Replies

1. 
   Stuart | Dec 26, 2004 05:06am | #1

   I thought it was commonly used on systems subject to freezing, like in garage floors or driveways.  I just read this at http://www.radiant-floor-heating.com/hydronicexplained.htm:

   Glycol systems should be checked at least once a year to ensure the system pH levels have not dropped below recommended levels. Glycol in general is acidic. The inhibitors that are added to them help neutralize the system pH, and help protect the system components. As the system ages, the inhibitors break down, causing the system pH to drop. At this point more inhibitors should be added to the radiant floor heating and snow melt systems. The system will reach a point where it will require a complete flush and re-fill. This is usually around 5-7 years.

2. 
   DavidThomas | Dec 26, 2004 09:51am | #2

   You're right, antifreeze has corrosion inhibitors in it (note that water has none). Gycol has a somewhat higher vicosity but the pumps are fine with that (and it is much lower than the viscosity of water below 32F!)

   Of, course the heating system must be entirely separate from the potable plumbing. Any hard-piped connection must have a check-valve in it.

   David Thomas   Overlooking Cook Inlet in Kenai, Alaska
3. 
   Piffin | Dec 26, 2004 06:35pm | #3

   Your fittings are likely bronze, not steel, so rust would not be an issue, but according to one of my heating guys, the book on the subject tells him that when using antifreeze, it should be totally replaced every three years, because it will break down, and leave a chemical change that can cause corrosion in the fittings.

   We use antifreeze in all outr installations. Some HOs chnge it and some don't.

   BTW, the reason we use it is because so many of these homes get shut down for a few months every winter here, and the ones that are lived in around the year are subject to regular power outages where pipes copuld then freeze, but I don't see a need fror the antifreeze when the heat system will be staying on. is this breakage happening in the same spot repeatedly? Time to find out why abnd fix that

    

    

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1. 
   WorkshopJon | Dec 26, 2004 10:37pm | #4

   Piffin,

   I think I'm going to recommend putting some kind of antifreeze into her system.  Any idea what types of antifreeze are commonly used?   Obviously, there are plenty of different ones out there on the market.

   Jon

1. 
   Piffin | Dec 27, 2004 01:03pm | #5

   No idea. The subs take care of me. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

2. 
   johnnyd | Dec 27, 2004 04:59pm | #6

   Go to a plimbing supply house and get propolene glycol that is designed for heating systems.

3. 
   WayneL5 | Dec 30, 2004 01:59am | #11

   The guy who installed my radiant floor heating system was a trained engineer, and had installed just under 1,000,000 feet of tubing in his business.  He used antifreeze in the system he installed for me.

   There are two common bases for antifreeze, ethylene glycol and propylene glycol.  Ethylene glycol has better heat capacity for the same level of freeze protection and is less expensive.  But, it's considerably more toxic to animals and the environment (and you).  It's the stuff that vehicle engine antifreeze is made from.  Propylene glycol is more expensive but much less toxic.  It is for that reason used as the antifreeze for potable water systems such as in campers.  After it is flushed with plain water the few parts per million remaining are not harmful to drink.

   Usually ethylene glycol based antifreezes are dyed lime and propylene glycol antifreezes are dyed red.

   With both types the mixture carries less heat per gallon than plain water, therefore the system sizing calculations take this into account when antifreeze is to be used.  Propylene glycol requires more derating than ethylene glycol.  They increase pumping power a bit.

   In a vehicle you need protection for the coldest place you will ever park your car.  Most homes don't need protection down to the same temperature so less antifreeze is used, reducing the derating of thermal capacity.

   Commercial antifreeze mixtures contain a number of additives which are specific to the conditions and materials of the system.  Therefore, you should buy an antifreeze made specially for hot water heating systems.  It should be propylene glycol based for safety.

   I recommend mixing it with distilled water rather than tap water.  The mineral content of tap water is sometimes very high, and you will buy yourself years of service by starting with pure water.  You can buy it in gallon jugs in a pharmacy for cheap.  Measure and mix in a clean plastic barrel and fill your system with it.

   Be aware that the instruments used to test for concentration (thus freeze protection) are different for the two types of antifreeze, and if you use the instrument for the wrong material it will not read right.  Not even close.

4. 
   GCourter | Dec 27, 2004 05:54pm | #7

   I have used "LOW TOX" antifreeze in all of my radiant heat systems, use a 50% mix.  But keep in mind that it must be a closed system, or you need to monitor how much water is being added over time.  I agree with some of the other posts that the fittings are brass and/or bronze and you should not have a "rust" problem.

5. 
   timkline | Dec 29, 2004 10:52pm | #8

   I'm with Piffin that you would be better off solving the root of the problem than complicating your life with antifreeze.

   It usually takes moving (cold) air over a heated pipe to get it to freeze.  You need to find and stop the air leak.

    

   carpenter in transition

6. 
   csnow | Dec 29, 2004 11:34pm | #9

   Get the stuff that is designed for heating systems.  Propylene Glycol is surprisingly reactive with most metals, particularly aluminum.  The heating system stuff is different than the stuff sold for winterizing potable water systems, like for RVs and Boats.

   Another consideration is that heat transfer for glycol solutions is significantly less than pure water.  A weak concentration of propylene glycol can also cause bacteria to grow.

   Anyways, looking for articles, I found this, which has some useful info, but I would keep looking because there is a lot out there on the subject.

   http://www.infras.gov.ab.ca/Content/doctype306/production/TechPres28.pdf

1. 
   WorkshopJon | Dec 30, 2004 12:05am | #10

   Thanks for the link.  I read it and forwarded it on to my sister.

   Jon