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TriangleTube HMG-30N

Skyline Member Posts: 151
edited February 2020 in THE MAIN WALL
The combi-boiler in question is TriangleTube HMG-30N, NG 120K BTU/HR, 42 Gallon storage, about 20 years old. The house is ~1,300 sqf with one bathroom, two zones and two people live in the house. There had been couple of minor/major issues during it's lifetime that had been addressed, but not much standard maintenance had been done.

The heat is working just fine, but have issues with DHW as of late. It used to have endless hot water, but as of late, even with a short shower, the water is getting colder by the end; not cold, cold, but not as pleasant as at the beginning. If the other person takes a shower right after, it's not as pleasant from the start to the end, but never actually gets unpleasantly cold.

I did turn up the water temperature, that resulted in really hot water at the beginning, but even then the water temperature drops with prolonged use, like showering, doing dishes, etc.

This is an issue that may, or may not be be simple to remediate. I am open to suggestions and will try them.

Since this unit is about 20 years old, is it worth for calling the contractor to fix it, or it's time to replace the boiler?



  • unclejohn
    unclejohn Member Posts: 1,833
    It may just need a thorough cleaning.
  • Skyline
    Skyline Member Posts: 151
    unclejohn said:

    It may just need a thorough cleaning.

    That's possible, but...

    It's doubtful that you meant external cleaning; albeit the air intake might be one of the candidates. The very first time the contractor charged me to vacuum out the boiler, I've place a automobile air filter on the air intake:

    While it is possible that the blower still need some cleaning, there isn't much else that comes to mind.

    If you meant internal cleaning, such as firing chamber, storage tank, etc., could you provide some details how that should be done?


  • Skyline
    Skyline Member Posts: 151
    After further research and talking to some plumbers, the source the DHW issue had been identified.

    There are two possible conditions for this issue:
    • Thermostatic mixing valve failed
    • Cold water dip tube
    The Taco 5000-2 is the low hanging fruit, replacing the dip tube is probably not worth for with a 20 years old combi-boiler.

    Instead of replacing the mixing valve, the adjusting cap was turned 360 degree to clockwise and counter clockwise, while the hot water is running close by. Turning it counter clockwise actually made the the water lukewarm, while the opposite way made the water very hot at the sink. After settling at just not hot enough to burn water temperature, this issue is resolved. This has been verified by using the the shower, the initial temperature held steady, even during long showers.

    Question about the Taco 5000-2...

    When the temperature adjustment turned, is it normal that it leaks water around the adjustment screw? The leak did stop, once the screw was not moved.

    I'd rather replace the mixing valve, but I cannot find the same one. Taco still has them, but they are brass, instead of mine, that's silver color, more likely nickle plated.

    Would the brass color one be an exact replacement?

    Not being familiar with other brand, could Watts 3/4" union mixing valve or other brand be an exact replacement as well? There are limited space available and the unions connect to sweat copper pipes.


  • SuperTech
    SuperTech Member Posts: 2,016
    Don't use the Watts. Use Caleffi, Taco or Honeywell.
  • Skyline
    Skyline Member Posts: 151
    Thanks SuperTech...

    Brand does not matter, Taco, Honeywell, Caleffi would be just fine.

    Are these three-ways thermostatic mixing valves have the same dimensions? The two that interesting is in the drawing below, marked with red line:

    CJBULL Member Posts: 3
    more than likely the diptube has started to deteriorate and not delivering the incoming cold water to the bottom of the tank