Original message
| BruJan
 |  "Necessity of glycol in hot water heating"
, posted Sun 10 Dec 13:20  
Our local library is a 40 year old steam (5 to 10 psi) system and we are considering converting it to hot water. Our heating engineer says it is mandatory to set up and use a glycol system which adds about $4,000 to the conversion cost. He says it would prevent freezing and would protect the existing steam coil in the air handler. How necessary is the glycol addition?
Bruce R.
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Replies:
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| evildberg
| "Re(1):Necessity of glycol in hot water heati" , posted Mon 11 Dec 18:39
Absolutely necessary if you live in a climate that drops below freezing regularly in the winter and you have any coils or heat transfer units of any sort that come into contact with or could come into contact with outside air. I have had to add glycol to systems that should not have any outside air in contact with them but have frozen and bursted. Example would be a baseboard only system with zone valves on each zone in an apartment building.
I had baseboard freeze in occupied rooms because people would turn down the heat at night and open the window slightly which would be behind a dresser or some peice of furnature. The cold air would fall and trap behind the furnature and because the heat wasn't calling baseboard would freeze and burst open in that section.
This is a scenario where one would think there would be no chance of a freeze up. When you have outside air passing through coils you always have the chance of freeze up especially if there is a damper actuator or linkage failure. It could also happen if there was a flow issue in the water side of the coil.
Glycol is almost always needed in heating systems in areas that the winter temps dip well below freezing.
If I may offer a suggestion, I would reccomend flushing the system with water several times to remove any sediment in the system before adding a glycol mix to it. This will hopefully prevent you from having to instal filter systems in the loop to remove old scale, buildup and rust from the system.
Good luck and fill to the corect percentage for proper freeze / burst protection
Union Pipefitter (service) Minneapolis MN local 539
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| | fitter597
| "Re(2):Necessity of glycol in hot water heati" , posted Wed 1 Aug 23:03
Evildberg is 100% correct and you should listen to him and your Heating Engineer.
Pipefitters Local 597
" We do it right the first time"
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