Flushing Poly-B System

KeenGreen

I have a customer that is changing out his old Super Hot boiler to a new Navien wall hung Combi boiler.
The old system did not have a heat exchanger installed. He had his system flushed every couple of years and needless to say the lines were filled with black sludge-like gunk.
I have suggested the Navien Combi be installed with a heat exchanger on the heating side to isolate the Poly-B system from the boiler.
My question is: I want my customer to have his lines flushed and cleaned properly before the new system is installed. What is product is recommended for the best cleaning of the system? Should an inhibitor be used as well? I have access to Fernox products, but am open to suggestions.
Thank you.
Jeff Green

kcopp

Fernox cleaner works well. You would be better served to also use a power flushing machine to blow out all the junk from inside the piping. A purge alone will help but not as well as a machine...

hot_rod

hydronic cleaners will loosen up some of the sludge that may be adhered, but as Kevin mentioned you need good flow, above 5 fps to move heavy sludge particles thru a tube or pipe.

A 1/2 hp or larger flush pump, do small sections at a time to get maximum flow and velocity.

kcopp

Certainly use an Inhibitor in the system. Also a good Magnetic/ Air/ dirt separator would be a good step. I like the Caleffi 5461.

hot_rod

Here is an example of a section of copper tube I cut out of my wood boiler/ solar/ mod con piping today to add a BTU meter. The system was cleaned and filled with a Rhomar 922 inhibitor when installed with new tube and components.

The Rhomar adds a very thin, a couple micron thick layer of film provider. This protects the tubing and all metal surfaces in the boiler, heat exchangers, etc from attack from aggressive water or poor water conditions. Including those caused by O2 ingress as it also has O2 scavengers in the mix. Very cheap insurance for multi thousand dollar hydronic systems

Clean with a detergent, add good fill water, use hydronic inhibitors 3 step process.

Required by manufacturers to maintain boiler warranty these days, by the way.