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clogged piping after radiator removal/install for tile work

ch4man Member Posts: 296
I got involved with a HO who last year had a condensing boiler installed in a ~90 year old home. CI 1st and 2nd floor, very old fin/tube in basement.
i hear it worked just fine until a few weeks ago when during a remodel one CI rad was pulled and reinstalled.

we found 2 circulator impellers and the spirovent packed with black crud. we flushed those but still have restricted flow. the condensing lennox ( sorry i forget the exact model) is reacting to poor flow by ramping way down resulting in input to heat the house.

the boiler (lennox) claims a helical fin/tube heat exchanger. that was also flushed

this is beyond what the people i work for want to get into but I always want to learn so....

is this rare or somewhat common occurance?

there is/was glycol, is it a factor?

how would one go about flushing a 2 circuit, reverse return CI gravity with CI rads house built some 90-100 years ago? what equipment would be needed to be effective in flushing? house water pressure, trash pump? or is there specially designed tools for this.

thank you......


  • nicholas bonham-carter
    When the new Lennox was installed, was the system flushed then?
    Is glycol really needed? There are other methods of freeze protection for any piping which is too close to an outside wall.
    Rhomar makes various cleaners for the whole system, which are added, circulated and drained out. Additional chemicals are added later to keep things pretty for the long haul.
    If the system is old enough, I suspect the piping is less clogged than the boiler heat exchanger itself. The type of heat exchanger, (aluminum, stainless,etc.) will determine the chemistry involved.
    Test the black crud with a magnet to see if it is rust. If so there may be an air leak in the system, (automatic radiator vents?), which must be corrected. —NBC
  • ch4man
    ch4man Member Posts: 296
    I cant answer what happened at install, it wasnt done by us. no i dont believe glycol is needed. there is no outdoor slabs.
    again we were brought in after the fact, but as I understand all was fine until the system was disturbed when one rad was pulled for a remodel.
    if whatever is clogging the system is rust, are the chemicals effective?