System: closed hydronic system with Buderus oil fired cast iron boiler and Buderus 50+ gal indirect hot water tank with cathodic protection (electric)
Age: Installed new 2004
Problem: No boiler water flowing through the 1 1/2" copper manifold.
Description of System: Manifold feeds 4 radiant heat zones with PEX and ONIX tubing and 2 fin tubed baseboard zones. PEX is encased in the concrete basement floor. ONIX is staple up radiant heat and used to connected the fin tubing.
Cause: 1 1/2" Spirovent screen was found to be plugged. The photos show the 1 1/2" manifold, Spirovent, Spirovent screen and water being flushed from system.
Solution: Replaced Spriovent screen and a new head on Spirovent. Now the water is flowing through the manifold.
Question: Why is there so much particulate matter in the boiler water? So much it plugged the Spirovent. Where is the stuff coming from and why.
Mineral deposits, rust particles, organic material could all contribute to that sludge especially if you have a leak and the autofill valve keeps adding water. The impeller from the circulator could also contribute to that or the insides of the boiler itself (more so with a CI heat exchanger rather than aluminum or SS). Water, if it's not being lost and replaced, reaches an equilibrium in a closed system, otherwise, the mineral content, and reactivity of the water can stay high.
Jim, thank you. Yes the system has an auto fill, but if it were leaking - I would see the water somewhere in the house except for the basement radiant heat. I typically shut the domestic water off to the house when we leave - it's a weekend home. I will check the pressure on the system when I return before turning the water on. If there is a leak, the pressure would drop from 15 psi to something less, right?
I am not sure what you mean bythe impeller from the circulator could contribute? As you can see from the photo, there are 7 circulators in this system. There is a "main" circulator just for the 1 1/2" manifold that circulates water through the boiler and manifold. This runs any time any zone calls for heat except the domestic hot water zone. And yes it is a cast iron boiler.
Not sure what material the impeller is made of in the circulator. There is likely some steel in the system, and that will rust until all of the free oxygen is used up in the water. If you shut the water off, then yes, you'd likely see the pressure drop if there was a leak in the boiler but not necessarily...it might not leak unless a pump was running and then a drop or two over a long enough time span so it can evaporate before you'd notice. You would see mineral deposits, though, after awhile. Ideally, once a boiler system is filled, it never needs to be topped up. If it does get topped up, that adds new free oxygen (and other gasses) disolved in the water, and those will react until they become more stable (eg., any iron rusts, using up the oxygen). Those disolved gasses can also make things like acid, and then that does it's thing on stuff until it is neutralized into salts. The water that was installed, probably was potable, but that doesn't mean it had all organic material both dead and/or removed. So, adding new stuff is not your friendly solution if you have a leak...fixing it is. Sounds like you may not have one.
Today I dropped off the sludge and some of the "dirty" water to a forensic chemistry lab to see what's in it. They will be looking for iron, copper, epdm rubber, components of stainless steel. We'll see. Next time I am at the house I will shut off the boiler fill valve. The system should hold pressure at 15 psi, indefinately. We'll see. The impeller on the Taco circulator is non-metallic. I haven't checked out the Grundfos circulators yet. I'll let you know what the laboratory finds.
Have you verified that the onix tube and the PEX is the type with an oxygen barrier, meant for radiant heating?
Early onix and PEX for potible without a oxygen barrier would do this, allowing oxygen to constantly permeate into the system.
System was installed in 2004. I believe the ONIX is of the radiant heat type with aluminum shield. The plumber / installer said it was designed for this purpose and system was designed by a heating engineer. I will verify the markings on the tubing to confirm.
My lab results came back this morning. "The material is primarily iron oxide. There is a lesser amount of copper. No zinc, chromium or nickel from brass or stainless steel. Also no rubber. It appears that there is a path for oxygen into the system. Analysis indicates oxides and color indicates primarily hematite which is indicative of oxygenated water."
The PEX is encased in concrete, in the basement floor. Actually it is staped to 2" foam insulation board on 6" crushed stone with 4" of concrete poured on top. will check out the PEX markings too, if possible. Very little is exposed above the concrete - but I will check it out.
I am going to shut down the auto-fill. That will confirm whether there is a leak or not.