anti-freeze & galvanized pipes
anti-freeze & galvanized pipes
(OP)
I’ve got an old run-around-coil heat-recovery system, which is handling about 12 cu m/sec of air. Heat is extracted from the exhaust air streams with 4-row coils and the water is pumped to 6-row coils to heat the supply air. The system seems to recover about 50% of the available heat, when it runs in winter.
The original system had a ‘summer cooling’ mode that cooled the air with cold water pumped through the supply coils from a cold water storage tank. I abandoned this feature because it is now illegal and was never a good idea.
The problem is that, because the system once handled domestic cold water, all the existing pipework is galvanized. It has always been filled with plain water and the supply coils have frozen several times. I now want to put anti-freeze into the system. I understand that the usual anti-freeze mixtures (ethylene or propylene glycols) will usually have di-potassium phosphate corrosion inhibitor, which will react with the zinc.
Can anyone suggest any different antifreeze solutions which are compatible with the zinc, or will I have to replace all the old pipework? I tried a couple of large chemical suppliers, but they were not helpful. Any other bright ideas would be welcomed.
TIA
The original system had a ‘summer cooling’ mode that cooled the air with cold water pumped through the supply coils from a cold water storage tank. I abandoned this feature because it is now illegal and was never a good idea.
The problem is that, because the system once handled domestic cold water, all the existing pipework is galvanized. It has always been filled with plain water and the supply coils have frozen several times. I now want to put anti-freeze into the system. I understand that the usual anti-freeze mixtures (ethylene or propylene glycols) will usually have di-potassium phosphate corrosion inhibitor, which will react with the zinc.
Can anyone suggest any different antifreeze solutions which are compatible with the zinc, or will I have to replace all the old pipework? I tried a couple of large chemical suppliers, but they were not helpful. Any other bright ideas would be welcomed.
TIA





RE: anti-freeze & galvanized pipes
Remember...
"If you don't use your head, your going to have to use your feet."
RE: anti-freeze & galvanized pipes
Since you do not need the anticorrosion properties you could use just the glycol with water and all should be fine.
Chemical suppliers should be able to sell this to you - just make vary clear you do not want any additves in it, just the base product.
RE: anti-freeze & galvanized pipes
Does anyone know if it is just the corrosion inhibitors which re-act with the zinc, or will glycols (ethylene or propylene) re-act with the zinc as well?
Thank you both.
RE: anti-freeze & galvanized pipes
As for running glycol/water solutions in galvanized pipe I have seen this done extensively in industrial chiller loops without major degradation. Check with the manufacturer of the glycol for their recommendations for galvinized pipe service. The anti-corrosion additve packages can be formulated to specific requirements.
saxon
RE: anti-freeze & galvanized pipes
-The old system had a 'summer cooling' mode.......I abandoned it because it is now illegal and was never a good idea.
First off: What makes the system illegal? Secondly cold storage is something that we're using up here in Canada (8 months of winter means we can get all the cold we need), why do you not like the idea?