Hydronic heating system with strange scaling that is causing blockages

CharlieO · January 2022

Hello,
I was recently called out to a customer that was experiencing a lack of heating for a portion of their hot water radiant system. It is a large home with multiple zones of hydronic heat. The home is heated with a Weil-McLain ultra 155(natural gas) boiler that is around 11 years old. The main part of the home is heated by cast iron radiators and the large addition is heated by radiant floor tubing(staple up for a majority of it except for the basement where it is in the slab). The lack of heating was occurring in the radiant portion. The radiant side of the system is broken into 6 different zones controlled by individual circulators(with mixing valves) and a primary circulator to feed the secondary loop(radiant portion). I found the primary circulator was not moving any water. It was drawing amperage and the capacitor was good, but I was not getting any heat to transfer into the primary loop. So I planned on replacing the circulator. I isolated the radiant zone and drained it down so I could replace the circulator and when I took it apart I found a tremendous amount of scaling inside the circulator. I proceeded to purge the system from both directions to remove as much scale from the system as I could. Once I removed as much as I could I reinstalled the circualtor and the system transferred heat properly. But I am concerned about future issues with scale build up in other parts of the system. I checked all of the radiant tubes for the individual zones and found that they were all oxygen barrier tubes but the main tubing(+- 60' of this tubing and 1-1/4" diameter) from the boiler to the radiant panel is a strange brand and I could not find any information printed on the tubing stating that it has an oxygen barrier.... In regards to the scale- it looks to be forming on the inside of the copper tubing and is dark in color and is brittle yet solid. You can break it easily enough with your fingers. It is not magnetic. When we originally installed the boiler we did install the sentinel 100 that came with the boiler but that was quite some time ago..... If indeed it is forming on the inside of the copper pipe and then scaling off what would cause this?
Has anyone seen anything quite like this before?

Jamie Hall · January 2022

What's your water quality like? Any treatment? That looks from this distance

like some kind of copper oxide.

hot_rod · January 2022

mama y e send some chunks to Sentinel for analysis. Hopefully it was an aluminum friendly conditioner for that boiler.

How hot is the system running? Any makeup water being added?

One component of hydronic conditioners is a film provider. It puts a very thin protective layer on the metals, it looks like that color, but not that much.

Cast iron radiators do flake off deposits, especially with constant O2 ingress

Non barrier tube and high operating temperatures are a bad mix, always.

CharlieO · January 2022

Thank for responding fellas- sorry I didn't get back to you sooner.
I have not had the scale tested-I'll need to find out who does that locally...I also need to test a water sample...
The system is running up to 180° F. There is an automatic fill on the system but the valve has been closed and we only add water at the yearly maintenance if needed- and it hasn't needed fresh water added that often.
I had to stop out last Friday night due to lack of heat and found that a few radiators were not heating. I'm fairly certain that this is due to build up of the scale at either the main house zone circulator or the flow check valve. I also was able to find the brand and nomenclature on a section of the unknown PEX tube that is most likely not oxygen barrier tubing.... It is in fact Wirsbo-evalPEX with no indication of it being an oxygen barrier tube. I contacted Uponor/Wirsbo to see if they can give me more information on the tubing.
At this point I think my plan of attack is as follows:
1-Wait to hear back from Uponor/Wirsbo about the pipe specs. If I find that the tubing is not oxygen Barrier tubing then that will give us the information needed to resolve this issue. If the tubing is oxygen barrier tubing I will test the water and scale to determine what else may be causing it to form.
2- If the tubing is not oxygen barrier tubing we can replace all of the suspect tube with new oxygen barrier tubing to eliminate any future issues and while the system is drained I can remove the circulators and the flow checks to remove any scale blockages and then once the system is refilled I can add the sentinel 100 additive to proper levels.
Since there is a fair amount of scale floating around in the system do you think some type of dirt separator would be a good idea? I am thinking that it would make sense to add that prior to both circulators.... Your thoughts?
Thanks again for your help. It is refreshing to have some outside input.

CharlieO · January 2022

Update- I just heard back from Uponor and apparently the Wirsbo-evalpex is an oxygen barrier tube... So now I think I should test the scale and water and install the strainers before the circualtors and add some water conditioner and monitor it yearly.... I also sent Sentinel an email about identifying the scale so we can identify what the culprit is... Once we know that then we should be able to stop the scale...

CharlieO · January 2022

@hot_rod
I was thinking of installing a typical wye strainer in multiple locations to help clean the system but some of the scale is pretty large so I was hoping to have a full port drain to allow me to blow down any future scale. I was looking at some of the dirt mags and dirt separators but I'm nervous that the ports are too small.. What are your thoughts?

hot_rod · January 2022

I would go with a separator not a strainer. As strainers plug they reduce flow and heat output. With that much crud I would use a device that is both a particle separator and a magnetic separator

Even if I didn’t work for Caleffi, I would recommend this product 🙂

Easy to clean, no disassembly required.

Run a cleaner, do a good power flush, then fill with good water.

CharlieO · January 2022

@hot_rod
Thanks Bob, I appreciate your input. Since this system is polluted with scale should I install one in the supply and return lines? I really want to protect the boiler and the circulators from becoming plugged.

CharlieO · January 2022

@hot_rod
After thinking about it some, It wouldn't make sense to install one in the supply after the boiler if there is one in the return prior to the boiler.... No debris should get through the separator so that would just be an expensive redundant item. Your thoughts please.

PC7060 · January 2022

@hot_rod - I have a similar separator to the unit shown but doesn’t have the upper magnetic rod (standard versus pro).

Is it possible to install the magnetic rod in the standard unit by removing the upper plug and threading in the magnet rod assembly?

The rod assembly looks threaded into the standard body but I assume the screen is also different to accommodate the rod.

hot_rod · January 2022

Right you are, the mesh media inside is different. Here is what you have.

hot_rod · January 2022

CharlieO said:
@hot_rod
After thinking about it some, It wouldn't make sense to install one in the supply after the boiler if there is one in the return prior to the boiler.... No debris should get through the separator so that would just be an expensive redundant item. Your thoughts please.

Yes the return at the boiler is the better location. It will take multiple passes to remove all them particles and maybe a weekly flush at first.

The key is to power flush as much out first. To do that you need to be able to get flow rates up around 5 fps or more.
Maybe a 3/4 garden hose connected to house pressure, or a flush cart that can move 12 gpm or more.

PC7060 · January 2022

hot_rod said:
Right you are, the mesh media inside is different. Here is what you have.

I deeply envious of the Pro version but can't come up with a good reason to change it out.
Maybe another inline ...?

Hydronic heating system with strange scaling that is causing blockages

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