System water in a heating system

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Old 02-23-18, 02:13 PM
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System water in a heating system

This is primarily to heat tech, not the handy man. We’re always trying to eliminate air in the system. We’re indoctrinated with the elimination of the deadly “microbubbles” oxygen entrainment corrodes the cast iron.
I agree, oxygen will oxidize iron in the presence of water. The argument is if yo drain or change out boiler water, it is more oxygen rich than the boiler water. That all sounds good and most just accept that, but if tap water is H2O, what is the chemical makeup of boiler water. Under that theory, it’s no longer H2O, but something else. Heated water, under either heat , or cold , causes elements to fall out of suspension. But the amount of oxygen in tap water and boiler water is actually identical. H2O is H2O. The nasty ness of boiler water is the elements from the equipment dissolving in the presence of water. I once had a professor once tell us in the 90s, If you attempt to clean this piping system with chemicals, you just might get a big reward of removing lots of encrusted dirt and spring a leak where none existed before.... your thoughts...
 

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Old 02-23-18, 02:49 PM
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Yes H2O is water. However there is H2O and additional air in the heating system. Every time you empty and refill the system you trap additional air in the water stream. Eventually it will be forced out but it can take quite a while.

Do you have a problem there ?
 
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Old 02-23-18, 03:47 PM
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h,
Water is water but boiler water, once the air or oxygen is removed is what we call dead water which I believe has no corrosive contaminates to attack the cast iron which is what you want

Fresh water is the boilers worst enemy because all fresh water has air and contaminates. You may not notice it so much out of a faucet because there is nothing for it to attack, but a boiler is a closed loop system that traps the oxygen which is deadly to boilers until removed.

If you keep adding fresh water you keep adding oxygen. Once the air is bled and the water dead there is nothing to deteriorate the cast.

I have never asked but I suspect that is why steam boilers only have a 10 yr. warranty on the castings and hot water usually has at least 20, because steam constantly has fresh water being added.

Although steam boilers are basically open and release air every cycle air is always present.

About chemicals. I was working for a housing authority and a chemical salesman wanted to treat our 30 yr. old boilers in a highrise building. My boss, who knew nothing about boilers or anything mechanical thought it was a good idea and didn't think it was necessary to get my opinion.

The chemicals were put in the boilers. One day I get a call for a leak in the boiler room. When I got there almost every joint in the place was leaking, from the double tap boiler nipples to other fittings. This seemed to happen overnight. Looking around I found some drums that said boiler treatment in the room.

Calling the boss to see if anybody had been there he told me what he had done. I had him come done and look at his handy work and explain why you don't do that. He thought it was coincidence that it wasn't the chemicals.

We called the salesman and explained what happened and his response was. "That's the downside of waiting 30 yrs. to add chemicals, but once the leaks are fixed it would keep the system clean. He just didn't think it was important to mention at the time of the sale.

He never came back but the damage was done.

Your professor was exactly right and I know from personal experience.

Just my thoughts from my experiences.
 
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Old 02-23-18, 05:31 PM
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The only place air ( which is actually about 70% nitrogen , an inert gas ) should be trapped in the highest point in the system which is likely copper. If properly purged, there should be little oxygen is in the system , there should be twice as much hydrogen in the system as well, because when the water is heated this compound should give off two molecules of hydrogen for every molecule of oxygen. These are vented out thru the air scoop though in the hydronic system , provided it was installed properly. The system temperatures never get that hot to separate the two though, save a steam boiler which re-condenses to its original state. The killer with steam boilers is the formation of carbonic acid in steam systems. This is usually faulted by poor insulation practices. If steam systems were kept at a 8 PH, they would last longer however, nobody will monitor that... itís too much work. Heat and water will break down almost anything.
 
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Old 02-23-18, 06:26 PM
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I'm no chemist. I'll take your word for it.
 
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Old 02-24-18, 02:51 AM
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To Hvac01453 statement from [email protected]:31 pm.. If properly purged, there should be little oxygen is in the system , there should be twice as much hydrogen in the system as well, because when the water is heated this compound should give off two molecules of hydrogen for every molecule of oxygen. WHAT? Heat does not break down water or change it's state. That would be called " electrolysis". Also, "heat and water will break down almost anything" Excuse me . Get your facts straight. Here's a little bit of history; that has something to say about boilers and water. Hot water and especially steam systems before the middle 1950's lasted longer without water treatment of any kind because the piping most of the time was made of wrought iron, similar to cast iron (very hard) and resistant to degradation. Sometime around 1950 the company that made wrought iron pipe went out of business and installers had to switch to steel pipe which would corrode and degrade more quickly than wrought iron. And by the way, you said that." Under that theory , it's no longer H2O but something else. if tap water is H2O what is the chemical make up of boiler water " ( it's still H2O) "WOW1" I may be retired for 10 years but I do not think the physics of water have changed. Great discussion, I am much smarter now. Thank you
 
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