I am concerned with my lines freezing in my boiler system. Can I just use used antifreeze or do they make something special for boilers? If so is it better then antifreeze? Will added the antifreeze increase or decrease the heat transfer?
There are antifreezes made for that specific purpose. It has to be able to take a higher temperature than a car antifreeze could stand. It costs about $900 for enough to fill a typical boiler. I had a friend who put that in his vacation home boiler because he leaves the heat off except when he is there. He had a small boiler repair job done and the plumber left out the antifreeze to save him money. Sure enough the repair failed, the house froze, and the water did $30,000 worth of damage by the time that it was discovered.
If you are asking this question it might be in your best interest to call a plumber, but if you want to do it on your own. Go to a plumbing supply store and buy cryotek antifreeze, made for hot water heating systems. It's non corrosive, and protects up to extreme temperatures. You will need to purchase a costly booster pump to inject the antifreeze, and properley bleed the system. Also buy the test strips to see how much protection yo have. GL..........Rich
