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Mod con troubles

TWar Member Posts: 6
Hi guys,

I ran into a real head scratcher the other day on a new boiler I installed.

The boiler is an NTI TI200 with a primary/secondary setup.  About 2 1/2 months after install it started to make loud banging noises with pressure gauge jumping accordingly indicating boiling in the heat exchanger.  After much investigation the problem is still not readily apparent.  The primary pump is functioning properly and the boiler and piping has been descaled and flushed thoroughly.  The boiler was replaced when the manufacturer could not dignose the problem and 2 1/2 months later it has started again with the new boiler.  The funny thing is is that the more work that is done to it the worse it gets.  There is definetly flow thru the boiler which is why I cannot figure out the cause of the boiling. 

This boiler runs perfectly for me on any other systems I have installed.

Thanks for any help you guys can give.


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Got drawings and pictures?

    Sounds like an under circulation, negative pressure fluid condition or over fire condition...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    100 Percent Water?

    Any glycol in this system? If so what percentage of mix? What's the pressure gauge say when this happens?  Boilers high limit is 250 degrees. I'd also be worried about any glue joints in the vent close to the boiler.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • RobbieDo
    RobbieDo Member Posts: 131

    I have installed many of these. Had a issue with one of them and it had a tankless on demand domestic water heater on it? Does yours have a tankless? What is the water pressure coming into the house? What size is primary pump? As Mark said pics would help and a drawing too. Thanks
  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669

    Any chance you have a leak in the system underground and the boiler is taking on fresh water and you now have a limed up heat exchanger?  Does this system have a large amount of water in the system and you filled it with real bad water?
  • Plumdog_2
    Plumdog_2 Member Posts: 873

    I had one that plugged up the pump(s) with pieces of scale that came out of the heat exchanger. Pulled apart the pumps and poked out the chunks, flushed pipes in both directions. Used a concentrated de-scaler pumped thru the heat exchanger (this was a sight to behold!) and followed up with week-long use of factory supplied cleaner, then treatment. Any time one of those type heat exchangers is exposed to boiling or banging, you are likely to have scale on the inside of the tubes. 
  • TWar
    TWar Member Posts: 6
    problem found

    Hey guys,

    Thanks for all the input.  I found the problem today.  There was a whole bunch of garbage in the system.  I guess the flushing was not able to clear all of it out.  I believe the problem was with the pump used to flush it.  It was not powerful enough to flush all the crud out of the floor piping (an old 2" steel pipe goes into the floor to the most distant zones).  When it was flushed the water came out clear but after prolonged use the circulators slowly brought more out of the system and deposited it into the boiler.  I am now in the process of descaling and will be adding a Fernox iron filter to the system to catch all the random garbage coming out slowly.

    Lesson learned on replacing an old cast iron boiler with a new mod con.  MAKE SURE THE SYSTEM IS EXTEMELY CLEAN.  Also the fact that the old system uses poly-b tubing will make regular maintenance a must as oxidation will keep occuring.
  • Brad White
    Brad White Member Posts: 2,398
    edited March 2011

    A truckload of crud and non-barrier tubing. Otherwise is this connected to old iron piping?

    When connecting to old systems I use a Neptune Filter Feeder plus a wye strainer with full port blow-off valve. Some rare earth magnets in the filter bag to harvest stray iron. Makes life a lot easier.  I will have to look up the Fernox filter you mentioned.

    For the non-barrier tubing, any chance of getting a plate exchanger in there? Otherwise chemical treatment with O2 scavengers.

    But glad you found the issue! I am surprised when the first boiler was changed out this was not evident, assuming it was the same problem.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • bob eck
    bob eck Member Posts: 930
    Mod con troubles

    what is the name of the Fernox iron filter that you used. can you please email me with what you paid for that filter. thanks Bob
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Hydro Separator

    You may also want to get rid of the pri/sec and install a low loss header. Will give you added protection for the boiler. Plus you can blow it down.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • Nron_13
    Nron_13 Member Posts: 164
    Caleffi products

    use a caleffi dirt seperator on the return line to the boiler it should remove the crud from you system and its easy to clean
  • VictoriaEnergy
    VictoriaEnergy Member Posts: 126
    Spirotherm combo unit

    Spirotherm now has a combined hydraulic seperator/air eliminator/dirt seperator that looks like it'd be the ticket for this type of install.  Has anyone tried one of these yet?  I've been happy with the Spirovent microbublers in the past, so I was thinking of giving one a try.
    Home Owners Please Note:

    You are receiving advice from some very skilled pros completely free of charge. One of the reasons I participate is to sharpen my own troubleshooting skills. So; did we get it right? I would be grateful if you extend this courtesy back by posting the final outcome of the issue you are inquiring about. Thanks
  • ScottMP
    ScottMP Member Posts: 5,884

    We install wye strainers on any old system being replaced with a Mod/Con.

    The heat exchangers are just to tight for all the old crud in these systems.

  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    Y strainer

    I install a Y strainer before the pump on every high efficient boiler.
This discussion has been closed.