Corrosion protection needed?

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  #1  
Old 09-30-16, 12:08 PM
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Corrosion protection needed?

I have a 3 zone + DHW hydronic system with a Munchkin high-efficiency boiler, installed roughly 2006. The heat zones are copper piped with slant fin baseboards. I don't have much info on the system from the previous owner, but the stickers indicate it was installed by a reputable local contractor.

I recently did a small amount of work on the system and had to drain out some water. When doing so I used some of those cryotek test strips and found about 30% glycol (which is appropriate for my climate) and no indication of any corrosion protection (which I assume is a pH measurement).

Is this something to be concerned with? I'm fairly new to hydronic systems and don't have much experience with maintenance and modification.
 
  #2  
Old 09-30-16, 03:07 PM
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Anti-corrosion additives are seldom recommended for hydronic systems - an effective air removal device or system is normally all that is necessary.

I wonder about the glycol. Is this system unattended for stretches during freezing weather? Glycol is messy and can seep out of tiny leaks that plain water wouldn't, and glycol, which is toxic, can present disposal issues. Personally, I would prefer to avoid using hydronic heat in situations where freeze protection is required.
 
  #3  
Old 09-30-16, 04:12 PM
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I did just replace the automatic air purger, so I should be good there.

The previous owners wintered in Florida, so they probably did leave the system off at least for some portion of the winter. That would explain the glycol charge.

I don't turn the system off, and also have an automatic standby generator, so the chances of freezing are slim. If I ever have cause to drain the system I would be hesitant to recharge it with glycol for the reasons you mentioned.

While we're on the topic, what type of water is preferred to charge the system? I have fairly hard well water with some iron content. I also have a softener for the household water. The refill valve is plumbed to the raw well water. Which option is better? Or if I have to replace a large amount of water should I bring in cleaner water (distilled, filtered, etc)?
 
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Old 09-30-16, 05:09 PM
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I think either raw well water or softened water would be OK. Some people are concerned with chloride ions in the softener water, but unless you have stainless steel piping or fittings, not a problem, in my opinion, so my preference is softened water. Even with stainless steel, I wouldn't worry about it.

The iron in the raw well water shouldn't be a problem. In systems with ferrous metal, iron gets readily into the circulating water - and promptly gets converted to a harmless form of iron oxide that turns the circulating water black and maybe stinks. Ignore it.

I wouldn't consider figuring out a way to use "cleaner" water for a major refill - too much trouble, and not worth it.

If the heat is turned off or goes off for an extended time in the winter, and you are majorly absent, freezing up of the hydronic heating system could be a problem - but so is your domestic water plumbing, your furniture, and your piano tuning. If we're away, and there is very cold weather, I can check the indoor temperature over the internet - and call a neighbor, if necessary. The neighbor has the key and knows what plumber/hvac guy to call.
 
  #5  
Old 10-01-16, 08:01 AM
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If you are going to drain and refill the system with water add a boiler cleaner. Do not know what it did for the boiler but I found it made a major difference raising the radiator/convector surface temperature.

Search Results for boiler cleaner at The Home Depot
 
  #6  
Old 10-03-16, 09:23 AM
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My hot-water system is over 60 years old. The piping is mostly black steel, but some copper was added later for a room addition. The heat emitters are cast-iron baseboard units. When I've opened up the system for maintenance or alterations, the inside wall of the piping and fittings is like new, clean as a hound's tooth - no corrosion or scale.

We are on city water. No corrosion inhibitor or cleaners have ever been added to the system. I don't routinely drain and refill the system unless necessary for maintenance - which is seldom. Our conventional expansion tank (not a bladder type) is equipped with Bell & Gossett Airtrol fittings that continuously remove any air from the circulating water and return it to the tank.
 

Last edited by gilmorrie; 10-03-16 at 09:48 AM.
  #7  
Old 10-03-16, 09:17 PM
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The 60 years old system I used the cleaner on was all copper except for cast iron boiler. City water here is artesian with no minerals or other issues.

After adding cleaner, you could smell the higher surface temperate of the aluminum fin convectors. Apparently the cleaner removed some kind of film that impeded heat transfer.

There did not seem to be any downside to using cleaner and feel that for $10 it was worth it. These cleaners are widely used in industrial and commercial systems.
 
 

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