iron sediment in flat plate heat exchanger

mostlybirch · January 10

Hello,

I'm finishing putting together the closed loop radiant circuit for a garage slab heat system. Boiler feed DHW and will heat a glycol mix radiant system through a flat plate heat exchanger. Friend gave me a large 60 plate SS brazed heat exchanger of unknown origin to see if I could use it. Saw some dark sediment in the bottom and began flushing it. Black sediment flushed from both sides of the HX, tested with a magnet and it is iron. Flushed probably 40 gallons through each side, still getting small amounts of dark sediment (less and less).

Am I fighting a losing battle trying to use this instead of shelling $400 for a new unit? Haven't started with any cleaning agents like CLR or acid. One side of this will have DHW so want to be safe.

Thanks

mattmia2 · January 10

Try soaking it in acid like citric acid or vinegar. If it is fouled the transfer will be degraded. Should find the manufacturer's transfer calculator and see if it is suitable for your application.

hot_rod · January 10

Take it to a radiator repair shop, they will cook it clean in their tanks.

Is it a brazed or bolted type?

mostlybirch · January 10

How will I know if it is fouled? I'll try vinegar tomorrow.

It's a brazwd type, B3-27-60 similar to this unit

https://www.dudadiesel.com/choose_item.php?id=HX2760

Mad Dog_2 · January 10

I put all my HXs in with unions & service valves. Doesn't hurt to try & use it...it's FREE...mad Dog

hot_rod · January 10

A valve like this with a 1" G union nut would be perfect to service in place or remove for a acid bath. I think I have a fitting to make this work.

Screenshot 2025-01-10 at 9.27.38 AM.png

hot_rod · January 10

I'd wonder what that used HX was flowing. Oil or some other non potable fluid? Hard water scale is often white or blueish.

I think officially it should have an NSF 61 listing to be used on potable water.

hot_rod · January 10

1" is a common size HX connection on residential sized plates.

This tankless valve opens the side port when the valve is in the off position. So you could use a tankless water heater cleaner kit to flush a HX with.

Screenshot 2025-01-10 at 10.40.56 AM.png

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mostlybirch · January 10

Thanks hot_rod. I have some webstone drain ball valves for just that case. Of course once I got a hold of them I found that they weren't lead-free compliant so I can only these particular drains on the glycol side. Will have to get others for the DHW side.

I can't find any NSF61 cert for this HX, is there potential for lead in a brazed HX?

mostlybirch · January 10

This HX could have been used for anything, looks like they are sometimes used in turbocharged motors.

I soaked the internals with white vinegar last night which pulled a lot of sediment, water came out black to green, pulling copper?

hot_rod · January 10

https://forum.heatinghelp.com/discussion/comment/1833711#Comment_1833711

I wouldn't worry about the stainless as much as the old leaded brass valves. Who knows whatb type of brazing zod they use to build them.

As long as you get it clean inside. I might try a few cleaners. CLR works, the tankless cleaners are citrus acid.

A kit like this is handy as you get some flow through all the plates instead of just a soak. There are a lot of small honeycomb passages in those plate HXers. I doubt soaking alone will clean it very well.

Any kind of plastic sump pump would work, put it into a 5 gallon bucket let it circulate for a day. It will warm as it circulates also.

Screenshot 2025-01-10 at 3.45.35 PM.png

mostlybirch · January 11

I had purchases new drain valves, these here. Didn't notice they weren't lead-free until they landed

https://www.amazon.com/dp/B00CL0H4N8?ref=fed_asin_title&th=1

I'll try circulating CLR now

mostlybirch · January 11

Still getting black sediment flakes coming up. Maybe more CLR pumping will eventually get it all.

hot_rod · January 11

You know, a new properly sized HX isn’t all that expensive

Not knowing where that hx has spent its life

iron sediment in flat plate heat exchanger

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