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Mod/Con Boiler ?

SV9_9SV9_9 Posts: 37Member
I have a Burnham FCM 120 that has been in service for 8 years. I would like to know what the typical service life of the burner tube is? It has been cleaned regularly and appears to be firing properly. Q#2 The boiler water pH is stable at 9.0, Burnham specifies 6.5 to 8.5 Is it critical to stay within these parameters? If so what should I add to the water to bring the pH down a bit? Is Fernox 1 corrosion inhibitor compatible with an aluminum heat exchanger? Will it change the pH? Is it advisable to use it?
Thanks, J


  • hot_rodhot_rod Posts: 12,309Member
    Is there a conditioner chemical, or glycol in the system now? That ph is high for just tap water.

    If it is just tap water, check the TDS and hardness also. Those two, if high, will start scaling boiler surfaces and reduce efficiency. Enough scale and you get hot spots that can lead to corrosion.

    If the water is out of Burnham spec, I would run a cleaner in the system, at temperature and through all the zones.

    Drain, flush and start out with good quality water. If you do add conditioners be sure they are compatible with that boiler. Rhomar and Fernox have cleaner/ inhibitor kits that are compatible with all metals.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • SV9_9SV9_9 Posts: 37Member
    Just city tap water. There has never been any additives used. I have cast iron radiators supplied with hePex tubing. What is optimal in respect to hardness and TDS?
  • newagedawnnewagedawn Posts: 549Member
    that ph is really high for city tap, might want to ask the city why, it can be fixed by them, and if asking about the blast tube , thats where the nozzle assembly is?,right? ive seen them last 80 yrs, i actually have a customer with an original 1920's burner and his blast tube is still intact, not sure your asking the right question here maybe your asking about the combustion chamber???
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • SV9_9SV9_9 Posts: 37Member
    Hi, Thanks for your response, I was asking about the blast tube as you refer to it. Burnham refers to it as the "burner". In respect to the pH values I stated earlier, 9.0 is from a boiler water sample. The cold tap water is very close to neutral. 6.8 to 7.0, I apologize for the omission. I just re-calibrated my tester and rechecked the tap water and the boiler water. (The boiler water is clear with no visible sediment). The values remain essentially the same. Tap at 6.8 and boiler water at 8.9, I have been testing the boiler water periodically for the past three or four years. I have had to drain and refill the system a few times for repairs and changes to the heat emitter piping. The pH always stabilizes right around 9.0 after a few weeks. My real concern is whether or not this pH value is problematic,(aluminum heat exchanger) and if so what I need to do to correct it. The original installer had no interest in any of this water testing, and advised me not to worry about it. I am not sure if this is relevant, but there are two coalescing air vents in the system. One in the boiler loop and one in the zone header. I know this is redundant, but the vent in the zone header doesn't do any work in the summer when there is only call for DHW. I was getting air in the DHW loop, so I added a second vent on the supply side of the boiler loop where it should have been located from the start. Thanks again for any thoughts.
  • hot_rodhot_rod Posts: 12,309Member
    Also check TDS and hardness. The minerals in the water are what cause scaling and boiler failures. High mineral water also also can cause problems in the circulators and other components.

    Pn , hardness and TDS.

    Here is the water spec for that boiler, although acceptable TDS seem fairly high?

    7GPG on the hardness! It's not often you find that in public or well water, so treatment may be required.

    The best way to treat water is DI, or RO, it will handle hardness and TDS without raising conductivity as softeners do.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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