxygen barrier is just thin coating. Can deteriorate in sunlight and of course abrasion.
It is a constant fight that cannot be overlooked.
So oxygen will permeate thru pex and pipe joints into the system even though it's fighting pressure to enter?
I am a long ways out of my basic chemistry days but here is just a tid bit...
Oxygen Molecules...there is a much needed bond from O molecules to many other elemental molecules to become stable...oxides, as in iron oxide FeO2 better known as rust and another plentiful one is hydrogen oxide or H2O better known as water. These examples of single elements are unstable until becoming bonded as in theses cases to oxygen molecule(s).

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