iron oxide

StevenB

We worked on a system yesterday that clearly was lacking flow through the system. We found that the Spirovent air collector was completely plugged with iron oxides. To get the customer through the night we removed the element and the system heated perfectly. My question is, where did the oxygen come from? The system is a combination of convective heat and radiant heat supplied through a low temperature subloop. The radiant is done with staple up Onyx tubing. I'm assuming the Onyx is allowing oxygen adsorption since I see no other source of air in the system. The low temp loop is very cool at less than 100 degrees. Any other thoughts on this? There has been no complaints of air in the system.

kcopp

Been there....

dealt w/ that. I have a system about a year ago and had the exact same issue. plugged up the circs, spirovent and was blowing the prv. Onyx is not such a good tubing for radiant, unless you separate it from the ferrous parts of the system w/ a HX.  I replaced the circs, replaced the spiro element and cleaned up the system w/ Rhomar products. There is a heavy O2 inhibitor in the system now. The system is 12 yrs. old. here is the post w/ pix.

http://www.heatinghelp.com/forum-thread/140883/Anyone-seen-this#p1262544

StevenB

Thanks

I think you're correct but it seems that Onyx should have an oxygen barrier since it is designed for radiant. I always thought that low temps would reduce oxygen adsorption and this system runs at well below 100 degrees. We are going to chemically treat the water and warn the customer that there will be ongoing issues. I am sure the circs are looking like the photos you shot.

SWEI

cold water

Holds far more oxygen than hot water http://www.engineeringtoolbox.com/air-solubility-water-d_639.html

hot_rod

same

problem that you will see in polybutylene, solar roll and any of the other non-barrier tubes.



There are a number on magnetic dirt separators on the market, to help with fine particle removal. With a chronic problem you might need to add an automatic blow down valve!



Just don't put an ECM pump on the system, those magnetic particles seem to be attracted to the strong permanent magnets in the circs.



Some of the Colorado contractors specialize in flushing and rehabing those sludged non barrier systems. Talk to Heatmeister over in Dillion, Co.